Simultaneous determination of four trace level endocrine disrupting compounds in environmental samples by solid-phase microextraction coupled with HPLC

Author’s Accepted Manuscript Simultaneous determination of four trace level endocrine disrupting compounds in environmental samples by solid-phase microextraction coupled with HPLC Lingling Wang, Zhenzhen Zhang, Xu Xu, Danfeng Zhang, Fang Wang, Lei Zhang www.elsevier.com/locate/talanta

PII: DOI: Reference:

S0039-9140(15)00291-X http://dx.doi.org/10.1016/j.talanta.2015.04.043 TAL15543

To appear in: Talanta Received date: 29 January 2015 Revised date: 11 April 2015 Accepted date: 15 April 2015 Cite this article as: Lingling Wang, Zhenzhen Zhang, Xu Xu, Danfeng Zhang, Fang Wang and Lei Zhang, Simultaneous determination of four trace level endocrine disrupting compounds in environmental samples by solid-phase microextraction coupled with HPLC, Talanta, http://dx.doi.org/10.1016/j.talanta.2015.04.043 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Simultaneous determination of four trace level endocrine disrupting compounds in environmental samples by solid-phase microextraction coupled with HPLC

Lingling Wang, Zhenzhen Zhang, Xu Xu, Danfeng Zhang, Fang Wang, Lei Zhang; College of Chemistry, Liaoning University, 66 Chongshan Middle Road, Shenyang,Liaoning, 110036, People’s Republic of China

A B S T R A C T

：A simple, rapid, sensitive and effective method for the

simultaneous determination of four endocrine disrupting compounds (EDCs) (Bisphenol A (BPA), Bisphenol F (BPF), Bisphenol AF (BPAF) and Bisphenol AP (BPAP)) in environment water samples based on solid-phase microextraction (SPME) coupled with high performance liquid chromatography (HPLC) was developed. Multi-wall carbon nanotubes (MWCNTs) adsorbents showed a good affinity to the target analytes. These compounds were rapidly extracted within 10 min. Various experimental parameters that could affect the extraction efficiencies had been investigated in detail. Under the optimum conditions, the enrichment factors of the method for the target EDCs were found to be 500. Satisfactory precision and accuracy of the method were obtained in a low concentration range of 2.0-500.0 ng mL-1. The method detection limits were in the range of 0.10-0.30 ng mL-1. The high

*

Corresponding author. Tel.: +86 24 62207809; Fax: +86 24 62202380. E-mail address: [email protected] (L. Zhang). 1

pre-concentration rate and eƥciency of the method ensure its successful application in extraction of trace EDCs from large volumes of environmental water samples. The extraction recoveries in real samples ranged from 85.3-102.5% with the relative standard deviations (n= 5) less than 3.74%. Keywords: Solid-phase microextraction; Multi-walled carbon nanotubes; Endocrine disrupting compounds; Environment water samples; High performance liquid chromatography. 1. Introduction Bisphenol-type EDCs have a broad range of applications in industry (liners lacquers, adhesives, plastics, drink packages and food cans), agricultural purposes [1, 2]. Moreover, they are high production volume chemicals worldwide. Especially within the plastic compounds, the using of bisphenol-type EDCs in diverse domestic materials and products led to its presence in greater or lesser concentrations in food and drinking water. The adverse health effects of exposure to EDCs have been reported, such as decreased sperm count, reduced fertility, increased incidences of breast, ovarian and testicular cancers [3-8]. Although the concentration of these compounds is relatively low in water ( ng L−1 to g L−1), continuous release and chronic exposure to these substances can result in adverse effects on aquatic life, which can be a potential risk to human health. The monitoring of bisphenol-type EDCs in the aquatic environment has attracted considerable attention in recent years. Various analytical methods for these EDCs have been reported in the literature, such as capillary electrophoresis (CE)[9],

