Quantitative measurements overcome matrix effects

The solvent and other elements present in the sample cause matrix effects. These affect atomization efficiency, ionization efficiency, and therefore the strength of the MS signal. This directly impacts quantitative results. Signals may be suppressed or enhanced by matrix effects. Aqueous solutions act very differently from organic solvents, which in turn act differently from each other. The problem can be overcome for the most part by matrix matching (i.e., the standards used for calibration are matched for acid concentration, major elements, viscosity, etc. to the matrix of the samples being analyzed). This is similar to atomic absorption and atomic emission spectrometry where the same requirement in matching solvent and predominant matrix components is required for accurate quantitative analysis. The use of internal standards will also compensate for some matrix effects and will improve the accuracy and precision of ICP-MS measurements. 

The use of MALDI-MS for the measurement of low molecular mass compounds is widely accepted now [61], but quantification remains problematic. The main problem is the inhomogeneous distribution of the analytes within the matrix [62]. This leads to different amounts of ions and therefore to different signal intensities at various locations of a sample spot. The simplest and most effective way to overcome this problem is the use of an appropriate internal standard [63]. The use of deuterated compounds with a high molecular similarity to the analyte as internal standards leads to a linear correlation between relative signal intensities and relative amount of the compound to be quantified (Fig. 4b) [64]. Using this approach it is possible to quantitate substrates and products of enzyme catalyzed reactions. Two examples were shown recently by Kang and coworkers [64, 65]. The first was a lipase catalyzed reaction which produces 2-methoxy-N-[(lR)-l-phenylethyl]-acetamide (MET) using rac-a-... 

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