Development of sensitive high-performance liquid chromatography with fluorescence detection using 4-(4,5-diphenyl-1H-imidazol-2-yl)-benzoyl chloride as a labeling reagent for determination of bisphenol A in plasma samples

Challenges in the Analytical Preparation of a Biological Matrix in Analyses of Endocrine-Disrupting Bisphenols

Endocrine-disrupting chemicals (EDCs) are xenobiotics presented in a variety of everyday products that may disrupt the normal activity of hormones. Exposure to bisphenol A as EDC at trace and ultra-trace levels is associated with adverse health effects, and children are recognized as the most vulnerable group to EDCs exposure. In this review, a summary is presented of up-to-date sample preparation methods and instrumental techniques applied for the detection and quantification of bisphenol A and its structural analogues in various biological matrices. Biological matrices such as blood, cell-free blood products, urine, saliva, breast milk, cordial blood, amniotic and semen fluids, as well as sweat and hair, are very complex; therefore, the detection and later quantification of bisphenols at low levels present a real analytical challenge. The most popular analytical approaches include gas and liquid chromatography coupled with mass spectrometry, and their enhanced reliability and sensitivity finally allow the separation and detection of bisphenols in biological samples, even as ultra-traces. Liquid/liquid extraction (LLE) and solid-phase extraction (SPE) are still the most common methods for their extraction from biological matrices. However, many modern and environmentally safe microextraction techniques are currently under development. The complexity of biological matrices and low concentrations of analytes are the main issues for the limited identification, as well as understanding the adverse health effects caused by chronical and ubiquitous exposure to bisphenols and its analogues.

[Pharmaceutical analysis of chemicals related with daily life products for safe and secure]

An association between exposure to trace hazardous chemicals such as endocrine disrupting chemicals and an increased incidence of human endocrine disease might be continued to study. The accurate and sensitive analytical methods for determination of various chemicals in human biospecimen such as urine, blood and breast milk have been studied by techniques including chromatography. In order to obtain the safe and secure life, the pharmaceutical analytical approaches might be applicable with the hopes of realizing scientific risk assessment of the chemicals derived from daily life products as regulatory sciences.

Study on the migration of bisphenol-A from baby bottles by stir bar sorptive extraction-thermal desorption-capillary GC-MS

Migration of bisphenol-A (BPA), the principal monomer of polycarbonate (PC) baby bottles, was investigated using an aqueous migration simulant. BPA was determined in 200 mL water samples using stir bar sorptive extraction (SBSE) after in situ derivatization with acetic acid anhydride followed by thermal desorption (TD)-capillary GC-MS. The concentration of BPA was calculated using the deuterated internal standard d6-BPA. Calibration for BPA was shown to be linear in a concentration range from 1 ng/L to 10 microg/L with a correlation coefficient >0.99. The LOD for BPA (as acetate) was 0.12 ng/L and LOQ 0.40 ng/L (ppt). PC bottles were heated in a water bath and in a microwave oven at four different temperatures (37, 53, 65, and 85 degrees C). The higher the temperature, the more the BPA was released, and after a few heating cycles, the released concentrations became constant. At normal use, i.e. at 37 degrees C, concentrations are ca. 10 ng/L. No significant difference was noted between water bath and microwave heating illustrating that migration of BPA is mainly temperature dependent.

Automated on-line liquid chromatography–photodiode array–mass spectrometry method with dilution line for the determination of bisphenol A and 4-octylphenol in serum

A novel on-line liquid chromatography-photodiode array detection-mass spectrometry (LC-DAD-MS) system was established with restricted-access media (RAM) pre-column and dilution line combined with a column-switching valve. The serum samples were injected directly onto pre-column under diluted condition by dilution line. After elution of proteins in the serum, the analytes were backflushed onto an ODS analytical column using a six-port column-switching device. The influence of the composition of the mobile phase, for instance, organic modifer, ionic strength, pH, dilution times and the rotation time of the switching valve have been investigated using bisphenol A (BPA) and 4-octyphenol (4-OP) as analytes. The evaluations for peak responses and sensitivity were conducted by MS, and proteins were removed by RAM-column with DAD monitoring at 280 nm. The peak shape was improved by adding a dilution line, especially in the case of large volume injection (LVI), which increased the sensitivity of the analysis. The selective and sensitive quantification of BPA and 4-OP in serum sample could be finished within 25 min. The method had linearity in the range 0.1-500 ng/mL with a limit of quantification for BPA and 4-OP of 0.1 and 0.5 ng/mL, respectively. The recoveries were in the range of 80-101% with less than 9.0% RSDs. This on-line LC-MS method demonstrates potential application to evaluating the exposure and risk of BPA and 4-OP in human.

Analysis of environmental biomarkers in urine using an electrochemical detector

Phenols are present in the environment and are prevalent in human populations, as environmental contaminants, dietary components, or their metabolites. Many are potential endocrine-altering agents. Currently available methods analyze single components or single families of chemicals as biomarkers of exposure. In order to assess multiple biologically relevant exposures to such substances, we evaluated the feasibility of determining several phenols simultaneously in urine, using an electrochemical detector (ECD) in combination with high performance liquid chromatography (LC). Based on reported analyses in the literature and the ECD response, we selected four xenobiotic residues, including three phytoestrogens (enterolactone, daidzein, and genistein) and bisphenolA [BPA]. These compounds had detection limits below 1 microg/L in urine using the cleanup procedure (glucuronidase hydrolysis and C18 column) and the urine volume (2 mL) we employed. As a pilot study to demonstrate the method's utility, we determined urinary enterolactone, daidzein, genistein and BPA in samples from nine children and 24 adults.