2

electrochemistry (EC) [10], gas chromatography-mass spectrometry (GC-MS) [11, 12], high performance liquid chromatography (HPLC) with diode array detection (DAD) [13, 14], ultraviolet detection (UV) [15-18], fluorescence detection (FD) [19, 20] and mass spectrometry (MS) [21-23]. HPLC instruments are still widely applied to analyze these compounds because of their lower cost and greater robustness. Considering that bisphenol-type EDCs are present in the environment at trace concentrations, suitable techniques of preparation need to be applied to isolate and preconcentrate the analytes prior to their determination. Current techniques for the pre-concentration of bisphenol-type EDCs include solvent extraction[24], solid phase extraction (SPE)[14, 25-31], solid phase microextraction (SPME)[32] and liquid phase microextraction (LPME) [19, 33]. Among these methods, SPME can be easily automated and has been increasingly widely used in sample preparation for chromatographic analysis due to reducing the consumption of reagents, decreasing analysis times and increasing separation efficiency. Multi-wall carbon nanotubes (MWCNTs) as adsorbents have attacted increasing attention due to their high specific surface area, high reactivity, large micropore volume, unique hollow tube structure[34-36]. Because of their distinctive properties of sp2 hybridized carbon bonds, MWCNTs have exhibited great adsorptive affinity to a series of phenols pollutants from aqueous solutions[37], and found to be efficient adsorbents with a capacity that exceeds that of activated carbon. SPME based on MWCNTs is a relatively new “green analytical chemistry” sample preparation

3

technology [38, 39]. In our previous work, we have studied the adsorption behavior and mechanism of BPF, BPAF and BPAP on MWCNTs[40-42]. It is found that MWCNTs have excellent adsorption ability, high pre-concentration factor and rapid phase separation for bisphenol-type EDCs. To our knowledge, nowadays no method has been published for the simultaneous determination of BPA, BPF, BPAF and BPAP using MWCNTs as adsorbents in environment samples. In this investigation, a simple, rapid and sensitive method, which combines SPME technology for the extraction and simultaneous determination of four EDCs in environmental water samples, is presented. Experimental parameters affecting the extraction of target analytes, such as the amount of MWCNTs, extraction time, the pH and ionic strength of sample solution and elution conditions were investigated. The developed analytical procedure was proven to be effective, fast, and accurate for routine analyses. 2. Materials and methods 2.1. Materials and reagents MWCNTs (main range of diameter: 10-20 nm; specific surface area 100-160 m2g−1; purity: 97%) were purchased from Shenzhen Nanotech Port Co. Ltd. (Shenzhen, China). Analytical standard of Bisphenol A [2,2-bis(4-hydroxyphenyl) propane] (BPA), Bisphenol F [4,4ƍ-dih-ydroxydiphenylmethane] (BPF), Bisphenol AF [1,1,1,3,3,3-hexafluoro-2,2-bis(4-hyd-roxy-phenyl)propane] (BPAF) and Bisphenol AP [4,4ƍ-(1-Phenylethylidene)bisphenol](BPAP) were purchased from HEOWNS

4

Biochemical technology Co., Ltd. (Tianjin, China). The stock solution containing the analytes was prepared by dissolving appropriate amount of them in ethanol and stored at 4oC under dark conditions. The working solutions were obtained daily by appropriately diluting the stock solution with deionized water. Chromatographic grade methanol (MeOH) was purchased from Fisher Corporation (Pittsburgh, PA, USA). HPLC-grade deionised water was obtained from a MilliQ water purification system (MilliQ Water; Molsheim, France). Analytical grade sodium phosphate and sodium chloride were purchased from Beijing Chemical Co. (Beijing, China). Deionized water used throughout experiments was purified using a Sartorius Arium 611 system (Sartorius, Göttingen, Germany). 2.2. Sample preparation Real samples were taken from drinking water, river water, effluents and plastic food packaging bag. The effluents used in this study were taken from a municipal wastewater treatment plant (Shenyang, China), and river water was from Hunhe (Shenyang, China). Plastic food packaging bags were obtained from local maket. Suitable amounts of plastic packaging bag were added to a 100.00 mL beaker, then added suitable ethanol to dissolve them for 24 h. The extract was then evaporate using rotary evaporator at 30 oC, until the volume became 1–2 mL. The residue was dissolved with deionized water to the final volume of 250.00 mL. Upon reception, samples were filtered through 0.45 ȝm filters and the resulting solutions were referred to as sample solutions.

