Analysis of acrylamide in food products by in-line preconcentration capillary zone electrophoresis

Two in-line preconcentration capillary zone electrophoresis (CZE) methods (field amplified sample injection (FASI) and stacking with sample matrix removal (LVSS)) have been evaluated for the analysis of acrylamide (AA) in foodstuffs. To allow the determination of AA by CZE, it was derivatized using 2-mercaptobenzoic acid. For FASI, the optimum conditions were water at pH > or = 10 adjusted with NH3 as sample solvent, 35 s hydrodynamic injection (0.5 psi) of a water plug, 35 s of electrokinetic injection (-10 kV) of the sample, and 6s hydrodynamic injection (0.5 psi) of another water plug to prevent AA removal by EOF. In stacking with sample matrix removal, the reversal time was found to be around 3.3 min. A 40 mM phosphate buffer (pH 8.5) was used as carrier electrolyte for CZE separation in both cases. For both FASI and LVSS methods, linear calibration curves over the range studied (10-1000 microg L(-1) and 25-1000 microg L(-1), respectively), limit of detection (LOD) on standards (1 microg L(-1) for FASI and 7 microg L(-1) for LVSS), limit of detection on samples (3 ng g(-1) for FASI and 20 ng g(-1) for LVSS) and both run-to-run (up to 14% for concentration and 0.8% for time values) and day-to-day precisions (up to 16% and 5% for concentration and time values, respectively) were established. Due to the lower detection limits obtained with the FASI-CZE this method was applied to the analysis of AA in different foodstuffs such as biscuits, cereals, crisp bread, snacks and coffee, and the results were compared with those obtained by LC-MS/MS.     

Different strategies for the preconcentration and separation of parabens by capillary electrophoresis

Several strategies, namely, large volume sample stacking (LVSS), field‐amplified sample injection (FASI), sweeping, and in‐line SPE‐CE, were investigated for the simultaneous separation and preconcentration of a group of parabens. A BGE consisting of 20 mM sodium dihydrogenphosphate (pH 2.28) and 150 mM SDS with 15% ACN was used for the separation and preconcentration of the compounds by sweeping, and a BGE consisting of 30 mM sodium borate (pH 9.5) was used for the separation and preconcentration of the compounds by LVSS, FASI, and in‐line SPE‐CE. Several factors affecting the preconcentration process were investigated in order to obtain the maximum enhancement of sensitivity. The LODs obtained for parabens were in the range of 18–27, 3–4, 2, and 0.01–0.02 ng/mL, and the sensitivity evaluated in terms of LODs was improved up to 29‐, 77‐, 120‐, and 18 400‐fold for sweeping, LVSS, FASI, and in‐line SPE‐CE, respectively. These preconcentration techniques showed potential as good strategies for focusing parabens. The four methods were validated with standard samples to show the potential of these techniques for future applications in real samples, such as biological and environmental samples.     

场放大样品进样-压力辅助毛细管区带电泳测定饮用水中的百草枯

1 引 言 百草枯属有机杂环类季铵盐除草剂,由于它具有优良的除草效果,已广泛应用于多种作物的杂草防治.百草枯具有极强的水溶性,极易迁移至水体环境中,从而对饮用水的质量安全构成潜在威胁.目前,百草枯的残留检测方法主要有分光光度法[1]、液相色谱-质谱联用法[2]、气相色谱质谱联用法[3]和毛细管电泳法(CE) [4～6].采用分光光度法测定百草枯,不仅操作繁琐费时,而且灵敏度低.采用气相色谱法测定百草枯,通常需要衍生化,应用较少[3].采用液相色谱法测定百草枯,通常需要在流动相中添加离子对试剂[2].毛细管电泳具有分离效率高,分析速度快等优点,已被广泛用于水样中百草枯残留的测定.然而,毛细管电泳灵敏度不高,极大地限制了其在实际样品分析中的应用.场放大样品进样(FASI)是一种简单有效的在线富集方法,其富集倍数可达1000倍[7],可有效提高毛细管电泳技术的灵敏度,因此应用较为广泛.本实验建立了场放大样品进样-压力辅助毛细管区带电泳法(CZE),用于测定饮用水中百草枯的残留量.     