Size-exclusion flow extraction of bisphenol A in human urine for liquid chromatography–mass spectrometry

We report an approach for assessing human exposure to bisphenol A (BPA), which involves measuring the glucuronide in urine sample that were subjected to a novel size-exclusion flow extraction method. The present approach includes the addition of 13C(12)-BPA, enzymatic deconjugation, and the proposed sample preparation method. The sample solution is separated and detected by liquid chromatography-mass spectrometry (LC-MS). The following are used for the LC-MS: a reversed-phase separation column, electrospray ionization (ESI), negative mode, and single ion monitoring (SIM) with m/z 227 for BPA and m/z 239 for 13C(12)-BPA. The detection limit was 0.1 ng ml(-1) and the calibration curves (0.45-90 ng ml(-1)) had correlation coefficients exceeding 0.999. To urine samples requiring deglucuronidation, beta-glucuronidase was added followed by incubation at 37 degrees C for 3 h. After the enzymatic treatment, the samples were subjected to the extraction in the reversed-phase (ODS) and size-exclusion (GPC) modes. It was possible to extract, clean up and concentrate BPA in a single run of 20 min by means of the novel extraction method. The method enables the determination of standards and may be applied to the detection of trace amounts of BPA in human urine samples.

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.

Lophine derivatives as versatile analytical tools

Lophine (2,4,5-triphenylimidazole) derivatives as versatile analytical tools in biomedical sciences are described. Chemiluminescence (CL) and fluorescence (FL) properties of the lophine derivatives are first demonstrated including the CL reaction mechanism, effects of substituents on CL yields, FL spectral behaviors, etc. Next, analytical applications to the determination of metal ions such as cobalt (II) and chromium (VI) are discussed. Finally, the application studies of lophine derivatives as CL and FL reagents for the determination of organic substances in biological materials are presented. Among the derivatives, 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI) and 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) are studied, with their excellent properties as labeling reagents for fatty acids and amines and/or phenols, respectively, in high-performance liquid chromatography. The utility of boronic acid derivatives as CL enhancers is also discussed in this review.

Measurement of bisphenol A in human urine using liquid chromatography with multi-channel coulometric electrochemical detection

Environmental exposure levels of bisphenol A (BPA) in human were investigated by measuring BPA glucuronide (BPA-G) in urine. After enzymatic hydrolysis of glucuronide substances in urine, BPA was extracted with diethyl ether. The extract was analyzed using a column-switching HPLC system employing a C(8) and a C(18) column with multi-channel coulometric electrochemical detection (ECD). The sensitivity and selectivity provided with redox mode of ECD allowed measurement of low level BPA in hydrolyzed urine. The quantification limit of BPA-G in urine was 0.2 ng/ml. RSDs of the intraassay precision were less than 3% and recoveries of the method were over 96% when analyzing BPA spiked urine samples (1.0 and 10 ng/ml). In a group of 48 women students, the level of BPA-G in urine ranged from 0.2 to 19.1 ng/ml with a median concentration of 1.2 ng/ml. Normalized against urinary creatinine, BPA-G ranged from 0.1 to 11.9 ng/mg creatinine with a median of 0.77 ng/mg creatinine.

Metabolism and kinetics of bisphenol a in humans at low doses following oral administration

Bisphenol A is a widely used industrial chemical with many potential sources of human exposure. Bisphenol A is a weak estrogen and has been implicated as an "endocrine disruptor". This term is used for a variety of chemicals encountered in the environment which have estrogenic activity. It has been postulated that human exposure to these chemicals may elicit unwanted estrogenic effects in humans such as reduced fertility, altered development and cancer. Up to now the body burden of bisphenol A in humans is unknown. Therefore, we investigated the metabolism and toxicokinetics of bisphenol A in humans exposed to low doses since systemic bioavailability has a major influence on possible estrogenic effects in vivo. Human subjects (three males and three females, and four males for detailed description of blood kinetics) were administered d(16)-bisphenol A (5 mg). Blood and urine samples were taken in intervals (up to 96 h), metabolites formed were identified by GC/MS and LC-MS/MS and quantified by GC/MS-NCI and LC-MS/MS. d(16)-Bisphenol A glucuronide was the only metabolite of d(16)-bisphenol A detected in urine and blood samples, and concentrations of free d(16)-bisphenol A were below the limit of detection both in urine (6 nM) and blood samples (10 nM). d(16)-Bisphenol A glucuronide was cleared from human blood and excreted with urine with terminal half-lives of less than 6 h; the applied doses were completely recovered in urine as d(16)-bisphenol A glucuronide. Maximum blood levels of d(16)-bisphenol A glucuronide (approximately 800 nM) were measured 80 min after oral administration of d(16)-bisphenol A (5 mg). The obtained data indicate major species differences in the disposition of bisphenol A. Enterohepatic circulation of bisphenol A glucuronide in rats results in a slow rate of excretion, whereas bisphenol A is rapidly conjugated and excreted by humans due to the absence of enterohepatic circulation. The efficient glucuronidation of bisphenol A and the rapid excretion of the formed glucuronide result in a low body burden of the estrogenic bisphenol A in humans following oral absorption of low doses.