An improved method for simultaneous analysis of steroid and phenolic endocrine disrupting chemicals in biological samples

An improved method was developed for the simultaneous determination of eight steroid and phenolic endocrine disrupting chemicals, such as oestrone (E1), 17β-oestradiol (E2), oestriol (E3), 17α-ethynylestradoil (EE2), 4-nonylphenol (4-NP), bisphenol A (BPA), 4-tert-octylphenol (4-t-OP) and 4-cumylphenol (4-CP), in biological samples. The optimal extraction and clean-up procedures were investigated using microwave-assisted extraction (MAE), automated gel permeation chromatography (GPC) and solid phase extraction (SPE). As a consequence, the most efficient extraction was achieved by using MAE with methanol as solvent at an extraction temperature of 110°C for 20?min. The clean-up of extracts was carried out by GPC on a Biobeads S-X3 column with cyclohexane/ethyl acetate (1:1, v/v) as mobile phase. Target compounds were eluted in the fraction from 7–14?min retention time. Moreover, the cleanest extracts were obtained by solid phase extraction with C-18 cartridges after the elution with 15?mL ethyl acetate. The final sample extracts were derivatised using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) (1% trimethylchlorosilane, TMCS) as derivatisation reagent with pyridine as the solvent. Quantification was performed by gas chromatography-mass spectrometry (GC-MS) with electron ionisation (EI) and selected ion monitoring (SIM) mode. The method was validated by spiked samples which showed good recovery and reproducibility. The overall recoveries ranged between 55.1% and 100.6%, with relative standard deviations (RSD) of 2.3–12.7% for the entire procedure. Method detection limits (MDL) ranged from 0.3 to 0.7?ng?g^?1 dry weight (dw). Performance of the method was demonstrated by its application on tissues from fish exposed to high concentration of EDCs in the laboratory. The developed method is a promising approach for the analysis of steroid and phenolic endocrine disrupting chemicals in various biological samples.     

Sample Preparation Techniques—An Important Part in Trace Element Analysis for Environmental Research and Monitoring

Abstract

For the determination of minute amounts of elements in environmental samples combined analytical procedures are frequently employed. The combination of suitable sample preparation techniques with adequate detection methods lead to powerful analytical procedures. Decomposition methods are an important part of combined procedures for the determination of trace elements in solid samples. After a short summary of the potential sources for systematic errors two new decomposition methods are described that are suitable for the ashing of organic environmental samples. In one method the organic sample is ashed in a high-frequency excited oxygen plasma. The second method is a high pressure decomposition that permits mineralization of the sample in sealed quartz vessels with nitric acid at temperatures up to 320°C.

For both methods the ratio of sample weight to decomposition reagents is comparatively high. This makes these methods in combination with adequate detection methods suitable for the determination of elements at very low concentrations.

X-ray fluorescence spectrometry combined with adequate preconcentration methods is very well suited for the simultaneous determination of trace elements. Following a critical evaluation of various preconcentration techniques the analytical characteristics of filter paper with immobilized complexing agents are described. Particular emphasis is given to filter papers with dithiocarbamates as chelating group.     

Application of Capillary Zone Electrophoresis for the Analysis of Low Molecular Weight Organic Acids in Environmental Samples

Abstract

The applicability of a recently developed capillary zone electrophoretic (CZE) method for the determination of low molecular weight (LMW) organic acids in water was tested on five types of environmental samples (rainwater, water extract from peat, and soil water from two polluted sites). A full baseline resolved separation of fourteen commonly found LMW carboxylic acids in natural waters (malonic, oxalic, fumaric, maleic, formic, succinic, tartaric, glutaric, adipic, acetic, propionic, butyric, valeric and citric acids), was achieved within eight minutes. The limits of detection (2 X noise) were in the ranges 90–200 μg/l and 0.5 – 5 μg/l for hydrodynamic and electrokinetic injection, respectively. Two different CZE systems, a Waters Quanta 4000 and a Hewlett Packard HP ^3DCE system, were used and their performance compared.     

