- Email: [email protected]
Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone
Analytica Chimica Acta xxx (xxxx) xxx
Contents lists available at ScienceDirect
Analytica Chimica Acta journal homepage: www.elsevier.com/locate/aca
Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone Qiangqiang Fu a, b, c, 1, Chunlei Zhang b, 1, Jun Xie a, Zhaohui Li d, Lingbo Qu d, Xiaoli Cai c, Hui Ouyang c, Yang Song c, Dan Du c, *, Yuehe Lin c, **, Yong Tang a, *** a
Department of Bioengineering, Guangdong Province Engineering Research Center for Antibody Drug and Immunoassay, Jinan University, Guangzhou, 510632, PR China Department of Stomatology, The First Affiliated Hospital, Jinan University, Guangzhou, 510632, PR China c School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, 99164, USA d College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou, 450001, PR China b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
A novel ambient light sensor (ALS) based acetylcholinesterase (ACHE) colorimetric dipstick reader for organophosphate pesticides testing was reported. The ALS based ACHE colorimetric dipstick reader has the advantages of easy to operate, low cost, high accuracy and versatility. Results of the ALS based ACHE colorimetric dipstick reader were comparable with results from GC-MS and Ellman assay.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 August 2019 Accepted 23 September 2019 Available online xxx
Organophosphate pesticides (OPs) are widely used around the world to control pests in agricultural, residential, and commercial settings. Ingestion of high-dose OPs could lead to acute toxicity, and persistent influence on health could result from acute poisoning or long-term exposure to low dose OPs. An easy to operate, low cost and home available OPs testing platform is urgently needed. Ambient light sensor (ALS) based smart phone colorimetric reader has the advantages of easy to operate, low cost, high accuracy and versatility. In this work, a novel ALS based smart phone colorimetric dipsticks (CDs) reader was reported for rapid monitoring OPs. In this method, acetylcholinesterase (ACHE) CDs was used to test OPs and results were analyzed using an ALS based reader according to the absorbance of ACHE CDs. The results obtained using the ALS based CDs reader were comparable to those obtained using gas chromatography-mass spectrometry (GC-MS) and Ellman assay. The ALS based CDs reader has the
Keywords: Colorimetric dipstick reader Smart phone Ambient light sensor Organophosphate pesticides Chlorpyrifos
Abbreviations: Organophosphate pesticides, OPs; acetylcholinesterase, ACHE; ambient light sensor, ALS; gas chromatography-mass spectrometry, GC-MS; colorimetric dipsticks, CDs; thin layer chromatography, TLC; gas chromatography, GC; gas chromatography-mass spectrometry, GC-MS; high performance liquid chromatography, HPLC; liquid chromatography-mass spectrometry, LC-MS; polyethylene terephthalate, PET; linear detection range, LDR; limit of detection, LOD; coefficient of variation, C.V. * Corresponding author. ** Corresponding author. *** Corresponding author. E-mail addresses: [email protected] (D. Du), [email protected] (Y. Lin), [email protected] (Y. Tang). 1 These authors contributed equally to this work. https://doi.org/10.1016/j.aca.2019.09.059 0003-2670/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
2
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
advantages of portable, low cost, and high accuracy, and therefore could act an effective platform for OPs monitoring. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Organophosphate pesticides (OPs) are nerve-targeting agents, functioning by inhibiting the action of acetylcholinesterase (ACHE) in nerve cells, which are widely used around the world to control pests in agricultural, residential, and commercial settings. OPs can be absorbed by ingestion, and they can cause serious poisoning to human body. The toxicity of OPs is not only limited to the acute phase, the chronic effects resulting even from low levels of OPs exposure have long been noted. Chromatography represents the most widely used methods for detection of OPs, including thin layer chromatography (TLC) [1], gas chromatography (GC) [2], gas chromatography-mass spectrometry (GC-MS) [3e5], high performance liquid chromatography (HPLC) [6], liquid chromatographymass spectrometry (LC-MS) [7], etc [5,8]. However, these methods are used limitedly in professional laboratories due to the requirement for sophisticated instruments, high maintenance costs, and professional operators. ACHE CDs are widely used in the pesticide residues preliminary screening due to its easy readout, low cost and simple operation. However, the current ACHE CDs are read by naked eyes and obtained a yes/no result, so the accuracy is very low. Therefore, a portable and low cost ACHE CDs reader is urgently required for enhancing their accuracy. Smart phone based analytical devices could be an excellent candidate for CDs reader. Currently, permanent physical sensors of a smart phone, including digital cameras [9e14], wireless devices [15,16], USB ports [17], audio jacks [18,19], and others [20,21] have been applied for preparation of biosensors. In the case of CDs, results were first obtained using digital cameras, followed by analysis using software [22]. Consequently, captured images were initially divided into RGB (red, green, blue) values, followed by a calculation of the corresponding target concentrations according to these RGB values. The standard RGB scale assigns a whole-number value from 0 to 255 for each of these three colors in a given tone, such that [0, 0, 0] corresponds to absolute black and [255, 255, 255], to true white. Therefore, a good smart phone camera should be able to distinguish until 16777216 colors in theory [23,24]. However, in the actual detection, the color change of dipsticks is limited. For example, the RGB values of dipsticks changing from white to blue change from [255, 255, 255], [254, 254, 255] … … to [0, 0, 255]. The RGB image analysis only captures 256 color changes, indicative of its low accuracy. Additionally, different brands of smart phones have different camera characteristics, in terms of megapixel count, sensitivity of the CMOS sensor, camera lens quality, aperture dimension, etc [25,26]. As a result, the image captured from one smart phone and its corresponding color channels may be different from those of another smart phone. Ambient light sensors (ALS) are installed in all types of smart phones in order to sense the environment lighting conditions and allow for the adjustment of the screen’s backlight to comfortable levels for the viewer. Moreover, ALS can directly sense light intensity, so it does not need to consider the sensitivity of CMOS sensor, camera lens quality, aperture dimension, etc [25,27,28]. Furthermore, the current smart phone ALS can sense the light intensity of 0 luxe100000 Lux, indicative of a high accuracy of ALS based colorimetric reader. In this study, we developed an ALS based ACHE CDs reader for OPs monitoring. The optical attachment of ALS based ACHE CDs
