Single drop microextraction coupled with matrix-assisted laser desorption/ionization mass spectrometry for rapid and direct analysis of hydrophobic peptides from biological samples in high salt solution.

ABSTRACT

Single drop microextraction (SDME) coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been applied for direct analysis of hydrophobic peptides (valinomycin and gramicidin D) from biological samples (urine and plasma) in high salt solution. The optimal conditions such as selection of extraction solvent, stirring rate, extraction time, effect of salt concentration and matrix-to-analyte ratio were investigated. The limits of detection (LODs) were found to be 73 nM to 170 nM for valinomycin and 96 nM to 5.5 µM for gramicidin D in high salt solution (1.7 M of NaCl) in MALDI-MS. The current approach can enhance the LODs by 11-320-fold for gramicidin D analysis in water, urine and plasma in high salt solution. Furthermore, the current approach has been successfully demonstrated for real-world sample analysis (ß-carotene from carrots) by MALDI-MS. The current approach is a rapid, simple and efficient clean-up platform for direct analysis of hydrophobic molecules in biological samples from high salt solution.