Analysis of low molecular weight compounds using MALDI- and LDI-TOF-MS: Direct detection of active pharmaceutical ingredients in different formulations

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a high throughput, easy to use analytical technique. The simple sample preparation of this technique and its tolerance to the presence of contaminants are among its advantages. In contrast, depending on the matrix used, MALDI can ionize and generates ions in the low m/z range that complicate the interpretation of the spectra of low molecular weight compounds. To address this issue, one can envisage the use of tunable ionic matrices that can reduce the low m/z interferents. In this work, the ionic matrices triethylammonium -cyano-4-hydroxycinnamate and diisopropylammonium -cyano-4-hydroxycinnamate were used to directly analyze 14 pharmaceutical drugs in different formulations (coated tablets, noncoated tablets, capsules, and solutions). This methodology enabled the detection of their active compounds with minimum sample preparation, thus providing a straightforward approach for the forensic analysis of pharmaceutical drugs in the quest for detecting counterfeits. LDI-MS experiments were also performed, and the active ingredient in all of the medicines analyzed were detected. However, MALDI-MS spectra for the medicines analyzed herein showed less or no fragmentation than LDI-MS, which makes the analysis easier.