reader is a lightweight (~70 g), compact (87 69 30 mm), 3D printed housing that contains an inexpensive, 2 battery (1.5 V), electronic switch, and wiring components to connect the electronics (Fig. 1a). In order to eliminate the interference of ambient light, the ALS based CDs reader was added to a black plastic shell. In the ALS based CDs reader, an LED light was installed as an excitation light source. In order to match the maximum absorption spectra of the ACHE CDs, a 645 nm LED was selected as a light source. In the device, the LED excitation intensity remains constant and the absorbance of ACHE CDs for different concentrations of pesticides is different. Therefore, ALS can sense different light intensities in an OPs concentration-dependent manner. In the CDs, ACHE could catalyze indophenol acetate (red) to acetic acid and indigo (blue), while OPs are able to inhibit this catalytic activity. As shown in Fig. 1, the ACHE CDs are primarily comprised of two pieces of paper (red and white, respectively) pasted on a plastic plate. ACHE and indophenol acetate are preloaded onto the white paper and the red paper, respectively (Fig. 1b). For the detection of OPs, liquid sample was first added onto the white paper and incubated for 3 min. Then the ACHE CDs were folded to overlap the two pieces of paper. Consequently, ACHE on white paper will catalyze the indophenol acetate loaded on the red paper. If there is no OPs residue present in the sample, the ACHE catalytic activity cannot be inhibited. Therefore, indigo is produced on the white paper and its color will change to blue, resulting in low transmitted light as measured by ALS (Fig. 1c). If a high concentration of OPs sample is loaded, the pesticides will inhibit the ACHE activity (Fig. 1d) and a high transmitted light will be measured. Chlorpyrifos is the most widely used OPs at present. Therefore, in the main text, we study the performance of the ALS based ACHE CDs reader by detecting chlorpyrifos. 2. Materials and experiments 2.1. Materials and reagents Parathion, methyl parathion, malathion, carbaryl, chlorpyrifos, and fenitrothion were purchased from Ocean Tech (U.S.A.). ACHE CDs were purchased from Hubei Saiyang biotech (Wuhan, china). In regards to the ACHE CDs, refer to the previous literature (International Journal of Analytical Chemistry, 2014, Article ID 536823). LEDs (645 nm) were obtained from Shenzhen Octai Co., Ltd (Shenzhen, China). The battery (1.5 V) was obtained from VSAI (Shenzhen, China). Wires were purchased from a local store. Vegetable samples were purchased from a local supermarket in Pullman. The liquid ACHE inhibition assay (Ellman Assay) kit was purchased from Guangzhou Lvzhou biotech (Guangzhou, China). 2.2. Apparatus The absorbance of Ellman assay was measured using a Synergy H1 Hybrid Multi-Mode Microplate Reader (Bio-Tek Instruments, Inc.). Gas Chromatography-Mass Spectrometry (GC-MS, Thermo Fisher) was used to test the chlorpyrifos in cabbage sample extracts. A HUAWEI Honor 6 smart phone was used for development of the ALS based CDs reader. The 3D printer was purchased from the SHINING 3D (Hangzhou, China). Polylactice acid was used for fabrication of the device.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
2.3. Design of the ALS based ACHE CDs reader The smart phone CDs reader was drawn using software, followed by processing by the printer software, 3D star. In the print setup, the print mode was set as quality and the supporting way was internal and external support. In the ALS based CDs reader, the wavelength of the emission LED light was 645 nm. A free smart application Light Meter was used to display the measured transmitted light intensity at the screen. 2.4. ACHE CDs for OPs detection This procedure was carried out as described in the instructions regarding ACHE CDs. In order to ensure the stability and reproducibility of the test results, the ACHE CDs used in this experiment were purchased from commercial companies, rather than manufactured in our laboratory. Researchers or users can easily test pesticides at home in the absence of professional equipment and materials. The supporting material of dipsticks was white polyethylene terephthalate (PET) sheet. Filter paper was used for loading red and white paper. Filter paper was adhered onto the white PET sheet using a transparent adhesive. In order to construct a calibration line, pesticide standards were diluted in water to a series of concentrations. Chlorpyrifos was used at concentrations of 0, 2.5, 5, 10, 20, 40, 80 and 160 mg/mL. Parathion, methyl parathion, malathion, carbaryl, and fenitrothion were used at concentrations of 0, 0.5, 1, 2, 4, 6, 8 and 10 mg/mL. A 30 mL volume of sample was added to the white area of the CDs. Following a 10-min incubation, the ACHE CDs were folded along the folding line in the middle (Fig. 1b) to make the red and white areas overlap. In this procedure, the folded ACHE CDs were placed in the two palms in order to maintain the temperature of the enzymatic pronunciation at approximately 37 C while making the red and white filter paper come close together. After 3 min, the ACHE CDs were inserted into the ALS based CDs reader. Then the switch of the ALS based CDs reader was turned on and the transmitted light intensity was measured using the free android application Light Meter. 2.5. Detection of chlorpyrifos in vegetable samples In order to validate that the ALS based CDs reader could be used to monitor chlorpyrifos levels in vegetable samples, vegetable samples were extracted using PBS buffer and then spiked with different concentrations of chlorpyrifos. The concentrations of spiked chlorpyrifos were tested using the AChE CDs, a liquid Ellman
3
assay and GC-MS, respectively. This procedure was carried out by following the “China methods and standards for rapid determination of pesticide residues (GB/T 5009199-2003)". In detail, 1 g of vegetable sample was added to 2 mL PBS buffer and gently shaken. Following a 2-min incubation, liquid was collected in a centrifuge tube, and then spiked with different concentrations of chlorpyrifos. Next, 30 mL liquid in a centrifuge tube was added to the white area of the CDs. Following another 10-min incubation, the CDs were folded along the folding line to make the red and white areas overlap. After 3 min, the CDs were inserted into the ALS based CDs reader, and the transmission light intensity was measured within 1 min. 3. Results and discussion 3.1. Principle of ACHE CDs for OPs detection
3.2. Feasibility investigation of ALS based ACHE CDs reader In order to investigate the feasibility of this smart phone CDs reader, 0, 10, and 100 mg/mL of chlorpyrifos were tested. As depicted in Fig. 2a, the measured transmission light intensity was found to be enhanced with increasing pesticide concentrations. This result agrees with the design of the smart phone CDs reader, demonstrating the feasibility of this method. Transmission light intensities of CDs measured for 0, 10, and 100 mg/mL of chlorpyrifos samples were measured using ALS based CDs reader with five duplicate measurements. Result of each duplicate was found to be equal (Fig. 2b), thereby demonstrating the stability of this developed ALS based CDs reader. In the preliminary experiment, transmission light intensity ranged from 56 lux to 120 lux, and it is hard to discern the slight color change of the CDs because the bottom plate of the commercialized paper is white, which reduces the measured light intensity. In this study, we peeled off the blue test paper of the used CDs and pasted it on a transparent plastic sheet, and the intensity of the transmitted light after going through blue test paper was measured by the smart phone CDs reader. The intensity of the measured transmitted light for the detection of 100 mg/mL chlorpyrifos on blue test paper was 7576 lux and was 2652 lux for 0 mg/mL chlorpyrifos (Fig. S1). Compared with white bottom plate-based CDs, the light intensity by using transparent CDs for 0 and 100 mg/mL chlorpyrifos is more obvious, which can improve the precision of
Fig. 1. Principle of ALS based CDs reader for OPs testing. a. Schematic diagram of OPs detection using the ALS based ACHE CDs reader. b. Schematic diagram of ACHE CDs. c. When a low OPs concentration was applied, low intensity of transmitted light was measured. d. When a high concentration of OPs was applied, high intensity of transmitted light was measured.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
4
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
Fig. 2. Performance investigation of ALS based CDs reader. a. Preliminary experiment of chlorpyrifos detection by using ALS based CDs reader. b. Stability of ALS based CDs reader.
