State Key Laboratory of Crop Stress Biology in Arid Areas

Yangling, China

State Key Laboratory of Crop Stress Biology in Arid Areas

Yangling, China
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Sun J.,Northwest University, China | He H.,Northwest University, China | Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas
Journal of Separation Science | Year: 2014

A simple method that consumes low organic solvent is proposed for the analysis of phthalic acid esters in Chinese white spirit using dispersive liquid-liquid microextraction coupled with sweeping-micellar electrokinetic chromatography. Tetrachloromethane and white-spirit-containing ethanol were used as the extraction and dispersing solvents, respectively. The electrophoresis separation buffer was composed of 5 mM β-cyclodextrin, 50 mM sodium dodecyl sulfate and 25 mM borate buffer (pH 9.2) with 9% acetonitrile, enabling the baseline resolution of the analytes within 13 min. Under the optimum conditions, satisfactory linearities (5-1000 ng/mL, r ≥ 0.9909), good reproducibility (RSD ≤ 6.7% for peak area, and RSD ≤ 2.8% for migration time), low detection limits (0.4-0.8 ng/mL) and acceptable recovery rates (89.6-105.7%) were obtained. The proposed method was successfully applied to 22 Chinese white spirits, and the content of dibutyl phthalate in 55% of the samples exceeded the Specific Migration Limit of 0.3 mg/kg established by the domestic and international regulations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Chen J.,Northwest University, China | Sun J.,Northwest University, China | Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas
Analytical Letters | Year: 2013

A very simple, sensitive, and reliable method for the routine determination of riboflavin in cereal grains by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was established. Two on-line concentration techniques, namely, stacking in reverse migrating micelles (SRMM) and sweeping, were examined to enhance the detection signal. The optimum separation buffer consisted of 20 mM phosphoric acid and 140 mM sodium dodecyl sulfate (SDS), and a hydrodynamic injection of 30 s at 0.5 psi was confirmed for the introduction of a sample. In addition, it was found that salt in sample matrix influenced the performance of SRMM, showing the standard addition method was required for the quantitative analysis. The linearity of the method was good with a range of 0.5-500 ng/mL (r = 0.9990). The limit of detection (LOD) was 0.29 ng/mL at a signal-to-noise ratio of 3. This procedure presented was successfully applied to determine riboflavin in 18 samples of 9 types of cereal grains. The recovery rates varied from 94% to 98%, and the relative standard deviation (RSDs) was less than 4.1%. © 2013 Copyright Taylor and Francis Group, LLC.


Cao J.,Northwest University, China | Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Bai W.,Northwest University, China | And 2 more authors.
Analytical Letters | Year: 2013

A novel method for the determination of the migration of bisphenol A (BPA) from polycarbonate water bottles has been developed by using dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography for compliance with the regulatory specific migration limit. Experimental parameters, including the type and volume of extractants and dispersers, the sample solution pH, addition of salt, extraction time, and temperature, were examined and optimized. Under the optimum conditions, average recovery rates for the real samples varied from 82% to 98%, with relative standard deviation values less than 3.6%. The method offered excellent linearity over a range of 0.8-600 μg L-1 with a correlation coefficient of r = 0.9999. Intra-day and inter-day repeatability values expressed as relative standard deviation were 3.9% and 6.9%, respectively. The method quantitation limit and detection limit were 0.7 and 0.2 μg L-1, respectively. The developed method was successfully applied to the determination of the migration of bisphenol A from 26 polycarbonate water bottles collected locally. The findings indicated the migration from the used bottles was significantly higher than the new ones, and the migration amounts from one sample was very close to the regulatory specific migration limit, and the amounts from seven samples exceeded the daily intake limit for infants. © 2013 Copyright Taylor and Francis Group, LLC.


Liu S.,Northwest Agriculture and Forestry University | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Xie Q.,Northwest Agriculture and Forestry University | Chen J.,Northwest Agriculture and Forestry University | And 3 more authors.
Journal of Chromatography A | Year: 2013

