Development of an On-Column Trace Enrichment Method for the Determination of Sub-μg/L Bisphenol A in Bottled Water by RP-HPLC with Fluorescent Detection

A simple extraction-free, on-column trace enrichment liquid chromatographic method for the determination of trace levels of bisphenol A (BPA) in bottled water samples has been developed. It was found possible to determine ng/L (ppt) levels of BPA by the direct introduction of 6 mL of sample water to the HPLC column utilising fluorescence detection (Exλ = 274 nm, Emλ = 314 nm). Following the loading of the sample and the chromatographic focusing of the BPA on the analytical column, a simple switch from the aqueous sample to the isocratic chromatographic elution step of 50% acetonitrile/deionised water was undertaken. Using a BPA concentration of 0.596 μg/L the effect of sample volume was investigated over the range 1.0 to 12 mL. A linear relationship with the sample volume introduced to the HPLC column and the resulting peak height for BPA was found over the entire range investigated (R2 = 0.999). Using a sample volume of 6.0 mL, a well-defined chromatographic peak was recorded for BPA over the concentration range of 0.1 μg/L to 6.25 μg/L (R2 = 0.9998). A limit of detection of 0.058 μg/L for BPA was calculated based on 3 δ. A mean recovery of 100% with an associated %CV of 7.6% (n = 5) was obtained for a bottled spring water sample fortified with 1.25 μg/L BPA. Samples can be processed in under 12 minutes, much faster than that commonly reported for conventional offline extraction and chromatographic-based methods. The results show that the optimised method holds promise for the determination of BPA in such samples.

Polycarbonate-coated magnetic nanoparticles for the extraction of imipramine and its primary metabolite from urine

This study introduces a reliable and inexpensive magnetic dispersive solid phase extraction to extract imipramine and its primary metabolite (desipramine) from urine samples. To accomplish this aim, Fe3 O4 magnetic nanoparticles were synthesized by sonication, subsequently, polycarbonate was precipitated gradually onto the surface of them to form the adsorbent. Extraction recoveries of 85% and 76%, enrichment factors of 57 and 51, limits of detection of 2.5 and 2.8 μg/L, and limits of quantification of 8.3 and 9.3 μg/L were obtained for imipramine and desipramine under the optimal conditions, respectively. In addition, relative standard deviations for intra- (n = 6) and inter-day (n = 5) precisions at two concentrations (50 and 100 μg/L of each analyte) were less than or equal to 4%. Short extraction time, good repeatability, high enrichment factors, and simplicity are the main advantages of the proposed method.

Solvent-assisted dispersive micro-solid phase extraction of bisphenols using iron(III) thenoyltrifluoroacetonate complex (Fe(TTA)3) as a new nanostructured sorbent: a proof of concept

In this work, we describe for the first time the use of iron(III) thenoyltrifluoroacetonate complex (Fe(TTA)₃) as a novel sorbent for solvent-assisted dispersive micro-solid phase extraction (SA-dμSPE) of bisphenols from water samples. The extraction procedure is based on the formation of nanoparticles in situ following the rapid injection of a methanolic solution of Fe(TTA)₃ into the stirred aqueous sample. Herein, the synthesis of Fe(TTA)₃ and study of the essential parameters of the preparative procedure are described. The optimized procedure allowed for efficient enrichment of bisphenols from various water samples, chosen as model contaminants and matrix, within 2.5 min. The sorbent was collected by centrifugation, dissolved in methanol, and injected to perform HPLC with spectrophotometric detection. The limits of detection and quantification obtained ranged from 1.0-3.1 and 3.1-7.5 μg L^-1, respectively. Intraday and interday precisions of <7% relative standard deviation (RSD) and <8% RSD with analyte recoveries ranging between 70-117% (103.8% on average) were obtained for the analysis of river water, wastewater treatment plant effluent, and bottled water.

Application of a modified MWCNT-based d-µSPE procedure for determination of bisphenols in soft drinks

Herein, a facile dispersive micro-solid phase extraction (d-µSPE) procedure using carboxylated multi-walled carbon nanotubes modified with silver nanoparticles (Ag/MWCNTs-COOH) was successfully developed for the adsorption and subsequent determination of low levels of two well-known contaminants, namely bisphenol A and S (BPA and BPS) in water and soft drink samples. The detection and measurement of the above-mentioned compounds were performed by HPLC-UV instrument. The applied d-µSPE procedure has several advantages such as rapidity, high degree of sensitivity, precision and efficiency. A combination of polar/non-polar interactions seems to play a key role in the adsorption process. Under the optimized conditions, the calibration curves were linear over the concentration range of 1-500 µg/L for the both targets. The practical limit of quantifications (LOQ) for the both analytes were determined to be 1.0 µg/L. The average relative recoveries obtained from the fortified samples varied between 92 and 110% with the relative standard deviations (RSD%) of 2.9-9.5%.