this assay. Therefore in future work, CDs with transparent sheet is a good choice to further improve the accuracy of ACHE CDs. In this work, we researched the universality of ALS based CDs reader for 7 brands of smart phones. The transmitted light intensities of blue test paper pasted on the transparent plastic sheet were measured by ALS based CDs reader. For the same concentration of pesticide samples, although the light intensity measured by different smart phones was different, the ratios of light intensity between the blank and pesticide samples were kept as equal (Fig. S1). Therefore, the obtained calibration curve set up by this ratio can be well used for other type of smart phones without any modifications.
were tested using commercial ACHE CDs. When a low concentration of chlorpyrifos was applied, the color of the ACHE CDs changed to blue. With increasing chlorpyrifos concentrations, the color of the ACHE CDs changed towards white. Accordingly, results of the CDs were analyzed using the ALS based reader. As shown in Fig. 3a, along with increasing concentrations of chlorpyrifos, the measured transmitted light intensities were observed to increase (Fig. 3b). A linear detection range (LDR) within 5e80 mg/mL was fitted between the chlorpyrifos concentration and the transmitted light intensity (Fig. 3c) and the calculated limit of detection (LOD) was 3.3 mg/mL based on the 3s/slope rule.
3.3. Performance of ALS based CDs reader for chlorpyrifos detection
3.4. Performance of ALS based CDs reader for other pesticides test
In this work, different concentrations of chlorpyrifos samples
In this work, other pesticides were also analyzed using the ALS based CDs reader. As depicted in Table 1 (detailed results are displayed in Figs. S2eS6), indicating that the reported ALS based CDs reader can be widely used for the rapid detection of various pesticides.
Table 1 Test results of six kinds of OPs by using the ALS based CDs reader. Pesticide
LDR (mg/mL)
LOD (mg/mL)
Linear correlation
Chlorpyrifos Parathion Parathion methyl Malathion Fenitrothion Carbaryl
5e100 1e8 0.5e6 0.5e6 0.5e6 1e8
3.3 0.52 0.46 0.45 0.47 0.51
0.982 0.998 0.996 0.983 0.988 0.980
Note. Each value represents the mean of three independent experiments (n ¼ 3).
Fig. 3. Performance of ALS based CDs reader for chlorpyrifos testing. a. Image of CDs for different concentrations of chlorpyrifos samples. b. Transmitted light measured using the ALS based CDs reader for different concentrations of chlorpyrifos. c. Calibration curve of ALS based CDs reader for chlorpyrifos. Each value represents the mean of three independent experiments (n ¼ 3).
Fig. 4. Comparison of results from the Ellman assay read with a spectrometer and the commercial ACHE CDs read with the ALS based CDs reader for chlorpyrifos monitoring. Each value represents the mean of three independent experiments (n ¼ 3).
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
5
Table 2 Comparison of GC-MS and ALS based CDs reader for chlorpyrifos monitoring. Spiked concentration (mg/mL)
Mean (mg/mL) ±S.D.
C.V. (100%)
Recovery (100%)
Detected by GC-MS
Recovery (100%)
10 20 30 50 70 90
7.62 ± 1.01 14.81 ± 1.38 27.59 ± 3.18 42.92 ± 6.28 58.16 ± 3.13 72.37 ± 5.61
13.25 9.31 11.52 14.6 5.38 7.75
76.2 74.1 86.76 85.84 83.08 80.41
11.041 19.268 33.319 50.439 74.321 90.801
110.41 96.34 111.06 100.878 106.173 100.89
Note. Mean: Average of chlorpyrifos concentrations in cabbage samples tested by the ALS based CDs reader (n ¼ 3). S.D.: Standard deviation of chlorpyrifos concentration tested in the cabbage sample (n ¼ 3). Coefficient of variation (C.V.) ¼ (S.D./Mean) 100%. Recovery (%) ¼ (Detected concentration/Spiked concentration) 100%.
3.5. Comparison of results from the ALS based CDs reader and image processing methods The pesticide testing results using the proposed ALS based CDs reader was compared with those from conventional image processing methods. In this work, we used ImageJ to analyze images of CDs tests for each pesticide captured using a smart phone. Compared to the results obtained from image processing, the results from our developed ALS based CDs reader were found to possess a better linear relationship (Figs. S67e12). 3.6. Comparison of Ellman assay, GC-MS and the ALS based CDs reader for chlorpyrifos monitoring We studied the interference of vegetable samples for chlorpyrifos detection. Different concentrations of chlorpyrifos were spiked into cabbage sample extracts, followed by testing using the CDs. These results were read using the ALS based CDs reader and commercial Ellman assay kit. According to China National Standards GB/T 5009199-2003 for the Ellman assay, the inhibition rate of positive samples should be greater than 50%. In the case of the results obtained from the ALS based CDs reader, the inhibition rate was calculated as follows:
rapid monitoring organophosphate pesticides. Results of the ALS based CDs reader were comparable with those from GC-MS and Ellman assays. The ALS based CDs reader has advantages of portable, low cost, and high accuracy and therefore could be an effective platform for OPs monitoring, especially at home. In future work, we will aim to focus on the development of a smart phone application applied to the ALS based CDs reader that could assist with computing, storage, and sharing of test results. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments F.Q and Y.T would like to acknowledge the financial support from the National Key Research and Development Program of China (2016YFD0500600), China; the Technology Research Program of Guangzhou City (201508020100), China; China Postdoctoral Science Foundation (2018M640882), China; The Science and Technology Program of Panyu (2018-Z04-13), China.
(i0-i)/(i0-ic)*100%
Appendix A. Supplementary data
where i0 represents the transmitted light intensity of the negative sample, i represents the transmitted light intensity of the analyzed sample, and ic represents the transmitted light intensity of the blank control. Among these 14 samples, 9 samples exhibited an inhibition rate greater than 50% and were determined to be positive samples (Fig. 4). In regards to the results obtained from the Ellman assay, 8 samples were determined to be positive samples. In comparison with the Ellman assay, the coincidence rate of results obtained from the ALS based CDs reader was determined to be 92.86%. These results indicate that our developed method possesses great prospects to be widely used in the preliminary screening of pesticide residues in vegetable samples. Chlorpyrifos was spiked into cabbage sample extracts, and was then tested by ALS based CDs reader and GC-MS, respectively. As shown in Table 2, the recovery of the CDs read by ALS based CDs reader for chlorpyrifos monitoring was 74.1e86.76%, which was lower than that of GC-MS (96.34e111.06%), however, it is still of great significance due to its low cost, easy operation and reading, especially when considered for the application of in-home pesticide testing.
Supplementary data to this article can be found online at https://doi.org/10.1016/j.aca.2019.09.059.
