title: Fluorescent derivatization combined with aqueous solvent-based dispersive liquid-liquid microextraction for determination of butyrobetaine, l-carnitine and acetyl-l-carnitine in human plasma.
abstract: A novel aqueous solvent-based dispersive liquid-liquid microextraction (AS-DLLME) method was combined with narrow-bore liquid chromatography and fluorescence detection for the determination of hydrophilic compounds. A remover (non-polar solvent) and extractant (aqueous solution) were introduced into the derivatization system (acetonitrile) to obtain a water-in-oil emulsion state that increased the mass transfer of analytes. As a proof of concept, three quaternary ammonium substances, including butyrobetaine, l-carnitine and acetyl-l-carnitine, were also used as analytes and determined in pharmaceuticals, personal care products, food and human plasma. The analytes were derivatized with 4-bromomethylbiphenyl for fluorescence detection and improved retention in the column. The linear response was 10-2000nM for l-carnitine and acetyl-l-carnitine with a good determination coefficient (r(2)>0.998) in the standard solution. The detection limit for l-carnitine and acetyl-l-carnitine was 4.5 fmol. The method was also successfully applied to a 1μL sample of human plasma. In the linearity calculations for determining butyrobetaine, l-carnitine and acetyl-l-carnitine in human plasma, the determination coefficients ranged from 0.996 to 0.999. Linear regression exhibited good reproducibility and a relative standard deviation better than 7.50% for the slope and 9.06% for the intercept. To characterize highly hydrophilic compounds in various samples, the proposed method provides good sensitivity for a small sample volume with a low consumption of toxic solvents.
authors: Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
authors: Yi-Ching
authors: YC
authors: Chen
authors: Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 80708, Taiwan.
authors: Chia-Ju
authors: CJ
authors: Tsai
authors: Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; Ph.D. Program in Toxicology, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 80708, Taiwan; Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan. Electronic address: chfeng@kmu.edu.tw.
authors: Chia-Hsien
authors: CH
authors: Feng
mesh_terms: D001622:Betaine / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D002331:Carnitine / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification*; D002853:Chromatography, Liquid / Q000379:methods; D005453:Fluorescence; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D057230:Limit of Detection; D059627:Liquid Phase Microextraction / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D001622:Betaine; C002889:gamma-butyrobetaine; D002331:Carnitine
keywords: Aqueous solvent-based dispersive liquid-liquid microextraction; Fluorescence derivatization; Narrow-bore liquid chromatography; l-carnitine