- Email: [email protected]
Colorimetric and fluorescent sensing of rhodamine using polymethacrylate matrix
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Short Communication
Colorimetric and fluorescent sensing of rhodamine using polymethacrylate matrix N.A. Gavrilenko a, N.V. Saranchina b, E.A. Kambarova c, E.V. Urazov a, M.A. Gavrilenko a,⁎ a b c
National Research Tomsk Polytechnic University, Tomsk, Pr. Lenina, 30, 634050, Russia National Research Tomsk State University, Tomsk, Pr. Lenina, 36, 634050, Russia Taraz State University, Taraz, str. Suleymenov, 7, 080012, Kazakhstan
a r t i c l e
i n f o
Article history: Received 9 December 2018 Received in revised form 2 May 2019 Accepted 9 May 2019 Available online 11 May 2019 Keywords: Rhodamine Optode Polymethacrylate matrix Fluorometry Solid phase spectrophotometry Oilfield water
a b s t r a c t This is a description of the tracer analysis method involving colorimetric and fluorescent measurements based on solid phase extraction of rhodamine into transparent polymethacrylate matrix. Concentration of rhodamine in PMM is measured as spectrophotometric absorption level at 535 nm and fluorescence at 554 nm. The calibration graphs are linear within the ranges 0.02–0.10 mg∙L−1 and 0.002–0.06 mg∙L−1 and detection limits 0.014 mg∙L−1 and 0.0005 mg∙L−1 are calculated for colorimetric and fluorescent measurements, respectively. The method has been successfully used for determination of rhodamine in groundwater. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Numerous compounds from various chemical families can be used as chemical tracers to track distribution of drilling fluid; for example, the review [1] mentions mineral substances, a number of colourants, magnetic and radioactive materials, a total of 200 substances. Xanthene dyes have the advantage of physical and chemical stability and low limit of detection by fluorescent detection. Fluorescent dyes as chemical tracers are used to track distribution of drilling fluid including groundwater investigations [2,3]. Fluorescent dyes exhibit such advantages as resistant to biodestruction, flocculation and simple hydrochemical behavior, high sensitivity of analytical signal and improved durability in drilling fluid [4]. The most important advantage of fluorescent probes is the low detection limit. However, matrix effects and low concentration of rhodamine in real samples make its direct determination difficult. Analytical methods for rhodamine determination are HPLC [4,5], VIS spectrophotometry [6,7], and spectrofluorometry [8,9]. Therefore, it is necessary to develop a preconcentration procedure for rhodamine. Solid phase extraction is widely used because it is simple, fast and offers higher preconcentration factor. Moreover, this method requires the use of smaller amounts of organic solvents [10]. We suggest using a transparent polymethacrylate matrix for solid phase extraction of ⁎ Corresponding author. E-mail address: [email protected] (M.A. Gavrilenko).
https://doi.org/10.1016/j.saa.2019.05.011 1386-1425/© 2019 Elsevier B.V. All rights reserved.
rhodamine. The polymer matrices have been in the limelight of attention because of the potential they have as solid-phase extraction materials [11–15]. One of them, transparent polymethacrylate polymer (TPP) consists of polymethacrylate (PMA) as a base polymer and polyethylene glycol (PEG) as a modifier with hydrophilic chains. Solid phase extraction of target substances using TPP can be achieved on the basis of same mechanism as for the liquid extraction systems [16,17]. Solid phase extraction using TPP plates has been implemented to determine metal ions [18] and xanthene dyes [19]. The purpose of this study is development of a simple method for spectrophotometric and fluorimetric determination of rhodamine with prior solid phase extraction of the target substance into TPP. 2. Experimental 2.1. Preparation of polymethylmethacrylate matrix TPP is a special transparent polymer matrix containing functional groups designed to extract substances for subsequent analysis. Transparent 10 × 10 cm (0.60 ± 0.04) mm polymethacrylate plates were prepared by radical block polymerization of methacrylate with 5% PEG 400 and (alkyl)acrylates of alkaline metals at 60–70 °C for 3–4 h. These plates were then cut into 6.0 × 8.0 mm working plates weighing about 0.05 g each. The polymethacrylate matrix was placed into a 25.0 mL tube containing rhodamine oil solution and H2O. The tube was placed in a rotator
2
N.A. Gavrilenko et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
