Mass spectrometry (MS) with low temperature plasma (LTP) as an ionization source is one of the widely used ambient methods in analyzing various bio-chemical samples for their detection, identification, differentiation, etc. While the LTP-MS allows selective analysis of a sample with low-molecular weight without thermal damages, it has difficulties desorbing a target molecule from the sample surface with a low volatility. Hence, for the purpose of enhancing the desorption and ionization efficiencies of the LTP-MS when analyzing the fatty acids, two methods were compared: directly heating the sample surface and increasing the vapor pressure of the fatty acid itself by derivatization. In addition, the fatty acids in Drosophila were directly analyzed with the LTP-MS. As a result, it was found that the LTP-MS detection efficiency was enhanced with the derivatization as much as with the heating condition while there was little synergy in employing both of the heating and derivatization together. (C) 2017 Elsevier B.V. All rights reserved.