Abstract
This work describes a new extraction method with hollow-fiber liquid-phase microextraction based on facilitated pH gradient transport for analyzing hippuric acid and mandelic acid in aqueous samples. The factors affecting the metabolites extraction were optimized as follows: the volume of sample solution was 10 mL with pH 2 containing 0.5 mol·L−1 sodium chloride, liquid membrane containing 1-octanol with 20% (w/v) tributyl phosphate as the carrier, the time of extraction was 150 min, and stirring rate was 500 rpm. The organic phase immobilized in the pores of a hollow fiber was back-extracted into 24 µL of a solution containing sodium carbonate with pH 11, which was placed inside the lumen of the fiber. Under optimized conditions, the high enrichment factors of 172 and 195 folds, detection limit of 0.007 and 0.009 µg·mL−1 were obtained. The relative standard deviation (RSD) (%) values for intra- and inter-day precisions were calculated at 2.5%–8.2% and 4.1%–10.7%, respectively. The proposed method was successfully applied to the analysis of these metabolites in real urine samples. The results indicated that hollow-fiber liquid-phase microextraction (HF-LPME) based on facilitated pH gradient transport can be used as a sensitive and effective method for the determination of mandelic acid and hippuric acid in urine specimens.
Highlights
Environmental and occupational exposure to the aromatic solvents toluene and ethylbenzene is frequent because these compounds are commonly used as solvents in making paints, dyes, paint thinners, rubber, adhesives, pharmaceutical products and plastic materials
hippuric acid (HA), mandelic acid (MA), methanol-gradient grade, ethyl acetate, 1-decanol, trioctylamine (TOA), tributyl phosphate (TBP), trioctylphosphine oxide (TOPO), n-dodecane, 1-octanol, sodium chloride, sodium carbonate, acetic acid, and hydrochloric acid were obtained from Merck (Darmstadt, Germany)
Salinity that the efficiency and increased with the stirring speed up to 500 rpm, while the extraction decreased at higher rates because at high stirring rates, air-bubbles are generated, which results in loss of solvent, The sample stirring rate in hollow-fiber liquid-phase microextraction, as in other microextraction thereby reducing the precision
Summary
Environmental and occupational exposure to the aromatic solvents toluene and ethylbenzene is frequent because these compounds are commonly used as solvents in making paints, dyes, paint thinners, rubber, adhesives, pharmaceutical products and plastic materials. A novel microextraction technique called hollow-fiber liquid-phase microextraction (HF-LPME) has been used in different environmental and biological samples for different analytes to overcome these problems [17,20,21,22,23,24,25,26,27] In environmental application, both HF-LPME in its two- and three-phase modes have been used to determine various types of contaminants include pesticides, insecticides, aromatic amines, BTEX, phenolic compounds, polychlorinated biphenyls, polynuclear aromatic hydrocarbons, muconic acid and drugs in soil, water and wastewater matrices [17,23,28,29,30,31,32,33]. A simple protocol of the HF-LPME based on facilitated pH gradient transport method was represented for the assessment of toluene and ethylbenzene exposure
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