Determination of cyanobacterial cyclic peptide hepatotoxins in drinking water using CE

Four cyanobacteria hepatotoxins microcystin LR, microcystin RR, microcystin YR, and nodularin were simultaneously determined in drinking water using CZE and MEKC coupled with UV detection. The toxins were satisfactorily separated in both CZE and MEKC modes. Detection limits were in the range of 0.82–4.81 μg/mL, with R² values of 0.994–0.999. The linearity range tested for the standards was 5–100 μg/mL and RSD percentages were in the range of 1.0–2.5% for retention time and 3.0–10.2% for peak area. When a known amount of standard was spiked into a known volume of water and extracted, recoveries were 90.3% (RR), 101.5% (nodularin), 90.6% (YR), and 88.2% (LR). The use of SPE enabled cleanup and pre‐concentration of a real sample to achieve a 100‐fold concentration factor. Detection limits after SPE of the real sample spiked with microcystins were 0.090 μg/L (RR), 0.076 μg/L (YR), and 0.110 μg/L (LR), with RSD percentage values of 9.9–11.7% for peak area and 2.2–3.3% for retention time. The technique developed provides an alternative method for determining microcystins at levels of concentration that will be able to meet WHO drinking water guidelines for microcystins.     

Enhanced sensitivity and resolution for the analysis of paralytic shellfish poisoning toxins in water using capillary electrophoresis with amperometric detection and field‐amplified sample injection

The profiling of the most lethal paralytic shellfish poisoning toxins (PSTs) in freshwater has increased the need to establish an alternative analytical method with high sensitivity and resolution. In this paper, a coupling technique of field‐amplified sample injection (FASI) and CE with end‐column amperometric detection (CE‐AD) was developed to improve the detection sensitivity and separation of PSTs by electrokinetically injecting a water plug of analytes to the capillary filled with a high‐conductivity BGE. Parameters affecting FASI and CE process were carefully adjusted to achieve the highest response and resolution. Separation selectivity for PSTs, especially for the analogues and epimers, was greatly enhanced by using 40 mM Britton–Robinson buffer (pH 9.5) as BGE, which altered the EOF and mobility of the analytes that interacted with polyborate ions. Satisfactory linear relationship between peak current and concentration of toxins were gained over a wide range of 1.95–254 μg/L. The detection limits (S/N = 3) for five PSTs ranged from 0.63 to 3.11 μg/L, which are below the health alert level in drinking water. In comparison with the up‐to‐date reporting chromatographic methods, the FASI‐CE‐AD method was simple, low‐cost, selective, and sensitive enough for direct quantification of PSTs at very low levels, implying a potential for screening and monitoring of PSTs in surface waters.     

Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with field‐amplified sample injection in capillary electrophoresis for the determination of beta(2)‐agonists in bovine urine

Dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME–SFO) was for the first time combined with field‐amplified sample injection (FASI) in CE to determine four β₂‐agonists (cimbuterol, clenbuterol, mabuterol, and mapenterol) in bovine urine. Optimum BGE consisted of 20 mM borate buffer and 0.1 mM SDS. Using salting‐out extraction, β₂‐agonists were extracted into ACN that was then used as the disperser solvent in DLLME–SFO. Optimum DLLME–SFO conditions were: 1.0 mL ACN, 50 μL 1‐undecanol (extraction solvent), total extraction time 1.5 min, no salt addition. Back extraction into an aqueous solution (pH 2.0) facilitated direct injection of β₂‐agonists into CE. Compared to conventional CZE, DLLME–SFO–FASI–CE achieved sensitivity enhancement factors of 41–1046 resulting in LODs in the range of 1.80–37.0 μg L^?1. Linear dynamic ranges of 0.15–10.0 mg L^?1 for cimbuterol and 15–1000 μg L^?1 for the other analytes were obtained with coefficients of determination (R²) ≥ 0.9901 and RSD% ≤5.5 (n = 5). Finally, the applicability of the proposed method was successfully confirmed by determination of the four β₂‐agonists in spiked bovine urine samples and accuracy higher than 96.0% was obtained.     

