Purification of quadrol for microsequencing in the spinning-cup sequenator

Treatment of Quadrol buffer with isothiocyanatophenylthiocarbamylaminoethylaminopropyl glass (DITC glass) substantially reduces the impurities observed when this buffer is used with the spinning cup sequenator. Use of DITC glass-treated Quadrol buffer permits identification of PTH-amino acids from protein degradations down to 100 pmol.