Hongmei Hu

Ultrasound‐assisted extraction and solid‐phase extraction as a cleanup procedure for organochlorinated pesticides and polychlorinated biphenyls determination in aquatic samples by gas chromatography with electron capture detection

The feasibility of developing a quick, easy, efficient procedure for the simultaneous determination of organochlorinated pesticides and polychlorinated biphenyls in aquatic samples using gas chromatography with electron capture detection based on solid-phase extraction was investigated. The extraction solvent (n-hexane/acetone, cyclohexane/ethyl acetate, n-hexane/dichloromethane, n-hexane) for ultrasound-assisted solid-liquid extraction and solid-phase extraction columns (florisil, neutral alumina, acidic alumina, aminopropyl trimethoxy silane, propyl ethylenediamine, aminopropyl trimethoxy silane/propyl ethylenediamine, graphitized carbon black and silica) for cleanup procedure were optimized. The gas chromatography with electron capture detection method was validated in terms of linearity, sensitivity, reproducibility, and recovery. Mean recoveries ranged from 75 to 115% with relative standard deviations <13%. Quantification limits were 0.20-0.40 ng/g for organochlorinated pesticides and polychlorinated biphenyls. The satisfactory data demonstrated the good reproducibility of the method with relative standard deviations lower than 13%. In comparison to other related methods, this method requires less time and solvent and allows for rapid isolation of the target analytes with high selectivity. This method therefore allows for the screening of numerous samples and can also be used for routine analyses.

Rapid Determination of Catecholamines in Urine Samples by Nonaqueous Microchip Electrophoresis with LIF Detection

A method was developed for the rapid separation of catecholamines by nonaqueous microchip electrophoresis with LIF detection, A homemade pump-free negative pressure sampling device was used for rapid bias-free sampling in nonaqueous microchip electrophoresis, the injection time was 0.5 s and the electrophoresis separation conditions were optimized. Under the optimized conditions, the samples were separated completely in less than 1 min. The average migration times of the epinephrine, dopamine, and norepinephrine were 34.26, 43.81, and 50.07 s, with a relative standard deviation of 1.05, 1.26 and 0.89% (n = 7), respectively. The linearity of the method ranged from 0.0125 to 2.0 mg/L for epinephrine and 0.025∼4.0 mg/L for dopamine, and norepinephrine, with correlation coefficients ranging between 0.9978 and 0.9986. The detection limits of epinephrine, dopamine, and norepinephrine were 2.5, 5.0 and 5.0 μg/L, respectively. The recoveries of epinephrine, dopamine, and norepinephrine in spiked urine samples were between 86 and 103%, with relative standard deviations of 4.5∼6.8% (n = 5). The proposed nonaqueous microchip electrophoresis with laser induced fluorescence detection system combined with a pump-free negative pressure sampling device was a simple, inexpensive, energy efficient, miniaturized system that can be successfully applied for the determination of catecholamines in urine samples. This article is protected by copyright. All rights reserved.

Determination of benzene series compounds and chlorobenzenes in water sample by static headspace gas chromatography with flame ionization detection

A simple, efficient, solvent-free, and readily commercially available approach for the determination of eight benzene series compounds and 12 chlorobenzenes in water samples using the static headspace sampling and gas chromatography with flame ionization detection has been described in this paper. The proposed static headspace sampling method was initially optimized, and the optimum experimental conditions explored were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 70°C for 43 min. The linearity of the method ranged from 1 to 200 μg/L for 20 analytes, with correlation coefficients ranging between 0.9962 and 0.9994. The limits of detection were in the μg/L level, ranging between 0.15 and 0.4 μg/L. The relative recoveries of spiked benzene series and chlorobenzenes with external calibration method at different concentration levels in pure, tap, and sea water samples were 84-113, 78-115 and 85-119%, respectively, with relative standard deviations of 3.8-6.8, 4.1-5.8, and 4.8-5.4% (n = 5), respectively. That this method can be successfully applied to the determination of benzene series compounds and chlorobenzenes in pure, tap, and sea water samples, simultaneously.

Determination of chlorobenzenes in pure, tap, and sea water by static headspace gas chromatography-electron capture detection

A simple, efficient, solvent-free, and commercial readily available approach for determination of 11 chlorobenzenes (CBs) in water samples using the static headspace (HS) sampling and gas chromatography-electron capture detector has been described. The proposed static HS sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% (w/v) sodium chloride placed in a 20 mL vial and stirred at 70°C for 30 min. The linearity of the method ranged from 0.16 to 8.0 μg/L for dichlorobenzene isomers, 0.0176~0.88 μg/L for trichlorobenzene isomers, 0.004~0.2 μg/L for tetrachlorobenzene isomers, and from 0.001 to 0.05 μg/L for pentachlorobenzene and hexachlorobenzene, with correlation coefficients ranging between 0.9992 and 0.9999. The limits of detection were in the low μg/L level, ranging between 0.0002 and 0.04 μg/L. The relative recoveries of spiked CBs with external calibration or standard addition method at different concentration levels in pure, tap, and sea water samples were 83~116%, 89~108%, and 93~112%, respectively, and with relative standard deviations of 1.9~6.3%, 1.6~5.4%, and 2.5~5.7% (n = 5), respectively. It is concluded that this method can be successfully applied for the determination of CBs in pure, tap, and sea water samples.