Field‐amplified sample injection combined with capillary electrophoresis for the simultaneous determination of five chlorophenols in water samples

A sensitive method of CZE‐ultraviolet (UV) detection based on the on‐line preconcentration strategy of field‐amplified sample injection (FASI) was developed for the simultaneous determination of five kinds of chlorophenols (CPs) namely 4‐chlorophenol (4‐CP), 2‐chlorophenol (2‐CP), 2,4‐dichlorophenol (2,4‐DCP), 2,4,6‐trichlorophenol (2,4,6‐TCP), and 2,6‐dichlorophenol (2,6‐DCP) in water samples. Several parameters affecting CZE and FASI conditions were systematically investigated. Under the optimal conditions, sensitivity enhancement factors for 4‐CP, 2‐CP, 2,4‐DCP, 2,4,6‐TCP, and 2,6‐DCP were 9, 27, 35, 43, and 43 folds, respectively, compared with the direct CZE, and the baseline separation was achieved within 5 min. Then, the developed FASI‐CZE‐UV method was applied to tap and lake water samples for the five CPs determination. The LODs (S/N = 3) were 0.0018–0.019 µg/mL and 0.0089–0.029 µg/mL in tap water and lake water, respectively. The values of LOQs in tap water (0.006–0.0074 µg/mL) were much lower than the maximum permissible concentrations of 2,4,6‐TCP, 2,4‐DCP, and 2‐CP in drinking water stipulated by World Health Organization (WHO) namely 0.3, 0.04, and 0.01 µg/mL, respectively, and thereby the method was suitable to detect the CPs according to WHO guidelines. Furthermore, the method attained high recoveries in the range of 83.0–119.0% at three spiking levels of five CPs in the two types of water samples, with relative standard deviations of 0.37–8.58%. The developed method was proved to be a simple, sensitive, highly automated, and efficient alternative to CPs determination in real water samples.     

Online preconcentration by electrokinetic supercharging for separation of endocrine disrupting chemical and phenolic pollutants in water samples

Online preconcentration using electrokinetic supercharging (EKS) was proposed to enhance the sensitivity of separation for endocrine disrupting chemical (methylparaben (MP)) and phenolic pollutants (2‐nitrophenol (NP) and 4‐chlorophenol (CP)) in water sample. Important EKS and separation conditions such as the concentration of BGE; the choice of terminating electrolyte (TE); and the injection time of leading electrolyte (LE), sample, and TE were optimized. The optimum EKS‐CE conditions were as follows: BGE comprising of 12 mM sodium tetraborate pH 10.1, 100 mM sodium chloride as LE hydrodynamically injected at 50 mbar for 30 s, electrokinetic injection (EKI) of sample at –3 kV for 200 s, and 100 mM CHES as TE hydrodynamically injected at 50 mbar for 40 s. The separation was conducted at negative polarity mode and UV detection at 214 nm. Under these conditions, the sensitivity of analytes was enhanced from 100‐ to 737‐fold as compared to normal CZE with hydrodynamic injection, giving LOD of 4.89, 5.29, and 53 μg/L for MP, NP and CP, respectively. The LODs were adequate for the analysis of NP and CP in environmental water sample having concentration at or lower than their maximum admissible concentration limit (240 and 2000 μg/L for NP and CP). The LOD of MP can be suitable for the analysis of MP exists at mid‐microgram per liter level, even though the LOD was slightly higher than the concentration usually found in water samples (from ng/L to 1 μg/L). The method repeatabilities (%RSD) were in the range of 1.07–2.39% (migration time) and 8.28–14.0% (peak area).     