for 15 min. The polymethacrylate matrix containing the extracted rhodamine was taken out, dried with filter paper and its absorbance at 535 nm or fluorescence at 554 nm was read against a blank membrane prepared under identical conditions excluding the analyte. 2.2. Solutions and reagents The rhodamine (Merck) used in this study had the following characteristics: purity 98.7%, red colour, Amax 530 nm. A stock of 50 mg·L−1 rhodamin solution was prepared by dissolving an accurately weighed portion of rhodamin in water. The working solution of rhodamine used in the experiment was prepared by diluting the stock solution with tap water or formation water on the day of experiment. The target pH level was achieved using HCl, NaOH and citrated buffer solutions; all reagents used were chemically pure and analytical grade ones. 2.3. Apparatus The absorption spectra of TPP and solutions were recorded using an Evolution 201 spectrophotometer (Thermo Fisher Scientific Inc., USA) against an initial polymer plate prepared under the same conditions. Fluorescence emission spectrum was measured using a Solar CM 2203 spectrofluorometer. The pH values were measured using an I-160 ionometer (Izmeritelnaya Tekhnika NPO, Russia) with a pH-selective glass electrode. The absolute error for the ionometer is ±0.02 рН and it was calibrated at 25°С using buffer solutions with pH 1.00 and 9.18. 3. Results and discussion 3.1. Solid phase extraction Compared to the widely used adsorbents like activated carbon, foam, Al2O3 and silica, polymethacrylate matrix is more expedient thanks to its selectivity and transparency [20,21]. Transparent TPP is coloured pink-red after solid phase extraction of rhodamine from the solutions. Absorption spectra and fluorescence spectra of rhodamine in water solution and in TPP with different dye concentrations are shown in Fig. 1a, b. The main absorption band of rhodamine for TPP is located between 510 and 550 nm. For the matrix it is broader compared to the absorption band of the water solution. For the matrix, the absorption maximum is
extended and shifted to the long-wavelength area of 534–536 nm. Absorption at the wavelength of 535 nm is selected as the analytical signal for solid phase spectrophotometric determination of rhodamine in formation water. Changes in the absorption maximum indicate that the rhodamine molecules in TPP are partially aggregated at low concentrations. It is known that the molecular orbitals of aggregates are delocalized at small distances between molecules, hence the displacement of the absorption and luminescence spectra occurs as a result of splitting of the electron energy levels [22]. The fluorescence spectra of rhodamine in TPP are slightly broader compared to the spectrum of rhodamine in the solution. The absorption maximum of rhodamine in the polymethacrylate matrix is 554 nm and it coincides with the absorption maximum of the dye in water or waterethanol solutions after solid phase extraction from solutions with concentrations below 0.06 mg∙L−1. An increase in the concentration of rhodamine in a solution to 0.4 mg∙L−1 results in a shift of the dye absorption maximum in TPP to the longer-wave area. The fluorescence intensity at the wavelength of 554 nm is taken as an analytical signal for solid phase determination of rhodamine in formation water. This is convenient for measuring minimal concentrations of the dye in the solution and estimation of the detection limit. Increasing concentration of rhodamine in TPP conditions proportional increase of the absorption rate to the maximum of 0.06 mg∙L−1 and of fluorescence intensity until the solution concentration is 0.10 μg∙L−1. Further increase in the concentration of rhodamine solution slows down growth of absorption and fluorescence of rhodamine in TPP (Fig. 2a,b), since aggregates of organic dyes fluoresce slightly [23]. Hydrophobic nature of the sorbent favors extraction of organic substances from solutions [24]. Extraction of such substances using TPP can be divided into two broad steps. In the first step, an aqueous sample containing rhodamine is brought into contact with TPP, where some of the dye is sorbed onto its surface. In the second part of the process, the rhodamine dissolved in the polymer matrix, diffuses into the body of TPP. pH has a strong effect upon the adsorption capacity as it influences chemical interactions between dye molecules and TPP in a solution. TPP contains oxygen groups on its surface, e.g. strong carboxylic groups and carbonyl groups, which are nucleophilic in nature. As pH of a dye solution decreases, more dye molecules are protonated and get adsorbed on the surface or into the body of TPP. This happens because dye molecules become nucleophilic at pH b3. At this acidity level of
Fig. 1. a – Absorption spectra of rhodamine in water solution (1) and polymethacrylate matrix after contact with 0.4 mg∙L−1 rhodamine solution of concentration (2); b – Fluorescence spectra of rhodamine in water solution (1) and in polymethacrylate matrix after contact with rhodamine solutions of different concentrations, μg∙L−1: (2) – 0.1; (3) – 0.2; (4) – 0.4.
N.A. Gavrilenko et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
3
Fig. 2. a – Absorption spectra of polymethacrylate matrix after contact with rhodamin solutions of different concentrations, mg∙L−1: 1 – 0; 2 – 0.02; 3 – 0.04; 4 – 0.06; 5 – 0.08; 6 – 0.10; 7 – 0.15; 8 – 0.20; b – Fluorescence spectra of polymethacrylate matrix after contact with rhodamin solutions of different concentrations, μg∙L−1: 1 – 0; 2 – 0.01; 3 – 0.02; 4 – 0.04; 5 – 0.06; 6 – 0.08; 7 – 0.10.
