LC/MS determination of bisphenol A in river water using a surface-modified molecularly-imprinted polymer as an on-line pretreatment device

A new analytical method for the determination of bisphenol A (BPA) by LC/MS was developed and applied to environmental water samples. Quantitative MS detection of BPA was carried out in the negative mode. In order to preconcentrate the target compound yet prevent serious contamination of the water samples from the experimental environment, we employed column switching HPLC coupled with a pretreatment column of surface-modified molecularly-imprinted polymers. The recovery of BPA from a spiked environmental water sample was 102% and the repeatability of actual determinations of water samples containing 20 ng/L of BPA was 5.4% RSD. By modifying the surfaces of the molecularly-imprinted polymer particles packed in the pretreatment column, interference from the water samples was effectively removed, resulting in a significant increase in sensitivity and more reliable results. This method was successfully applied to the trace determination of BPA in environmental water samples using LC/MS.     

Novel surface modified molecularly imprinted polymer focused on the removal of interference in environmental water samples for chromatographic determination

Uniformly sized molecularly imprinted polymers (MIPs) for bisphenol A (BPA) with surface modification and immobilized intervals of functional monomers afforded by utilizing 4,4'-methylenebisphenol as a pseudo component have been prepared. MIPs for BPA were prepared using 4-vinyl pyridine immobilized in the most effective interval and ethylene glycol dimethacrylate as a functional monomer and cross-linking agent, respectively. Prepared MIPs showed significant selectivity for BPA retention and removal performance for interference in actual samples as the HPLC stationary phase compared to those of ordinary MIPs. These MIPs were employed as pretreatment media of column switching HPLC and the HPLC system provided a detection limit of 0.36 ppt when electrochemical detection was used. Actual samples, including Suwannee River natural organic matter (NOM), were applied and BPA was detected in the NOM even if widely used UV detection was employed.     

Preparation of uniformly sized molecularly imprinted polymers for phenolic compounds and their application to the assay of bisphenol A in river water.

Uniformly sized molecularly imprinted polymers, which can recognize bisphenol A (BPA), have been prepared by a multi-step swelling and polymerization method using BPA or a structurally related analogue of BPA [p-t-octylphenol (OP) or p-t-butylphenol (BP)] as the template molecule, 4-vinylpyridine as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The BP-imprinted polymer showed higher molecular recognition ability for BPA than the OP-imprinted polymer. The BPA- and BP-imprinted polymers were applied for the assay of a trace amount of BPA in river water using column-switching HPLC with fluorescence detection: A BPA-imprinted polymer was used for removal of BPA from the pretreatment eluent as the trap column, and a BP-imprinted polymer was used for selective pretreatment and enrichment of BPA in river water as the pretreatment column. The calibration graph, constructed from peak area data plotted versus BPA concentration, was linear with a correlation coefficient of >0.999 in the concentration ranges of 25-1000 ppt. The limit of quantitation was 25 ppt with a 5-ml injection. The column-switching HPLC system was successfully applied for the assay of BPA in river water.     

Shielded molecularly imprinted polymers prepared with a selective surface modification

Uniformly sized, molecularly imprinted polymers (MIPs) of bisphenol A (BPA), one of many potential endocrine disruptors, were prepared by selective surface modification and immobilized at intervals of functional monomers with 4,4′‐methylenebisphenol as a pseudotemplate. MIPs for BPA were prepared with 4‐vinyl pyridine immobilized at the most effective interval and with ethylene glycol dimethacrylate monomer as a functional crosslinker. The prepared MIPs were surface‐modified with both polar and ionic monomers with different modification methods and then evaluated to reveal their selectivity and retention characteristics. Some of the modified MIPs showed significant selectivity for BPA retention when they were used as high‐performance liquid chromatography (HPLC) stationary phases, in comparison with ordinary MIPs. This effect of molecular imprinting was retained even after the surface modification of MIPs. The MIPs employed as pretreatment media for a column‐switching HPLC system provided a detection limit as low as 1 ng/L (ppt) by electrochemical detection. Actual samples, including Suwannee River natural organic matter (NOM), were analyzed for BPA, and BPA was quantitatively detected in NOM even with the combination with widely used UV detection because of the effective removal of interference afforded by an effective surface modification of the MIPs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2048–2060, 2005     

Determination of bisphenol A in environmental water at ultra-low level by high-performance liquid chromatography with an effective on-line pretreatment device

We have developed a simple HPLC method for the microanalysis of bisphenol A (BPA), which is often contained in environmental water and is known as an endocrine disrupter. HPLC coupled with electrochemical detection requires a simpler procedure of pretreatment compared to GC-MS. In this study, we analyzed BPA using molecularly imprinted polymer as an on-line pretreatment device. This polymer has molecular recognition sites and provides specific selectivity in extraction process. Due to this effect, the detection limit obtained with this HPLC was 0.36 ng/l. This method applied to environmental water and purified water samples containing 2-70 ng/l of BPA successfully. Furthermore, UV detection was performed in some actual analyses.     

