A modified QuEChERS method for the determination of some herbicides in yogurt and milk by high performance liquid chromatography.

A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was applied to the extraction of triazines and phenylureas from milk and yogurt. The herbicides was extracted by the mixture of ethyl acetate and n-hexane and cleaned by primary secondary amine (10mg/mL). The frozen-out centrifugation was applied to further remove fatty. The proposed method can achieve efficient extraction and cleanup. Some experimental parameters, such as extraction method, extraction solvent and adsorbent, pH of sample solution, extraction time and amount of primary secondary amine and sodium chloride were investigated and optimized. The precision and absolute recoveries of eight herbicides vary from 0.07 to 5.86% and from 78.9 to 99.9%, respectively. The detection limits for simeton, monuron, chlorotoluron, simetryne, atrazine, karmex, ametryne and propazine range from 0.15 to 0.35 ng/mL.

Pneumatic nebulization gas-solid extraction of some pesticides in liquor.

In general, solid phase extraction (SPE) was applied to the separation and concentration of analytes from liquid samples. However, the SPE generally cannot be applied directly to the separation and concentration of analytes from liquor in which the concentration of ethanol is high, because the ethanol can elute the analytes from the SPE column and the analytes can hardly been adsorbed onto the column. In the work, the pneumatic nebulization coupled with gas-solid extraction (PN-GSE) was applied to the extraction of several pesticides, including fenuron, chlortoluron, karmex, linuron and prebane, from liquor samples. The high concentration of ethanol in the liquor samples cannot elute the analytes from the SPE column. The high performance liquid chromatography was applied to the separation and determination of the analytes. Experimental parameters affecting the performances of PN-GSE, such as types and amount of packed material of the column, temperature of the spray chamber, flow rate of carrier gas, pumping rate of gas and volume of elution solvent were examined and optimized. The limits of detection for the analytes were in the range of 0.19-0.26 µg L⁻¹. Liquor samples were analyzed and the recoveries of the analytes in spiked samples were from 91.0 to 106.3%. The relative standard deviations were lower than 6.5%.

Extraction of eight triazine and phenylurea herbicides in yogurt by ionic liquid foaming-based solvent floatation.

The ionic liquid foaming-based solvent floatation (ILF-SF) was developed for extracting triazines and phenylureas from yogurt. These analytes were separated and determined by high performance liquid chromatography. Some experimental parameters, such as the pH value of floatation solution, extraction solvent, kind of ionic liquid and floatation time were investigated and optimized. The mixture of n-propyl alcohol and ethyl acetate was used as extraction solvent and 1-hexyl-3-methylimidazolium hexafluorophosphate was used as foaming agent. The precision and recoveries of eight herbicides vary from 0.17 to 6.90% and from 86.5 to 118.7%, respectively. The detection limits for simeton, simazine, chlortoluron, isoproturon, ametryn, propazine, prometryne and prebane are 0.59, 0.44, 0.44, 0.46, 0.32, 1.01, 0.34 and 0.23 µgL(-1), respectively. The enrichment factors for the solvent floatation range from 11.6 to 18.6 for the eight herbicides.

Ionic liquid foam floatation coupled with solid phase extraction for separation and determination of hormones by high-performance liquid chromatography.

The foaming property of ionic liquids (ILs) was found and the factors that can influence foamability of the ILs were investigated. Based on the property of the ILs, the foam floatation-solid phase extraction (FF-SPE) was developed. The IL-based FF-SPE was applied to the extraction and concentration of steroid hormones, including corticosterone, 17-ß-estadiol, 17-α-estradiol, 19-nortestosterone, estrone, testosterone, 17-α-hydroxyprogesterone, medroxyprogesterone, chloromadinon 17-acetate, norethisterone acetate, medroxyprogesterone-17-acetate, progesterone, 17-ß-estradiol 3-benzoate and testosteron 17-propionate in water samples and then the steroid hormones were determined by high-performance liquid chromatography. The extraction and concentration were performed synchronously in 10 min. Some experimental conditions were examined and optimized. The recoveries ranged from 50.6% to 95.2% for lake water sample and from 53.4% to 98.7% for rain water sample. The precision ranged from 2.43% to 7.43% for the lake water sample and 2.07-7.01% for rain water sample. Based on the foaming property of ILs, the application of foam floatation should be widened.

Ionic liquid-based homogeneous liquid-liquid microextraction for the determination of antibiotics in milk by high-performance liquid chromatography.

Ionic liquid-based homogeneous liquid-liquid microextraction (IL-based HLLME) high-performance liquid chromatography was developed and applied to the extraction, separation and determination of some antibiotics in milk. The proteins and lipids were removed by adding salt and adjusting the pH value. The homogeneous extraction was applied to the improvement of recoveries for IL phase and analytes. The experimental parameters of the IL-based HLLME, including salt concentration in sample solution, pH value of sample solution, volume of [C(6)MIM][BF(4)], amount of ion-pairing agent (NH(4)PF(6)), and extraction time, were evaluated. The limits of detection for enoxacin, pefloxacin, norfloxacin, enrofloxacin, sulfamethoxazole and sulfadimethoxine were 15.8, 7.07, 5.13, 4.00, 7.79 and 8.33 µg L(-1), respectively. When the proposed method was applied to the analysis of milk samples the recoveries of the analytes ranged from 92.5 to 118.6% and relative standard deviations were lower than 7.00%.