4. Conclusion The ALS based smart phone based colorimetric dipstick reader has the advantages of easy to operate, low cost, high accuracy and versatility. In this work, we report a novel ALS based CDs reader for
References [1] O. Tiryaki, Method validation for the analysis of pesticide residues in grain by thin-layer chromatography, Accred Qual. Assur. 11 (2006), 514-514. [2] S.R. Rissato, M.S. Galhiane, F.R.N. Knoll, B.M. Apon, Supercritical fluid extraction for pesticide multiresidue analysis in honey: determination by gas chromatography with electron-capture and mass spectrometry detection, J. Chromatogr. A 1048 (2004) 153e159. [3] F.J. Biros, Recent applications of mass spectrometry and combined gas chromatography-mass spectrometry to pesticide residue analysis, Residue Rev. 40 (1971) 1. [4] S. Wang, P. Qi, S. Di, J. Wang, S. Wu, X. Wang, Z. Wang, Q. Wang, X. Wang, C. Zhao, Q. Li, Significant role of supercritical fluid chromatography - mass spectrometry in improving the matrix effect and analytical efficiency during multi-pesticides residue analysis of complex chrysanthemum samples, Anal. Chim. Acta 1074 (2019) 108e116. [5] E. Lehmann, C. Oltramare, L.F. de Alencastro, Development of a modified QuEChERS method for multi-class pesticide analysis in human hair by GC-MS and UPLC-MS/MS, Anal. Chim. Acta 999 (2018) 87e98. [6] T. Tuzimski, J. Sherma, High Performance Liquid Chromatography in Pesticide Residue Analysis, Crc Press, 2015. ~ es, The role of the liquid chromatography-mass spectrometry in [7] J. Man pesticide residue determination in food, Crit. Rev. Anal. Chem. 38 (2008) 93e117. [8] W. Tang, J. Yang, F. Wang, J. Wang, Z. Li, Thiocholine-triggered reaction in personal glucose meters for portable quantitative detection of organophosphorus pesticide, Anal. Chim. Acta 1060 (2019) 97e102. [9] L. Li, Z. Liu, H. Zhang, W. Yue, C.W. Li, C. Yi, A point-of-need enzyme linked aptamer assay for Mycobacterium tuberculosis detection using a smartphone, Sens. Actuators B Chem. 254 (2018) 337e346.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
6
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
[10] H. Zhang, L. Xue, F. Huang, S. Wang, L. Wang, N. Liu, J. Lin, A capillary biosensor for rapid detection of Salmonella using Fe-nanocluster amplification and smart phone imaging, Biosens. Bioelectron. 127 (2019) 142e149. [11] Y. Shan, B. Wang, H. Huang, D. Jiang, X. Wu, L. Xue, S. Wang, F. Liu, On-site quantitative Hg2þ measurements based on selective and sensitive fluorescence biosensor and miniaturized smartphone fluorescence microscope, Biosens. Bioelectron. 132 (2019) 238e247. [12] L. Zheng, G. Cai, S. Wang, M. Liao, Y. Li, J. Lin, A microfluidic colorimetric biosensor for rapid detection of Escherichia coli 0157:H7 using gold nanoparticle aggregation and smart phone imaging, Biosens. Bioelectron. 124 (2019) 143e149. [13] H. Sun, Y. Jia, H. Dong, L. Fan, J. Zheng, Multiplex quantification of metals in airborne particulate matter via smartphone and paper-based microfluidics, Anal. Chim. Acta 1044 (2018) 110e118. [14] A. Soni, S.K. Jha, Smartphone based non-invasive salivary glucose biosensor, Anal. Chim. Acta 996 (2017) 54e63. [15] J.R. Montenegro-Burke, T. Phommavongsay, A.E. Aisporna, T. Huan, D. Rinehart, E. Forsberg, F.L. Poole, M.P. Thorgersen, M.W. Adams, G. Krantz, Smartphone analytics: mobilizing the lab into the cloud for omic-scale Analyses, Anal. Chem. 88 (2016) 9753e9758. [16] X. Bao, S. Jiang, Y. Wang, M. Yu, J. Han, A remote computing based point-ofcare colorimetric detection system with a smartphone under complex ambient light conditions, Analyst 143 (2018) 1387e1395. [17] P.B. Lillehoj, M.C. Huang, N. Truong, C.M. Ho, Rapid electrochemical detection on a mobile phone, Lab Chip 13 (2013) 2950. [18] J.R. Buser, A. Wollen, E.K. Heiniger, S.A. Byrnes, P.C. Kauffman, P.D. Ladd, P. Yager, Electromechanical cell lysis using a portable audio device: enabling challenging sample preparation at the point-of-care, Lab Chip 15 (2015) 1994. [19] E. Aronoffspencer, A.G. Venkatesh, A. Sun, H. Brickner, D. Looney, D.A. Hall,
[20]
[21]
[22] [23]
[24]
[25] [26] [27]
[28]
Detection of Hepatitis C core antibody by dual-affinity yeast chimera and smartphone-based electrochemical sensing, Biosens. Bioelectron. 86 (2016) 690. Q. Fu, Z. Wu, F. Xu, X. Li, C. Yao, M. Xu, L. Sheng, S. Yu, Y. Tang, A portable smart phone-based plasmonic nanosensor readout platform that measures transmitted light intensities of nanosubstrates using an ambient light sensor, Lab Chip 16 (2016) 1927e1933. Q. Fu, Z. Wu, X. Li, C. Yao, S. Yu, W. Xiao, Y. Tang, Novel versatile smart phone based Microplate readers for on-site diagnoses, Biosens. Bioelectron. 81 (2016) 524e531. V. Oncescu, M. Mancuso, D. Erickson, Cholesterol testing on a smartphone, Lab Chip 14 (2014) 759e763. A.K. Yetisen, J.L. Martinez-Hurtado, A. Garcia-Melendrez, F.d.C. Vasconcellos, C.R. Lowe, A smartphone algorithm with inter-phone repeatability for the analysis of colorimetric tests, Sens. Actuators B Chem. 196 (2014) 156e160. D. Quesada-Gonz alez, A. Merkoçi, Mobile phone-based biosensing: an emerging “diagnostic and communication” technology, Biosens. Bioelectron. 92 (2017) 549e562. S. Dutta, Point of care sensing and biosensing using ambient light sensor of smartphone: critical review, Trac. Trends Anal. Chem. 110 (2019) 393e400. D. Zhang, Q. Liu, Biosensors and bioelectronics on smartphone for portable biochemical detection, Biosens. Bioelectron. 75 (2016) 273e284. Q. Yang, R. Cai, W. Xiao, Z. Wu, X. Liu, Y. Xu, M. Xu, H. Zhong, G. Sun, Q. Liu, Q. Fu, J. Xiang, Plasmonic ELISA for sensitive detection of disease biomarkers with a smart phone-based reader, Nanoscale Res. Lett. 13 (2018). S. Yu, W. Xiao, Q. Fu, Z. Wu, C. Yao, H. Shen, Y. Tang, A portable chromium ion detection system based on a smartphone readout device, Anal. Methods 8 (2016) 6877e6882.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
Contents lists available at ScienceDirect
Analytica Chimica Acta journal homepage: www.elsevier.com/locate/aca
Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone Qiangqiang Fu a, b, c, 1, Chunlei Zhang b, 1, Jun Xie a, Zhaohui Li d, Lingbo Qu d, Xiaoli Cai c, Hui Ouyang c, Yang Song c, Dan Du c, *, Yuehe Lin c, **, Yong Tang a, *** a
Department of Bioengineering, Guangdong Province Engineering Research Center for Antibody Drug and Immunoassay, Jinan University, Guangzhou, 510632, PR China Department of Stomatology, The First Affiliated Hospital, Jinan University, Guangzhou, 510632, PR China c School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, 99164, USA d College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou, 450001, PR China b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
A novel ambient light sensor (ALS) based acetylcholinesterase (ACHE) colorimetric dipstick reader for organophosphate pesticides testing was reported. The ALS based ACHE colorimetric dipstick reader has the advantages of easy to operate, low cost, high accuracy and versatility. Results of the ALS based ACHE colorimetric dipstick reader were comparable with results from GC-MS and Ellman assay.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 August 2019 Accepted 23 September 2019 Available online xxx
