Scholz Karoline, Dekant Wolfgang, Völkel Wolfgang, Pähler Axel
Department of Toxicology, University of Würzburg, Germany.
J Am Soc Mass Spectrom. 2005 Dec;16(12):1976-84. doi: 10.1016/j.jasms.2005.08.003. Epub 2005 Oct 24.
A sensitive and specific liquid chromatography-mass spectrometry (LC-MS) method based on the combination of constant neutral loss scans (CNL) with product ion scans was developed on a linear ion trap. The method is applicable for the detection and identification of analytes with identical chemical substructures (such as conjugates of xenobiotics formed in biological systems) which give common CNLs. A specific CNL was observed for thioethers of N-acetyl-L-cysteine (mercapturic acids, MA) by LC-MS/MS. MS and HPLC parameters were optimized with 16 MAs available as reference compounds. All of these provided a CNL of 129 Da in the negative-ion mode. To assess sensitivity, a multiple reaction monitoring (MRM) mode with 251 theoretical transitions using the CNL of 129 Da combined with a product ion scan (IDA thMRM) was compared with CNL combined with a product ion scan (IDA CNL). An information-dependent acquisition (IDA) uses a survey scan such as MRM (multiple reaction monitoring) to generate "informations" and starting a second acquisition experiment such as a product ion scan using these "informations." Th-MRM means calculated transitions and not transitions generated from an available standard in the tuning mode. The product ion spectra provide additional information on the chemical structure of the unknown analytes. All MA standards were spiked in low concentrations to rat urines and were detected with both methods with LODs ranging from 60 pmol/mL to 1.63 nmol/mL with IDA thMRM. The expected product ion spectra were observed in urine. Application of this screening method to biological samples indicated the presence of a number of MAs in urine of unexposed rats, and resulted in the identification of 1,4-dihydroxynonene mercapturic acid as one of these MAs by negative and positive product ion spectra. These results show that the developed methods have a high potential to serve as both a prescreen to detect unknown MAs and to identify these analytes in complex matrix.
基于线性离子阱，开发了一种将恒定中性丢失扫描（CNL）与产物离子扫描相结合的灵敏且特异的液相色谱-质谱（LC-MS）方法。该方法适用于检测和鉴定具有相同化学亚结构的分析物（如生物系统中形成的外源性物质共轭物），这些分析物会产生共同的CNL。通过LC-MS/MS观察到N-乙酰-L-半胱氨酸硫醚（巯基尿酸，MA）的特定CNL。使用16种可作为参考化合物的MA对质谱和高效液相色谱参数进行了优化。所有这些在负离子模式下均提供了129 Da的CNL。为评估灵敏度，将使用129 Da的CNL结合产物离子扫描（IDA thMRM）的具有251个理论跃迁的多反应监测（MRM）模式与结合产物离子扫描的CNL（IDA CNL）进行了比较。信息依赖采集（IDA）使用诸如MRM（多反应监测）的全扫描来生成“信息”，并使用这些“信息”启动第二个采集实验，如产物离子扫描。Th-MRM是指计算出的跃迁，而非在调谐模式下从可用标准品产生的跃迁。产物离子谱提供了有关未知分析物化学结构的额外信息。所有MA标准品均以低浓度添加到大鼠尿液中，两种方法均检测到了这些标准品，IDA thMRM的检测限范围为60 pmol/mL至1.63 nmol/mL。在尿液中观察到了预期的产物离子谱。将这种筛选方法应用于生物样品表明，未接触大鼠的尿液中存在多种MA，并通过负离子和正离子产物离子谱鉴定出1,4-二羟基壬烯巯基尿酸是其中一种MA。这些结果表明，所开发的方法具有很高的潜力，可作为检测未知MA的预筛选方法，并在复杂基质中鉴定这些分析物。
