title: Improved solvent collection system for a dispersive liquid-liquid microextraction of organochlorine pesticides from water using low-density organic solvent.
abstract: In this study, the organochlorine pesticides (OCPs) levels in lake and tap water samples were determined by a dispersive liquid-liquid microextraction method using a low-density organic solvent and an improved solvent collection system (DLLME-ISCS). This method used a very small volume of a solvent of low toxicity (11  μL of 1-nonanol and 400  μL of methanol) to extract OCPs from 10  mL water samples prior to the analysis by GC. After centrifugation in the dispersive liquid-liquid microextraction, there was a liquid organic drop floating between the water surface and the glass wall of the centrifuge tube. The liquid organic drop (with some water phase) was transferred into a microtube (3  mm×15  mm) with a syringe. The organic and aqueous phases were separated in the microtube immediately. Then, 1  μL of the organic solvent (which was in the upper portion of liquid in the microtube) was easily collected by a syringe and injected into the GC-ECD system for the analysis. Under optimum conditions, the linear range of this method was 5-5000  ng/L for most of the analytes. The correlation coefficient was higher than 0.997. Enrichment factors ranged from 1309 to 3629. The relative recoveries ranged from 73 to 119% for lake water samples. The LODs of the method ranged from 0.7 to 9.4  ng/L. The precision of the method ranged from 1.0 to 10.8% for lake water.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Chu-Chi
authors.initials: CC
authors.lastname: Chang
authors.forename: Shuo-Yang
authors.initials: SY
authors.lastname: Wei
authors.forename: Shang-Da
authors.initials: SD
authors.lastname: Huang
mesh_terms: D005591:Chemical Fractionation / Q000295:instrumentation / Q000379:methods*; D006843:Hydrocarbons, Chlorinated / Q000032:analysis / Q000302:isolation & purification*; D009930:Organic Chemicals / Q000737:chemistry*; D010575:Pesticides / Q000032:analysis / Q000302:isolation & purification*; D012997:Solvents / Q000737:chemistry*
chemical_list: D006843:Hydrocarbons, Chlorinated; D009930:Organic Chemicals; D010575:Pesticides; D012997:Solvents