HPLC-DAD and PARAFAC for the determination of bisphenol-A and another four bisphenols migrating from BPA-free polycarbonate glasses

Loofah sponge-based solid-phase extraction in combination with high-performance liquid chromatography-fluorescence detection (HPLC-FLD) for analysis of bisphenols in environmental water

Loofah sponges (LS) were simply treated by alkaline solution and then used as solid-phase extraction (SPE) adsorbent to extract bisphenols from environmental water samples for the first time. As natural material, LS exhibited excellent adsorption performance for bisphenol compounds due to their particular functional groups such as hydroxyl, carboxyl, amino, and other active groups. Key extraction conditions were optimized, including adsorbent amount, washing solvent volume, sample pH, ionic strength, sample loading flow rate, eluent type, and elution solvent volume. Under the optimal extraction conditions (200 mg adsorbent amount and 5.0 mL eluent volume), a method was developed for analyzing five bisphenols in environmental waters by combining LS-based SPE with high-performance liquid chromatography-fluorescence detection (HPLC-FLD). This analytical method showed excellent linearity within BP concentration range of 0.5-500 ng/mL and low detection limits (0.077-0.225 ng/mL). The recoveries of five bisphenols ranged from 78.6 % to 112 % with inter-day and inter-day precision less than 5.1 %. This method was successfully applied to the analysis of bisphenols in water samples with various water sources including river, lake, tap water, bottled water, and barrelled water. The proposed analytical method is low-cost, efficient, and sensitive, offering an alternative strategy for monitoring bisphenols in enviromental water.

Organic conjugated polymer nanoparticles enhanced tyrosinase electrochemical biosensor for selective, sensitive and rapid detection of bisphenol A

Bisphenol A (BPA) has been widely used in the production of polycarbonate (PC) plastics, flame retardants and epoxy resins, which is one of the most important endocrine disrupting chemicals and can cause damage to the estrogen system of human. In this work, organic conjugated polymer nanoparticles (CPNPs) were synthesized through nanoprecipitation method using liposome 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)-2000] (DSPE-mPEG2000) coated poly[(4,4'-bis(2-ethylhexyl)-dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-4,7-di(4-hexyl-2-thienyl)-5,6-difluoro-2,1,3-benzothiadiazole] (PDTS-hDTBT) and poly[(4,4'-bis(2-ethylhexyl)-dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-4,7-di(4-(2-ethylhexyl)-2-thienyl)-5,6-difluoro-2,1,3-benzothiadiazole] (PDTS-ehDTBT). These two polymers have different side chains, which can affect the configuration of the polymers, thereby affecting the π-π interaction between BPA and CPNPs. The resultant two CPNPs were explored as extremely attractive matrix for tyrosinase immobilization to construct electrochemical biosensing platforms for sensitive and rapid detection of BPA in water environments. The electrochemical performance of these two biosensors was significantly enhanced, benefiting from the large specific surface area and excellent biocompatibility of CPNPs, as well as the strong π-π interaction between CPNPs and BPA. The current response of PDTS-ehDTBT-Tyr-Chi/GCE exhibited a good linear relationship with BPA concentration ranging from 0.02 to 3.0 μM with a low detection limit of 11.83 nM and a high sensitivity of 0.9724 μA μM-1 cm-2. The fabricated biosensor was further used for BPA detection in actual samples with a recovery rate of 92.0 %-99.4 %. With the remarkable advantages, CPNPs-based biosensor provides a highly sensitive detection tool for rapid detection of BPA in actual samples, which has broad application prospects.

Monolithic 3D structural-substrate SERS sensing platform for ultrasensitive and highly-specific analysis of trace bisphenol A

Constructing advanced substrates with excellent features is promising for sensitive surface-enhanced Raman spectroscopy (SERS) detection. Here a novel capillary monolithic 3D structural-substrate SERS platform with Au@cDNA@Ag@Cyanine 3-aptamer nanoparticles (Au@cDNA@Ag@Cy3-Apt NPs) was fabricated for rapid, highly specific profiling of ultra-trace Bisphenol A (BPA). The proposed SERS platform combined both in-capillary SERS and aptamer-affinity recognition strategies, in which the superior SERS properties of Au-Ag NPs, aptamer selectivity, and the advantages of capillary monolith were integrated. A 3D hierarchically porous network was constructed in the monolithic column, which was endowed with rich hotspots for SERS, rapid sample permeation, and better analysis efficiency than most plane-shaped SERS modes. By varying the amount of Ag+ precursor, the Ag-shell thickness on SERS was finely tuned to guarantee Cy3 label in proximity to the plasmonic surface. Based on the biorecognition of aptamer, the selective identification of BPA occurred and exhibited a significant change in SERS intensity without obvious interference. As a result, the monolithic SERS platform featured facile operation, excellent specificity, and rapid analysis (10 min, much less than the solution-based or planar substrate SERS modes). Ultra-high sensitivity and robust reproducibility for BPA analysis was achieved with a low limit of detection (LOD) at 9.12 × 10-4 ng/L. The feasibility of this SERS platform for monitoring BPA in water and milk samples was also validated. This work lights a new access to capillary monolithic SERS-sensing platform for ultrasensitive and specific analysis of BPA.