Flame Photometric Determination of Submicrogram Quantities of Boron

A procedure for the determination of submicrogram amounts of boron in aqueous solutions is described. The method is based on measuring the chemiluminescence of the molecular species BO_x in either an air/hydrogen or air/acetylene flame. Detection limits obtained with these flames were 0.004 and 0.06 ppm, respectively. Potential interferences may be removed by ion-exchange chromatography. The procedure is applicable to the determination of boron in potable waters.     

Methylmercury and inorganic mercury determination in blood by using liquid chromatography with inductively coupled plasma mass spectrometry and a fast sample preparation procedure

Despite the necessity to differentiate chemical species of mercury in clinical specimens, there are a limited number of methods for this purpose. Then, this paper describes a simple method for the determination of methylmercury and inorganic mercury in blood by using liquid chromatography with inductively coupled mass spectrometry (LC-ICP-MS) and a fast sample preparation procedure. Prior to analysis, blood (250 μL) is accurately weighed into 15-mL conical tubes. Then, an extractant solution containing mercaptoethanol, l-cysteine and HCl was added to the samples following sonication for 15 min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 5 min on a C18 reverse-phase column with a mobile phase containing 0.05% (v/v) mercaptoethanol, 0.4% (m/v) l-cysteine, 0.06 mol L⁻¹ ammonium acetate and 5% (v/v) methanol. The method detection limits were found to be 0.25 μg L⁻¹ and 0.1 μg L⁻¹ for inorganic mercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). The proposed method was also applied to the speciation of mercury in blood samples collected from fish-eating communities and from rats exposed to thimerosal. With the proposed method there is a considerable reduction of the time of sample preparation prior to speciation of Hg by LC-ICP-MS. Finally, after the application of the proposed method, we demonstrated an interesting in vivo ethylmercury conversion to inorganic mercury.     

Development of a broad selective molecularly imprinted polymers-based solid phase extraction of contraceptive drug levonorgestrel from water samples

A broad selective molecularly imprinted polymers-based solid phase extraction (MISPE) for levonorgestrel (LNG) from water samples was developed. Using LNG as a template molecule, acrylamide (AA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as linking agent and bulk polymerisation as a synthetic method, the molecularly imprinted polymers (MIPs) were synthesised and characterised. The MIPs displayed a high specific rebinding for LNG with the imprinting factor of 3.71. The Scatchard analysis showed that there was at least one class of binding site for LNG formed in the MIPs with the dissociation constant of 8.046?µg?mL^?1. The results of selectivity testing indicated that the MIPs also exhibited high cross-reactivity with structurally related compounds (estrone, methylprednisolone and ethinyl estradiol), but no recognition with non-structurally related compound (indomethacin), suggesting that the MIPs could be used as a broad recognition absorbent. MISPE column was prepared by packing MIPs particles into a common SPE cartridge. The MISPE extraction conditions including loading, washing and eluting solutions were carefully optimised. Water samples spiked with LNG were extracted by MISPE column and detected by high-performance liquid chromatography. The recoveries were found to be 79.97?～?132.79% with relative standard deviations (RSD) of 1.92?～?10.43%, indicating the feasibility of the prepared MIPs for LNG extraction.     

Microextraction by packed sorbent and liquid chromatography–tandem mass spectrometry as a tool for quantification of peptides in plasma samples: determination of sensory neuron‐specific receptors agonist BAM8‐22 and antagonist BAM22‐8 in plasma samples

Microextraction by packed sorbent (MEPS) is a miniaturized, solid‐phase extraction (SPE) technique that works online with gas chromatography (GC) and liquid chromatography (LC). Not only is the automation process with MEPS advantageous, but the much smaller volumes of the samples, solvents and dead space in the system also provide other significant advantages such as the speed and the simplicity of the sample preparation process. In this study MEPS has been evaluated for quantification of sensory neuron‐specific receptors agonist (BAM8‐22). Owing to the instability of BAMs, the focus was on fast extraction and determination of the peptide online using LC‐MS/MS. Sorbents such as C2, C8 and ENV+ (hydroxylated polystyrene–divinylbenzene copolymer) were investigated in the present study. MEPS‐C8 gave the best results compared with C2 and ENV and it was used for the method validation. The calibration curve was obtained within the concentration range of 20.0–3045 nmol/L in plasma. The regression correlation coefficients for plasma samples were ≥0.99 for all runs (n = 6). The between‐batch accuracy and precision for BAM8‐22 ranged from ?13 to ?2.0% and from 4.0 to 14%, respectively. Additionally, the accuracy and precision for BAM22‐8 ranged from ?13 to 7.0% and from 3.0 to 12%, respectively. The present method was used for pharmacokinetic studies for BAMs in plasma samples. Copyright © 2012 John Wiley & Sons, Ltd.     