Determination of bisphenol A with effective pretreatment medium using automated column-switching HPLC with fluorescence detection

A practical way for reducing contaminants, such as humic acids, and solving column-clogging problem in environmental water analysis with liquid chromatography is proposed. Detection interference by contamination is one of the most important issues of the environmental analyses. Moreover, due to the recent smaller diameter and fine particle size of an analytical column for HPLC system, a column-clogging problem is another practical difficulty as well. We found it possible to solve these problems by employing column-switching HPLC, which consists of a pretreatment column containing surface-modified polymer particles and flow changeover valves for cleaning the remaining matrices in the pretreatment column prior to analysis. This method was successfully applied to actual HPLC-fluorescence detection of bisphenol A. Limit of detection (LOD) in real sample was <0.7 ng/L. Repeatability was around 1.4% and recovery was around 97% or more. A particular pressure increase was not observed in 150 repeated analyses of real river water samples.     

Development and characterization of an immunoaffinity monolith for selective on-line extraction of bisphenol A from environmental water samples

Matrix interference and contamination from analytical procedures are two major issues in the detection of trace level of bisphenol A (BPA) in environmental water. In this paper, we report a highly selective and efficient method for on-line extraction of BPA from water samples followed by quantification with liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI/MS/MS). Poly(ethylene dimethacrylate-glycidyl methacrylate) monolith was synthesized in 50 mm × 4.6 mm i.d. stainless steel cartridges and the epoxy-groups on the surface of the monolith were hydrolyzed and oxidized to aldehyde functions. Antibodies against BPA were covalently immobilized onto the monolithic column via Schiff base reaction. The optimum application buffer and elution buffer were found to be pH 5.5 phosphate buffered saline (PBS) and methanol–water (70:30, v/v), respectively. The obtained immunoaffinity monolithic columns were on-line coupled to LC–MS/MS using column-switching valves and the system was applied to analyze BPA in real environmental water samples. The method achieved a detection limit of 0.3 ng L⁻¹ using a sample volume of 100 mL. The linear calibration range was 1.0–160 ng L⁻¹. Samples including tap water, lake water and effluent from municipal sewage treatment plant were all measured with satisfactory results.     

Investigation of diazo‐derivatization of bisphenol A and its applicability for quantitation in food safety inspections using high‐performance liquid chromatography

Bisphenol A (BPA) is a common additive in food packaging materials, and many methods have been discovered to limit BPA for the sake of food safety. This study aims to find a more sensitive quantification method for BPA. It was determined that a diazo derivative of BPA could be obtained when reacted with a stable and inexpensive reagent, p‐methylaniline, exhibiting an increased response in the ultraviolet spectrum than that of nonreacted BPA. Based on this discovery, an accurate method of BPA quantitation was established using a precolumn derivatization HPLC method. The results of this study showed the low limit of detection and the limit of quantitation for BPA were 3.6 and 10.9 pg/mL on‐column, respectively. This method is proven to have much higher sensitivity and a lower limit of detection than direct HPLC determination methods. This method is robust, easily handled, sensitive and cost‐effective for the quantitation of BPA. In addition, the broad application of this method to determine BPA content in plastic bottled drinking water, distilled water, tap water, milk, Sprite and grape juice was demonstrated in this paper.     

Liquid phase microextraction with in situ derivatization for measurement of bisphenol A in river water sample by gas chromatography-mass spectrometry

A new method that involves liquid phase microextraction (LPME) with in situ derivatization and gas chromatography-mass spectrometry (GC-MS) is described for the determination of trace amounts of bisphenol A (BPA) in river water samples. The LPME conditions, such as the type of extraction solvent and the extraction time, are investigated. Then, the extract is directly injected into GC-MS. The detection limit and the quantification limit of BPA in river water sample are 2 and 10pgml(-1) (ppt), respectively. The calibration curve for BPA is linear with a correlation coefficient of >0.999 in the range of 10-10,000pgml(-1). The average recoveries of BPA in river water samples spiked with 100 and 1000pgml(-1) BPA are 104.1 (RSD: 8.9%) and 98.3 (RSD: 3.2%), respectively, with correction using the added surrogate standard, bisphenol A-(13)C(12). This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of BPA in liquid samples.     

Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching

Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Evaluation of an on-line coupled continuous flow liquid membrane extraction and precolumn system as trace enrichment technique by liquid chromatographic determination of bisphenol A

An on-line coupled continuous flow liquid membrane extraction (CFLME) and C₁₈ precolumn system was developed for sample preconcentration in liquid chromatography determination. After preconcentration by CFLME, which is based on the combination of continuous flow liquid–liquid extraction and supported liquid membrane, bisphenol A (BPA) was enriched in 960 μl of 1 mol l⁻¹ NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C₁₈ precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto a C₁₈ analytical column for separation and detected at 220 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor, and enrichment time were optimized. The proposed method presents a detection limit of 0.03 μg l⁻¹ (S/N=3) when 60 ml samples was enriched with an enrichment time of 30 min. Compared with C₁₈ based column-switching procedure, this proposed procedure presents similar sample throughput and lower detection limits. The proposed method was successfully applied to determine BPA in tap water, river water, and municipal sewage effluent samples.     

Electrochemical Detection of Phenylurea Herbicides in Liquid Chromatography

Abstract

This paper describes the electrochemical detection of ten phenylurea herbicides after on-line trace enrichment on a small C18 precolumn and liquid chromatography on a C18 analytical column. The method presented shows sub-ppb sensitivity in surface water samples without extensive sample pretreatment. Electrode contamination occurs but does not seriously interfere in the routine analysis of such samples. Selective determination (at 1. 0 V) of metoxuron in the presence of other phenylureas allows the detection of 30 ppt of the herbicide in surface water.     

Simultaneous HPLC determination of phenylurea herbicides and their corresponding anilines in water after on-line preconcentration

On-line preconcentration on a short C₁₈ column, prior to HPLC with UV and electrochemical detection, has been used for determination of some phenylurea herbicides and their possible degradation products, substituted anilines, in water samples. With electrochemical detection the detection limit at a signal-to-noise ratio of 3 was 5 ppt for 4-chloroaniline and 4-bromoaniline and 7 ppt for 3,4-dichloroaniline; with UV detection the detection limit was ca 300 ppt for all analytes.     

Trace Enrichment and HPLC Analysis of Chlorophenols in Environmental Samples,Using Precolumn Sample Preconcentration and Electrochemical Detection

Abstract

A HPLC method has been developed for trace analysis of chlorophenols in the 0.2–2 ppb range from spiked water samples. Simple liquid-liquid extraction followed by on-line preconcentration of total mono- and dichlorophenols has been performed using a divinylbenzene-styrene copolymeric sorbent (PRP₁) as packing material for the precolumn. The chlorophenols have been eluted from the precolumn on an analytical column (5μm LiChrosorb RP-18, 12.5 cm × 4 mm) by use of a switching valve system followed by separation. Detection was carried out with an electrochemical detector. The linearity of the detector response has been proved over two orders of magnitude. The detection limit of chlorophenols by means of the electrochemical method is in the lower picogram range. The recoveries of the isomeric chlorophenols from spiked river water samples having initial concentrations of 2ppb are usually 70–90%. The procedure has been applied to drinking water and river water.     

Low-level calibration study for a new ion chromatographic column to determine borate in deionized water

In the semiconductor industry, there is interest in determining borate at sub-ppb levels in ultrapure water, since borate is an early breakthrough ion from ion-exchange resin beds. Although dissolved silica is the most common species currently used to monitor the breakdown of the deionization systems, it is thought that borate probably breaks through earlier than silicate. To be of use as an early-warning indicator, borate must be determined at ppt levels. This paper discusses benchtop results with several new column products designed to deliver low-ppt detection limits for boron as borate. The system uses a prototype borate-specific concentrator column that is coupled to an ion-exclusion separator and suppressed-conductivity detection. The acidic eluent, containing mannitol, quantitatively elutes the borate from the concentrator. The analytical separation is performed using a specially designed ion-exclusion column. Data presented are from two multilevel calibration studies. Included is a discussion of detection-limit calculations and recommended formats for reporting results.     

Pre‐concentration of trace amount of bisphenol A in water samples by palm leaf ash and determination with high‐performance liquid chromatography

Palm leaf ash was characterized and used as low‐cost adsorbent for solid‐phase extraction and preconcentration of bisphenol A (BPA) in real water samples. Analysis of BPA was carried out using HPLC involving Eurospher 100–5‐C₁₈ (25 cm × 4.5 mm, particle size 5 μm) column and water–acetonitrile (40:60, v/v) as mobile phase. The adsorption was achieved quantitatively at a pH of 6 with elution by 3 mL acetonitrile. The limits of detection and enrichment factor were 0.02 μg L^?1 and 333, respectively. Under optimum conditions the relative standard deviation (RSD) was 2% (n = 10). Comparison of qualification criteria of presented preconcentration procedure with other research indicated that palm leaf ash adsorbent was better than many of the adsorbents in terms of cost and reusability. Also, the limit of detection, precision and enrichment factor were comparable and even better than the previously reported methods. Finally, the efficiency of method was computed by determination of trace amounts of BPA in sea, river, mineral and tap waters with recoveries of 93.3–105.5% and RSDs of 0.61–3.12%.. Briefly, the developed solid‐phase extraction and Preparative layer chromatography (PLC) methods may be used for bisphenol A monitoring in any environmental water sample. Copyright © 2016 John Wiley & Sons, Ltd.     