Electrokinetic supercharging focusing in capillary zone electrophoresis of weakly ionizable analytes in environmental and biological samples

Five non‐steroidal anti‐inflammatory drugs, naproxen, fenoprofen, ketoprofen, diclofenac and piroxicam, were separated and analyzed by electrokinetic supercharging in CZE. Three different setups of the ITP technique were assayed for the separation and preconcentration of these five non‐steroidal anti‐inflammatory drugs. For the setup that gave the best results, we evaluated the influence of different parameters on separation and preconcentration efficiency such as sample pH, concentration of the leading stacker, BGE composition, electrokinetic injection time, composition and hydrodynamic injection of the solvent plug and of the terminating stacker. In the selected setup, the BGE (10 mM Na₂B₄O₇ + 50 mM NaCl in 10% of MeOH aqueous solution) contained the leading electrolyte while the terminating electrolyte, hydrodynamically injected after the sample (50 mbar×12 s), was 50 mM of CHES. Prior to sample injection at (700 s at −2 kV) a short plug of MeOH (50 mbar ×3 s) was hydrodynamically injected. The results show that this strategy enhanced detection sensitivity 2000‐fold compared with normal hydrodynamic injection, providing detection limits of 0.08 μg/L for standard samples with good repeatability (values of relative standard deviation, %RSD < 1.03%). Method validation with river water samples and human plasma demonstrated good linearity, with detection limits of 0.9 and 2 μg/L for river water samples and human plasma samples, respectively (as well as satisfactory precision in terms of repeatability and reproducibility).     

Field amplified sample injection‐capillary zone electrophoresis for the analysis of amprolium in eggs

Veterinary medicines are widely administered to farm animals since they keep animals healthy at overcrowded conditions. Nevertheless the continuous administration of medicines to farm animals can frequently lead to the presence of residues of veterinary drugs in consumption products. Amprolium is a quaternary ammonium compound used in the treatment of coccidiosis. In this paper, a method based on CZE to analyze residues of amprolium in eggs was developed and validated for the first time. Parameters such as electrolyte type, concentration, and pH were optimized. In order to improve sensitivity, field‐amplified sample injection (FASI) was used for in‐line preconcentration after a quick and simple sample treatment based on SPE (Envi‐Carb). During method‐validation studies using egg samples, a matrix interference was found at the migration time of amprolium. This compound was identified as thiamine and confirmed by MSⁿ experiments using CEcoupled to MS (CE‐MS) with an ion‐trap mass analyzer. CZE conditions were reoptimized to separate thiamine from amprolium allowing the quantification of amprolium in eggs at concentrations down to 75 μg/kg, which are far below the MRL‐legislated values.     

Solid-phase extraction and field-amplified sample injection–capillary zone electrophoresis for the analysis of benzophenone UV filters in environmental water samples

A field-amplified sample injection–capillary zone electrophoresis (FASI-CZE) method for the analysis of benzophenone (BP) UV filters in environmental water samples was developed, allowing the separation of all compounds in less than 8 min. A 9- to 25-fold sensitivity enhancement was obtained with FASI-CZE, achieving limits of detection down to 21–59 μg/L for most of the analyzed BPs, with acceptable run-to-run and day-to-day precisions (relative standard deviations lower than 17 %). In order to remove water sample salinity and to enhance FASI sensitivity, an off-line solid-phase extraction (SPE) procedure using a Strata X polymeric reversed-phase sorbent was used and afforded recoveries up to 72–90 % for most BPs. With the combination of off-line SPE and FASI-CZE, limits of detection in the range 0.06–0.6 μg/L in a river water matrix, representing a 2,400- to 6,500-fold enhancement, were obtained. Method performance was evaluated by quantifying a blank river water sample spiked at 1 μg/L. For a 95 % confidence level, no statistical differences were observed between found concentrations and spiked concentrations (probability at the confidence level, p value, of 0.60), showing that the proposed off-line SPE-FASI-CZE method is suitable for the analysis of BP UV filters in environmental water samples at low microgram per liter levels. The method was successfully applied to the analysis of BPs in river water samples collected up- and downstream of industrialized and urban areas, and in some drinking water samples.     

