Health and Biomedical Sciences
Permanent URI for this community
Browse
Browsing Health and Biomedical Sciences by Author "Farrell, E. Sebastian"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Behavior of Model Ionic Compounds under Thermospray Liquid/Liquid Extraction Conditions(1997) Farrell, E. SebastianOur previously reported procedure for the extraction of semivolatile and nonvolatile organic compounds from aqueous samples by thermospray liquid/liquid extraction was extended to the extraction of charged organic compounds from water. By thermally disrupting or extricating the solvation shell of hydrated ions, the thermospray process facilitates the extraction of these analytes from the aqueous matrix. The effects of probe temperature, probe flow rate, and sample pH on the extraction efficiency of model compounds such as phenylalanine, benzoate ion, p-toluenesulfonate ion, and naphthalenetrisulfonic acid trisodium salt were investigated. Under optimized conditions, the percent recoveries for these compounds were 95, 97, 91, and 13%, respectively.Item Design and Evaluation of a New Thermospray Liquid/Liquid Extractor for the Extraction of Semivolatile and Nonvolatile Organic Compounds from Water(1996) Farrell, E. SebastianThe recovery of several semivolatile organic compounds (SVOCs) using a new thermospray liquid/liquid extractor (TSLLE) was investigated. The base system includes a 300 mL multiport extraction vessel, jacketed in a 500 mL cooling flask, a dual-stage condenser for progressive cooling, several thermospray probes, and solvent/sample delivery systems. Aqueous mixtures of SVOCs were used to evaluate the TSLLE. For most compounds, recovery values of 80−100% were obtained during a single cycle in <1 h. The design, evaluation, and extraction capability of the TSLLE are discussed.Item Improving the Recovery of Ionic Solutes from Aqueous Media by Modified Thermospray Liquid-Liquid Extraction Conditions(2000) Farrell, E. SebastianOur previously reported procedure for the extraction of charged compounds from aqueous samples by thermospray liquid−liquid extraction (TSLLE) was essentially a one-step extraction involving large sample volumes. In this report, recirculative extraction, analysis of small sample volumes, the halide ion effect, and the effect of solvency or solvent modification on the extraction efficiency of benzoic acid (BA) by TSLLE were investigated. Compared to the one-step procedure that resulted in an extraction efficiency of only 28% for BA in n-hexane, recirculative TSLLE resulted in a BA recovery of 65% after five extraction cycles. When applied to sample volumes of 5−10 mL, TSLLE extracted BA with a precision of 2.8−6.1%. NaF, NaCl, and NaBr were also used to enhance analyte recovery. NaF gave the best recovery, 104%, for BA relative to the 88% obtained by batch processing. Some improvements in the extraction efficiency was observed when solvent modifiers such as methanol, ethanol, and 2-propanol were used.Item Rapid Removal of Selected Volatile Organic Compounds from Gaseous Mixtures Using a New Dispersive Vapor Extraction Technique: A Feasibility Study(2010) Farrell, E. SebastianA new dispersive vapor extraction (DVE) technique for rapid removal of selected volatile organic compounds (VOCs) from gaseous mixtures was investigated. In this technique, less than 1.0 mL of a volatile solvent was vaporized for 8 min in a 250-mL flask containing a gaseous mixture. The flask was then cooled under running tap water for 2-3 min to induce condensation of the vapor and co-extraction of the VOCs from the headspace. The technique was tested over a concentration range of 4-23 ppb, and resulted in extraction efficiencies ranging from 80 to 97% for the VOCs tested. Because of its simplicity and the relatively short sampling time, DVE could potentially lead to high sample throughput and rapid air analysis.Item Spectrophotometric Determination of Bromate Ions Using Phenothiazines(1995) Farrell, E. SebastianA highly sensitive spectrophotometric method for the determination of bromate ion is described. The method is based on the reduction of aqueous bromate ion by a phenothiazine in acidic conditions to produce a colored species. The method is suitable for bromate ion determination in the 1–700 μg/l range. For the most sensitive reagent, trifluoperazine, the limit of detection and limit of quantitation were calculated to be 0.67 and 2.25 μg/l, respectively.