# MALDI/TOF-MS

##### Matrix-assisted laser desorption/ionization time of flight mass spectrometry

MALDI/TOF-MS analysis of permethylated glycosphingolipids is performed in the linear or reflector positive ion mode using α-dihyroxybenzoic acid (DHBA, 20mg/mL solution in 50%methanol: water) as a matrix. More detailed sample preparation protocols for the MALDI/TOF-MS analysis are described in Protocol_6 of the sample preparation steps.

### AB Sciex 5800

Mode of operation:

• Reflector (for most of GSLs)
• Linear (for large GSLs if the size of the analyte is out of the detection limit of Reflector mode)

Polarity:

• Positive (for all permethylated GSLs)
• Negative (for charged GSLs those carry strong charge(s) and retain its charge after permethylation, e.g. Sulfatides)

Laser intensity: ~ 4000 * *Optimum laser intensity depends on the performance of the laser in each instrument, so it should be determined experimentally.

### Bruker Microflex

Mode of operation:

• Reflector (for most of GSLs)
• Linear (for large GSLs if the size of the analyte is out of the detection limit of Reflector mode)

Polarity:

• Positive (for all permethylated GSLs)
• Negative (for charged GSLs those carry strong charge and retain the charge after permethylation, e.g. Sulfatides)

Laser intensity: ~ 60%* *Optimum laser intensity depends on the performance of the laser in each instrument, so it should be determined experimentally.