the medium, extraction of eosine and fluoresceine is b10% in their simultaneous presence. Thus selectivity of rhodamine solid-phase extraction was reached through lowering pH of the medium. 3.2. Validation and application Thus, the study of absorption and fluorescence properties of rhodamin after its extraction from solution into polymethacrylate matrix demonstrates suitability of polymethacrylate matrix for direct determination of rhodamine. Fig. 3a,b shows the calibration curve for rhodamine with colorimetric and fluorescent measurements based on solid phase extraction into transparent polymethacrylate matrix. Table 1 summarizes linear equations, correlation coefficients (r), and linear ranges of determined concentration (RDC) for rhodamine and the limit of detection (LOD). The results of rhodamine determination are presented in Tables 2 and 3. Validity of the results was monitored using the standard addition method. In order to determine rhodamine, we poured aliquots of oilfield water into 50 mL flasks, then added 10.0 mL of 0.1 mol·L−1 nitric acid and 1.0 mL of rhodamine solution with accurate concentration and
diluted the mixture with distilled water to the mark. Determination precision is expressed as the relative standard deviation (RSD). The results show that the proposed procedure for determining rhodamine has satisfactory accuracy and reproducibility. Accuracy of the methodology has been validated using the standard addition method. Reproducibility has been evaluated by repeating the proposed sequence 6 times for each sample. The obtained results show that the proposed method is suitable for determination of rhodamine in real samples. 4. Conclusion The developed transparent polymer-based device was used for detection of rhodamine in oilfield water. The developed optical sensor for rhodamine determination is simple, rapid, and highly sensitive. Thus, the transparent polymethacrylate matrix can be used for solid phase extraction of rhodamine with direct colorimetric, spectrophotometric and fluorescence measurements. This method allows spectrophotometric determination of rhodamine in the range of concentrations 0.02–0.10 mg∙L−1 and fluorescence determination in
Fig. 3. Calibration curve for rhodamine: a – with spectrophotometric measurements; b – with measurement of fluorescence intensity.
4
N.A. Gavrilenko et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
Table 1 Analytical characteristics of rhodamine determination using TPP. Techniques
Linear equation
r
Spectrophotometric measurement, mg·L−1 Fluorescent measurement, μg·L−1
А535 = 0.541с + 0.006 I554 = 102с + 0.233
0.997
RDC
LOD
0.02–0.10
0.014
0.999 0.002–0.060 0.0005
Table 2 Results of rhodamine determination in model formation water solutions (n = 5–6; P = 0.95). Added, mg·L−1
0.01 0.03 0.07
Determined By spectrophotometrically measurement
By fluorescent measurement
Found, mg·L−1
Found, mg·L−1
RSD, %
0.010 ± 0.002 0.03 ± 0.01 0.07 ± 0.02
15 12 6
0.010 ± 0.005 0.04 ± 0.01 0.08 ± 0.03
RSD, % 18 14 13
Table 3 Spectrophotometric determination of rhodamine in oilfield water samples. Formation water
Added (μgL−1)
Found ± SD (μgL−1)
Recovery, %
Snezhnoe oilfield
0 40 120 240 0 40 120 240
30.8 ± 0.5 69 ± 0.8 152.3 ± 1.8 260.2 ± 4.1 9.1 ± 0.5 51 ± 2.5 121.8 ± 5.2 229.1 ± 7.7
_ 97.45 101 96.08 – 102.5 101.7 95.46
Festivalnoe oilfield
the range of 0.002–0.06 mg∙L−1 and detection limits 0.014 mg∙L−1 and 0.0005 mg∙L−1 as well as fast and easy sample preparation. Acknowledgements This project was supported by the Russian Science Foundation project 18-19-00203 and Tomsk Polytechnic University CE Program. References [1] C. Serres-Piole, H. Preud'homme, N. Moradi-Tehrani, C. Allanic, H. Jullia, R. Lobinski, Water tracers in oil field applications: guidelines, J. Pet. Sci. Eng. 98–99 (2012) 22–39. [2] J. Yan, Y. Xu, H. Zhu, Test and the monitor techniques of waterflood front and fracture, Fault-Block Oil & Gas Field, vol. 12, 2005, pp. 59–62.