Simultaneous separation and analysis of camptothecin alkaloids in real samples by large‐volume sample stacking in capillary electrophoresis

Large‐volume sample stacking (LVSS) is commonly used as an effective online preconcentration method in capillary zone electrophoresis (CZE). In this paper, the method LVSS combined with CZE has been proposed to analyze camptothecin alkaloids. Optimum separation can be achieved in the following conditions: pH 9.0; 25mm borate buffer containing 20 mm sulfobutylether‐β‐cyclodextrin and 20 mm ionic liquid 1‐ethyl‐3‐methyllimidazole l ‐lactate; applied voltage 20 kV; and capillary temperature 25 °C. The LVSS was optimized as hydrodynamic injection 4 s at 5.0 psi and the polarity switching time was 0.17 min. Under the above conditions, the analytes could be separated completely in <20 min and the detector response was increased compared with conventional hydrodynamic injection. The limits of detection were between 0.20 and 0.78 μg/L. A good linearity was obtained with correlation coefficients from 0.9991 to 0.9997. The recoveries ranged from 97.72 to 103.2% and the results demonstrated excellent accuracy. In terms of the migration time and peak area, the experiment was reproducible. The experimental results indicated that baseline separation can be obtained and this method is suitable for the quantitative determination of camptothecin alkaloids in real samples.     

Simultaneous determination of aripiprazole and its active metabolite,dehydroaripiprazole, in plasma by capillary electrophoresis combining on‐column field‐amplified sample injection and application in schizophrenia

A sensitive high‐performance CZE combining on‐column field‐amplified sample injection (FASI) has been developed for simultaneous determination of aripiprazole and its active metabolite, dehydroaripiprazole, in human plasma. A sample pretreatment by means of liquid–liquid extraction (LLE) (diethyl ether) with subsequent quantitation by FASI‐CZE was used. The separation of aripiprazole and dehydroaripiprazole was performed using a BGE containing 150 mM phosphate buffer (pH 3.5) with 40% methanol and 0.02% PVA as a dynamic coating to reduce interaction of analytes with the capillary wall. Before sample loading, a methanol plug (0.3 psi, 6 s) was injected to permit FASI for stacking. The samples were injected electrokinetically (10 kV, 30 s) to introduce sample cations and the applied voltage was 20 kV with on‐column detection at 214 nm. Several parameters affecting the separation and sensitivity of the drug and its active metabolite were studied, including reconstitution solvent, organic modifier, pH and concentration of phosphate buffer. The linear ranges of the method for test drug and its active metabolite, in plasma using amlodipine as an internal standard, were over the range 5.0–100.0 ng/mL. One female volunteer (25 years old) was orally administered a single dose of 10 mg aripiprazole (Abilify^®, Otsuka) and blood samples were drawn over a 60 h period for pharmacokinetic study. The method was also applied to monitor the concentration of aripiprazole and dehydroaripiprazole in plasma collected after oral administration of 20 or 30 mg aripiprazole (Abilify^®, Otsuka) daily at steady state in one schizophrenic patient.     

Determination of ethyl glucuronide in human serum by capillary zone electrophoresis and an immunoassay

Ethyl glucuronide (EtG) is a marker of recent alcohol consumption. For the optimization of the analysis of EtG by CZE with indirect absorbance detection, the use of capillaries with permanent and dynamic wall coatings, the composition of the BGE, and various sample preparation procedures, including dilution with water, ultrafiltration, protein precipitation, and SPE, were investigated. Two validated screening assays for the determination of EtG in human serum, a CZE‐based approach and an enzyme immunoassay (EIA), are described. The CZE assay uses a coated capillary, 2,4‐dimethylglutaric acid as an internal standard, and a pH 4.65 BGE comprising 9 mM nicotinic acid, ε‐aminocaproic acid and 10% v/v ACN. Proteins are removed via precipitation with ACN prior to analysis and the LOQ is 0.50 mg/L. The EIA is based upon commercial reagents which are promoted for the determination of urinary EtG. Krebs–Ringer solution containing 5% BSA is used as a calibration matrix. All samples are ultrafiltered prior to analysis of the ultrafiltrate on a Mira Plus analyzer. Assay calibration ranged between 0 and 2 mg/L and the upper reference limit was determined to be 0.05 mg/L. Both assays proved to be suitable for the analysis of samples from different individuals. For EtG levels above 0.50 mg/L, good agreement was observed for the comparison of the results of the two methods.     

