title: Multivariate optimization of the hollow fibre liquid phase microextraction of muscimol in human urine samples.
abstract: A liquid phase microextraction based on hollow fibre followed by liquid chromatographic determination was developed for the extraction and quantitation of the hallucinogenic muscimol from urine samples. Method applicability on polar hallucinogens was also tested on two alkaloids, a psychedelic hallucinogen, tryptamine and a polar amino acid, tryptophan which exists in its charged state in the entire pH range. A multivariate design of experiments was used in which a half fractional factorial approach was applied to screen six factors (donor phase pH, acceptor phase HCl concentration, carrier composition, stirring rate, extraction time and salt content) for their extent of vitality in carrier mediated liquid microextractions. Four factors were deemed essential for the effective extraction of each analyte. The vital factors were further optimized for the extraction of single-spiked analyte solutions using a central composite design. When the simultaneous extraction of analytes was performed under universal factor conditions biased towards maximizing the enrichment of muscimol, a good composite desirability value of 0.687 was obtained. The method was finally applied on spiked urine samples with acceptable enrichments of 4.1, 19.7 and 24.1 obtained for muscimol, tryptophan and tryptamine respectively. Matrix-based calibration curves were used to address matrix effects. The r(2) values of the matrix-based linear regression prediction models ranged from 0.9933 to 0.9986. The linearity of the regression line of the matrix-based calibration curves for each analyte was directly linked to the analyte enrichment repeatability which ranged from an RSD value of 8.3-13.1%. Limits of detection for the developed method were 5.12, 3.10 and 0.21ngmL(-1) for muscimol, tryptophan and tryptamine respectively. The developed method has proven to offer a viable alternative for the quantitation of muscimol in human urine samples.
authors.affiliation: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Somandla
authors.initials: S
authors.lastname: Ncube
authors.affiliation: Faculty of Chemistry, Opole University, Pl. Kopernika 11, 45-040 Opole, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Poliwoda
authors.affiliation: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, 2050, South Africa.
authors.forename: Hlanganani
authors.initials: H
authors.lastname: Tutu
authors.affiliation: Faculty of Chemistry, Opole University, Pl. Kopernika 11, 45-040 Opole, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Wieczorek
authors.affiliation: Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg, 2050, South Africa. Electronic address: luke.chimuka@wits.ac.za.
authors.forename: Luke
authors.initials: L
authors.lastname: Chimuka
mesh_terms: D000704:Analysis of Variance; D002138:Calibration; D006801:Humans; D057230:Limit of Detection; D059627:Liquid Phase Microextraction / Q000379:methods*; D008297:Male; D008962:Models, Theoretical; D015999:Multivariate Analysis; D009118:Muscimol / Q000737:chemistry / Q000652:urine*; D012015:Reference Standards; D015203:Reproducibility of Results; D014363:Tryptamines / Q000652:urine; D014364:Tryptophan / Q000652:urine; D055815:Young Adult
chemical_list: D014363:Tryptamines; D009118:Muscimol; C030820:tryptamine; D014364:Tryptophan
keywords: Central composite design; Hallucinogen; Hollow fibre liquid phase microextraction; Muscimol; Urine sample