Improved method for the determination of endocrine-disrupting chemicals in urine of school-age children using microliquid-liquid extraction and UHPLC-MS/MS

The presence of endocrine-disrupting chemicals in our daily life is increasing every day and, by extension, human exposure and the consequences thereof. Among these substances are bisphenols and parabens. Urine is used to analyze the exposure. The determination of 12 bisphenol homologues and 6 parabens is proposed. A procedure based on a method previously developed by our research group in 2014 is improved. The extraction yield is higher, because the new protocol is 5 times more efficient. Also, a comparison between calibration with pure standards and matrix calibration, to calculate the matrix effect, was also made. A high grade of matrix effect for all analytes was observed. In terms of validation, the limits of detection (LOD) were between 0.03 and 0.3 ng mL^-1 and limits of quantification (LOQ) 0.1 to 1.0 ng mL^-1, respectively, and the recovery is higher than 86.4% and lower than 113.6%, with a RSD lower than 13.5% in all cases. A methodology for accurate and sensitive quantification of bisphenol homologues together with parabens in human urine using UHPLC-MS/MS was developed. The method was successfully applied to 30 urine samples from children.

Biomass magnetic porous carbon prepared from mangosteen shell for the preconcentration of 3 bisphenols from beverages followed by liquid chromatographyquadrupoleorbitrap high-resolution mass spectrometry determination

Natural biomass magnetic porous carbon was successfully prepared via a cost-effective and green route using mangosteen shell as raw material. The prepared magnetic porous carbon was used as a magnetic solid phase extraction adsorbent for bisphenols enrichment from beverages followed by high-performance liquid chromatographyquadrupole Orbitrap high-resolution mass spectrometry. Parameters affecting extraction efficiency including sample solutionpH, adsorbent amount, extraction time, eluent type and volume were optimized. Results showed that biomass magnetic porous carbon had excellent adsorption properties for bisphenols due to its large specific surface area and abundant functional groups, which could form hydrogen bonding and π-π stacking with bisphenols. The enrichment factor of 3 bisphenolswere in the range of15∼19. Under optimum conditions, favorable linearity for all analytes was obtained with correlation coefficients higher than 0.998. Recoveries of spiked samples were in the range of 88.5%∼105.1% with relative standard deviation of 3.4%∼5.5%. These results demonstrated thatmagnetic porous carbon may be a promising adsorbent for enrichment of aromatic compounds. This article is protected by copyright. All rights reserved.

Recent advances in analysis of bisphenols and their derivatives in biological matrices

Biomonitoring is a very useful tool to evaluate human exposure to endocrine-disrupting compounds (EDCs), like bisphenols (BPs), which are widely used in the manufacture of plastics. The development of reliable analytical methods is key in the field of public health surveillance to obtain biomonitoring data to determine what BPs are reaching people's bodies. This review discusses recent methods for the quantitative measurement of bisphenols and their derivatives in biological samples like urine, blood, breast milk, saliva, and hair, among others. We also discuss the different procedures commonly used for sample treatment, which includes extraction and clean-up, and instrumental techniques currently used to determine these compounds. Sample preparation techniques continue to play an important role in the analysis of complex matrices, for liquid matrices the most commonly employed is solid-phase extraction, although microextraction techniques are gaining importance in this field, and for solid samples ultrasound-assisted extraction. The main instrumental techniques used are liquid and gas chromatography coupled with mass spectrometry. Finally, we present data on the main parameters obtained in the validation of the revised methods. This review focuses on various methods developed and applied for trace analysis of bisphenols, their conjugates, halogenated derivatives, and diglycidyl ethers in biological samples to enable the required selectivity and sensitivity. For this purpose, a review is carried out of the most recent relevant publications from 2016 up to present.

Rapid exposure monitoring of six bisphenols and diethylstilbestrol in human urine using fabric phase sorptive extraction followed by high performance liquid chromatography - photodiode array analysis

A novel fabric phase sorptive extraction protocol is developed for rapid exposure monitoring of six bisphenol analogues, including bisphenol A, bisphenol S, bisphenol F, bisphenol E, bisphenol B, bisphenol C, and diethylstilbestrol (DES) from human urine prior to high-performance liquid chromatography-photodiode array analysis. FPSE sample pretreatment protocol ensures the harmonization of the proposed method with the principles of Green Analytical Chemistry (GAC). Among eighteen evaluated FPSE membranes, sol-gel poly (ethylene glycol) (PEG) coated cellulose FPSE membrane resulted in the most efficient extraction. This polar FPSE membrane effectively exploits a number of advantageous features inherent to FPSE including sponge-like porous architecture of the sol-gel sorbent coating, favorable surface chemistry, flexibility and built-in permeability of cellulose fabric substrate, high primary contact surface area for rapid sorbent-analyte interaction, expanded pH, solvent and thermal stability as well as reusability of the FPSE membrane. Optimization was centered on the evaluation of critical parameters, namely the size of the FPSE membrane, the elution solvent mixture, the volume of the sample, the extraction time, the elution time, the kind of the external agitation mechanical stimulus, the ionic strength and the pH of the sample. The chromatographic separation was achieved on a Spherisorb C18 column and a gradient elution program with mobile phase consisted of 0.05 ammonium acetate solution and acetonitrile. The total analysis time was 17.4 min. The developed method was validated in terms of linearity, sensitivity, selectivity, precision, accuracy, stability, and ruggedness. The limits of detection and quantification varied from 0.26-0.62 ng/mL and 0.8-1.9 ng/mL, respectively. The relative recoveries were calculated between 90.6 and 108.8%, while the RSD values were <10% in all cases. The effectiveness of the proposed method was confirmed by its successful implementation in the bioanalysis of real urine samples.