5

2.3. SPME procedure The SPME procedure is illustrated in Scheme1. In the extraction procedure, 40.0 mg MWCNTs were added into 250 mL of sample solution spiked with BPA, BPF, BPAF and BPAP. The mixture was shaken for 10 min at 180 rpm, the solid/liquid phases were separated by centrifuging for 5 min at 5000 rpm. Then the target analytes were ultrasonically eluted from the MWCNTs with 1.0 mL of ACN/0.1 mol L-1 Na3PO4 (2:3, V:V) for 2 min. The eluent was separated from MWCNTs by centrifuging. Then the eluent was evaporated to dryness under a mild nitrogen stream at room temperature. Finally, the residue was dissolved with 0.5 mL mobile phase and filtered through a 0.45 ȝm PTFE filter membrane before HPLC analysis. Scheme 1. Schematic procedure for SPME of target compounds from water samples.

2.4. HPLC-DAD analysis The HPLC system (Agilent 1100, Palo Alto, CA, USA) consisted of an automatic sampler and diode array detector. The separation was performed on a SB-C18 (150 mm×4.6 mm, 5 ȝm) column (Agilent, Palo Alto, CA, USA), using an isocratic mobile phase consisting of 40% water and 60% methanol. The flow rate and column temperature were set at 1.0 mL min-1 and 30oC, respectively. The detection wavelength was set at 275 nm. The injection volume of analytical solution was 20 ȝL.

6

3. Results and discussion 3.1. Optimization of extraction conditions To achieve the best extraction efficiency for four EDCs, extraction conditions were optimised by analysing spiked samples (adding 2.0 ȝg of four EDCs into 10 mL blank water samples). The experimental parameters, including the amount of MWCNTs, extraction time, the pH and ionic strength of sample solution and elution conditions, were investigated. 3.1.1. Amount of the MWCNTs Different amounts of the MWCNTs in a range of 10-60 mg were applied to extract four EDCs (BPA, BPF, BPAF and BPAP from the sample solution. The results indicated that 40 mg MWCNTs were enough for the extraction, and further increasing the amount of the adsorbents gave no significant improvement for the recoveries of four EDCs. Therefore, 40 mg was selected as the amount of the adsorbents. 3.1.2. Effect of pH and ionic strength of sample solution The effect of different initial pH values ranging from 2.0 to 12.0 was studied. The adsorption maxima generally occurred in a broad range of pH value from 4.0 to 8.0. Generally, the pH of natural four EDCs solution was close to 5.2. In this study, the sample solutions were used directly without any pH adjustment. In general, the solution pH plays an important role in the SPME process because it influences the state of target analytes and the surface charge of adsorbents. As

7

shown in Fig.1(A), higher extraction capacities for four EDCs were obtained when pH values ranging from 4.0 to 8.0. The pKa values of BPA, BPF, BPAF and BPAP were 9.5, 10.0, 8.3 and 10.0 , respectively. In a rang of pH values from 4.0 to 8.0, four EDCs existed as neutral molecules. Nearly all of them carried no net electrical charge, which resulted in little electrostatic attraction or repulsion with MWCNTs. Consequently, the adsorption mechanism might be attributed to ʌ-ʌ interactions, H-bonds and hydrophobic occurred between the MWCNTs and four EDCs[40-42]. In order to investigate the influence of the ionic strength, adsorption experiments were carried out in the presence of 0, 0.02, 0.2, 0.5 and 1.0 mol L-1 NaCl, respectively. Results showed that the adsorption percentages were no significant effect with increasing NaCl concentrations (0.02–1.0 mol L-1). In this experiment, the sample solutions without adjusting ionic strength were adopted. 3.1.3. Extraction time SPME is not an exhaustive process but an equilibrium process, in which the target analytes are partitioned between the sample matrix and adsorbents. The equilibrium time refers to the time after which the amount of extracted target analytes remains constant. The effect of sample extraction time was investigated within 2–30 min. It can be seen from Fig.1(B) that the recoveries of them increased by extending the extraction time from 2 min to 10 min, and subsequently decreased from 10 min to 30 min. Therefore, 10 min was chosen as the extraction time in this study. Fig. 1. Optimization of extraction conditions: effect of pH on the recoveries of four EDCs (A) and effect of extraction times on the recoveries of four EDCs (B).