Organophosphate pesticides (OPs) are widely used around the world to control pests in agricultural, residential, and commercial settings. Ingestion of high-dose OPs could lead to acute toxicity, and persistent influence on health could result from acute poisoning or long-term exposure to low dose OPs. An easy to operate, low cost and home available OPs testing platform is urgently needed. Ambient light sensor (ALS) based smart phone colorimetric reader has the advantages of easy to operate, low cost, high accuracy and versatility. In this work, a novel ALS based smart phone colorimetric dipsticks (CDs) reader was reported for rapid monitoring OPs. In this method, acetylcholinesterase (ACHE) CDs was used to test OPs and results were analyzed using an ALS based reader according to the absorbance of ACHE CDs. The results obtained using the ALS based CDs reader were comparable to those obtained using gas chromatography-mass spectrometry (GC-MS) and Ellman assay. The ALS based CDs reader has the
Keywords: Colorimetric dipstick reader Smart phone Ambient light sensor Organophosphate pesticides Chlorpyrifos
Abbreviations: Organophosphate pesticides, OPs; acetylcholinesterase, ACHE; ambient light sensor, ALS; gas chromatography-mass spectrometry, GC-MS; colorimetric dipsticks, CDs; thin layer chromatography, TLC; gas chromatography, GC; gas chromatography-mass spectrometry, GC-MS; high performance liquid chromatography, HPLC; liquid chromatography-mass spectrometry, LC-MS; polyethylene terephthalate, PET; linear detection range, LDR; limit of detection, LOD; coefficient of variation, C.V. * Corresponding author. ** Corresponding author. *** Corresponding author. E-mail addresses: [email protected] (D. Du), [email protected] (Y. Lin), [email protected] (Y. Tang). 1 These authors contributed equally to this work. https://doi.org/10.1016/j.aca.2019.09.059 0003-2670/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
2
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
advantages of portable, low cost, and high accuracy, and therefore could act an effective platform for OPs monitoring. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Organophosphate pesticides (OPs) are nerve-targeting agents, functioning by inhibiting the action of acetylcholinesterase (ACHE) in nerve cells, which are widely used around the world to control pests in agricultural, residential, and commercial settings. OPs can be absorbed by ingestion, and they can cause serious poisoning to human body. The toxicity of OPs is not only limited to the acute phase, the chronic effects resulting even from low levels of OPs exposure have long been noted. Chromatography represents the most widely used methods for detection of OPs, including thin layer chromatography (TLC) [1], gas chromatography (GC) [2], gas chromatography-mass spectrometry (GC-MS) [3e5], high performance liquid chromatography (HPLC) [6], liquid chromatographymass spectrometry (LC-MS) [7], etc [5,8]. However, these methods are used limitedly in professional laboratories due to the requirement for sophisticated instruments, high maintenance costs, and professional operators. ACHE CDs are widely used in the pesticide residues preliminary screening due to its easy readout, low cost and simple operation. However, the current ACHE CDs are read by naked eyes and obtained a yes/no result, so the accuracy is very low. Therefore, a portable and low cost ACHE CDs reader is urgently required for enhancing their accuracy. Smart phone based analytical devices could be an excellent candidate for CDs reader. Currently, permanent physical sensors of a smart phone, including digital cameras [9e14], wireless devices [15,16], USB ports [17], audio jacks [18,19], and others [20,21] have been applied for preparation of biosensors. In the case of CDs, results were first obtained using digital cameras, followed by analysis using software [22]. Consequently, captured images were initially divided into RGB (red, green, blue) values, followed by a calculation of the corresponding target concentrations according to these RGB values. The standard RGB scale assigns a whole-number value from 0 to 255 for each of these three colors in a given tone, such that [0, 0, 0] corresponds to absolute black and [255, 255, 255], to true white. Therefore, a good smart phone camera should be able to distinguish until 16777216 colors in theory [23,24]. However, in the actual detection, the color change of dipsticks is limited. For example, the RGB values of dipsticks changing from white to blue change from [255, 255, 255], [254, 254, 255] … … to [0, 0, 255]. The RGB image analysis only captures 256 color changes, indicative of its low accuracy. Additionally, different brands of smart phones have different camera characteristics, in terms of megapixel count, sensitivity of the CMOS sensor, camera lens quality, aperture dimension, etc [25,26]. As a result, the image captured from one smart phone and its corresponding color channels may be different from those of another smart phone. Ambient light sensors (ALS) are installed in all types of smart phones in order to sense the environment lighting conditions and allow for the adjustment of the screen’s backlight to comfortable levels for the viewer. Moreover, ALS can directly sense light intensity, so it does not need to consider the sensitivity of CMOS sensor, camera lens quality, aperture dimension, etc [25,27,28]. Furthermore, the current smart phone ALS can sense the light intensity of 0 luxe100000 Lux, indicative of a high accuracy of ALS based colorimetric reader. In this study, we developed an ALS based ACHE CDs reader for OPs monitoring. The optical attachment of ALS based ACHE CDs
reader is a lightweight (~70 g), compact (87 69 30 mm), 3D printed housing that contains an inexpensive, 2 battery (1.5 V), electronic switch, and wiring components to connect the electronics (Fig. 1a). In order to eliminate the interference of ambient light, the ALS based CDs reader was added to a black plastic shell. In the ALS based CDs reader, an LED light was installed as an excitation light source. In order to match the maximum absorption spectra of the ACHE CDs, a 645 nm LED was selected as a light source. In the device, the LED excitation intensity remains constant and the absorbance of ACHE CDs for different concentrations of pesticides is different. Therefore, ALS can sense different light intensities in an OPs concentration-dependent manner. In the CDs, ACHE could catalyze indophenol acetate (red) to acetic acid and indigo (blue), while OPs are able to inhibit this catalytic activity. As shown in Fig. 1, the ACHE CDs are primarily comprised of two pieces of paper (red and white, respectively) pasted on a plastic plate. ACHE and indophenol acetate are preloaded onto the white paper and the red paper, respectively (Fig. 1b). For the detection of OPs, liquid sample was first added onto the white paper and incubated for 3 min. Then the ACHE CDs were folded to overlap the two pieces of paper. Consequently, ACHE on white paper will catalyze the indophenol acetate loaded on the red paper. If there is no OPs residue present in the sample, the ACHE catalytic activity cannot be inhibited. Therefore, indigo is produced on the white paper and its color will change to blue, resulting in low transmitted light as measured by ALS (Fig. 1c). If a high concentration of OPs sample is loaded, the pesticides will inhibit the ACHE activity (Fig. 1d) and a high transmitted light will be measured. Chlorpyrifos is the most widely used OPs at present. Therefore, in the main text, we study the performance of the ALS based ACHE CDs reader by detecting chlorpyrifos. 