Jitlada Vichapong

Vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet combined with HPLC for the determination of neonicotinoid pesticides.

A microextraction procedure based on vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with solidification of floating organic droplet (VSLLME-SFO) for preconcentration of neonicotinoid pesticides, including acetamiprid, clotianidin, nitenpyram, imidacloprid, and thiamethoxam, has been developed. In VSLLME-SFO process, the addition of surfactant (as an emulsifier), could be enhance the mass-transfer from the aqueous solution into the extraction solvent. The extraction solvent could be dispersed into the aqueous by vortex process. Other experimental parameters affected the extraction efficiency, including the kind and concentration of salt, concentration and volume of HCl, kind and concentration of surfactant and its volume, kind and volume of extraction solvent, vortex time and the centrifugation extraction time, were also optimized. The optimum extraction conditions of VSLLME-SFO were 10.00 mL of sample, 0.3% (w/v) Na2SO4, 50 µL of 0.050 mol L(-1) SDS, 1.0 mol L(-1) HCl (400 µL), 150 µL of octanol, vortex time 1 min and centrifugation time 10 min. The sediment phase was analyzed by subjecting it to HPLC using a mobile phase of 25% acetonitrile in water, at a flow rate of 1.0 mL min(-1), and photodiode array detection at 254 nm. Under the optimum extraction conditions, high enrichment factors (20-100 fold) and low limit of detection (0.1-0.5 μg L(-1)) could be obtained. This method provided high sensitivity, low toxic organic solvents used, and simplicity of the extraction processes. The proposed method was successfully applied in the analysis of neonicotinoids in fruit juice and water samples.

In-coupled syringe assisted octanol–water partition microextraction coupled with high-performance liquid chromatography for simultaneous determination of neonicotinoid insecticide residues in honey

A simple and fast method namely in-coupled syringe assisted octanol-water partition microextraction combined with high performance liquid chromatography (HPLC) has been developed for the extraction, preconcentration and determination of neonicotinoid insecticide residues (e.g. imidacloprid, acetamiprid, clothianidin, thiacloprid, thiamethoxam, dinotefuran, and nitenpyram) in honey. The experimental parameters affected the extraction efficiency, including kind and concentration of salt, kind of disperser solvent and its volume, kind of extraction solvent and its volume, shooting times and extraction time were investigated. The extraction process was carried out by rapid shooting of two syringes. Therefore, rapid dispersion and mass transfer processes was created between phases, and thus affects the extraction efficiency of the proposed method. The optimum extraction conditions were 10.00 mL of aqueous sample, 10% (w/v) Na2SO4, 1-octanol (100µL) as an extraction solvent, shooting 4 times and extraction time 2min. No disperser solvent and centrifugation step was necessary. Linearity was obtained within the range of 0.1-3000 ngmL(-1), with the correlation coefficients greater than 0.99. The high enrichment factor of the target analytes was 100 fold and low limit of detection (0.25-0.50 ngmL(-1)) could be obtained. This proposed method has been successfully applied in the analysis of neonicotinoid residues in honey, and good recoveries in the range of 96.93-107.70% were obtained.

A preconcentration method for analysis of neonicotinoids in honey samples by ionic liquid-based cold-induced aggregation microextraction.

A preconcentration approach based on ionic liquid-based cold-induced aggregation microextraction for determination of neonicotinoid insecticide residues in honey samples before high-performance liquid chromatographic analysis has been developed. Room temperature ionic liquid [C4MIM][PF6] (extraction solvent) and SDS (emulsifier) was used for extraction of the target analytes. The parameters affecting the extraction efficiency were optimized. The optimum microextraction conditions were 200µL room temperature ionic liquids [C4MIM][PF6] containing 0.05molL(-1) SDS, 0.75g sodium carbonate, vortex agitation speed of 1800rpm for 30s and centrifugation at 3500rpm for 10min. Under optimum conditions, the high enrichment factors of 200 could be obtained, leading to low limit of detection (0.01µgL(-1) for all analytes) with the relative standard deviations lower than 2.68% and 5.38% for retention time and peak area, respectively. Good recoveries for the spiked target neonicotinoids at three different concentrations of honey samples were obtained in 86-100% and relative standard deviations were lower than 8.1%. The results demonstrated that the proposed method can be used as an alternative powerful method for the simultaneous determination of the studied insecticides in real honey samples.

Determination of Benzimidazole Anthelminthics in Eggs by Advanced Microextraction with High-Performance Liquid Chromatography

A simple magnetic stirring assisted surfactant-enhanced-emulsification microextraction with high-performance liquid chromatography analysis was developed for the determination of benzimidazoles in eggs. Thiabendazole, mebendazole, albendazole, and fenbendazole were selected as model compounds. The extraction method was based on the rapid injection of emulsifier (Triton X-114) and extraction solvent (1-octanol) into a magnetically stirred aqueous solution to form a cloudy trinary component solvent (aqueous solution/extraction solvent/emulsifier) system. No centrifugation step was necessary. Salt addition, concentration of Triton X-114, type and volume of extraction solvent, extraction time, and stirring rate were optimized. Under the optimized conditions (5% (w/v) sodium sulfate, 0.75% (w/v) Triton X-114, extraction solvent: 300 µL octanol; extraction time: 5 min; stirring rate: 1000 rpm), linearity was observed between 0.05 and 1000 µg L−1 and enrichment factors were between 100 and 300. Low limits of detection and high enrichment factors were obtained.

Determination of β-agonists in Porcine Meats by Ion-Pair Extraction and High Performance Liquid Chromatography

ABSTRACT Ion-paired extraction was employed for the determination of salbutamol, clenbuterol, and ractopamine. Tetrabutylammonium bromide was used as the ion-pairing agent and water–acetonitrile was the extraction solvent. The concentration and pH of the buffer, salt addition, concentration of tetrabutylammonium bromide, and type and volume of extraction solvent were optimized. No centrifugation step was required. Matrix interferences from real samples were eliminated using matrix-matched calibration. Under the optimum conditions, a linear calibration relationship was present from 0.0025 to 3 µg mL−1 with an enrichment factor of more than 25. This method was combined with high-performance liquid chromatography for the determination of β-agonists in porcine meats with low limits of detection, high recovery, and rapid analysis.

Cationic Micellar Precipitation for Simultaneous Preconcentration of Benzimidazole Anthelmintics in Milk Samples by High-Performance Liquid Chromatography

A method using micellar precipitation process using cationic surfactant cetyltrimethyl ammonium bromide at ambient temperature was investigated for simultaneous determination of benzimidazoles coupled with high-performance liquid chromatography (HPLC) analysis. The studied benzimidazoles was selected as model compounds including thiabendazole, albendazole, mebendazole, and fenbendazole. The experimental parameters affected the extraction efficiency, including the kind and concentration of salt, pH, concentration of CTAB, volume of 1-octanol, and the centrifugation extraction time, was optimized. The optimum extraction condition: 0.030 mol L -1 CTAB, 10% (m/v) NaCl, pH 4.0, 300 µL 1-octanol and centrifugation time 10 min. Under optimum conditions, enrichment factors of between 60 and 90 fold were obtained, leading to lower limit of detection in the range of 0.5-0.7 µg L -1 , depending on the analytes. The calibration range of the method was linear over the wide range of 0.5-1000 µg L -1 , with correlation coefficients more than 0.999. Finally, the proposed method was successfully applied in the analysis of benzimidazoles in milk samples.