[3] C. Agca, G.A. Pope, K. Sepehrnoori, Modelling and analysis of tracer flow in oil reservoirs, J. Pet. Sci. Eng. 4 (1990) 3–19. [4] T.-L. Chiang, Y.-C. Wang, W.-H. Ding, Trace determination of rhodamine B and rhodamine 6G dyes in aqueous samples by solid-phase extraction and highperformance liquid chromatography coupled with fluorescence detection, J. Chin. Chem. Soc. 59 (2012) 515–519. [5] R. Wen, D. Zeng, Z. Yang, L. Jiang, M. Ma, B. Chen, T.A. Van Beek, Rapid analysis of illegal cationic dyes in foods and surface waters using high temperature direct analysis in real time high-resolution mass spectrometry, J. Agric. Food Chem. 66 (2018) 7542–7549. [6] A.F. Kamaruddin, M.M. Sanagi, W.A. Wan Ibrahim, D.S.Md. Shukri, A.S.A. Keyon, Polypyrrole-magnetite dispersive micro-solid-phase extraction combined with ultraviolet-visible spectrophotometry for the determination of rhodamine 6G and crystal violet in textile wastewater, J. Sep. Sci. 40 (2017) 4256–4263. [7] N. Xiao, J. Deng, K. Huang, S. Ju, C. Hu, J. Liang, Application of derivative and derivative ratio spectrophotometry to simultaneous trace determination of rhodamine B and rhodamine 6G after dispersive liquid-liquid microextraction, Spectrochim. Acta A 128 (2014) (2014) 312–318. [8] J. Yan, J.-M. Cen, X.-C. Tan, S.-F. Tan, Y.-Y. Wu, H. Zhang, Q. Wang, Determination of trace rhodamine B by spectrofluorometry and magnetic solid phase extraction based on a 3D reduced graphene oxide composite, Anal. Methods 9 (2017) 5433–5440. [9] V.K. Gupta, N. Mergu, L.K. Kumawat, A new multifunctional rhodamine-derived probe for colorimetric sensing of Cu(II) and Al(III) and fluorometric sensing of Fe (III) in aqueous media, Sensors Actuators B Chem. 223 (2016) 101–113. [10] H.N. Kim, Z. Guo, W. Zhu, J. Yoon, H. Tian, Recent progress on polymer-based fluorescent and colorimetric chemosensors, Chem. Soc. Rev. 40 (2011) 79–93. [11] N.C. Dias, M.D. Porter, J.S. Fritz, Principles and applications of colorimetric solidphase extraction with negligible depletion, Anal. Chim. Acta 558 (2006) 230–236. [12] S. Matsuoka, K. Yoshimura, Recent trends in solid phase spectrometry: 2003–2009, Anal. Chim. Acta 664 (2010) 1–18. [13] A. Molina-Díaz, J.F. Garcia-Reyes, B. Gilbert-Lopez, Solid-phase spectroscopy from the point of view of green analytical chemistry, Trends Anal. Chem. 29 (2010) 655–666. [14] F.R.P. Rocha, I.M.Jr. Raimundo, L.S.G. Teixeira, Direct solid-phase optical measurements in flow systems, Anal. Lett. 44 (2011) 528–559. [15] S.B. Savvin, V.V. Kuznetzov, S.V. Sheremet'ev, A.V. Mikhailova, Optical chemical sensors (micro- and nanosystems) for analysis of liquids, Russ. J. Gen. Chem. 78 (2008) 2418–2429. [16] V.V. Apyari, S.G. Dmitrienko, V.M. Ostrovskaya, E.K. Anaev, Y.A. Zolotov, Use of polyurethane foam and 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline for determination of nitrite by diffuse reflectance spectroscopy and colorimetry, Anal. Bioanal. Chem. 39 (2008) 1977–1982. [17] D.A. Bruzewicz, M. Reches, G.M. Whitesides, Low-cost printing of poly (dimethylsiloxane) barriers to define microchannels in paper, Anal. Chem. 80 (2008) 3387–3392. [18] N.A. Gavrilenko, T.N. Volgina, M.A. Gavrilenko, Colorimetric sensor for determination of thiocyanate in fossil and drill waters, Mendeleev Commun. 27 (2017) 529–530. [19] M.A. Gavrilenko, N.A. Gavrilenko, S.K. Amerkhanova, A.S. Uali, A.A. Bilyalov, Trace determination of rhodamine and eosine in oil-water reservoir using solid-phase extraction, Adv. Mater. Res. 880 (2014) 276–281. [20] R. Jain, M. Mathur, S. Sikarwar, A. Mittal, Removal of the hazardous dye rhodamine B through photocatalytic and adsorption treatments, J. Environ. Manag. 85 (2007) 956–964. [21] M. Soylak, Y.E. Unsal, E. Yilmaz, M. Tuzen, Determination of rhodamine B in soft drink, waste water and lipstick samples after solid phase extraction, Food Chem. Toxicol. 49 (2011) 1796–1799. [22] T. Wagersreiter, S. Mukamel, Optical activity of electronically delocalized molecular aggregates: nonlocal response formulation, J. Chem. Phys. 105 (1996) 7995–8010. [23] V.I. Yuzhakov, Aggregation of dye molecules and its influence on the spectral luminescent properties of solutions, Russ. Chem. Rev. 61 (1992) (1992) 1114–1141. [24] J.-H. Huang, K.-L. Huang, S.-Q. Liu, A.T. Wang, C. Yan, Adsorption of rhodamine B and methyl orange on a hypercrosslinked polymeric adsorbent in aqueous solution, Colloids Surf. A Physicochem. Eng. Asp. 330 (2008) 55–61.
