Liquid Chromatography-Mass Spectrometry in Drug Analysis

JENN-FENG SHEEN AND GUOR-RONG HER*

Department of Chemistry, National Taiwan University, Taipei,Taiwan, Republic of China

ABSTRACT

   Atmospheric ionization is the most important development for LC/MS in recent years. Two atmospheric pressure ionization methods, electrospray ionization(ESI) and atmospheric pressure chemical ionizatlon (APCI) are described. Electrospray is most suited to compounds of high polarity or thermolabile because ionization of electrospray is performed in solution, and vaporization of analyte before ionization is not necessary. The optimal flow rate of electrospray, in general, is in the range of 40-200 ul/min, although the upper limit is about 1 ml/min. Atmospheric pressure chemical ionization utilizes the constituent of mobile phase and water vapor as the reagent gas for chemical ionization. This method is best suited for compounds of low to medium polarity. APCI can take higher flow rate than ESI and it can directly couple with conventional 4.6mmID packed column (1-2 ml/min) without splitting. Two examples are used to illustrate the potential of using LC-API/MS system in drug analysis.

Key words: Atmospheric ionization, LC/MS, electrospray ionizatlon, atmospheric pressure chemical ionization