Solvent-free mechanochemical preparation of graphene oxide-Fe3 O4 and its application in magnetic dispersive solid-phase extraction of illegal dyes in food samples

A simple, green, and efficient mechanochemical approach was developed herein to prepare tunable magnetic graphene oxide nanoparticles. The obtained nanoparticles were successfully used as adsorbents in a magnetic dispersive solid-phase extraction method to extract three cationic dyes (i.e., thioflavine T, auramine-O, and basic orange 2) found in food samples. Our proposed approach also utilized high-performance liquid chromatography with ultraviolet detection. Several key variables affecting the extraction recovery were investigated. These included the sample pH, amount of extractant, extraction time, sample volume, elution solvent type and volume, and the stability and reusability of the magnetic graphene oxide nanoparticles. Under optimized conditions, the calibration curve was linear at a concentration range of 0.005-1.0 μg/mL with a correlation coefficient of 0.9992-0.9996. Moreover, the limits of detection were determined at 0.97-1.35 μg/mL. The extraction mechanism was investigated via ultraviolet-visible spectrophotometry and zeta-potential analyses. The developed method was used to analyze the above-mentioned cationic dyes in bean products and yellow fish samples. Notably, satisfactory spiked recoveries ranging from 90.7 to 104.9% were achieved.

Application of magnetic nanomaterials in bioanalysis

The importance of magnetic nanomaterials and magnetic hybrid materials, which are classified as new generation materials, in analytical applications is increasingly understood, and research on the adaptation of these materials to analytical methods has gained momentum. Development of sample preparation techniques and sensor systems using magnetic nanomaterials for the analysis of inorganic, organic and biomolecules in biological samples, which are among the samples that analytical chemists work on most, are among the priority issues. Therefore in this review, we focused on the use of magnetic nanomaterials for the bioanalytical applications including inorganic and organic species and biomolecules in different biological samples such as primarily blood, serum, plasma, tissue extracts, urine and milk. We summarized recent progresses, prevailing techniques, applied formats, and future trends in sample preparation-analysis methods and sensors based on magnetic nanomaterials (Mag-NMs). First, we provided a brief introduction of magnetic nanomaterials, especially their magnetic properties that can be utilized for bioanalytical applications. Second, we discussed the synthesis of these Mag-NMs. Third, we reviewed recent advances in bioanalytical applications of the Mag-NMs in different formats. Finally, recently literature studies on the relevance of Mag-NMs for bioanalysis applications were presented.

A new approach based on inversion of a partial least squares model searching for a preset analytical target profile. Application to the determination of five bisphenols by liquid chromatography with diode array detector

The paper shows a procedure for selecting the control method parameters (factors) to obtain a preset 'analytical target profile' when a liquid chromatographic technique is going to be carried out for the simultaneous determination of five bisphenols (bisphenol-A, bisphenol-S, bisphenol-F, bisphenol-Z and bisphenol-AF), some of them regulated by the European Union. The procedure has three steps. The first consists of building a D-optimal combined design (mixture-process design) for the control method parameters, which are the composition of the ternary mobile phase and its flow rate. The second step is to fit a PLS2 model to predict six analytical responses (namely, the resolution between each pair of consecutive peaks, and the initial and final chromatographic time) as a function of the control method parameters. The third final step is the inversion of the PLS2 model to obtain the conditions needed for attaining a preset analytical target profile. The computational inversion of the PLS2 prediction model looking for the Pareto front of these six responses provides a set of experimental conditions to conduct the chromatographic determination, specifically 22% of water, mixed with 58% methanol and 20% of acetonitrile, keeping the flow rate at 0.66 mL min^-1. These conditions give a chromatogram with retention times of 2.180, 2.452, 2.764, 3.249 and 3.775 min for BPS, BPF, BPA, BPAF and BPZ, respectively, and excellent resolution among all the chromatographic peaks. Finally, the analytical method is validated under the selected experimental conditions, in terms of trueness and precision. In addition, the detection capability for the five bisphenols were: 596, 334, 424, 458 and 1156 μg L^-1, with probabilities of false positive and of false negative equal to 0.05.