Guohong Xie

Trace determination of organophosphorus pesticides in environmental samples by temperature-controlled ionic liquid dispersive liquid-phase microextraction

This paper described a new approach for the determination of organophosphorus pesticides by temperature-controlled ionic liquid dispersive liquid-phase microextraction prior to high-performance liquid chromatography with ultraviolet detection. Methylparathion and phoxim, two of the typical organophosphorus pesticides, were used as the model analytes for the investigation of the development and application of the new microextraction method. 1-Hexyl-3-methylimidazolium hexafluorophosphate [C6MIM][PF6] was used as the extraction solvent and the factors affecting the extraction efficiency such as the volume of [C6MIM][PF6], pH of working solutions, extraction time, centrifuging time, dissoluble temperature and salt effect were optimized. Under the optimal extraction conditions, methylparathion and phoxim exhibited good linear relationship in the concentration range of 1-100 ng mL(-1). The detection limits were 0.17 ng mL(-1) and 0.29 ng mL(-1), respectively. Precisions of proposed method (RSDs, n=6) were 2.5% and 2.7%, respectively. This proposed method was successfully applied in the analysis of four real environmental water samples and good spiked recoveries over the range of 88.2-103.6% were obtained. These results indicated that temperature-controlled ionic liquid dispersive liquid-phase microextraction had excellent application prospect in environmental field.

Temperature-controlled ionic liquid-liquid-phase microextraction for the pre-concentration of lead from environmental samples prior to flame atomic absorption spectrometry.

Hydrophobic ionic liquid could be dispersed into infinite droplets under driving of high temperature, and then they can aggregate as big droplets at low temperature. Based on this phenomenon a new liquid-phase microextraction for the pre-concentration of lead was developed. In this experiment, lead was transferred into its complex using dithizone as chelating agent, and then entered into the infinite ionic liquid drops at high temperature. After cooled with ice-water bath and centrifuged, lead complex was enriched in the ionic liquid droplets. Important parameters affected the extraction efficiency had been investigated including the pH of working solution, amount of chelating agent, volume of ionic liquid, extraction time, centrifugation time, and temperature, etc. The results showed that the usually coexisting ions containing in water samples had no obvious negative effect on the recovery of lead. The experimental results indicated that the proposed method had a good linearity (R=0.9951) from 10 ng mL(-1) to 200 ng mL(-1). The precision was 4.4% (RSD, n=6) and the detection limit was 9.5 ng mL(-1). This novel method was validated by determination of lead in four real environmental samples for the applicability and the results showed that the proposed method was excellent for the future use and the recoveries were in the range of 94.8-104.1%.

Determination of bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol by temperature-controlled ionic liquid dispersive liquid-phase microextraction combined with high performance liquid chromatography-fluorescence detector

Present study described a simple, sensitive, and viable method for the determination of bisphenol A, 4-n-nonylphenol and 4-tert-octylphenol in water samples using temperature-controlled ionic liquid dispersive liquid-phase microextraction coupled to high performance liquid chromatography-fluorescence detector. In this experiment, 1-octyl-3-methylimidazolium hexafluorophosphate ([C(8)MIM][PF(6)]) was used as the extraction solvent, and bisphenol A, 4-n-nonylphenol and 4-tert-octylphenol were selected as the model analytes. Parameters affecting the extraction efficiency such as the volume of [C(8)MIM][PF(6)], dissolving temperature, extraction time, sample pH, centrifuging time and salting-out effect have been investigated in detail. Under the optimized conditions, good linear relationship was found in the concentration range of 1.0-100 μg L(-1) for BPA, 1.5-150 μg L(-1) for 4-NP, and 3-300 μg L(-1) for 4-OP, respectively. Limits of detection (LOD, S/N=3) were in the range of 0.23-0.48 μg L(-1). Intra day and inter day precisions (RSDs, n=6) were in the range of 4.6-5.5% and 8.5-13.3%, respectively. This method has been also successfully applied to analyze the real water samples at two different spiked concentrations and excellent results were obtained.

