INTRODUCTION

The commonest forms of mass spectrometry require the sample under investigation to be in the gaseous phase for analysis. In the case of studies by GC/MS, samples also spend considerable time in the vapour phase during their elution through the chromatographic column and transfer into the ion source of the mass spectrometer. To be suitable for examination by electron, chemical and field ionization mass spectrometry, compounds must be both volatile and stable with respect to thermal decomposition and rearrangement in the gaseous phase. Many substances do not meet these requirements and, consequently, are not directly amenable to these types of mass spectrometry In such cases, the analysis may be approached in three distinct ways. Firstly, formation of a derivative that imparts volatility and gas-phase stability to a troublesome compound may render it suitable for traditional (EI, CI or FI) mass spectrometry. Secondly, recourse may be made to the more specialized techniques for the analysis of involatile compounds, such as laser desorption and electrospray mass spectrometry. Lastly, and usually less satisfactorily, volatile pyrolysis products of the involatile material may be analysed to gain some information about the original structure. Most of this chapter is concerned with the first of these approaches: derivatization. For this part of the discussion, it is assumed that a mass spectrometer suitable for examining involatile substances is not available and that intact molecules (as opposed to pyrolysis products) are to be analysed.