8

3.1.4. Effect of eluting solvent Desorption of the target analytes from the adsorbents was performed by

!

sonication. Different eluents, including acetonitrile(ACN), methanol MeOH , ACN /0.1 mol L-1 Na3PO4(2:3, v/v), and MeOH /0.1 mol L-1 Na3PO4 (2:3, v/v) were studied. The results (Fig.2) showed that the highest overall desorption efficiency for the target analytes was attained by using ACN /0.1 mol L-1 Na3PO4 (2:3, v/v) which was selected as the elution solvent in the subsequent experiments. 3.1.5. Desorption time The effect of desorption time on the recoveries of the target analytes was investigated in the range of 1.0–5.0 min. The results (Fig.2) indicated that the recoveries were enhanced by increasing the desorption time from 1.0 to 2.0 min, and then remained almost constant with further increase in time. Therefore, the desorption time of 2 min was selected for subsequent experiments. 3.1.6. Effect of volume of eluent The eluent volume affects the sensitivity of the method, as it determines the maximum preconcentration factor that can be achieved for the target analytes. During the desorption process, the effect of eluent volume was studied ranging from 0.5 to 3.0 mL. The results (Fig.2) showed that 1.0 mL of the eluent was enough to desorb the target analytes. Therefore, 1.0 mL of the eluent was selected for the further experiments.

9

Fig. 2. Optimization of desorption conditions: effect of eluent, desorption time and volume of eluent on the recoveries of four EDCs.

3.2. Effect of sample volume The effect of sample volume on quantitative analysis of the four EDCs was investgated in the range of 10.0-300.0 mL. A series of 2.0 ȝg of the target analytes were diluted to 10.0, 50.0, 100.0, 150.0, 200.0, 250 and 300.0 mL with deionized water. Then, the SPME procedure was performed under the optimum conditions as described in the experimental section. The results indicated that the recoveries of four EDCs had no changed obviously with the sample volumes up to 250.0 mL. However, a decrease in the recoveries was observed at higher sample volumes. Therefore, a sample volume of 250.0 mL was considered to be the optimal sample volume. 3.3. Interference studies Various inorganic ions and organic matter are often contained in the industrial wastewater, which may have a potentially competitive adsorption effect on BPA, BPF, BPAF and BPAP, so it is necessary to investigate the effect of co-existing ions and natural organic matter (NOM) on the adsorption of them. 3.3.1.Effect of co-existing ions The sample solutions contained Na+, K+, NH4+, Mg2+, Cu2+, Zn2+, Ni2+, Pb2+, NO3-, HCO3-, CO32-, SO42-, SO32- and PO43-, respectively, and their mixed ions were applied in the co-existing ions investigation. The concentrations of all these ions in