Development of micro-solid phase extraction with titanate nanotube array modified by cetyltrimethylammonium bromide for sensitive determination of polycyclic aromatic hydrocarbons from environmental water samples

This paper described a simple and novel analytical technique for the determination of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. A micro-solid phase extraction (μ-SPE) was developed utilizing cetyltrimethylammonium bromide modified ordered TiO(2) nanotube array. The experimental results indicated that modified TiO(2) nanotube arrays demonstrated an excellent merit on the preconcentration of PAHs, and there were excellent linear relationships between peak area and the concentration of PAHs in the range of 0.2-100 μg L(-1) and 1.0-100 μg L(-1), respectively. The detection limits of proposed method for the targeted PAHs were in the range of 0.026-0.82 μg L(-1) (S/N = 3). The real-world environmental water samples were used to validate the applicability of the proposed method and good spiked recoveries were in the range of 75.0-114%. All these results demonstrated that this new μ-SPE technique was a viable alternative to conventional enrichment techniques for the extraction and analysis of PAHs in complex samples.

Sensitive determination of phenols from water samples by temperature-controlled ionic liquid dispersive liquid-phase microextraction

This paper established a new determination method for phenols using temperature-controlled ionic liquid dispersive liquid-phase microextraction prior to high-performance liquid chromatography. In this experiment, 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) was employed as the extraction solvent for the enrichment of 2-chlorophenol, 2-naphthol, 2,4-dinitrophenol, and 2,4-dichlorophenol. Parameters that may affect the extraction efficiency including the volume of [C8MIM][PF6], dissoluble temperature, extraction time, sample pH, amount of ethanol, centrifugation time and salting-out effect have been investigated in detail. Under the optimal conditions, they have good linear relationships over the concentration range of 1.0-100 ng mL-1 for 2-chlorophenol, 2-naphthol, 2,4-dinitrophenol, and 1.5-150 ng mL-1 for 2,4-dichlorophenol, and excellent detection sensitivity with limits of detection (LOD, S/N = 3) in the range of 0.27-0.68 μg L-1. Intra day and inter day precisions of the proposed method (RSDs, n = 6) were 2.1-3.7% and 5.1-7.2%, respectively. The proposed method has been successfully applied to analyze real water samples spiked with two different concentrations and good spiked recoveries over the range of 85.8-117.0% were obtained. These results indicated that the proposed method would be competitive in the analysis of phenols in the future.

Temperature‐controlled ionic liquid‐dispersive liquid‐phase microextraction for preconcentration of chlorotoluron, diethofencarb and chlorbenzuron in water samples

This article describes a new, rapid and sensitive method for the determination of chlorotoluron, diethofencarb and chlorbenzuron from water samples with temperature-controlled ionic liquid-dispersive liquid-phase microextraction. In the preconcentration procedure, ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM] [PF(6)] was employed as the extraction solvent. The parameters, such as volume of [C(6)MIM] [PF(6)], sample pH, extraction time, centrifuging time, temperature and salting-out effect, were investigated in detail. Under the optimal extraction conditions, it has been found that three analytes had excellent LODs (S/N=3) in the range of 0.04-0.43 microg/L. The RSDs (n=6) were in the range of 1.3-4.7%. The proposed method was evaluated with lake water, tap water and melted snow water samples. The experimental results indicated that the proposed method had excellent prospect and would be widely used in the future.

Determination of paraquat and diquat preconcentrated with N doped TiO2 nanotubes solid phase extraction cartridge prior to capillary electrophoresis

This paper describes a new method for rapid and sensitive determination of paraquat (PQ) and diquat (DQ) by solid phase extraction with N doped TiO2 nanotubes cartridge prior to capillary electrophoresis. Several factors that would affect the extraction efficiency were optimized and the optimal conditions were as followed: sample volume, 500 mL; sample pH, pH 9.0; eluant, 1 mol L−1 HCl/methanol: 70/30 (v/v); eluant volume, 3 mL; sample flow rate, 2.5 mL min−1. Under the optimal conditions, the linear ranges and detection limits were 2.5–100 μgL−1, 5–50 μg L−1 and 1.95 μg L−1, 2.59 μg L−1 for PQ and DQ, respectively. The proposed method was successfully applied to the analysis of PQ and DQ in several environmental water samples, and the spiked recoveries were over the range of 84.15–95.38%. These results indicated that N doped TiO2 nanotubes had better enrichment ability for PQ and DQ as a novel SPE adsorbent material, and maybe have good application prospect for monitoring other pollutants in the environment.