Application of pneumatic nebulization single-drop microextraction for the determination of organophosphorous pesticides by gas chromatography-mass spectrometry.

Organophosphorous pesticides (OPPs) including dichlorvos, diazinon, malathion, phenamiphos and chlorpyrifos, in water samples were extracted by pneumatic nebulization single-drop microextraction (PN-SDME) and then determined by gas chromatography-mass spectrometry (GC-MS). Experimental parameters affecting the performances of PN-SDME, such as flow rate of carrier gas, extraction time and microdrop volume, were examined and optimized. The limits of detection for the analytes were in the range of 0.0014-0.0019 µg/mL. The linear range was 0.0050-0.50 µg/mL, except dichlorvos (0.0070-0.50 µg/mL). Water samples were analyzed and the recoveries of the analytes in the spiked water samples were from 75.2 to 105.3%. The relative standard deviations were lower than 12.7%.

Determination of the active constituents in Arnebia euchroma (Royle) Johnst. by ionic liquid-based ultrasonic-assisted extraction high-performance liquid chromatography.

Shikonin and ß,ß'-dimethylacrylshikonin in Arnebia euchroma (Royle) Johnst. were extracted by ionic liquid-based ultrasonic-assisted extraction (IL-based UAE) and determined by high-performance liquid chromatography (HPLC). The dried powder of A. euchroma (Royle) Johnst. was mixed with a room temperature ionic liquid [C(6)MIM][BF(4)] to form a suspension, and then the ultrasonic extraction was performed in a water bath at ambient temperature. The calibration curve showed good linear relationship (r>0.9998) in the concentration range of 1.75-140 µg/mL for shikonin and 2.15-1360 µg/mL for ß,ß'-dimethylacrylshikonin. The recoveries were between 69.79% and 82.35%. The IL-based UAE is free of volatile organic solvents, and consumes less sample, time and solvent, compared with regular ultrasonic and Soxhlet extraction. There was no obvious difference in the extraction yields of active constitutions obtained by the three extraction methods.

Solvent (ionic liquid) impregnated resin-based extraction coupled with dynamic ultrasonic desorption for separation and concentration of four herbicides in environmental water.

A new method was developed for the determination of monolinuron, propazine, linuron, and prebane in environmental water samples. The solvent (ionic liquid) impregnated resin (IL-SIR)-based extraction coupled with dynamic ultrasonic desorption (DUSD) was applied to the separation and concentration of the analytes. The high performance liquid chromatography (HPLC) was applied to the determination of the analytes. The ionic liquid [C(6)MIM][PF(6)] was immobilized on Diaion HP20 resin by immersing the resin in ethanol solution containing [C(6)MIM][PF(6)]. The effect of extraction parameters, including pH value of sample solution, salt concentration in sample and extraction time, and elution conditions, including the concentration of ethanol in elution solvent, the flow rate of elution solvent and the ultrasonic power, were examined and optimized. The limits of detection and quantification for the analytes were in the range of 0.15-0.29 µg L(-1) and 0.51-0.98 µg L(-1), respectively. Some environmental water samples were analyzed and the analytical results were satisfactory.

Determination of phenylurea and triazine herbicides in milk by microwave assisted ionic liquid microextraction high-performance liquid chromatography.

The determination of phenylurea and triazine herbicides in milk based on microwave assisted ionic liquid microextraction (MAILME) coupled with high-performance liquid chromatographic separation was described. The experimental parameters of the MAILE, including type and amount of ionic liquid, microwave extraction power, extraction time and salt concentration in sample, were evaluated by a univariate method and orthogonal screening. When 60 microL of [C(6)MIM][PF(6)] was used as extraction solvent the target compounds can be isolated from the 4 mL of milk. The MAILME is quick (7 min) and simple. The detection limits for isoproturon, monolinuron, linuron, propazine, prometryne, terbutryn and trietazine are 0.46, 0.78, 1.00, 1.21, 1.96, 0.84 and 1.28 microg L(-1), respectively. The proposed method was applied to the analysis of milk samples and the recoveries of the analytes ranged from 88.4 to 117.9% and relative standard deviations were lower than 7.43%.

Determination of triazines in honey by dispersive liquid-liquid microextraction high-performance liquid chromatography.

Dispersive liquid-liquid microextraction (DLLME) high-performance liquid chromatography (HPLC) was developed for extraction and determination of triazines from honey. A room temperature ionic liquid, 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM][PF(6.)], was used as extraction solvent and Triton X 114 was used as dispersant. A mixture of 175 microL [C(6)MIM][PF(6)] and 50 microL 10% Triton X 114 was rapidly injected into the 20 mL honey sample by syringe. After extraction, phase separation was performed by centrifugation and the sedimented phase was analyzed by HPLC. Some experimental parameters, such as type and volume of extraction solvent, concentration of dispersant, pH value of sample solution, salt concentration and extraction time were investigated and optimized. The detection limits for chlortoluron, prometon, propazine, linuron and prebane are 6.92, 5.84, 8.55, 8.59 and 5.31 microg kg(-1), respectively. The main advantages of the proposed method are simplicity of operation, low cost, high enrichment factor and extraction solvent volume at microliter level. Honey samples were analyzed by the proposed method and obtained results indicated that the proposed method provides acceptable recoveries and precisions.