三相中空纤维膜液相微萃取-高效液相色谱法测定水中痕量双酚A

建立了三相中空纤维膜液相微萃取-高效液相色谱(HF-LPME-HPLC)方法,用于分析测定水中痕量双酚A的含量.设计了三相中空纤维膜液相微萃取系统,优化的HP-LPME最佳萃取条件为:萃取剂为正辛醇,接受相NaOH浓度为0.09 mol/L,样品溶液pH=4.0,NaC1加入量为30 g/L,搅拌速度为900 r/min,萃取时间为60 min.萃取后取20 μL接受相进行色谱分析.在最佳萃取条件下,方法的线性范围为0.5～200 μg/L(r＞ 0.999),检出限(信噪比为3)为0.2 μg/L;富集因子为241;方法RSD＜3.2％ (n=3).在实际环境水样中添加5,20和50μg/L的双酚A标准物质,加标平均回收率为92.8％～101.9％.表明本方法可用于水中痕量双酚A的快速准确测定.     

Continuous solid-phase extraction and preconcentration of bisphenol A in aqueous samples using molecularly imprinted columns

A bisphenol A (BPA) molecularly imprinted polymer, the composition of which was optimised using a chemometric approach, has been applied to the selective preconcentration of the template from aqueous samples. The selectivity of the polymer toward BPA and related compounds was evaluated chromatographically. The BPA-imprinted polymer was packed in a column and used for continuous on-column solid-phase extraction (MISPE) of aqueous samples followed by subsequent analysis by HPLC with fluorescence detection of the eluted fractions. The composition of the washing solvent applied in the MISPE procedure was optimised to favour the specific interactions of the MIP with BPA and to remove the non-selectively bound matrix components. The MISPE method has proven to be effective for selective preconcentration of BPA in aqueous samples (recoveries >84% obtained in the eluate for 10–100 mL sample volumes) enabling detection and quantification limits of 1.0 and 3.3 ng mL^–1, respectively (based on 25 mL sample size). Analytical recoveries were between 92 and 101% for river water samples spiked with known amounts of BPA (30, 60, and 80 ng mL^–1); relative standard deviations (RSD) were lower than 5.0%.     

Development and validation of an LC‐MS/MS method for simultaneous quantitative analysis of free and conjugated bisphenol A in human urine

Bisphenol A (BPA) is an environmental endocrine‐disrupting chemicals that is widely used in common consumer products. There is an increasing concern regarding human exposure to BPA owing to the potential adverse effects associated with its estrogenic activity. For assessing environmental exposure to BPA, it is essential to have a sensitive, accurate and selective analytical method, especially one that can detect low BPA levels in complex sample matrices. In this study, we developed and validated an accurate, sensitive, and robust liquid chromatography–tandem mass spectrometry method for simultaneous quantification of free BPA and BPA β‐d ‐glucuronide (BPA‐gluc) concentrations in human urine with only a single injection. Calibration curves were linear over a concentration range of 1–100 ng/mL for BPA and 10–1000 ng/mL for BPA‐gluc. The levels of the analytes were determined quantitatively with HPLC/ESI‐MS/MS by using negative electrospray ionization in the select ion monitoring mode and a pentaflouraphenyl propyl column. The validated method was applied to the analysis of spot urine specimens collected from randomly selected healthy human subjects. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of urinary free cortisol by high performance liquid chromatography with sulphuric acid-ethanol derivatization and column switching.

A rapid and highly sensitive determination method for urinary free cortisol has been developed using reversed phase high performance liquid chromatography (HPLC) with a precolumn for sulphuric acid-ethanol fluorescence derivatization and column switching. Urinary cortisol, eluted from the octadecylsilane-bonded silica (ODS) minicolumn with 90% aqueous ethanol, was derivatized with the addition of sulphuric acid only at ambient temperature. Cortisol derivatives injected directly onto the ODS precolumn were purified on-line. After switching the columns, the cortisol derivative was separated on an ODS analytical column with a retention time of 15.3 min and monitored at an emission wavelength of 520 nm (exitation wavelength of 365 nm) to decrease the detection limit to 0.26 microgram/dL (signal-to-noise ratio = 3). The automated HPLC operation resulted in good reproducibility and recovery of the stable cortisol derivative at 5 degrees C.