40 research outputs found
Headspace solid-phase microextraction using poly(ethylene glycol) grafted multi-walled carbon nanotube fibers for the determination of methyl tert-butyl ether in water samples
Determination of melamine in soil samples using surfactant-enhanced hollow fiber liquid phase microextraction followed by HPLCâUV using experimental design
Surfactant-enhanced hollow fiber liquid phase (SE-HF-LPME) microextraction was applied for the extraction of melamine in conjunction with high performance liquid chromatography with UV detection (HPLCâUV). Sodium dodecyl sulfate (SDS) was added firstly to the sample solution at pH 1.9 to form hydrophobic ion-pair with protonated melamine. Then the protonated melamineâdodecyl sulfate ion-pair (MelâDS) was extracted from aqueous phase into organic phase immobilized in the pores and lumen of the hollow fiber. After extraction, the analyte-enriched 1-octanol was withdrawn into the syringe and injected into the HPLC. Preliminary, one variable at a time method was applied to select the type of extraction solvent. Then, in screening step, the other variables that may affect the extraction efficiency of the analyte were studied using a fractional factorial design. In the next step, a central composite design was applied for optimization of the significant factors having positive effects on extraction efficiency. The optimum operational conditions included: sample volume, 5 mL; surfactant concentration, 1.5 mM; pH 1.9; stirring rate, 1500 rpm and extraction time, 60 min. Using the optimum conditions, the method was analytically evaluated. The detection limit, relative standard deviation and linear range were 0.005 Όg mLâ1, 4.0% (3 Όg mLâ1, n = 5) and 0.01â8 Όg mLâ1, respectively. The performance of the procedure in extraction of melamine from the soil samples was good according to its relative recoveries in different spiking levels (95â109%)
Determination of volatile organic compounds in environmental water samples using three solid-phase microextraction fibers based on solâgel technique with gas chromatographyâflame ionization detector
Determination of triazole fungicides using hollow fiber liquid phase microextraction prior to gas chromatography-mass spectrometry analysis
A two phase hollow fiber liquid phase microextraction (HF-LPME) and gas chromatography mass spectrometry (GC-MS) method for the separation and determination of triazole fungicides, namely, penconazole, hexaconazole, diclobutrazole and diniconazole, is described. The extraction conditions were optimized for the four triazole fungicides as follows: extractant solvent, toluene; extraction time, 20 min; stirring rate, 720 rpm; no salt addition; and no pH adjustment. Under the optimal extraction conditions, the method showed good linearity (r2 = 0.997â0.999), acceptable reproducibility (RSD% = 6â9%), low limit of detection (0.3â0.8 ÎŒg·Lâ1), and satisfactory relative recoveries. The linear range is 1â5000 ÎŒg·Lâ1. The developed HF-LPME method was applied for the determination of triazole fungicides in farm, river, and tap water and also grape juice samples