Quantitative analysis of free fatty acids in gout by disposable paper-array plate based MALDI MS

The quantitative determination of small molecules by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI TOF MS) was always challenging, due to low sensitivity and interferences of matrix and other contaminants on sample plates. Here we report a disposable paper-array (PA) plate in MALDI TOF MS analysis for quantitative analysis of serum free fatty acids (FFAs) with less interference and higher sensitivity, compared with conventional stainless steel (SS) plate. The disposable PA plate was low cost and environmentally friendly. In particular, it was more sensitive in FFAs detection with ~8-34-fold sensitivity increase for eight FFAs as compared to SS plate. Eight serum FFAs in gout patients were investigated using this disposable PA plate. The quantitative results showed good linearity of all eight FFAs between 0.1 and 2.5 mM with correlation coefficients between 0.994 and 0.999 and limits of detection (LODs) between 8.6 and 104.2 μM. Mann-Whitney U test, principal component analysis (PCA) and random forest categorizer allowed the clear separation of gout patients from healthy controls, according to eight FFAs levels in serum detected by disposable PA plate based MALDI TOF MS.