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Short Communication
Colorimetric and fluorescent sensing of rhodamine using polymethacrylate matrix N.A. Gavrilenko a, N.V. Saranchina b, E.A. Kambarova c, E.V. Urazov a, M.A. Gavrilenko a,⁎ a b c
National Research Tomsk Polytechnic University, Tomsk, Pr. Lenina, 30, 634050, Russia National Research Tomsk State University, Tomsk, Pr. Lenina, 36, 634050, Russia Taraz State University, Taraz, str. Suleymenov, 7, 080012, Kazakhstan
a r t i c l e
i n f o
Article history: Received 9 December 2018 Received in revised form 2 May 2019 Accepted 9 May 2019 Available online 11 May 2019 Keywords: Rhodamine Optode Polymethacrylate matrix Fluorometry Solid phase spectrophotometry Oilfield water
a b s t r a c t This is a description of the tracer analysis method involving colorimetric and fluorescent measurements based on solid phase extraction of rhodamine into transparent polymethacrylate matrix. Concentration of rhodamine in PMM is measured as spectrophotometric absorption level at 535 nm and fluorescence at 554 nm. The calibration graphs are linear within the ranges 0.02–0.10 mg∙L−1 and 0.002–0.06 mg∙L−1 and detection limits 0.014 mg∙L−1 and 0.0005 mg∙L−1 are calculated for colorimetric and fluorescent measurements, respectively. The method has been successfully used for determination of rhodamine in groundwater. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Numerous compounds from various chemical families can be used as chemical tracers to track distribution of drilling fluid; for example, the review [1] mentions mineral substances, a number of colourants, magnetic and radioactive materials, a total of 200 substances. Xanthene dyes have the advantage of physical and chemical stability and low limit of detection by fluorescent detection. Fluorescent dyes as chemical tracers are used to track distribution of drilling fluid including groundwater investigations [2,3]. Fluorescent dyes exhibit such advantages as resistant to biodestruction, flocculation and simple hydrochemical behavior, high sensitivity of analytical signal and improved durability in drilling fluid [4]. The most important advantage of fluorescent probes is the low detection limit. However, matrix effects and low concentration of rhodamine in real samples make its direct determination difficult. Analytical methods for rhodamine determination are HPLC [4,5], VIS spectrophotometry [6,7], and spectrofluorometry [8,9]. Therefore, it is necessary to develop a preconcentration procedure for rhodamine. Solid phase extraction is widely used because it is simple, fast and offers higher preconcentration factor. Moreover, this method requires the use of smaller amounts of organic solvents [10]. We suggest using a transparent polymethacrylate matrix for solid phase extraction of ⁎ Corresponding author. E-mail address: [email protected] (M.A. Gavrilenko).
https://doi.org/10.1016/j.saa.2019.05.011 1386-1425/© 2019 Elsevier B.V. All rights reserved.
rhodamine. The polymer matrices have been in the limelight of attention because of the potential they have as solid-phase extraction materials [11–15]. One of them, transparent polymethacrylate polymer (TPP) consists of polymethacrylate (PMA) as a base polymer and polyethylene glycol (PEG) as a modifier with hydrophilic chains. Solid phase extraction of target substances using TPP can be achieved on the basis of same mechanism as for the liquid extraction systems [16,17]. Solid phase extraction using TPP plates has been implemented to determine metal ions [18] and xanthene dyes [19]. The purpose of this study is development of a simple method for spectrophotometric and fluorimetric determination of rhodamine with prior solid phase extraction of the target substance into TPP. 2. Experimental 2.1. Preparation of polymethylmethacrylate matrix TPP is a special transparent polymer matrix containing functional groups designed to extract substances for subsequent analysis. Transparent 10 × 10 cm (0.60 ± 0.04) mm polymethacrylate plates were prepared by radical block polymerization of methacrylate with 5% PEG 400 and (alkyl)acrylates of alkaline metals at 60–70 °C for 3–4 h. These plates were then cut into 6.0 × 8.0 mm working plates weighing about 0.05 g each. The polymethacrylate matrix was placed into a 25.0 mL tube containing rhodamine oil solution and H2O. The tube was placed in a rotator
2
N.A. Gavrilenko et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
