Analytes for FAB-MS

For FAB/LSIMS, the analyte should be soluble to at least 0.1 mgml in some solvent or even better directly in the matrix concentrations of 0.1-3 [jg piP in the matrix are ideal. In case of extremely low solubility, additives such as other solvents, acids or surfactants can help. [74] 

The analyte may be neutral or ionic. Solutions containing metal salts, e.g., from buffers or excess of noncomplexed metals, may cause a confusingly large number of signals due to multiple proton/metal exchange and adduct ion formation. [91] The mass range up to 3000 u is easily covered by FAB, samples reaching up to about twice that mass still may work if sufficient solubility and some ease of ionization are combined. 

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