Division of Metabolic and Nutritional Medicine, Dr. von Hauner Children's Hospital, University of Munich Medical Centre, Munich, Germany.
Ann Nutr Metab. 2012;61(4):314-21. doi: 10.1159/000342774. Epub 2012 Dec 3.
BACKGROUND/AIMS: Excretion of urinary compounds in spot urine is often estimated relative to creatinine. For the growing number of liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays of urine-excreted molecules, a fast and accurate method for determination of creatinine is needed.
A high-throughput flow injection tandem mass spectrometry method for exact quantitation of creatinine in urine has been developed and validated. Sample preparation used only two-step dilution for protein precipitation and matrix dilution. Flow injection analysis without chromatographic separation allowed for total run times of 1 min per sample. Creatinine concentrations were quantitated using stable isotope dilution tandem mass spectrometry. Selectivity and coelution-free quantitation were assured by qualifier ion monitoring.
Method validation revealed excellent injection repeatability of 1.0% coefficient of variation (CV), intraday precision of 1.2% CV and interday precision of 2.4% CV. Accuracy determined from standard addition experiments was 106.1 ± 3.8%. The linear calibration range was adapted to physiological creatinine concentrations. Comparison of quantitation results with a routinely used method (Jaffé colorimetric assay) proved high agreement (R(2) = 0.9102).
The new method is a valuable addition to the toolbox of LC-MS/MS laboratories where excretion of urinary compounds is studied. The 'dilute and shoot' approach to isotope dilution tandem mass spectrometry makes the new method highly accurate as well as cost- and time-efficient.
背景/目的：尿液中化合物的排泄通常相对于肌酐进行估计。对于越来越多的尿液中排泄分子的液相色谱-串联质谱（LC-MS/MS）分析，需要一种快速准确的肌酐测定方法。
开发并验证了一种用于尿液中肌酐精确定量的高通量流动注射串联质谱法。样品制备仅使用两步稀释进行蛋白质沉淀和基质稀释。无需色谱分离的流动注射分析允许每个样品的总运行时间为 1 分钟。使用稳定同位素稀释串联质谱法定量肌酐浓度。通过 qualifier 离子监测确保选择性和无共洗脱定量。
方法验证显示出 1.0%变异系数（CV）的出色注射重复性、1.2%日内精密度和 2.4%日间精密度。从标准添加实验确定的准确度为 106.1 ± 3.8%。线性校准范围适应于生理肌酐浓度。与常规使用的方法（Jaffé 比色法）的定量结果比较证明了高度一致性（R² = 0.9102）。
该新方法是 LC-MS/MS 实验室中研究尿液化合物排泄的有用工具。用于同位素稀释串联质谱法的“稀释和进样”方法使新方法具有高度准确性和成本效益，同时也节省时间。
