Potassium ion ionization of desorbed species (K+IDS): a rapid method for the screening of urine for organic acidemias

What Is the Opposite of Pandora's Box? Direct Analysis, Ambient Ionization, and a New Generation of Atmospheric Pressure Ion Sources

The introduction of DART and DESI sources approximately seven years ago led to the development of a new series of atmospheric pressure ion sources referred to as "ambient ionization" sources. These fall into two major categories: spray techniques like DESI or plasma techniques like DART. The selectivity of "direct ionization," meaning analysis without chromatography and with little or no sample preparation, depends on the mass spectrometer selectivity. Although high resolution and tandem mass spectrometry are valuable tools, rapid and simple sample preparation methods can improve the utility of ambient ionization methods. The concept of ambient ionization has led to the realization that there are many more ways to form ions than might be expected. An interesting example is the use of a flint-and-steel spark source to generate ions from compounds such as phenolphthalein and Gramicidin S.

Mass spectrometric analysis of cardiac glycosides by the desorption/ionization technique potassium ion ionization of desorbed species

The analysis of cardiac glycosides by the desorption/ionization (D/I) mass spectrometric technique potassium ion ionization of desorbed species (K+IDS) is presented. K+IDS mass spectra of digitonin, digoxin, digoxigenin, digitoxin and ouabain are discussed to demonstrate the capabilities of this D/I method. The K+IDS analysis consists of two steps: thermal desorption of neutral molecules representative of the analyte, followed by gas-phase addition of K+ ions to these species. Structural and molecular weight information of the cardiac glycosides is obtained with the K+IDS technique. The most intense peak in the K+IDS mass spectrum of an analyte, M, is frequently the [M]K+ ion. Interpretation of the K+IDS mass spectra is simple, since one thermal degradation mechanism dominates. This mechanism is a 1,2-elimination process. A variation of the original K+IDS technique, performed by changing the ionizing metal from K+ to Na+ (i.e. Na+IDS), is presented for the analysis of digoxin. The Na+IDS mass spectrum of digoxin contains more structural information than the K+IDS mass spectrum of that compound. This may lead to a means of controlling the types of information obtainable with this D/I technique by varying the cation that is thermionically generated. K+IDS analyses can be performed rapidly, no sample derivatization is necessary, no matrix is required and little instrument modification is necessary.