10

solution were kept at 1.0×10−3 mol L−1 in each case. Both Pb2+ and PO43- caused a remarkable decrease in the recoveries of four EDCs. However, the complex composition of metal ions and many other ionic species had no obvious negative effect on the recoveries of them, suggesting the potential application of MWCNTs as adsorbents for the extraction of four EDCs in environment samples. 3.3.1.Effect of humic acid In order to evaluate the effect of NOM (with humic acid as the model) on the extraction of four EDCs from sample solutions, sample solutions containing 5.0 mg L−1 of humic acid were extracted by the proposed method. The experimental results indicated that recoveries of all target analytes had no changed obviously when the concentration of humic acid was 5.0 mg L−1 dissolved total organic carbon (TOC). The TOC contents in the water samples investigated in the present study are less than 3.5 mg L−1 for river water samples[43]. Hence, humic acid did not interfere with determination of the target analytes in environment samples. 3.4. Stability of the MWCNTs The stability of MWCNTs was evaluated by checking the cycle number dependence of recoveries for 200 ng mL-1 of four EDCs, using the same MWCNTs for subsequent cycles. The results indicate that no obvious decrease in the recoveries of the target analytes was observed even after a 8-cycle run of MWCNTs for the adsorption and desorption of BPA, BPF, BPAF and BPAP (Fig.3), suggesting that the MWCNTs were suitable for the long-term repetitive adsorption/desorption of bisphenol-type EDCs, and the MWCNTs are promising adsorbents for the effective

11

extraction of bisphenol-type EDCs in environmental water samples. Fig. 3. Reusability of the MWCNTs as SPME adsorbents for extraction of four EDCs

3.5. Method evaluation 3.5.1. Analytical performances Under optimal experimental conditions, a series of experiments were performed to obtain linear ranges, precision, the limit of detection (LOD) and quantification (LOQ). All the experiments were performed in triplicate. Good linearities were observed in the range of 2.0-500.0 ng mL-1 for a sample volume of 250.0 mL with the correlation coefficients (r2) ranging from 0.9981 to 0.9994. The limit of detection (LOD=3SD/b, SD is standard deviation of the response, n=9; b: slope of the the calibration curve ) and the limit of quantization (LOQ=10SD/b) were obtained in the range of 0.10-0.30 ng mL-1 and 0.35-1.00 ng mL-1, respectively. The results (Table.1) showed that the LODs of the target analytes were at low ng mL-1 level. Additionally, the proposed method showed good precision with the run-to-run and day-to-day RSDs in the range of 1.26–3.45% (n=6) and 3.72–4.84% (n=3), respectively. Enrichment factor (EF) was calculated by following equations: EF = c a c s

(1)

where ca and cs are the concentrations of the target analytes in analytical and sample solutions, respectively. In order to calculate the EFs for the target analytes, five replicates were conducted for the sample solutions V=250 mL) containing 200 ng mL-1 of the target analytes. It was found that the EF of 500 was obtained under

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optimal conditions. Table.1 Analytical performance for BPA, BPF, BPAF and BPAP obtained by SPME -HPLC-DAD Application of proper quality assurance/quality control (QA/QC) procedures is vital for the measurement results to be treated as a source of reliable analytical information. In this procedures, the estimation of uncertainty of the final results and traceability is necessary. According to the Guide to the Expression of Uncertainty in Measurement (GUM)[44], the uncertainties of analytical results including the amount of sample used for a determination, recovery (trueness), analyte concentration, calibration and repeatability were calculated. The expanded uncertainty of the target analytes determination is obtained using the formula[45]: U = kc (ur ( sample) ) 2 + (ur ( cal ) ) 2 + (ur (true ) ) 2 + (ur ( rep ) )2 + (ur ( LOD ) ) 2 ur ( LOD ) =

LOD cdet

(2) (3)

Where U is expanded uncertainty, k is the coverage factor, for which 2 is usually chosen to obtain a confidence level of approximately 95%, c is average concentration of the analyte, ur(sample) is relative standard uncertainty of sample mass determination, ur(cal) is relative standard uncertainty of calibration step, ur(true) is relative standard uncertainty of recovery determination, ur(rep) is relative standard uncertainty of repeatability, ur(LOD) is relative standard uncertainty of LOD determination and cdet is is the concentration of the taget analyte.

