Alagandula Ravali, Zhou Xiang, Guo Baochuan
Department of Chemistry, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH, 44115, USA.
Rapid Commun Mass Spectrom. 2017 Jan 15;31(1):39-46. doi: 10.1002/rcm.7763.
Liquid chromatography/tandem mass spectrometry (LC/MS/MS) is the gold standard of urine drug testing. However, current LC-based methods are time consuming, limiting the throughput of MS-based testing and increasing the cost. This is particularly problematic for quantification of drugs such as phenobarbital, which is often analyzed in a separate run because they must be negatively ionized.
This study examined the feasibility of using a dilute-and-shoot flow-injection method without LC separation to quantify drugs with phenobarbital as a model system. Briefly, a urine sample containing phenobarbital was first diluted by 10 times, followed by flow injection of the diluted sample to mass spectrometer. Quantification and detection of phenobarbital were achieved by an electrospray negative ionization MS/MS system operated in the multiple reaction monitoring (MRM) mode with the stable-isotope-labeled drug as internal standard.
The dilute-and-shoot flow-injection method developed was linear with a dynamic range of 50-2000 ng/mL of phenobarbital and correlation coefficient > 0.9996. The coefficients of variation and relative errors for intra- and inter-assays at four quality control (QC) levels (50, 125, 445 and 1600 ng/mL) were 3.0% and 5.0%, respectively. The total run time to quantify one sample was 2 min, and the sensitivity and specificity of the method did not deteriorate even after 1200 consecutive injections.
Our method can accurately and robustly quantify phenobarbital in urine without LC separation. Because of its 2 min run time, the method can process 720 samples per day. This feasibility study shows that the dilute-and-shoot flow-injection method can be a general way for fast analysis of drugs in urine. Copyright © 2016 John Wiley & Sons, Ltd.
液相色谱/串联质谱法（LC/MS/MS）是尿液药物检测的金标准。然而，当前基于液相色谱的方法耗时较长，限制了基于质谱检测的通量并增加了成本。对于苯巴比妥等药物的定量分析而言，这一问题尤为突出，因为这类药物通常需单独进行分析，原因是它们必须进行负离子化。
本研究以苯巴比妥作为模型系统，考察了采用无需液相色谱分离的直接进样流动注射法对药物进行定量分析的可行性。简要而言，首先将含有苯巴比妥的尿液样本稀释10倍，随后将稀释后的样本直接进样至质谱仪进行流动注射分析。采用电喷雾负离子化MS/MS系统，以稳定同位素标记药物作为内标，在多反应监测（MRM）模式下实现对苯巴比妥的定量和检测。
所开发的直接进样流动注射法呈线性，苯巴比妥的动态范围为50 - 2000 ng/mL，相关系数>0.9996。在四个质量控制（QC）水平（50、125、445和1600 ng/mL）下，批内和批间变异系数及相对误差分别为3.0%和5.0%。定量一个样本的总运行时间为2分钟，即使在连续进样1200次后，该方法的灵敏度和特异性仍未降低。
我们的方法无需液相色谱分离即可准确、可靠地对尿液中的苯巴比妥进行定量分析。由于其2分钟的运行时间，该方法每天可处理720个样本。这项可行性研究表明，直接进样流动注射法可成为尿液中药物快速分析的通用方法。版权所有© 2016约翰威立父子有限公司。