In this study, two novel sample extraction methods for the analysis of bisphenol A (BPA) in edible oils were developed by using liquid-liquid extraction followed by a dispersive liquid-liquid microextraction (LLE-DLLME) and reversed-phase dispersive liquid-liquid microextraction (RP-DLLME). RP-DLLME showed a superior characteristic over LLE-DLLME and other previously reported procedures because of its easy operation, short extraction time, high sensitivity, low organic solvent consumption and waste generation. The optimized extraction conditions of RP-DLLME for 1.0g of edible oil diluted in 4mL of n-hexane were: extractant, 100μL 0.2M sodium hydroxide solution (80% methanol, v/v); extraction time, 1min; centrifugation, 3min. The determination of BPA was carried out by high performance liquid chromatography coupled with a DAD detector. The method offered excellent linearity over a range of 0.010-0.5μgg-1 with a correlation coefficient of r>0.997. Intra-day and inter-day repeatability values expressed as relative standard deviation were 1.9% and 5.9%, respectively. The quantitation limit and detection limit were 6.3 and 2.5ngg-1. The target analyte was detected in 5 out of 16 edible oil samples. The recovery rates in real samples ranged from 89.5 to 99.7%. © 2013 Elsevier B.V.


He H.,Northwest Agriculture and Forestry University | Liu S.,Northwest Agriculture and Forestry University | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Meng Z.,Northwest Agriculture and Forestry University | Hu S.,Northwest Agriculture and Forestry University
Journal of Chromatography A | Year: 2014

The current routes to couple dispersive liquid-liquid microextraction (DLLME) with capillary electrophoresis (CE) are evaporation of water immiscible extractants and backextraction of analytes. The former is not applicable to extractants with high boiling points, the latter being effective only for acidic or basic analytes, both of which limit the further application of DLLME-CE. In this study, with 1-octanol as a model DLLME extractant and six phenols as model analytes, a novel method based on acetonitrile stacking and sweeping is proposed to accomplish large-volume injection of 1-octanol diluted with a solvent-saline mixture before micellar electrokinetic chromatography. Brij-35 and β-cyclodextrin were employed as pseudostationary phases for sweeping and also for improving the compatibility of sample zone and aqueous running buffer. A short solvent-saline plug was used to offset the adverse effect of the water immiscible extractant on focusing efficiency. The key parameters affecting separation and concentration were systematically optimized; the effect of Brij-35 and 1-octanol on focusing mechanism was discussed. Under the optimized conditions, with ~30-fold concentration enrichment by DLLME, the diluted extractant (8×) was then injected into the capillary with a length of 21. cm (42% of the total length), which yielded the overall improvements in sensitivity of 170-460. Limits of detection and qualification ranged from 0.2 to 1.0. ng/mL and 1.0 to 3.4. g/mL, respectively. Acceptable repeatability lower than 3.0% for migration time and 9.0% for peak areas were obtained. The developed method was successfully applied for analysis of the phenol pollutants in real water samples. © 2014 Elsevier B.V.


Fan Y.,Northwest University, China | Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Xie Q.,Northwest University, China
Talanta | Year: 2014

A very simple, fast and environmentally friendly sample extraction method was proposed for the analysis of phthalate esters (PAEs, di-isobutyl phthalate (DIBP), dibutylphthalate (DBP), butylbenzylphthalate (BBP) and bis(2-ethylhexyl)phthalate (DEHP)) in alcoholic beverages by using conventional ionic liquid dispersive liquid-liquid microextraction. The samples were extracted by 160 μL 1-octyl-3-methylimidazolium hexafluorophosphate in the presence of appropriate amount of ethanol and 10% (w/v) sodium chloride solution; the enriched analytes in sedimented phases were analyzed by high performance liquid chromatography-diode array detector (HPLC-DAD). Under the optimum conditions, a satisfactory linearity (in the range of 0.02-1 μg mL-1 for white spirits and 0.01-0.5 μg mL-1 for red wines with the correlation coefficients (r) varying from 0.9983 to 1), acceptable recovery rates (88.5-103.5% for white spirits and 91.6-104.6% for red wines), good repeatability (RSD≤8.0%) and low detection limits (3.1-4.2 ng mL-1 for white spirits and 1.5-2.2 ng mL-1 for red wines) were obtained. The developed method was successfully applied for the determination of the four PAEs in 30 white spirits and 11 red wines collected locally, and the DBP content in 63% (19:30) white spirits exceeded the specific migration limit of 0.3 mg kg-1 established by international regulation. © 2013 Elsevier B.V.