Determination of Chlorobenzenes in Water Samples by Solid-Phase Disk Extraction and Gas Chromatography–Electron Capture Detection

A simple, rapid, sensitive and high throughput method is described, based on solid-phase disk extraction (SPDE) and gas chromatography-electron capture detection, for the determination of chlorobenzens (CBs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions were found to be as follows: 500 mL water sample (pH 2.5) extracted and enriched by an Empore 3-stn C18 (octadecyl) SPE disk at flow rate of 5 to 50 mL/min, eluted by 5 mL of acetone and 3 × 5 mL of methylene dichloride. The linearity of the method ranged from 0.02 to 0.4 µg/L for dichlorobenzene isomers, 0.0022-0.044 µg/L for trichlorobenzene isomers, 0.005-0.01 µg/L for tetrachlorobenzene isomers and 0.00025 to 0.005 µg/L for pentachlorobenzenes and hexachlorobenzenes, with correlation coefficients ranging between 0.9991 and 0.9999. The limits of detection were in the low ng/L level, ranging between 0.05 and 4 ng/L. The recoveries of spiked CBs with the external calibration method at different concentration levels in deionized/distilled water, tap water and sea water samples were 99-115, 91-106% and 96-110%, respectively, and with relative standard deviations of 4.5-7.6, 4.2-6.8 and 3.6-6.6% (n = 5), respectively. It is concluded that this method can successfully be applied for the determination of CBs in deionized/distilled water, tap water and sea water samples.

Determination of volatile chlorinated hydrocarbons in water samples by static headspace gas chromatography with electron capture detection

A simple, efficient, solvent-free, and commercial readily available approach for determination of five volatile chlorinated hydrocarbons in water samples using the static headspace sampling and gas chromatography with electron capture detection has been described. The proposed static headspace sampling method was initially optimized and the optimum experimental conditions found were 10 mL water sample containing 20% w/v sodium chloride placed in a 20 mL vial and stirred at 50ºC for 20 min. The linearity of the method was in the range of 1.2-240 μg/L for dichloromethane, 0.2-40 μg/L for trichloromethane, 0.005-1 μg/L for perchloromethane, 0.025-5 μg/L for trichloroethylene, and 0.01-2 μg/L for perchloroethylene, with coefficients of determination ranging between 0.9979 and 0.9990. The limits of detection were in the low μg/L level, ranging between 0.001 and 0.3 μg/L. The relative recoveries of spiked five volatile chlorinated hydrocarbons with external calibration method at different concentration levels in pure, tap, sea water of Jiaojiang Estuary, and sea water of waters of Xiaomendao were in the range of 91-116, 96-105, 86-112, and 80-111%, respectively, and with relative standard deviations of 1.9-3.6, 2.3-3.5, 1.5-2.7, and 2.3-3.7% (n = 5), respectively. The performance of the proposed method was compared with traditional liquid-liquid extraction on the real water samples (i.e., pure, tap, and sea water, etc.) and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of volatile chlorinated hydrocarbons in different water samples.

Determination of Trace Organophosphorus Pesticides in Water Samples by Solid Phase Disk Extraction and Gas Chromatography-Thermionic Specific Detector

A simple, rapid, sensitive, and high-throughput method based on solid-phase disk extraction (SPDE) and a gas chromatography–thermionic specific detector (GC-TSD) is described for the determination of organophosphorus pesticides (OPPs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions found were 500 mL water sample (pH 2.5–7.0) extracted and enriched by a C18 (octadecyl) solid phase extraction disk at flow rate of 5 to 50 mL/min and eluted by 5 mL of acetone and 3 × 5 mL methylene chloride. The linearity of the method ranged from 0.020 to 1.00 µg/L for dimethoate, methyl parathion, and malathion, with correlation coefficients ranging between 0.9976 and 0.9992. The concentration factors for OPPs were between 498 and 554. The limits of detection were in the ng/L level, ranging between 2.5 and 4 ng/L. The relative recoveries of spiked 3 OPPs (dimethoate, methyl parathion, and malathion) with external calibration method at different concentration levels in pure, fresh water, and sea water samples were 102–112%, 94–109%, and 99–104%, respectively, and with relative standard deviations of 4.1–6.2%, 3.4–4.6%, and 3.5–5.2% (n = 3), respectively. It is concluded that this method can be successfully applied for the determination of OPPs in pure water, fresh water, and sea water samples.

