Institute of Analytical Chemistry, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz, Austria.
J Chromatogr A. 2011 Aug 5;1218(31):5180-6. doi: 10.1016/j.chroma.2011.05.092. Epub 2011 Jun 1.
Direct analysis in real time (DART) time-of-flight mass spectrometry (TOF-MS) has been tested for its suitability as a detector for gradient elution HPLC. Thereby a strong dependency of signal intensity on the amount of organic solvent present in the eluent could be observed. Adding a make-up liquid (iso-propanol) post-column to the HPLC effluent greatly enhanced detection limits for early eluting compounds. Limits of detection achieved employing this approach were in the range of 7-27 μg L(-1) for the parabene test mixture and 15-87 μg L(-1) for the pharmaceuticals. In further investigations DART ionization was compared to several other widely used atmospheric pressure ionization methods with respect to signal suppression phenomena occurring in when samples with problematic matrices are analyzed. For this purpose extracts from environmental and waste water samples were selected as model matrices which were subsequently spiked with a set of six substances commonly present in personal care products as well as six pharmaceuticals at concentration levels between 100 μg L(-1) and 500 μg L(-1) corresponding to 100 ng L(-1) and 500 ng L(-1) respectively in the original sample. With ionization suppression of less than 11% for most analytes investigated, DART ionization showed similar to even somewhat superior behavior compared to atmospheric pressure chemical ionization (APCI) and atmospheric pressure photo ionization (APPI) for the Danube river water extract; for the more challenging matrix of the sewage plant effluent extract DART provided better results with ion suppression being less than 11% for 9 out of 12 analytes while values for APCI were lying between 20% and >90%. Electrospray ionization (ESI) was much more affected by suppression effects than DART with values between 26% and 80% for Danube river water; in combination with the sewage plant effluent matrix suppression >50% was observed for all analytes.
直接实时分析（DART）飞行时间质谱（TOF-MS）已被测试用于作为梯度洗脱 HPLC 的检测器。因此，可以观察到信号强度与洗脱液中有机溶剂含量有很强的依赖性。在 HPLC 流出物后添加柱上补加液（异丙醇）极大地提高了早期洗脱化合物的检测限。采用这种方法，对于对羟基苯甲酸酯测试混合物，检测限达到 7-27μg/L，对于药物，检测限达到 15-87μg/L。在进一步的研究中，DART 离子化与其他几种广泛使用的大气压离子化方法进行了比较，比较了在分析具有有问题基质的样品时出现的信号抑制现象。为此，选择环境和废水样品的提取物作为模型基质，随后用一组六种通常存在于个人护理产品中的物质以及六种药物对其进行了加标，浓度水平在 100μg/L 到 500μg/L 之间，相当于原始样品中的 100ng/L 到 500ng/L。对于大多数研究的分析物，DART 离子化的抑制率小于 11%，与大气压化学电离（APCI）和大气压光电离（APPI）相比，DART 离子化表现出相似甚至略优的行为，对于多瑙河河水提取物；对于污水处理厂流出物提取物这个更具挑战性的基质，DART 提供了更好的结果，抑制率小于 11%的分析物有 9 个，而 APCI 的值在 20%到>90%之间。与 DART 相比，电喷雾电离（ESI）受抑制效应的影响更大，对于多瑙河河水，值在 26%到 80%之间；与污水处理厂流出物基质结合，所有分析物的抑制率都超过 50%。