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography-DAD detection for the determination of sulfonylurea herbicides in water samples

A new method for the determination of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in water samples was developed by dispersive liquid–liquid microextraction coupled with high performance liquid chromatography-diode array detector. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction and disperser solvent, extraction time and salt addition, were investigated and optimised. Under the optimum conditions, the enrichment factors were in the range between 102 and 216. The linearity of the method was obtained in the range of 1.0–100 ng mL^?1 with the correlation coefficients (r) ranging from 0.9982 to 0.9995. The method detection limits were 0.2–0.3 ng mL^?1. The proposed method has been successfully applied to the analysis of target sulfonylurea herbicides in river, stream and well water samples with satisfactory results.     

Microwave-assisted solid phase extraction prior to ICP-MS determination of Pd and Pt in environmental and biological samples

A sensitive and selective microwave-assisted solid phase extraction procedure coupled to inductively coupled plasma-mass spectrometry (ICP-MS) is proposed for palladium (Pd) and platinum (Pt) quantification in environmental and biological samples. Pd and Pt were quantitatively retained on commercial thioureido propyl functionalised silica gel packed inside a home-made glass microcolumn, and later eluted with 0.5% thiourea solution under microwave irradiation, followed by ICP-MS determination. The main variables affecting the procedural stages (i.e., sorption and desorption) and ICP-MS determination were optimised. The best conditions found were: (a) sorption: sample acidity, 1?M HCl; sample flow rate, 3?mL?min^?1; (b) desorption: microwave radiation, power 800?W; eluent concentration, 0.5% thiourea; eluent flow rate, 0.5?mL?min^?1; (c) ICP-MS determination: nebuliser feeding, free aspiration (0.3?mL?min^?1); internal standard, Rh (5?µg?L^?1). Analyte recoveries were higher than 90% and concentration factors up to 90 and 92 were achieved for Pd and Pt, respectively. Depending on the conditions, the methodological limits of detection were down to 0.2?ng?L^?1 for both analytes and repeatability, expressed as RSD%, varied between 1.3 and 11.0%. A method selectivity evaluation showed that most of the ICP-MS interferents were either quantitatively separated or more than 86% eliminated, except for Cu (elimination efficiency around 30%). Finally, the method was successfully used to determine Pd in certified reference materials (i.e. human urine and serum) and Pd and Pt in PM₁₀ airborne particulate matter fractions.     

In-tube solid-phase microextraction coupled by in valve mode to capillary LC-DAD: Improving detectability to multiresidue organic pollutants analysis in several whole waters

A simple and fast capillary chromatographic method has been developed to identify and quantify organic pollutants at sub-ppb levels in real water samples. The major groups of pesticides (organic halogens, organic phosphorous, and organic nitrogen compounds), some hydrocarbons (polycyclic aromatic hydrocarbons), phthalates and some phenols such as phenol and bisphenol A (endocrine disruptors) were included in this study. The procedure was based on coupling, in-tube solid-phase microextraction (IT-SPME) by using a conventional GC capillary column (95% methyl–5% phenyl substituted backbone, 80 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve to capillary liquid chromatography with diode array detection. A comparative study between the IT-SPME manifold and a column-switching device using a C₁₈ column (35 mm × 0.5 mm i.d., 5 μm particle size) has been performed. The IT-SPME procedure was optimal, it allows reaching limits of detection (LODs) between 0.008 and 0.2 μg/L. No matrix effect was found and recoveries between 70 and 116% were obtained. The precision of the method was good, and the achieved intra- and inter-day variation coefficients were between 2 and 30%. This procedure has been applied to the screening analysis of 28 compounds in whole waters from several points of the Mediterranean coast (Valencia Community, Spain).