A pressure-assisted CEC with ESI-MS based on poly(1-hexadecene-co-trimethylolpropane trimethacrylate) monolithic column for rapid analysis of two beta(2)-agonists and three narcotics was established in this article. After the organic polymer-based monolithic column was prepared by an in-situ polymerization procedure, a systematic investigation of the pressure-assisted CEC separation and ESI-MS detection parameters was performed. Baseline separation of the studied analytes could be obtained using the solution containing 75% ACN v/v and 20 mmol/L ammonium acetate with pH 8.0 as running buffer, when applying separation voltage of 20 kV and assisted pressure of 5 bar. Under the optimized conditions, two beta(2)-agonists and three narcotics could be completely resolved and accurately determined within 15 min. Finally, the proposed method was successfully used for real urine samples detection.
A polar polymethacrylate-based monolithic column was introduced and evaluated as a hydrophilic interaction CEC stationary phase. The monolithic stationary phase was prepared by in situ copolymerization of a neutral monomer 2-hydroxyethyl methacrylate and a polar cross-linker N,N'-methylene bisacrylamide in a binary porogenic solvent consisting of dodecyl alcohol and toluene. The hydroxyl and amino groups at the surface of the monolithic stationary phase provided polar sites which were responsible for hydrophilic interactions. The composition and proportion of the polymerization mixture was investigated in detail. The mechanical stability and reproducibility of the obtained monolithic column preformed was satisfied. The effects of pH and organic solvent content on the EOF and the separation of amines, nucleosides, and narcotics on the optimized monolithic column were investigated. A typical hydrophilic interaction CEC was observed on the neutral polar stationary phase. The optimized monolithic column can obtain high-column efficiencies with 62,000-126,000 theoretical plates/m and the RSDs of column-to-column (n = 9), run-to-run (n = 5), and day-to-day (n = 3) reproducibility were less than 6.3%. The calibration curves of these five narcotics exhibited good linearity with R in the range of 0.9959-0.9970 and linear ranges of 1.0-200.0 μg/mL. The detection limits at S/N = 3 were between 0.2 and 1.2 μg/mL. The recoveries of the separation of narcotics on the column were in the range of 84.0-108.6%. The good mechanical stability, reproducibility, and quantitation capacity was suitable for pressure-assisted CEC applications.
A microemulsion electrokinetic capillary (MEEKC) chromatography method was online-coupled with fieldamplified sample injection (FASI) for the analysis of nucleosides and nucleobases, namely cytidine, guanosine, N 6 -methyladenosine, fluorouracil, thymine, adenine, mercaptopurine, 6-hydroxypurine, and guanine. A microemulsion background electrolyte containing 10 mM sodium dodecyl sulfate (SDS), 0.6%(v/v) 1-butanol, 0.5% (v/v) ethyl acetate and 98.9% (v/v) borate buffer (10 mM; pH 9.0) was used as the running buffer. An online field-amplified sample injection (FASI) technique was adopted to improve the detection sensitivity. Baseline separation of nine nucleosides was achieved within 12 min with detection limits (S/N ¼ 3) between 0.22 and 2.97 mg mL À1 with the DAD detector at 200 nm under optimized conditions. The proposed method was applied to the determination of nine nucleoside compounds in spiked urine and serum samples with the recoveries ranging 91.2-113% and 85.2-112% and the relative standard deviations (RSDs, n ¼ 3) at less than 5.90% and 8.22%, respectively.
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