for 15 min. The polymethacrylate matrix containing the extracted rhodamine was taken out, dried with filter paper and its absorbance at 535 nm or fluorescence at 554 nm was read against a blank membrane prepared under identical conditions excluding the analyte. 2.2. Solutions and reagents The rhodamine (Merck) used in this study had the following characteristics: purity 98.7%, red colour, Amax 530 nm. A stock of 50 mg·L−1 rhodamin solution was prepared by dissolving an accurately weighed portion of rhodamin in water. The working solution of rhodamine used in the experiment was prepared by diluting the stock solution with tap water or formation water on the day of experiment. The target pH level was achieved using HCl, NaOH and citrated buffer solutions; all reagents used were chemically pure and analytical grade ones. 2.3. Apparatus The absorption spectra of TPP and solutions were recorded using an Evolution 201 spectrophotometer (Thermo Fisher Scientific Inc., USA) against an initial polymer plate prepared under the same conditions. Fluorescence emission spectrum was measured using a Solar CM 2203 spectrofluorometer. The pH values were measured using an I-160 ionometer (Izmeritelnaya Tekhnika NPO, Russia) with a pH-selective glass electrode. The absolute error for the ionometer is ±0.02 рН and it was calibrated at 25°С using buffer solutions with pH 1.00 and 9.18. 3. Results and discussion 3.1. Solid phase extraction Compared to the widely used adsorbents like activated carbon, foam, Al2O3 and silica, polymethacrylate matrix is more expedient thanks to its selectivity and transparency [20,21]. Transparent TPP is coloured pink-red after solid phase extraction of rhodamine from the solutions. Absorption spectra and fluorescence spectra of rhodamine in water solution and in TPP with different dye concentrations are shown in Fig. 1a, b. The main absorption band of rhodamine for TPP is located between 510 and 550 nm. For the matrix it is broader compared to the absorption band of the water solution. For the matrix, the absorption maximum is
extended and shifted to the long-wavelength area of 534–536 nm. Absorption at the wavelength of 535 nm is selected as the analytical signal for solid phase spectrophotometric determination of rhodamine in formation water. Changes in the absorption maximum indicate that the rhodamine molecules in TPP are partially aggregated at low concentrations. It is known that the molecular orbitals of aggregates are delocalized at small distances between molecules, hence the displacement of the absorption and luminescence spectra occurs as a result of splitting of the electron energy levels [22]. The fluorescence spectra of rhodamine in TPP are slightly broader compared to the spectrum of rhodamine in the solution. The absorption maximum of rhodamine in the polymethacrylate matrix is 554 nm and it coincides with the absorption maximum of the dye in water or waterethanol solutions after solid phase extraction from solutions with concentrations below 0.06 mg∙L−1. An increase in the concentration of rhodamine in a solution to 0.4 mg∙L−1 results in a shift of the dye absorption maximum in TPP to the longer-wave area. The fluorescence intensity at the wavelength of 554 nm is taken as an analytical signal for solid phase determination of rhodamine in formation water. This is convenient for measuring minimal concentrations of the dye in the solution and estimation of the detection limit. Increasing concentration of rhodamine in TPP conditions proportional increase of the absorption rate to the maximum of 0.06 mg∙L−1 and of fluorescence intensity until the solution concentration is 0.10 μg∙L−1. Further increase in the concentration of rhodamine solution slows down growth of absorption and fluorescence of rhodamine in TPP (Fig. 2a,b), since aggregates of organic dyes fluoresce slightly [23]. Hydrophobic nature of the sorbent favors extraction of organic substances from solutions [24]. Extraction of such substances using TPP can be divided into two broad steps. In the first step, an aqueous sample containing rhodamine is brought into contact with TPP, where some of the dye is sorbed onto its surface. In the second part of the process, the rhodamine dissolved in the polymer matrix, diffuses into the body of TPP. pH has a strong effect upon the adsorption capacity as it influences chemical interactions between dye molecules and TPP in a solution. TPP contains oxygen groups on its surface, e.g. strong carboxylic groups and carbonyl groups, which are nucleophilic in nature. As pH of a dye solution decreases, more dye molecules are protonated and get adsorbed on the surface or into the body of TPP. This happens because dye molecules become nucleophilic at pH b3. At this acidity level of
Fig. 1. a – Absorption spectra of rhodamine in water solution (1) and polymethacrylate matrix after contact with 0.4 mg∙L−1 rhodamine solution of concentration (2); b – Fluorescence spectra of rhodamine in water solution (1) and in polymethacrylate matrix after contact with rhodamine solutions of different concentrations, μg∙L−1: (2) – 0.1; (3) – 0.2; (4) – 0.4.
N.A. Gavrilenko et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
3
Fig. 2. a – Absorption spectra of polymethacrylate matrix after contact with rhodamin solutions of different concentrations, mg∙L−1: 1 – 0; 2 – 0.02; 3 – 0.04; 4 – 0.06; 5 – 0.08; 6 – 0.10; 7 – 0.15; 8 – 0.20; b – Fluorescence spectra of polymethacrylate matrix after contact with rhodamin solutions of different concentrations, μg∙L−1: 1 – 0; 2 – 0.01; 3 – 0.02; 4 – 0.04; 5 – 0.06; 6 – 0.08; 7 – 0.10.
