Cai Sheng-Suan, Hanold Karl A, Syage Jack A
Syagen Technology, Inc., 1411 Warner Avenue, Tustin, California 92780, USA.
Anal Chem. 2007 Mar 15;79(6):2491-8. doi: 10.1021/ac0620009. Epub 2007 Feb 9.
In this work, we compared APPI and APCI for normal-phase LC/MS chiral analysis of five pharmaceuticals. Performance was compared both by FIA and by on-column analysis using a ChiralPak AD-H column under optimized conditions. By comparison, APPI generated more reproducible signals and was less susceptible to ion suppression than APCI. APPI generated higher peak area and lower baseline noise, and therefore much higher S/N ratios. APPI sensitivity (i.e., S/N ratio) was approximately 2-130 times higher than APCI by FIA and was approximately 2.6-530 times higher than APCI by on-column analysis depending on specific compounds. The better APPI sensitivity as compared to APCI was more dramatic by on-column analysis than by FIA. APCI sensitivity was degraded by ion suppression caused by LC column bleeding components and by elevated APCI baseline noise relative to APPI. On-column APPI LODs (at S/N = 3) were 83, 16, 17, 95, and 7 pg for enantiomer #1, and 104, 23, 19, 122, and 17 pg for enantiomer #2 for benzoin, naringenin, mianserin, mephenesin, and diperodon, respectively, on a Waters ZQ. APPI offers no concern of explosion hazard relative to APCI corona needle discharge or ESI high voltage discharge when flammable solvents (e.g., hexane) are used as mobile phases. Whether APPI dopants are required depends on the IP(s) of mobile-phase solvent(s) and solvent complexes, and photon energies of VUV lamps. Dopant was not necessary for hexane-based mobile phases due to their self-doping effects. Dopants did enhance Kr lamp APPI sensitivity when MeOH was used as the mobile phase. However, dopants became unnecessary for the MeOH mobile phase when the Ar lamp was used.
在本研究中，我们比较了大气压光致电离（APPI）和大气压化学电离（APCI）用于五种药物正相液相色谱/质谱手性分析的情况。在优化条件下，通过流动注射分析（FIA）以及使用ChiralPak AD-H柱的柱上分析对二者的性能进行了比较。相比之下，APPI产生的信号重现性更高，并且比APCI更不易受到离子抑制。APPI产生的峰面积更高，基线噪声更低，因此信噪比高得多。通过FIA，APPI的灵敏度（即信噪比）比APCI高约2至130倍；通过柱上分析，根据具体化合物的不同，APPI的灵敏度比APCI高约2.6至530倍。与APCI相比，APPI更好的灵敏度在柱上分析时比在FIA时表现得更为显著。APCI的灵敏度因液相色谱柱流失成分导致的离子抑制以及相对于APPI升高的APCI基线噪声而降低。在沃特世ZQ上，柱上APPI的检测限（信噪比=3时），安息香对映体#1分别为83、16、17、95和7皮克，对映体#2分别为104、23、19、122和17皮克；柚皮素、米安色林、美芬新和地哌冬的检测限与之类似。当使用易燃溶剂（如己烷）作为流动相时，相对于APCI电晕针放电或电喷雾电离（ESI）高压放电，APPI不存在爆炸危险。是否需要APPI掺杂剂取决于流动相溶剂和溶剂络合物的电离电位以及真空紫外灯的光子能量。由于基于己烷的流动相具有自掺杂效应，因此不需要掺杂剂。当使用甲醇作为流动相时，掺杂剂确实提高了氪灯APPI的灵敏度。然而，当使用氩灯时，甲醇流动相就不再需要掺杂剂了。