Analysis of low‐molecular mass aldehydes in drinking waters through capillary electrophoresis with laser‐induced fluorescence detection

The potential of CZE with LIF detection in the separation and determination of low‐molecular mass aldehydes involving precolumn derivatization with fluorescein 5‐thiosemicarbazide was investigated. Different variables that affect derivatization (pH, fluorescein 5‐thiosemicarbazide concentration, time and temperature) and separation (pH and concentration of the BGE, kind and concentration of surfactants at levels higher and lower than CMC, and applied voltage) were studied. The separation was conducted within 16 min by using borate buffer (60 mM; pH 10) with 10 μM polyethylene glycol tert‐octylphenyl ether as modifier. Good linearity relationships (correlation coefficients ranged from 0.9978 to 0.9994 for aldehydes) were obtained between the peak areas and concentration of the analytes (0.5–100 μg/L). The LODs for aldehydes were achieved at submicrogram‐per‐liter level (0.15–0.35 μg/L), which indicated that the proposed method surpassed other electrophoretric alternatives in terms of LOD, in many cases even at ca. 1000‐fold. The inter‐day precision (RSD, %) of the aldehydes ranged from 5.2 to 8.3%. Finally, the method was successfully applied to bottled drinking‐water samples, and the aldehydes were readily detected at 0.6–4.4 μg/L levels with average recoveries ranging from 99.1 to 103.5%.     

A convenient and sensitive method for haloacetic acid analysis in tap water by on‐line field‐amplified sample‐stacking CE–ESI‐MS

In this study, we propose a simple strategy based on flow injection and field‐amplified sample‐stacking CE–ESI‐MS/MS to analyze haloacetic acids (HAAs) in tap water. Tap water was passed through a desalination cartridge before field‐amplified sample‐stacking CE–ESI‐MS/MS analysis to reduce sample salinity. With this treatment, the signals of the HAAs increased 300‐ to 1400‐fold. The LODs for tap water analysis were in the range of 10 to 100 ng/L, except for the LOD of monochloroacetic acid (1 μg/L in selected‐ion monitoring mode detection). The proposed method is fast, convenient, and sensitive enough to perform on‐line analysis of five HAAs in the tap water of Taipei City. Four HAAs, including trichloroacetic acid, dichloroacetic acid, dibromoacetic acid, and monobromoacetic acid, were detected at concentrations of approximately 1.74, 1.15, 0.16, and 0.15 ppb, respectively.     

Highly sensitive and selective separation of intact parathyroid hormone and variants by sheathless CE‐ESI‐MS/MS

Parathyroid hormone (PTH) is a common clinical marker whose quantification relies on immunoassays, giving variable results as batch, brand, or target epitope changes. Sheathless CE‐ESI‐MS, combining CE resolution power and low‐flow ESI sensitivity, was applied to the analysis of PTH in its native conformation in the presence of related forms. Fused silica and neutral‐coated capillaries were investigated, as well as preconcentration methods such as transient isotachophoresis, field‐amplified sample injection (FASI), and electrokinetic supercharging (EKS). The method for the separation of PTH and its variants was first developed using fused‐silica capillary with UV detection. An acidic BGE was used to separate 1–84 PTH (full length), 7–84 PTH, and 1–34 PTH. Acetonitrile was added to the BGE to reduce peptide adsorption onto the capillary wall and transient isotachophoresis was used as analyte preconcentration method. The method was then transferred to a sheathless CE‐ESI‐MS instrument. When using a fused silica capillary, CE‐MS was limited to μg/mL levels. The use of a neutral coating combined with FASI or EKS allowed a significant increase in sensitivity. Under these conditions, 1–84 PTH, 7–84 PTH, and 1–34 PTH were detected at concentrations in the low ng/mL (FASI) or pg/mL (EKS) range.     