the medium, extraction of eosine and fluoresceine is b10% in their simultaneous presence. Thus selectivity of rhodamine solid-phase extraction was reached through lowering pH of the medium. 3.2. Validation and application Thus, the study of absorption and fluorescence properties of rhodamin after its extraction from solution into polymethacrylate matrix demonstrates suitability of polymethacrylate matrix for direct determination of rhodamine. Fig. 3a,b shows the calibration curve for rhodamine with colorimetric and fluorescent measurements based on solid phase extraction into transparent polymethacrylate matrix. Table 1 summarizes linear equations, correlation coefficients (r), and linear ranges of determined concentration (RDC) for rhodamine and the limit of detection (LOD). The results of rhodamine determination are presented in Tables 2 and 3. Validity of the results was monitored using the standard addition method. In order to determine rhodamine, we poured aliquots of oilfield water into 50 mL flasks, then added 10.0 mL of 0.1 mol·L−1 nitric acid and 1.0 mL of rhodamine solution with accurate concentration and
diluted the mixture with distilled water to the mark. Determination precision is expressed as the relative standard deviation (RSD). The results show that the proposed procedure for determining rhodamine has satisfactory accuracy and reproducibility. Accuracy of the methodology has been validated using the standard addition method. Reproducibility has been evaluated by repeating the proposed sequence 6 times for each sample. The obtained results show that the proposed method is suitable for determination of rhodamine in real samples. 4. Conclusion The developed transparent polymer-based device was used for detection of rhodamine in oilfield water. The developed optical sensor for rhodamine determination is simple, rapid, and highly sensitive. Thus, the transparent polymethacrylate matrix can be used for solid phase extraction of rhodamine with direct colorimetric, spectrophotometric and fluorescence measurements. This method allows spectrophotometric determination of rhodamine in the range of concentrations 0.02–0.10 mg∙L−1 and fluorescence determination in
Fig. 3. Calibration curve for rhodamine: a – with spectrophotometric measurements; b – with measurement of fluorescence intensity.
4
N.A. Gavrilenko et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 220 (2019) 117106
Table 1 Analytical characteristics of rhodamine determination using TPP. Techniques
Linear equation
r
Spectrophotometric measurement, mg·L−1 Fluorescent measurement, μg·L−1
А535 = 0.541с + 0.006 I554 = 102с + 0.233
0.997
RDC
LOD
0.02–0.10
0.014
0.999 0.002–0.060 0.0005
Table 2 Results of rhodamine determination in model formation water solutions (n = 5–6; P = 0.95). Added, mg·L−1
0.01 0.03 0.07
Determined By spectrophotometrically measurement
By fluorescent measurement
Found, mg·L−1
Found, mg·L−1
RSD, %
0.010 ± 0.002 0.03 ± 0.01 0.07 ± 0.02
15 12 6
0.010 ± 0.005 0.04 ± 0.01 0.08 ± 0.03
RSD, % 18 14 13
Table 3 Spectrophotometric determination of rhodamine in oilfield water samples. Formation water
Added (μgL−1)
Found ± SD (μgL−1)
Recovery, %
Snezhnoe oilfield
0 40 120 240 0 40 120 240
30.8 ± 0.5 69 ± 0.8 152.3 ± 1.8 260.2 ± 4.1 9.1 ± 0.5 51 ± 2.5 121.8 ± 5.2 229.1 ± 7.7
_ 97.45 101 96.08 – 102.5 101.7 95.46
Festivalnoe oilfield
the range of 0.002–0.06 mg∙L−1 and detection limits 0.014 mg∙L−1 and 0.0005 mg∙L−1 as well as fast and easy sample preparation. Acknowledgements This project was supported by the Russian Science Foundation project 18-19-00203 and Tomsk Polytechnic University CE Program. References [1] C. Serres-Piole, H. Preud'homme, N. Moradi-Tehrani, C. Allanic, H. Jullia, R. Lobinski, Water tracers in oil field applications: guidelines, J. Pet. Sci. Eng. 98–99 (2012) 22–39. [2] J. Yan, Y. Xu, H. Zhu, Test and the monitor techniques of waterflood front and fracture, Fault-Block Oil & Gas Field, vol. 12, 2005, pp. 59–62.
