title: Membrane assisted micro-solid phase extraction of pharmaceuticals with amino and urea-grafted silica gel.
abstract: Individual polar sorbents with surface-displayed amino groups (APS) and non-nucleophilic urea-groups (UPS), were prepared by chemical modification of granular silica gel with bifunctional silane coupling reagents. In this preliminary study, they were separately employed for micro-solid phase extraction (μ-SPE) of the quarternary salt of Amitriptyline (Ami), Carbamazepine (Cbz), Ketoprofen (Ket) and Diclofenac (Dfn) from aqueous samples in conjunction with high performance liquid chromatography. The resulting enrichment factors for both APS and UPS are comparable and exceeded those of μ-SPE involving commercial C18-silica gel sorbents. The presence of highly polar, but non-basic and non-nucleophilic surfaces on UPS prompted the development of a UPS-based μ-SPE method. Good linear correlation was found over a concentration range of 0-50 μg L(-1) with limits of detection ranging from 0.66 to 2.36 μg L(-1)). Limits of quantification between 1.61 and 7.88 μg L(-1) were obtained. HPLC analyses indicated that relative recoveries of 123% for Ami, 65.6% for Cbz, 71.2% for Ket and 66.5% for Dfn were obtained during μ-SPE of spiked (10 μg L(-1)) environmental water samples with percentage relative standard deviations (%RSD) of between 2.1% and 12.6%.
authors.affiliation: Graduate School of Integrative Sciences and Engineering, National University of Singapore, 28, Medical Drive, Singapore 117456, Singapore.
authors.forename: Tze Han
authors.initials: TH
authors.lastname: Lim
authors.forename: Lingna
authors.initials: L
authors.lastname: Hu
authors.forename: Cong
authors.initials: C
authors.lastname: Yang
authors.forename: Chaobin
authors.initials: C
authors.lastname: He
authors.forename: Hian Kee
authors.initials: HK
authors.lastname: Lee
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D057230:Limit of Detection; D008567:Membranes, Artificial; D004364:Pharmaceutical Preparations / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification*; D015203:Reproducibility of Results; D058428:Silica Gel / Q000737:chemistry*; D052617:Solid Phase Microextraction / Q000295:instrumentation / Q000379:methods; D014508:Urea; D014881:Water Supply / Q000032:analysis
chemical_list: D008567:Membranes, Artificial; D004364:Pharmaceutical Preparations; D058428:Silica Gel; D014508:Urea
keywords: %RSD; 3-aminopropyltriethoxy silane; 3-ureidopropyltrimethoxysilane; APS; APTES; Ami; Amino; Carbamazepine; Cbz; Dfn; Diclofenac; EF; EME; Enrichment factors; HILIC; HPLC; Ket; Ketoprofen; LC; LOD; LOQ; LPME; MA; MAME; MS; Membrane microextraction; ODS; PAC; Pharmaceuticals; Rr; SBME; SCR; SPE; SPME; Sil; Sorbents; UPS; UPTMS; Urea; commercial C18 silica gel; electromembrane extraction; enrichment factor; high-performance liquid chromatography; hydrophilic interaction liquid chromatography; limit of detection; limit of quantification; liquid chromatography; liquid phase microextraction; mass spectrometry detectors; membrane assisted microextraction; membrane-assisted; membrane-protected micro-solid phase extraction; percentage relative recovery; percentage relative standard deviation; pharmaceutically-active compounds; primary amino-grafted silica gel; quarternary salt of Amitriptyline; silane coupling reagent; solid bar microextraction; solid phase extraction; solid phase microextraction; unmodified silica gel; urea-grafted silica gel; μ-SPE