title: Using a postcolumn-infused internal standard for correcting the matrix effects of urine specimens in liquid chromatography-electrospray ionization mass spectrometry.
abstract: Matrix effects (MEs) are a major problem affecting the quantitative accuracy of liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) when analyzing complicated samples. While analyzing urine specimens, the wide diversity of endogenous materials and different urine concentrations may result in inaccurate quantification. In this study, we propose a postcolumn-infused internal standard (PCI-IS) strategy for universal correction of MEs in urine specimens. MEs can be effectively corrected by dividing the target analyte signal intensity by the PCI-IS intensity. To evaluate the performance of PCI-IS, we used 6 benzodiazepine (BZD) drugs in 5 different concentrations of urine matrixes as a test model. The divergence of the BZD drug signal responses in 5 different urine matrixes was expressed using their respective coefficients of variation (CV) to evaluate the efficiency of using PCI-IS in correcting matrix effects. The CV of the BZD drug signal intensities in these 5 different concentrations of the urine matrixes were reduced from 10 to 30% to less than 10% when the PCI-IS correction method was employed. When the PCI-IS method was used to correct the 6 BZDs in 25 real human urine samples, over 90% of the test results exhibited quantification errors of less than 20%, and all of the test results had quantification errors of less than 30%. These results demonstrate that the PCI-IS method can resolve the problem of inaccurate quantification that arises from the diversity of urine specimens. The PCI-IS method is particularly useful for clinical analysis or forensic toxicology to improve the quantification accuracy in an economical way.
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taiwan.
authors.forename: Hsiao-Wei
authors.initials: HW
authors.lastname: Liao
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taiwan.
authors.forename: Guan-Yuan
authors.initials: GY
authors.lastname: Chen
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taiwan.
authors.forename: I-Lin
authors.initials: IL
authors.lastname: Tsai
authors.affiliation: School of Pharmacy, College of Medicine, National Taiwan University, Taiwan. Electronic address: chkuo@ha.mc.ntu.edu.tw.
authors.forename: Ching-Hua
authors.initials: CH
authors.lastname: Kuo
mesh_terms: D001569:Benzodiazepines / Q000652:urine*; D002853:Chromatography, Liquid / Q000379:methods / Q000592:standards; D006801:Humans; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods / Q000592:standards; D016482:Urinalysis
chemical_list: D001569:Benzodiazepines
keywords: Benzodiazepine (BZD); LC–ESI-MS; Matrix effects; Postcolumn-infused internal standard (PCI-IS); Urine concentrations