MEKC–MS/MS method using a volatile surfactant for the simultaneous determination of 12 synthetic cannabinoids

This study describes a method for the simultaneous determination of 12 synthetic cannabinoids by MEKC–MS/MS using a volatile surfactant (ammonium perfluorooctanoate) as a constituent of the micellar pseudostationary phase. Although most synthetic cannabinoids comigrated by a CZE method, sufficient separation could be achieved by the proposed method. The best separation was made possible by 50 mM ammonium perfluorooctanoate in 20% v/v acetonitrile/water (apparent pH* 9.0) as the BGE, followed by MS detection using a sheath liquid composed of 5 mM ammonium formate in 50% v/v methanol/water mixed hydro‐organic solvent. The standard calibration curve for all analytes showed good linearity (r > 0.99). Satisfactory recoveries, ranging from 89.5 to 101.7%, were obtained. The LODs were 6.5–76.5 μg/g for the target analytes. This method appears to be a useful tool for the identification of synthetic cannabinoids in illegal herbal incense blends.     

Enhancing concentration and mass sensitivities for liquid chromatography trace analysis of clopyralid in drinking water

A theoretical treatment was developed and validated that relates analyte concentration and mass sensitivities to injection volume, retention factor, particle diameter, column length, column inner diameter and detection wavelength in liquid chromatography, and sample volume and extracted volume in solid‐phase extraction (SPE). The principles were applied to improve sensitivity for trace analysis of clopyralid in drinking water. It was demonstrated that a concentration limit of detection of 0.02 ppb (μg/L) for clopyralid could be achieved with the use of simple UV detection and 100 mL of a spiked drinking water sample. This enabled reliable quantitation of clopyralid at the targeted 0.1 ppb level. Using a buffered solution as the elution solvent (potassium acetate buffer, pH 4.5, containing 10% of methanol) in the SPE procedures was found superior to using 100% methanol, as it provided better extraction recovery (70–90%) and precision (5% for a concentration at 0.1 ppb level). In addition, the eluted sample was in a weaker solvent than the mobile phase, permitting the direct injection of the extracted sample, which enabled a faster cycle time of the overall analysis. Excluding the preparation of calibration standards, the analysis of a single sample, including acidification, extraction, elution and LC run, could be completed in 1 h. The method was used successfully for the determination of clopyralid in over 200 clopyralid monoethanolamine‐fortified drinking water samples, which were treated with various water treatment resins.     

Determination of Estrogenic Nonylphenol and Bisphenol a in River Water by Solid‐Phase Extraction and Gas Chromatography‐Mass Spectrometry

A simple and sensitive method is presented for the analysis of nonylphenol (NP) and bisphenol A (BPA), two well known hormonally active agents (HAAs), in the samples of river water. The method involves extraction of the sample by a graphitized carbon black (GCB) solid‐phase extraction, and determination by an ion‐trap gas chromatography‐mass spectrometry (GC‐MS). The large‐volume injection technique provides high precision and sensitivity for NP and BPA, to quantitation at < 0.05 μg/L in 200 mL of water samples. Recovery of NP and BPA in spiked water samples ranged from 80% to 85%. Relative standard deviations (RSD) of replicate analyses ranged from 1.6% to 6.9%. The concentrations of NP in rivers were in the range between 0.4 to 2.4 μg/L, which were below the threshold concentration (10 μg/L) for vitellogenin induction in fish, but 78%) of water samples from five rivers exceeded the predicted‐no‐effect concentration (PNEC) of 0.7 μg/L as proposed recently. The concentrations of BPA ranged from < 0.05 μg/L to 3.0 μg/L, which all were below the PNEC of 64 μg/L.