A new non-enzymatic biosensor for the determination of bisphenol-A

In this study, a new non-enzymatic carbon paste biosensor was developed for the determination of Bisphenol-A (BPA) based on Multiwalled Carbon Nanotube (MWCNT) modified Myoglobin (Mb). The measurement principle of the biosensor was developed based on the inhibition effect of BPA on the heme group of myoglobin in the presence of hydrogen peroxide. With the designed biosensor, measurements were taken in the potential range of (-0.15 V & +0.65 V) using the differential pulse voltammetry (DPV) method in the medium containing K₄[Fe(CN)₆]. The linear range for BPA was determined to be 100-1000 µM. Response time was calculated as 16 s. The limit of detection was set at 89 μM. As a result, it has been proven that MWCNT modified myoglobin based biosensor is an alternative method that can be used for BPA determination, giving very sensitive and fast results.

HPLC-CAD as a supplementary method for the quantification of related structure impurities for the purity assessment of organic CRMs

In organic purity assessment, chromatography separation with a suitable detector is required. Diode array detection (DAD) has been a widely used technique for high-performance liquid chromatography (HPLC) analyses, but its application is limited to compounds with sufficient UV chromophores. Charged aerosol detector (CAD), as a mass-dependent detector, is advantageous for providing a nearly uniform response for analytes, regardless of their structures. In this study, 11 non-volatile compounds with/without UV chromophores were analyzed by CAD using continuous direct injection mode. The RSDs of CAD responses were within 17%. For saccharides and bisphenols, especially, the RSDs were lower (2.12% and 8.14%, respectively). Since bisphenols exist in UV chromophores, their HPLC-DAD responses were studied and compared with CAD responses, with CAD showing a more uniform response. Besides, the key parameters of HPLC-CAD were optimized and the developed method was verified using a Certified Reference Material (CRM, dulcitol, GBW06144). The area normalization result of dulcitol measured by HPLC-CAD was 99.89% ± 0.02% (n = 6), consistent with the certified value of 99.8% ± 0.2% (k = 2). The result of this work indicated that the HPLC-CAD method could be a good complementary tool to traditional techniques for the purity assessment of organic compounds, especially for compounds lacking UV chromophores.

Three-dimensional ordered macroporous imprinted polymer for bisphenol A recognition

A novel kind of three-dimensional ordered macroporous molecular imprinted polymer (3DOM MIP) was prepared and studied. Monodisperse silica microspheres were used to form silica crystal template via simple centrifuge. In the presence of template molecule, acrylamide and trimethylolpropane trimethacrylate were co-polymerized in the interstices of crystal template bisphenol A (BPA). Hydrofluoric acid were employed to etch silica crystal and the mixed solvent of methanol with acetic acid were employed to extract template molecule. The results of SEM and FTIR confirmed the successful synthesis of 3DOM MIP. The obtained 3DOM MIP exhibited a rapid adsorption kinetics and a specific adsorption capacities toward template molecule because of the small size of MIP wall, which possessed much more effective imprinted cavies. Meanwhile, 3DOM MIP could selective recognized BPA from its structural analogues.

Chromatographic Applications in the Multi-Way Calibration Field

In this review, recent advances and applications using multi-way calibration protocols based on the processing of multi-dimensional chromatographic data are discussed. We first describe the various modes in which multi-way chromatographic data sets can be generated, including some important characteristics that should be taken into account for the selection of an adequate data processing model. We then discuss the different manners in which the collected instrumental data can be arranged, and the most usually applied models and algorithms for the decomposition of the data arrays. The latter activity leads to the estimation of surrogate variables (scores), useful for analyte quantitation in the presence of uncalibrated interferences, achieving the second-order advantage. Recent experimental reports based on multi-way liquid and gas chromatographic data are then reviewed. Finally, analytical figures of merit that should always accompany quantitative calibration reports are described.