K-4[FE(CN)(6)] GLYCEROL - A NEW LIQUID MATRIX SYSTEM FOR MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS-SPECTROMETRY OF HYDROPHOBIC COMPOUNDS/

Since the introduction of MALDI mass spectrometry, only a few liquid m atrix systems have been proposed. This paper reports a new liquid matr ix system consisting of glycerol and K-4[Fe(CN)(6)]. With this binary system, best results are achieved for hydrophobic compounds like triac ylglycerols, galactosyl diacylglycerols, phosphatidylcholines, phospha tidylethanolamines, ceramides and several chloroform soluble, syntheti c polymers. Only amounts of analyte in the femtomol range have been re quired to obtain good results with satisfactory mass resolution, mass accuracy and excellent shot-to-shot reproducibility. In all cases, onl y potassium adducts are formed. No protonated molecular ions could be detected. Potassium adducts of small peptides (up to approx, 3000 Da) and carbohydrates can also be generated with this matrix system but wi th lower sensitivity than in the case of hydrophobic compounds (picomo l to nanomol range). Additionally, sample preparation in the case of h ydrophilic compounds is critical and hard to reproduce. This is presum ably caused by the destruction of the thin UV absorbing matrix layer b y aqueous sample solutions.