化学
离子阱
质谱法
四极离子阱
电喷雾
电喷雾电离
羧酸
三级四极质谱仪
分析物
分子
分析化学(期刊)
化学电离
四极杆质量分析仪
离子
串联质谱法
选择性反应监测
电离
色谱法
有机化学
作者
Steven C. Habicht,Nelson R. Vinueza,Enada Archibold,Penggao Duan,Hilkka I. Kenttämaa
摘要
A mass spectrometric method has been developed for the identification of the carboxylic acid functional group in analytes evaporated and ionized by electrospray ionization (ESI). This method is based on gas-phase ion−molecule reactions of ammoniated ([M + NH4]+) and sodiated ([M + Na]+) analyte molecules with trimethyl borate (TMB) in a modified linear quadrupole ion trap mass spectrometer. The diagnostic reaction involves addition of the deprotonated analyte to TMB followed by the elimination of methanol. A variety of analytes with different func-tionalities were examined, and this reaction was only observed for molecules containing the carboxylic acid functionality. The selectivity of the reaction is attributed to the acidic hydrogen present in the carboxylic acid group, which provides the proton necessary for the elimination of methanol. The diagnostic products are easily identified based on the m/z value of the product ion, which is 72 Th (thomson) greater than the m/z value of the charged analyte, and also by the character-istic isotope pattern of boron. The applicability of this method for pharmaceutical analysis was demonstrated for three nonsteroidal anti-inflammatory drugs: ibuprofen, naproxen, and ketoprofen.
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