[3] C. Agca, G.A. Pope, K. Sepehrnoori, Modelling and analysis of tracer flow in oil reservoirs, J. Pet. Sci. Eng. 4 (1990) 3–19. [4] T.-L. Chiang, Y.-C. Wang, W.-H. Ding, Trace determination of rhodamine B and rhodamine 6G dyes in aqueous samples by solid-phase extraction and highperformance liquid chromatography coupled with fluorescence detection, J. Chin. Chem. Soc. 59 (2012) 515–519. [5] R. Wen, D. Zeng, Z. Yang, L. Jiang, M. Ma, B. Chen, T.A. Van Beek, Rapid analysis of illegal cationic dyes in foods and surface waters using high temperature direct analysis in real time high-resolution mass spectrometry, J. Agric. Food Chem. 66 (2018) 7542–7549. [6] A.F. Kamaruddin, M.M. Sanagi, W.A. Wan Ibrahim, D.S.Md. Shukri, A.S.A. Keyon, Polypyrrole-magnetite dispersive micro-solid-phase extraction combined with ultraviolet-visible spectrophotometry for the determination of rhodamine 6G and crystal violet in textile wastewater, J. Sep. Sci. 40 (2017) 4256–4263. [7] N. Xiao, J. Deng, K. Huang, S. Ju, C. Hu, J. Liang, Application of derivative and derivative ratio spectrophotometry to simultaneous trace determination of rhodamine B and rhodamine 6G after dispersive liquid-liquid microextraction, Spectrochim. Acta A 128 (2014) (2014) 312–318. [8] J. Yan, J.-M. Cen, X.-C. Tan, S.-F. Tan, Y.-Y. Wu, H. Zhang, Q. Wang, Determination of trace rhodamine B by spectrofluorometry and magnetic solid phase extraction based on a 3D reduced graphene oxide composite, Anal. Methods 9 (2017) 5433–5440. [9] V.K. Gupta, N. Mergu, L.K. Kumawat, A new multifunctional rhodamine-derived probe for colorimetric sensing of Cu(II) and Al(III) and fluorometric sensing of Fe (III) in aqueous media, Sensors Actuators B Chem. 223 (2016) 101–113. [10] H.N. Kim, Z. Guo, W. Zhu, J. Yoon, H. Tian, Recent progress on polymer-based fluorescent and colorimetric chemosensors, Chem. Soc. Rev. 40 (2011) 79–93. [11] N.C. Dias, M.D. Porter, J.S. Fritz, Principles and applications of colorimetric solidphase extraction with negligible depletion, Anal. Chim. Acta 558 (2006) 230–236. [12] S. Matsuoka, K. Yoshimura, Recent trends in solid phase spectrometry: 2003–2009, Anal. Chim. Acta 664 (2010) 1–18. [13] A. Molina-Díaz, J.F. Garcia-Reyes, B. Gilbert-Lopez, Solid-phase spectroscopy from the point of view of green analytical chemistry, Trends Anal. Chem. 29 (2010) 655–666. [14] F.R.P. Rocha, I.M.Jr. Raimundo, L.S.G. Teixeira, Direct solid-phase optical measurements in flow systems, Anal. Lett. 44 (2011) 528–559. [15] S.B. Savvin, V.V. Kuznetzov, S.V. Sheremet'ev, A.V. Mikhailova, Optical chemical sensors (micro- and nanosystems) for analysis of liquids, Russ. J. Gen. Chem. 78 (2008) 2418–2429. [16] V.V. Apyari, S.G. Dmitrienko, V.M. Ostrovskaya, E.K. Anaev, Y.A. Zolotov, Use of polyurethane foam and 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline for determination of nitrite by diffuse reflectance spectroscopy and colorimetry, Anal. Bioanal. Chem. 39 (2008) 1977–1982. [17] D.A. Bruzewicz, M. Reches, G.M. Whitesides, Low-cost printing of poly (dimethylsiloxane) barriers to define microchannels in paper, Anal. Chem. 80 (2008) 3387–3392. [18] N.A. Gavrilenko, T.N. Volgina, M.A. Gavrilenko, Colorimetric sensor for determination of thiocyanate in fossil and drill waters, Mendeleev Commun. 27 (2017) 529–530. [19] M.A. Gavrilenko, N.A. Gavrilenko, S.K. Amerkhanova, A.S. Uali, A.A. Bilyalov, Trace determination of rhodamine and eosine in oil-water reservoir using solid-phase extraction, Adv. Mater. Res. 880 (2014) 276–281. [20] R. Jain, M. Mathur, S. Sikarwar, A. Mittal, Removal of the hazardous dye rhodamine B through photocatalytic and adsorption treatments, J. Environ. Manag. 85 (2007) 956–964. [21] M. Soylak, Y.E. Unsal, E. Yilmaz, M. Tuzen, Determination of rhodamine B in soft drink, waste water and lipstick samples after solid phase extraction, Food Chem. Toxicol. 49 (2011) 1796–1799. [22] T. Wagersreiter, S. Mukamel, Optical activity of electronically delocalized molecular aggregates: nonlocal response formulation, J. Chem. Phys. 105 (1996) 7995–8010. [23] V.I. Yuzhakov, Aggregation of dye molecules and its influence on the spectral luminescent properties of solutions, Russ. Chem. Rev. 61 (1992) (1992) 1114–1141. [24] J.-H. Huang, K.-L. Huang, S.-Q. Liu, A.T. Wang, C. Yan, Adsorption of rhodamine B and methyl orange on a hypercrosslinked polymeric adsorbent in aqueous solution, Colloids Surf. A Physicochem. Eng. Asp. 330 (2008) 55–61.