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ur ( cal ) =

SDxy b

2 1 1 ( xsample − xm ) + + n p n ¦ ( xi − xm )

(4)

i =1

Where SDxy is residual standard deviation , b is the direction coefficient of the calibration curve, p is the number of measurements carried out for given sample, n is the total number of standard samples used for plotting the calibration curve, xsample is the concentration of sample, xm is the mean of all the concentration of a standard solution for which the measurement was made in order to plot a standard curve, xi is the concentration of standard solution. The related parameters were listed in Table 2. The uncertainty of the weight and/or volume of a sample are usually small, so ur(sample) is very often neglected during construction of the uncertainty budget[45].

Table.2 Calculated values of relative standard uncertainty and expanded uncertainty (U, k=2) for the determination of BPA, BPF, BPAF and BPAP in river water

3.5.2.

Application in real sample analysis

To evaluate the applicability of the present method, real samples were analyzed. It can be seen (Fig.4) that no significant interference peaks were found at the retention positions of four bisphenol-type EDCs. To evaluate the precision and accuracy of the proposed method, the spiked samples (10.0, 100.0, 200 ng mL-1) were analyzed and the analytical results were showed in Table 3. The recoveries of the target analytes obtained from real samples were in the range of 85.3-102.5%. The relative standard deviations (RSD) varied between 0.32% and 3.74% (n=5). It can be considered that the current method provides acceptable recoveries and precision for the simutaneous

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determination of BPA, BPF, BPAF and BPAP in real samples.

Table 3. Analytical results for the real sample.

Fig. 4. HPLC-DAD Chromatograms of the river water samples after pretreatment by SPME with the MWCNTs as adsorbents: blank river water sample (A) and the spiked river water sample with 10.0 ng mL-1.

3.6. Comparing with other methods The proposed method based on SPME (MWCNTs)-HPLC–DAD was compared with other methods as listed in Table 4. As can be seen from the table, the LODs of four bisphenol-type EDCs obtained by the proposed method were lower than that obtained by other sample pretreatment methods including SPME (Carbowax fiber), DMISPE (MIPs), DLLME ([C8MIM][PF6]), followed by HPLC analysis. Besides, compared to conventional absorbents or extractant, MWCNTs have high adsorption capacity and large special surface area, so an about 500 times high enrichment factor was

obtained.

Compared

with

SPE-HPLC-DAD,

SPE-GC-MS

and

HLB-SPE-HPLC-MS methods, the LODs of this method were lower than that obtained by SPE-GC-MS, but higher than that achieved by HLB-SPE-HPLC-MS method. Although the LODs of this method were higher than that obtained by HLB-SPE-HPLC-MS, the cost of the proposed method is lower and the opration is more convenient.

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Table 4. Comparison of the proposed method with other method for the determination of BPA, BPF, BPAF and BPAP.

4.

Conclusions In this research, MWCNTs-based SPME method coupled with HPLC was

developed for the sensitive simultaneous determination of four trace level EDCs in plastic food packaging bag and large volumes of environment water samples. Compared with traditional extraction materials, MWCNTs show excellent extraction ability and good stability, and it can be reused at least eight times without obvious decrease in the extraction efficiency. The method has the advantages of easy operation, short time-consuming, synchronous separation and enrichment for determination trace targets. The methods showed good linearity, reproducibility and precision, enrichment factors (EF) of more than 500 fold had been achieved for bisphenol-type EDCs. The excellent spiked recoveries of analytes in real samples indicated that the proposed method would be a valuable alternative for the analysis of these bisphenol-type EDCs in the future.

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Acknowledgements This work was supported by the National Natural Science Foundation of China (NSFC51178212), the Foundation of 211 Project for Innovative Talent Training of Liaoning University, the Foundation for Young Scholars of Liaoning University (No. 2013LDQN13), and the Science and Technology Foundation of Ocean And Fisheries of Liaoning Province (No. 201406; No. 201408). The authors also thank their colleagues and other students who participated in this study.