2. Materials and experiments 2.1. Materials and reagents Parathion, methyl parathion, malathion, carbaryl, chlorpyrifos, and fenitrothion were purchased from Ocean Tech (U.S.A.). ACHE CDs were purchased from Hubei Saiyang biotech (Wuhan, china). In regards to the ACHE CDs, refer to the previous literature (International Journal of Analytical Chemistry, 2014, Article ID 536823). LEDs (645 nm) were obtained from Shenzhen Octai Co., Ltd (Shenzhen, China). The battery (1.5 V) was obtained from VSAI (Shenzhen, China). Wires were purchased from a local store. Vegetable samples were purchased from a local supermarket in Pullman. The liquid ACHE inhibition assay (Ellman Assay) kit was purchased from Guangzhou Lvzhou biotech (Guangzhou, China). 2.2. Apparatus The absorbance of Ellman assay was measured using a Synergy H1 Hybrid Multi-Mode Microplate Reader (Bio-Tek Instruments, Inc.). Gas Chromatography-Mass Spectrometry (GC-MS, Thermo Fisher) was used to test the chlorpyrifos in cabbage sample extracts. A HUAWEI Honor 6 smart phone was used for development of the ALS based CDs reader. The 3D printer was purchased from the SHINING 3D (Hangzhou, China). Polylactice acid was used for fabrication of the device.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
2.3. Design of the ALS based ACHE CDs reader The smart phone CDs reader was drawn using software, followed by processing by the printer software, 3D star. In the print setup, the print mode was set as quality and the supporting way was internal and external support. In the ALS based CDs reader, the wavelength of the emission LED light was 645 nm. A free smart application Light Meter was used to display the measured transmitted light intensity at the screen. 2.4. ACHE CDs for OPs detection This procedure was carried out as described in the instructions regarding ACHE CDs. In order to ensure the stability and reproducibility of the test results, the ACHE CDs used in this experiment were purchased from commercial companies, rather than manufactured in our laboratory. Researchers or users can easily test pesticides at home in the absence of professional equipment and materials. The supporting material of dipsticks was white polyethylene terephthalate (PET) sheet. Filter paper was used for loading red and white paper. Filter paper was adhered onto the white PET sheet using a transparent adhesive. In order to construct a calibration line, pesticide standards were diluted in water to a series of concentrations. Chlorpyrifos was used at concentrations of 0, 2.5, 5, 10, 20, 40, 80 and 160 mg/mL. Parathion, methyl parathion, malathion, carbaryl, and fenitrothion were used at concentrations of 0, 0.5, 1, 2, 4, 6, 8 and 10 mg/mL. A 30 mL volume of sample was added to the white area of the CDs. Following a 10-min incubation, the ACHE CDs were folded along the folding line in the middle (Fig. 1b) to make the red and white areas overlap. In this procedure, the folded ACHE CDs were placed in the two palms in order to maintain the temperature of the enzymatic pronunciation at approximately 37 C while making the red and white filter paper come close together. After 3 min, the ACHE CDs were inserted into the ALS based CDs reader. Then the switch of the ALS based CDs reader was turned on and the transmitted light intensity was measured using the free android application Light Meter. 2.5. Detection of chlorpyrifos in vegetable samples In order to validate that the ALS based CDs reader could be used to monitor chlorpyrifos levels in vegetable samples, vegetable samples were extracted using PBS buffer and then spiked with different concentrations of chlorpyrifos. The concentrations of spiked chlorpyrifos were tested using the AChE CDs, a liquid Ellman
3
assay and GC-MS, respectively. This procedure was carried out by following the “China methods and standards for rapid determination of pesticide residues (GB/T 5009199-2003)". In detail, 1 g of vegetable sample was added to 2 mL PBS buffer and gently shaken. Following a 2-min incubation, liquid was collected in a centrifuge tube, and then spiked with different concentrations of chlorpyrifos. Next, 30 mL liquid in a centrifuge tube was added to the white area of the CDs. Following another 10-min incubation, the CDs were folded along the folding line to make the red and white areas overlap. After 3 min, the CDs were inserted into the ALS based CDs reader, and the transmission light intensity was measured within 1 min. 3. Results and discussion 3.1. Principle of ACHE CDs for OPs detection
3.2. Feasibility investigation of ALS based ACHE CDs reader In order to investigate the feasibility of this smart phone CDs reader, 0, 10, and 100 mg/mL of chlorpyrifos were tested. As depicted in Fig. 2a, the measured transmission light intensity was found to be enhanced with increasing pesticide concentrations. This result agrees with the design of the smart phone CDs reader, demonstrating the feasibility of this method. Transmission light intensities of CDs measured for 0, 10, and 100 mg/mL of chlorpyrifos samples were measured using ALS based CDs reader with five duplicate measurements. Result of each duplicate was found to be equal (Fig. 2b), thereby demonstrating the stability of this developed ALS based CDs reader. In the preliminary experiment, transmission light intensity ranged from 56 lux to 120 lux, and it is hard to discern the slight color change of the CDs because the bottom plate of the commercialized paper is white, which reduces the measured light intensity. In this study, we peeled off the blue test paper of the used CDs and pasted it on a transparent plastic sheet, and the intensity of the transmitted light after going through blue test paper was measured by the smart phone CDs reader. The intensity of the measured transmitted light for the detection of 100 mg/mL chlorpyrifos on blue test paper was 7576 lux and was 2652 lux for 0 mg/mL chlorpyrifos (Fig. S1). Compared with white bottom plate-based CDs, the light intensity by using transparent CDs for 0 and 100 mg/mL chlorpyrifos is more obvious, which can improve the precision of
Fig. 1. Principle of ALS based CDs reader for OPs testing. a. Schematic diagram of OPs detection using the ALS based ACHE CDs reader. b. Schematic diagram of ACHE CDs. c. When a low OPs concentration was applied, low intensity of transmitted light was measured. d. When a high concentration of OPs was applied, high intensity of transmitted light was measured.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
4
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
Fig. 2. Performance investigation of ALS based CDs reader. a. Preliminary experiment of chlorpyrifos detection by using ALS based CDs reader. b. Stability of ALS based CDs reader.