Temperature-controlled ionic liquid dispersive liquid-phase microextraction combined with HPLC with ultraviolet detector for the determination of fungicides

Present study described a simple, environmental benign, easy to operate, and determination method for fungicides including thiram, metalaxyl, diethofencarb, myclobutanil, and tebuconazole. The method is based on temperature-controlled ionic liquid dispersive liquid phase microextraction coupled to HPLC with ultraviolet detector. In the enrichment procedure, ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate [C(8)MIM][PF(6)] was used as the extraction solvent. Variable affecting parameters such as the volume of [C(8)MIM][PF(6)], temperature, extraction time, centrifuging time, and salting-out effect have been optimized in detail. Under the optimal conditions, this method has been found to have good linear relationship in the concentration range of 1.0-100 μg/L and excellent detection sensitivity with LODs (S/N = 3) in the range of 0.32-0.79 μg/L. Precisions of proposed method were in the range of 3.7-5.9% for intraday and 7.8-11.0% for interday (RSDs, n = 6). The proposed method was used for the analysis of real water samples and good spiked recoveries at two different spiked levels were achieved in the range of 84.6-102%.

Preconcentration and determination of pyrethroid insecticides in water with ionic liquid dispersive liquid-phase microextraction in combination with high performance liquid chromatography

This paper developed a new method with temperature controlled ionic liquid dispersive liquid-phase microextraction for the determination of pyrethroid insecticides such as fenpropathrin, fenvalerate and bifenthrin in water samples. The effect of alkyl chain length of ionic liquid 1-alkyl-3-methylimidazolium hexafluorophosphate and other parameters such as sample pH, temperature, salting-out effect and sample volume on the extraction efficiency were investigated in detail. Four different alkyl chain length ionic liquids ([CnMIM][PF6], n = 4, 6, 7, 8) were tested. The experimental results demonstrated that the alkyl chain length of ionic liquids (ILs) did have an important role on the extraction efficiency. The experimental results indicated that the longer alkyl chain length of ILs resulted in better extraction efficiency. Among the four ILs, 1-octyl-3-methylimidazolium hexafluorophosphate [C8MIM] [PF6] was the best one for extraction of the target analytes. Under the optimized conditions, three pyrethroid insecticides had limits of detection (LOD, S/N = 3) in the range of 0.34∼0.48 μg L-1. The precisions of the proposed method (RSDs, n = 6) with a spiked concentration of 20 μg L-1 were in the range of 2.0∼3.4%. The proposed method was evaluated with real water samples spiked at a concentration of 10 ng mL-1 and good spiked recoveries over the range of 89.2∼102.7% were obtained.

Investigation of the applicability of highly ordered TiO2 nanotube array for enrichment and determination of polychlorinated biphenyls at trace level in environmental water samples

Present study investigated the applicability of ordered TiO(2) nanotube arrays for the enrichment and determination of polychlorinated biphenyls (PCBs) in water samples. A new and reliable method was developed for the preconcentration and determination of PCBs by micro-solid phase equilibrium extraction in combination with gas chromatography and electron capture detection (GC-ECD), which exploited the special physical and chemical properties of ordered TiO(2) nanotube arrays. The experimental results indicated that low LODs were easily achieved in the range of 0.02-0.10 μg L(-1) for PCB-28, PCB-52, PCB-101, PCB-153, PCB-138, and PCB-180. The proposed method was validated with several real water samples, and good spiked recoveries have been obtained in the range of 95.8-110.5%. The experimental results demonstrated that TiO(2) nanotube arrays could be reused for over 200 times without the lost of the extraction efficiency. All these showed that TiO(2) nanotube arrays would be very useful in the enrichment and determination of trace pollutants.