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on-line

C30

solid-phase

extraction

coupled

with

high-performance

liquid

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20

Table

List of table/figure captions Table.1 Analytical performance for BPA, BPF, BPAF and BPAP obtained by SPME -HPLC-DAD. Table 2. Calculated values of relative standard uncertainty and expanded uncertainty (U, k=2) for the determination of BPA, BPF, BPAF and BPAP in river water. Table 3. Analytical results for the real sample (mean ± U, n = 5). Table 4. Comparison of the proposed method with other method for the determination of BPA, BPF, BPAF and BPAP. Fig.1. Optimization of extraction conditions: effect of pH on the recoveries of four EDCs (A) and effect of extraction times on the recoveries of four EDCs (B). (BPA, BPF, BPAF and BPAP concentrations: 200 ng mL−1; sample solution volume: 10 mL). Fig.2. Optimization of desorption conditions: effect of eluent, desorption time and volume of eluent on the recoveries of four EDCs. (MWCNTs: 40 mg; BPA, BPF, BPAF and BPAP concentration: 200 ng mL−1; sample solution volume: 10 mL; extraction time: 10 min). Fig.3. Reusability of the MWCNTs as SPME adsorbents for extraction of four EDCs. (MWCNTs: 40 mg; BPA, BPF, BPAF and BPAP concentration: 200 ng mL−1; extraction time: 10 min; desorption time: 2 min; eluent: 1 mL ACN /0.1 mol L-1 Na3PO4). Fig.4. HPLC-DAD Chromatograms of the river water samples after pretreatment by SPME with the MWCNTs as adsorbents: blank river water sample (A) and the spiked

river water sample with 10.0 ng mL-1. (MWCNTs: 40 mg; sample solution volume: 250 mL; extraction time: 10 min; desorption time: 2 min; eluent: 1 mL ACN /0.1 mol L-1 Na3PO4). Scheme 1. Schematic procedure for SPME of target compounds from water samples.

Table.1 Analytical performance for BPA, BPF, BPAF and BPAP obtained by SPME-HPLC-DAD Compound

Linear range (ng mL-1)

r2

LOD (ng mL-1)

LOQ (ng mL-1)

RSD(%)(n=6) Run to run

RSD(%)(n=3) Day to day

BPA BPF BPAF BPAP

2-500 2-500 2-500 2-500

0.9994 0.9981 0.9992 0.9989

0.10 0.12 0.30 0.20

0.35 0.40 1.00 0.70

1.26 3.45 3.14 2.56

3.72 4.84 3.82 4.27

Table.2 Calculated values of relative standard uncertainty and expanded uncertainty (U, k=2) for the determination of BPA, BPF, BPAF and BPAP in river water Compound

Concentration (ng mL-1)

ur(cal)

ur(true)

ur(rep)

ur(LOD)

(ng mL-1)

9.91 8.61 9.98 9.73

0.021 0.034 0.013 0.015

0.015 0.041 0.024 0.045

0.0051 0.0014 0.0013 0.0010

0.010 0.014 0.030 0.021

0.56 0.96 0.80 0.99

BPA BPF BPAF BPAP

Relative standard uncertainty

U

Table 3. Analytical results for the real samples (mean ± U, n = 5) Drinking water Samples

Spike −1

(ng mL )

BPA

BPF

BPAF

BPAP

0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0 a b

Found −1

(ng mL ) b

n.d. 9.87±0.65 100.2±3.97 203.4±5.01 n.d. 8.69±0.78 87.2±2.84 174.2±3.48 n.d. 9.85±0.73 99.1±2.54 198.8±2.94 n.d. 9.69±0.71 97.2±2.78 197.4±4.21

River water R

a

(%)

98.7 100.2 101.7 86.9 87.2 87.1 98.5 99.1 99.4 96.9 97.2 98.7

R: Recovery n.d. = not detectable.