this assay. Therefore in future work, CDs with transparent sheet is a good choice to further improve the accuracy of ACHE CDs. In this work, we researched the universality of ALS based CDs reader for 7 brands of smart phones. The transmitted light intensities of blue test paper pasted on the transparent plastic sheet were measured by ALS based CDs reader. For the same concentration of pesticide samples, although the light intensity measured by different smart phones was different, the ratios of light intensity between the blank and pesticide samples were kept as equal (Fig. S1). Therefore, the obtained calibration curve set up by this ratio can be well used for other type of smart phones without any modifications.
were tested using commercial ACHE CDs. When a low concentration of chlorpyrifos was applied, the color of the ACHE CDs changed to blue. With increasing chlorpyrifos concentrations, the color of the ACHE CDs changed towards white. Accordingly, results of the CDs were analyzed using the ALS based reader. As shown in Fig. 3a, along with increasing concentrations of chlorpyrifos, the measured transmitted light intensities were observed to increase (Fig. 3b). A linear detection range (LDR) within 5e80 mg/mL was fitted between the chlorpyrifos concentration and the transmitted light intensity (Fig. 3c) and the calculated limit of detection (LOD) was 3.3 mg/mL based on the 3s/slope rule.
3.3. Performance of ALS based CDs reader for chlorpyrifos detection
3.4. Performance of ALS based CDs reader for other pesticides test
In this work, different concentrations of chlorpyrifos samples
In this work, other pesticides were also analyzed using the ALS based CDs reader. As depicted in Table 1 (detailed results are displayed in Figs. S2eS6), indicating that the reported ALS based CDs reader can be widely used for the rapid detection of various pesticides.
Table 1 Test results of six kinds of OPs by using the ALS based CDs reader. Pesticide
LDR (mg/mL)
LOD (mg/mL)
Linear correlation
Chlorpyrifos Parathion Parathion methyl Malathion Fenitrothion Carbaryl
5e100 1e8 0.5e6 0.5e6 0.5e6 1e8
3.3 0.52 0.46 0.45 0.47 0.51
0.982 0.998 0.996 0.983 0.988 0.980
Note. Each value represents the mean of three independent experiments (n ¼ 3).
Fig. 3. Performance of ALS based CDs reader for chlorpyrifos testing. a. Image of CDs for different concentrations of chlorpyrifos samples. b. Transmitted light measured using the ALS based CDs reader for different concentrations of chlorpyrifos. c. Calibration curve of ALS based CDs reader for chlorpyrifos. Each value represents the mean of three independent experiments (n ¼ 3).
Fig. 4. Comparison of results from the Ellman assay read with a spectrometer and the commercial ACHE CDs read with the ALS based CDs reader for chlorpyrifos monitoring. Each value represents the mean of three independent experiments (n ¼ 3).
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
5
Table 2 Comparison of GC-MS and ALS based CDs reader for chlorpyrifos monitoring. Spiked concentration (mg/mL)
Mean (mg/mL) ±S.D.
C.V. (100%)
Recovery (100%)
Detected by GC-MS
Recovery (100%)
10 20 30 50 70 90
7.62 ± 1.01 14.81 ± 1.38 27.59 ± 3.18 42.92 ± 6.28 58.16 ± 3.13 72.37 ± 5.61
13.25 9.31 11.52 14.6 5.38 7.75
76.2 74.1 86.76 85.84 83.08 80.41
11.041 19.268 33.319 50.439 74.321 90.801
110.41 96.34 111.06 100.878 106.173 100.89
Note. Mean: Average of chlorpyrifos concentrations in cabbage samples tested by the ALS based CDs reader (n ¼ 3). S.D.: Standard deviation of chlorpyrifos concentration tested in the cabbage sample (n ¼ 3). Coefficient of variation (C.V.) ¼ (S.D./Mean) 100%. Recovery (%) ¼ (Detected concentration/Spiked concentration) 100%.
3.5. Comparison of results from the ALS based CDs reader and image processing methods The pesticide testing results using the proposed ALS based CDs reader was compared with those from conventional image processing methods. In this work, we used ImageJ to analyze images of CDs tests for each pesticide captured using a smart phone. Compared to the results obtained from image processing, the results from our developed ALS based CDs reader were found to possess a better linear relationship (Figs. S67e12). 3.6. Comparison of Ellman assay, GC-MS and the ALS based CDs reader for chlorpyrifos monitoring We studied the interference of vegetable samples for chlorpyrifos detection. Different concentrations of chlorpyrifos were spiked into cabbage sample extracts, followed by testing using the CDs. These results were read using the ALS based CDs reader and commercial Ellman assay kit. According to China National Standards GB/T 5009199-2003 for the Ellman assay, the inhibition rate of positive samples should be greater than 50%. In the case of the results obtained from the ALS based CDs reader, the inhibition rate was calculated as follows:
rapid monitoring organophosphate pesticides. Results of the ALS based CDs reader were comparable with those from GC-MS and Ellman assays. The ALS based CDs reader has advantages of portable, low cost, and high accuracy and therefore could be an effective platform for OPs monitoring, especially at home. In future work, we will aim to focus on the development of a smart phone application applied to the ALS based CDs reader that could assist with computing, storage, and sharing of test results. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments F.Q and Y.T would like to acknowledge the financial support from the National Key Research and Development Program of China (2016YFD0500600), China; the Technology Research Program of Guangzhou City (201508020100), China; China Postdoctoral Science Foundation (2018M640882), China; The Science and Technology Program of Panyu (2018-Z04-13), China.
(i0-i)/(i0-ic)*100%
Appendix A. Supplementary data
where i0 represents the transmitted light intensity of the negative sample, i represents the transmitted light intensity of the analyzed sample, and ic represents the transmitted light intensity of the blank control. Among these 14 samples, 9 samples exhibited an inhibition rate greater than 50% and were determined to be positive samples (Fig. 4). In regards to the results obtained from the Ellman assay, 8 samples were determined to be positive samples. In comparison with the Ellman assay, the coincidence rate of results obtained from the ALS based CDs reader was determined to be 92.86%. These results indicate that our developed method possesses great prospects to be widely used in the preliminary screening of pesticide residues in vegetable samples. Chlorpyrifos was spiked into cabbage sample extracts, and was then tested by ALS based CDs reader and GC-MS, respectively. As shown in Table 2, the recovery of the CDs read by ALS based CDs reader for chlorpyrifos monitoring was 74.1e86.76%, which was lower than that of GC-MS (96.34e111.06%), however, it is still of great significance due to its low cost, easy operation and reading, especially when considered for the application of in-home pesticide testing.
Supplementary data to this article can be found online at https://doi.org/10.1016/j.aca.2019.09.059.
