[Determination of biphenyl ether herbicides in water using HPLC with cloud-point extraction].

OBJECTIVE: To determine residues of multiple biphenyl ether herbicides simultaneously in water using high performance liquid chromatography (HPLC) with cloud-point extraction. METHODS: The residues of eight biphenyl ether herbicides (including bentazone, fomesafen, acifluorfen, aclonifen, bifenox, fluoroglycofenethy, nitrofen, oxyfluorfen) in water samples were extracted with cloud-point extraction of Triton X-114. The analytes were separated and determined using reverse phase HPLC with ultraviolet detector at 300 nm. Optimized conditions for the pretreatment of water samples and the parameters of chromatographic separation applied. RESULTS: There was a good linear correlation between the concentration and the peak area of the analytes in the range of 0.05-2.00 mg/L (r = 0.9991-0.9998). Except bentazone, the spiked recoveries of the biphenyl ether herbicides in the water samples ranged from 80.1% to 100.9%, with relative standard deviations ranging from 2.70% to 6.40%. The detection limit of the method ranged from 0.10 microg/L to 0.50 microg/L. CONCLUSION: The proposed method is simple, rapid and sensitive, and can meet the requirements of determination of multiple biphenyl ether herbicides simultaneously in natural waters.

[Determination of adenosine in food by high performance anion exchange chromatography].

OBJECTIVE: To establish a high performance anion chromatography method for the determination of adenosine in food. METHODS: Adenosine in the food sample was extracted with Acetonitrile-water, and separated with Amino PAC PA10 Amino acid-separation column, with 0.25 mol/L NaOH as the mobile phase. A pulse ampere detector with Au as working electrode was used throughout the experiment. RESULTS: A good linear result was produced for adenosine in the range of 1.00-20.00 microg/mL. The inner-day RSD of peak area and retention time for the standard adenosine solution were 4.97% and 0.47%, respectively. The intra-day RSD of peak area and retention time for the standard adenosine solution were 6.08% and 0.52%, respectively. The proposed method was applied to food and satisfactory results were obtained, with and average recoveries of 93.3%-106.7% and 8.86% of RSD. CONCLUSION: The high performance anion exchange chromatography method is a simple, accurate, and reliable method for measuring adenosine in food, which can be completed within 10 minutes.

[Detecting nicotine and its metabolite cotinine in human hair with capillary gas chromatography].

OBJECTIVE: To develop a rapid method for determination of nicotine and its metabolite cotinine in human hair with capillary gas chromatography with flame ionization detector. METHODS: The hair sample was digested by 1.5 mol/L sodium hydroxide solution. The nicotine and cotinine in the hair sample were extracted with a mixed solvent of dichloromethane-methanol (3:1). Aliquot of the extraction solution was vaporized with nitrogen flow and then methanol was added to dissolve the analysts. The analysts were tested with capillary gas chromatography. RESULTS: The detection limits (signal to noise ratio of 3:1) were 4.3 ng/mL for nicotine and 10 ng/mL for cotinine, respectively. The spiked recoveries were 90.33%-113.1% for nicotine with relative standard deviation (RSD) of 2.1%-7.0% and 92.92%-117.4% for cotinine with relative standard deviation (RSD) of 4.4%-8.9%, respectively. CONCLUSION: The proposed method is sensitive, simple, easy and rapid. It can be easily extended to large scale applications in tobacco epidemiology studies.

[Simultaneous determination of iron, copper and cobalt in food samples by diode array detection-flow injection analysis using partial least squares calibration model].

A flow injection-CCD-diode array detection spectrophotometric method using partial least squares (PLS) algorithm for the simultaneous determination of iron, copper and cobalt in food samples has been established. The method was based on the chromogenic reaction between metallic ions and 5-Br-PADAP in the presence of acetic acid-acetic sodium buffer solution (pH 5) containing 30 g x L(-1) ascorbic acid and 2% (phi) Triton X-100. The overlapped spectra of these complexes were collected by CCD diode array detector and the multi-wavelength absorbance data were processed using partial least squares algorithm. The reaction conditions and analytical parameters of FIA were investigated. The food samples can be analyzed without any separation after digestion, and the sampling rate was 45 x h(-1). The linear ranges of Fe2+, Cu+ and Co2+ were 0.2-10.0 microg x mL(-1), 0.1-5.0 microg x mL(-1), and 0.01-1.0 microg x mL(-1) and the detection limits were 0.2, 0.1 and 0.01 microg x mL(-1), respectively. The average recoveries of spiked samples were 89.4%-110.8% for the three elements. The relative standard deviation (RSD) of samples was in the range of 1.1%-12.1%. Comparing the proposed method with ICP-AES, the relative error was below 12.1%. Above all, this method is simple, quick, sensitive, selective, and easy to be apply and generalize.

[Determination of mannitol in health food by capillary gas chromatography].

OBJECTIVE: To develop a capillary gas chromatographic method for the determination of mannitol in health food. METHODS: Mannitol was extracted from the sample with water by ultrasonic wave. The aliquot of sample solution was acetylated to form mannitol hexacetate with lower boiling point. Then the derivative was separated with the use of SPB-608 capillary chromatographic column and determined by flame ionization detector (FID) at the column temperature of 180 degrees C, the detector temperature of 210 degrees C and the nitrogen flow rate of 30 mL/min. RESULTS: The linear range of this method was 0.05-10.00 mg/mL and the limit of detection of was 0.01 mg/mL. The within-day and between-days precisions were 4.4% and 7.3%-7.6%, respectively. The average recoveries were 84.6%-107.6%. Mannitol could be separated from glucose, inositol and sorbitol under the optimum chromatographic condition. CONCLUSION: The results demonstrate that the method has the advantages of simplicity, accuracy and sensitivity. It is suitable for the determination of mannitol in health food.

[Simultaneous determination of copper and iron by flow-injection catalytic kinetic spectrophotometry with multi-channel detector].

The simultaneous determination of copper and iron by catalytic kinetic spectrophotometric method with back propagating artifical neural net (BP-ANN) was studied based on the catalysis of Cu(II) and Fe(III) to the reaction of rhodamine B hydrogen peroxide in the range of pH 3-9. The determination was performed by the construction of pH gradient and a CCD-diode array detector with a microcomputer. The optimum conditions of reaction and flow injection were studied. The determination limits for copper and iron were 0.10 and 0.21 microgram.L-1, respectively. The sampling rate was 10 samples per hour. The proposed method has been used to determine Cu(II) and Fe(III) in certified reference materials and food samples with satisfactory results. The average values of spiked recovery were 93.3%-100.2% with RSD of 0.6%-7.5%.

[Determination of methanol and fusel oils in alcohol beverages using headspace solid-phase microextraction and gas chromatography].

A method for the determination of methanol and fusel oils in alcohol beverages using headspace solid-phase microextraction and gas chromatography (HS-SPME-GC) is presented. The solid phase was a coated epoxy resin. The extraction and chromatography conditions were optimized. Limits of detection were 0.02 mg/L-0.04 mg/L and relative standard deviations were in the range of 1.4%-4.1%. The proposed method showed better sensitivity in comparing with direct headspace gas chromatography(HS-GC, the National Standard method). This method was applied to evaluate real samples. The spiked recoveries in beer, wine and functional alcohol samples ranged from 80.8% to 110.3% for methanol and fusel oils. The results by HS-SPME-GC and HS-GC for alcohol samples coincided very well. The proposed method is simple, fast and accurate with high reproducibility, high sensitivity and low cost. It extends the applications of SPME.