Quantitative analysis of the molecular species of monosialogangliosides by continuous-flow fast-atom bombardment mass spectrometry

Negative-ion continuous-flow fast-atom bombardment mass spectrometry was evaluated as a means for the quantitative analysis of N-acetylneuraminyl-galactosyl-glucosyl-ceramide (NeuAc-GM3) and N-acetylgalactosaminyl-(N-acetylneuraminyl)galactosyl-glucosyl-ceramide (NeuAc-GM2). This study was carried out on a 7070-EQ mass spectrometer (VG Analytical, Manchester, UK) using a home-made continuous-flow fast-atom bombardment probe with a mixture of methanol + water + triethanolamine (70:27:3, v/v/v) as the mobile phase. Utilizing 100 ng of acetyl-lysogalactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)g alactosyl-glucosyl-ceramide (acetyl-lysoGM1) as an internal standard, standard curves for NeuAc-GM3 d18:1-16:0, NeuAc-GM3 d18:1-18:0 and Neuac-GM2 d18:1-18:0 were found to be linear over the range 5-250 ng, with associated correlation coefficients of 0.990-0.997. The lower limit of detection was found to be 2.5 ng. Satisfactory results could also be obtained when the calibration curves were derived from the deprotonated molecular ions of a mixture of the NeuAc-GM2 and NeuAc-GM3 classes. Using this approach, quantitative determination of NeuAc-GM3 d18:1-16:0 from rat adrenal gland was performed using N-acetylneuraminic acid assay as a test control. We found 278 +/- 36 ng of this species in 1 mg of tissue (three replicate experiments). The procedure represents a sensitive method for the quantitation of monosialogangliosides and its capability to give molecular species information.