4. Conclusion The ALS based smart phone based colorimetric dipstick reader has the advantages of easy to operate, low cost, high accuracy and versatility. In this work, we report a novel ALS based CDs reader for
References [1] O. Tiryaki, Method validation for the analysis of pesticide residues in grain by thin-layer chromatography, Accred Qual. Assur. 11 (2006), 514-514. [2] S.R. Rissato, M.S. Galhiane, F.R.N. Knoll, B.M. Apon, Supercritical fluid extraction for pesticide multiresidue analysis in honey: determination by gas chromatography with electron-capture and mass spectrometry detection, J. Chromatogr. A 1048 (2004) 153e159. [3] F.J. Biros, Recent applications of mass spectrometry and combined gas chromatography-mass spectrometry to pesticide residue analysis, Residue Rev. 40 (1971) 1. [4] S. Wang, P. Qi, S. Di, J. Wang, S. Wu, X. Wang, Z. Wang, Q. Wang, X. Wang, C. Zhao, Q. Li, Significant role of supercritical fluid chromatography - mass spectrometry in improving the matrix effect and analytical efficiency during multi-pesticides residue analysis of complex chrysanthemum samples, Anal. Chim. Acta 1074 (2019) 108e116. [5] E. Lehmann, C. Oltramare, L.F. de Alencastro, Development of a modified QuEChERS method for multi-class pesticide analysis in human hair by GC-MS and UPLC-MS/MS, Anal. Chim. Acta 999 (2018) 87e98. [6] T. Tuzimski, J. Sherma, High Performance Liquid Chromatography in Pesticide Residue Analysis, Crc Press, 2015. ~ es, The role of the liquid chromatography-mass spectrometry in [7] J. Man pesticide residue determination in food, Crit. Rev. Anal. Chem. 38 (2008) 93e117. [8] W. Tang, J. Yang, F. Wang, J. Wang, Z. Li, Thiocholine-triggered reaction in personal glucose meters for portable quantitative detection of organophosphorus pesticide, Anal. Chim. Acta 1060 (2019) 97e102. [9] L. Li, Z. Liu, H. Zhang, W. Yue, C.W. Li, C. Yi, A point-of-need enzyme linked aptamer assay for Mycobacterium tuberculosis detection using a smartphone, Sens. Actuators B Chem. 254 (2018) 337e346.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059
6
Q. Fu et al. / Analytica Chimica Acta xxx (xxxx) xxx
[10] H. Zhang, L. Xue, F. Huang, S. Wang, L. Wang, N. Liu, J. Lin, A capillary biosensor for rapid detection of Salmonella using Fe-nanocluster amplification and smart phone imaging, Biosens. Bioelectron. 127 (2019) 142e149. [11] Y. Shan, B. Wang, H. Huang, D. Jiang, X. Wu, L. Xue, S. Wang, F. Liu, On-site quantitative Hg2þ measurements based on selective and sensitive fluorescence biosensor and miniaturized smartphone fluorescence microscope, Biosens. Bioelectron. 132 (2019) 238e247. [12] L. Zheng, G. Cai, S. Wang, M. Liao, Y. Li, J. Lin, A microfluidic colorimetric biosensor for rapid detection of Escherichia coli 0157:H7 using gold nanoparticle aggregation and smart phone imaging, Biosens. Bioelectron. 124 (2019) 143e149. [13] H. Sun, Y. Jia, H. Dong, L. Fan, J. Zheng, Multiplex quantification of metals in airborne particulate matter via smartphone and paper-based microfluidics, Anal. Chim. Acta 1044 (2018) 110e118. [14] A. Soni, S.K. Jha, Smartphone based non-invasive salivary glucose biosensor, Anal. Chim. Acta 996 (2017) 54e63. [15] J.R. Montenegro-Burke, T. Phommavongsay, A.E. Aisporna, T. Huan, D. Rinehart, E. Forsberg, F.L. Poole, M.P. Thorgersen, M.W. Adams, G. Krantz, Smartphone analytics: mobilizing the lab into the cloud for omic-scale Analyses, Anal. Chem. 88 (2016) 9753e9758. [16] X. Bao, S. Jiang, Y. Wang, M. Yu, J. Han, A remote computing based point-ofcare colorimetric detection system with a smartphone under complex ambient light conditions, Analyst 143 (2018) 1387e1395. [17] P.B. Lillehoj, M.C. Huang, N. Truong, C.M. Ho, Rapid electrochemical detection on a mobile phone, Lab Chip 13 (2013) 2950. [18] J.R. Buser, A. Wollen, E.K. Heiniger, S.A. Byrnes, P.C. Kauffman, P.D. Ladd, P. Yager, Electromechanical cell lysis using a portable audio device: enabling challenging sample preparation at the point-of-care, Lab Chip 15 (2015) 1994. [19] E. Aronoffspencer, A.G. Venkatesh, A. Sun, H. Brickner, D. Looney, D.A. Hall,
[20]
[21]
[22] [23]
[24]
[25] [26] [27]
[28]
Detection of Hepatitis C core antibody by dual-affinity yeast chimera and smartphone-based electrochemical sensing, Biosens. Bioelectron. 86 (2016) 690. Q. Fu, Z. Wu, F. Xu, X. Li, C. Yao, M. Xu, L. Sheng, S. Yu, Y. Tang, A portable smart phone-based plasmonic nanosensor readout platform that measures transmitted light intensities of nanosubstrates using an ambient light sensor, Lab Chip 16 (2016) 1927e1933. Q. Fu, Z. Wu, X. Li, C. Yao, S. Yu, W. Xiao, Y. Tang, Novel versatile smart phone based Microplate readers for on-site diagnoses, Biosens. Bioelectron. 81 (2016) 524e531. V. Oncescu, M. Mancuso, D. Erickson, Cholesterol testing on a smartphone, Lab Chip 14 (2014) 759e763. A.K. Yetisen, J.L. Martinez-Hurtado, A. Garcia-Melendrez, F.d.C. Vasconcellos, C.R. Lowe, A smartphone algorithm with inter-phone repeatability for the analysis of colorimetric tests, Sens. Actuators B Chem. 196 (2014) 156e160. D. Quesada-Gonz alez, A. Merkoçi, Mobile phone-based biosensing: an emerging “diagnostic and communication” technology, Biosens. Bioelectron. 92 (2017) 549e562. S. Dutta, Point of care sensing and biosensing using ambient light sensor of smartphone: critical review, Trac. Trends Anal. Chem. 110 (2019) 393e400. D. Zhang, Q. Liu, Biosensors and bioelectronics on smartphone for portable biochemical detection, Biosens. Bioelectron. 75 (2016) 273e284. Q. Yang, R. Cai, W. Xiao, Z. Wu, X. Liu, Y. Xu, M. Xu, H. Zhong, G. Sun, Q. Liu, Q. Fu, J. Xiang, Plasmonic ELISA for sensitive detection of disease biomarkers with a smart phone-based reader, Nanoscale Res. Lett. 13 (2018). S. Yu, W. Xiao, Q. Fu, Z. Wu, C. Yao, H. Shen, Y. Tang, A portable chromium ion detection system based on a smartphone readout device, Anal. Methods 8 (2016) 6877e6882.
Please cite this article as: Q. Fu et al., Ambient light sensor based colorimetric dipstick reader for rapid monitoring organophosphate pesticides on a smart phone, Analytica Chimica Acta, https://doi.org/10.1016/j.aca.2019.09.059