Spike −1

Effluents

Found −1

(ng mL ) (ng mL )

0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0

R (%)

n.d. 9.91±0.56 99.1 99.5±3.26 99.5 201.8±5.75 100.9 n.d. 8.61±0.96 86.1 85.9±1.63 85.9 173.8±2.86 86.9 n.d. 9.98±0.80 99.8 100.9±3.04 100.9 198.2±2.63 99.1 n.d. 9.73±0.99 97.3 98.1±2.78 98.1 198.6±3.92 99.3

Spike −1

Plastic packaging bag

Found −1

(ng mL ) (ng mL )

0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0

R

Spike −1

(%) (ng mL )

n.d. 9.79±0.57 97.9 98.6±3.94 98.6 198.7±4.97 99.4 n.d. 8.54±0.59 85.3 85.8±1.54 85.8 172.2±1.79 86.1 n.d. 9.75±1.08 97.5 98.6±2.60 98.6 197.4±3.43 98.7 n.d. 9.76±0.70 97.6 97.9±3.00 97.9 197.1±2.89 98.5

0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0 0 10.0 100.0 200.0

Found −1

R

(ng mL )

(%)

3.26 13.08±0.52 102.36±3.65 208.33±5.23 n.d. 8.72±0.85 86.7±2.34 175.6±3.02 n.d. 9.92±0.98 99.5±2.72 201.6±3.21 n.d. 9.87±0.86 99.3±2.45 202.7±3.45

98.2 99.1 102.5 87.2 86.7 87.8 99.2 99.5 100.8 98.7 99.3 101.4

Table 4. Comparison of the proposed method with other method for the determination of BPA, BPF, BPAF and BPAP Analytical method SPME-HPLC-FLD DMISPE-HPLC-DAD DLLME-HPLC-FLD HLB-SPE-LC-MS/MS SPE-GC-MS SPME-HPLC-DAD

Adsorbent/ extractant

EF

Carbowax fiber MIPs [C8MIM][PF6] SPE cartridges SPE cartridges MWCNTs

100 40 153 100-300 125 500

LOD (ng mL-1)

Ref.

BPA

BPF

BPAF

BPAP

1.10 0.90 0.23 0.003 1.97 0.10

1.10 0.004 2.85 0.12

0.60 0.002 0.30

0.60 0.20

[20] [13] [19] [21] [11] This work

Figure

100

100

Recovery (%)

(B)

80 60 40

BPA BPF BPAF BPAP

20

80 60 BPA BPF BPAF BPAP

40 20

0 2

4

6

8

10

0

12

5

10

pH

15

20

25

30

Time (min)

Fig.1. Optimization of extraction conditions: effect of pH on the recoveries of four EDCs (A), and effect of extraction times on the recoveries of four EDCs (B).

100 80 BPA BPF BPAF BPAP

60 40

Solvent

4

PO 3

a /N

A C N

3

a /N eO H

M

M

eO

H

PO

0

4

20

A C N

Recovery (%)

Recovery (%)

(A)

1

1

2

3

Time (min)

5

0.5

1

2

3

Volume (mL)

Fig.2. Optimization of desorption conditions: effect of eluent, desorption time and volume of eluent on the recoveries of four EDCs.

100

Recovery (%)

80

BPA BPF BPAF BPAP

60

40

20

0

1st

2nd

3rd

4th

5th

6th

7th

8th

Cycle Fig.3. Reusability of the MWCNTs as SPME adsorbents for extraction of four EDCs.

8

BPA

6

BPF 4

BPAP BPAF

2

Response (mA)

10

0

B

A 0

2

4

6

8

10

12

Retention time (min)

Fig.4. HPLC-DAD Chromatograms of the river water samples after pretreatment by SPME with the MWCNTs as adsorbents: blank river water sample (A) and the spiked river water sample with 10.0 ng mL-1.

Scheme 1. Schematic procedure for SPME of target compounds from water samples.

*Graphical Abstract (for review)

Highlights: ŹFour
EDCs were simultaneously determined in environmental samples at trace levels Ź MWCNTs were efficiently used for enrichment and clean up ŹThe amount of MWCNTs, extraction time, pH and eluent were optimized ŹThe method was simple, rapid, sensitive, eco-friendly and reliable