Sample Pretreatment Method for Determination of Indicator Polychlorinated Biphenyls in Seafood using Ultrasonic Extraction Followed by Dispersive Solid-Phase Extraction and Gas Chromatography – Electron Capture Detection

A simple, rapid and novel method has been developed and validated for the determination of seven indicator polychlorinated biphenyls (PCBs) in seafood samples by gas chromatography coupled to electron capture detector. Freeze-dried samples were done first ultrasonic extraction by n-hexane:methylene chloride:acetone (3:1:1, v/v), and then one-step clean-up (dispersive solid-phase extraction clean-up) or two-step clean-up (concentrated sulfuric acid purification and dispersive solid-phase extraction clean-up) was selected according to the lipid contents of the samples, if the lipid content was no more than 1%, one-step clean-up was used, otherwise, two-step clean-up was chose. The linearity of this method ranged from 1.25 to 100 μg/L, with regression coefficients ranging between 0.9991 and 0.9998. The limits of detection were in low ng/g level, ranging between 0.005 and 0.0076 ng/g (wet weight). The recoveries of spiked seven PCBs with external calibration method at different concentration levels in Pseudosciaena polyactis, Penaeus vannamei and Sinonovacula constricta were in the range of 78-105%, 73-110% and 75-107%, respectively, and with relative standard deviations of 3.3-5.1%, 3.5-6.3% and 3.4-5.1% (n = 5), respectively. The performance of the proposed method was also compared with traditional soxhlet extraction and column chromatography clean-up on the same real seafood samples and comparable efficiencies were obtained. It is concluded that this method can be successfully applied for the determination of PCBs in different seafood samples.

Rapid and variable-volume sampling loading in nonaqueous microchip electrophoresis

Um esquema rapido e de volume variavel de carregamento de amostras para eletroforese nao-aquosa em microchip com fluorescencia induzida a laser (NAMCE-LIF) foi desenvolvido, incluindo um plugue de polimero poroso, uma bomba de microvacuo de baixo custo e uma fonte de alta tensao com potencial unico. O plugue de polimero poroso foi fabricado dentro do canal de separacao como uma valvula de selecao, que impedia o tampao de corrida do reservatorio de descarte de tampao (BW) de fluir de volta ao canal de separacao, mas permitia a migracao eletroforetica ao longo do canal de separacao. Aplicando uma pressao subatmosferica ao headspace do reservatorio de descarte (SW), amostra e tampao de corrida eram passados imediatamente ao SW. Concomitantemente, uma parte do fluxo de amostra era conduzido atraves do plugue de polimero poroso pela forca eletrica, formando uma zona de amostra no canal de separacao. O comprimento da zona de amostra injetada era proporcional ao tempo de injecao. O metodo proposto foi aplicado com sucesso na separacao de Rodamina 123 (Rh123) e Rodamina 6G (Rh6G). Os limites de deteccao para Rh123 e Rh6G baseados em S/N = 3 foram 0,63 e 0,48 nmol L - 1, respectivamente. O sistema provou possuir um potencial para aperfeicoamento de rendimento, repetibilidade, sensibilidade, desempenho da separacao da eletroforese nao aquosa em microchip e uma ampla gama de aplicacoes.

Rapid determination of catecholamines in urine samples by nonaqueous microchip electrophoresis with LIF detection: Electrodriven Separations

A method was developed for the rapid separation of catecholamines by nonaqueous microchip electrophoresis (NAMCE) with LIF detection, A homemade pump-free negative pressure sampling device was used for rapid bias-free sampling in NAMCE, the injection time was 0.5 s and the electrophoresis separation conditions were optimized. Under the optimized conditions, the samples were separated completely in <1 min. The average migration times of the epinephrine (E), dopamine (DA), and norepinephrine (NE) were 34.26, 43.81, and 50.07 s, with an RSD of 1.05, 1.26, and 0.89% (n = 7), respectively. The linearity of the method ranged from 0.0125 to 2.0 mg/L for E and 0.025~4.0 mg/L for DA and NE, with correlation coefficients ranging between 0.9978 and 0.9986. The detection limits of E, DA, and NE were 2.5, 5.0, and 5.0 μg/L, respectively. The recoveries of E, DA, and NE in spiked urine samples were between 86 and 103%, with RSDs of 4.5~6.8% (n = 5). The proposed NAMCE with LIF detection combined with a pump-free negative pressure sampling device is a simple, inexpensive, energy efficient, miniaturized system that can be successfully applied for the determination of catecholamines in urine samples.