Xie Q.,Northwest University, China | Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Fan Y.,Northwest University, China | And 2 more authors.
Analytical and Bioanalytical Chemistry | Year: 2014

A selective and low organic-solvent-consuming method of sample preparation combined with high-performance liquid chromatography with diode-array detection is introduced for analysis of phthalic acid esters in edible oils. Sample treatment involves initial liquid-liquid partitioning with acetonitrile, then QuEChERS cleanup by dispersive solid-phase extraction with primary secondary amine as sorbent. Preconcentration of the analytes is performed by ionic-liquid-based dispersive liquid-liquid microextraction, with the cleaned-up extract as disperser solvent and 1-hexyl-3-methylimidazolium hexafluorophosphate as extraction solvent. Under the optimized conditions, correlation coefficients (r) were 0.998-0.999 and standard errors (S y/x) were 2.67-3.37×103 for calibration curves in the range 50-1000 ng g-1. Detection limits, at a signal-to-noise ratio of 3, ranged from 6 to 9 ng g-1. Intra-day and inter-day repeatability, expressed as relative standard deviation, were in the ranges 1.0-6.9 % and 2.4-9.4 %, respectively. Recovery varied between 84 % and 106 %. The developed method was successfully used for analysis of the analytes in 28 edible oils. The dibutyl phthalate content of four of the 28 samples (14 %) exceeded the specific migration limit established by domestic and international regulations. © 2014 Springer-Verlag Berlin Heidelberg.


Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Xie Q.,Northwest University, China | Cao J.,Northwest University, China | And 3 more authors.
Journal of Separation Science | Year: 2013

The traditional for the determination of α-tocopherol in cereal grains includes saponification of a sample followed by liquid-liquid extraction, and it is time- and solvent consuming. In this study, a dispersive liquid-liquid microextraction (DLLME) method was developed to extract α-tocopherol in situ from the saponified grain sample solution. The DLLME experimental parameters including the type and volume of extractants, the volume of dispersers, the addition of salt and the extraction/centrifuging time were examined and optimized. The recommended analytical procedure showed excellent precision (relative SDs of the α-tocopherol amount of 3.1% over intraday and 7.2% over interday), high sensitivity (the detection limit of 1.9 ng/mL), and strong recovery values (88.9-102.5%). In addition, statistical analyses showed no significant difference between the detected amounts of α-tocopherol found by the standardized method and this new procedure. The method was successfully applied to determining the amounts and distribution of α-tocopherol in 14 cereal grain samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Xie Q.,Northwest University, China | Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Fan Y.,Northwest University, China | Zhang X.,Northwest University, China
Food Analytical Methods | Year: 2014

A dispersive liquid-liquid microextraction (DLLME) method coupled to high-performance liquid chromatography was developed for the analysis of α-tocopherol in grain samples. The DLLME parameters including the type and volume of extractants, the volume of disperser and the addition of salt were examined. The optimized DLLME procedure consisted in the formation of a cloudy solution promoted by the fast addition to the sample (5 mL of saponified sample solution diluted with 5 mL of water) of a mixture of carbon tetrachloride (extraction solvent, 80 μL) and ethanol (dispersive solvent, 200 μL) without the addition of salt, followed by shaking for 5 min and centrifuging for 3 min at 5,000 rpm. Intra- and inter-day repeatability expressed as % RSD were 3.5 and 7.6 %, respectively. The limit of detection and the limit of quantification were 1.9 and 6.3 μg L-1. The comparison of this method with the national standardized extraction method, supercritical carbon dioxide extraction, accelerated solvent extraction, and conventional heat-reflux extraction indicates that the DLLME was accurate (no significant differences at the 0.05 % probability level), high efficient, low organic solvent-consuming, and low cost. This procedure was successfully applied to 42 samples of 14 types of purple wheat, for which the content of α-tocopherol exhibited a significantly negative correlation with the pigment content measured by a spectrophotometer. The recovery rates ranged from 90.5 to 103.7 %. © 2013 Springer Science+Business Media New York.


Liu S.,Northwest University, China | Liu S.,State Key Laboratory of Crop Stress Biology in Arid Areas | Wang W.,Northwest University, China | Chen J.,Northwest University, China | Sun J.,Northwest University, China
International Journal of Molecular Sciences | Year: 2012

This paper describes a simple, sensitive and environmentally benign method for the direct determination of aniline and its derivatives in environmental water samples by capillary zone electrophoresis (CZE) with field-enhanced sample injection. The parameters that influenced the enhancement and separation efficiencies were investigated. Surprisingly, under the optimized conditions, two linear ranges for the calibration plot, 1-50 ng/mL and 50-1000 ng/mL (R > 0.998), were obtained. The detection limit was in the range of 0.29-0.43 ng/mL. To eliminate the effect of the real sample matrix on the stacking efficiency, the standard addition method was applied to the analysis of water samples from local rivers. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

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