Abstract
After adding the silylating agents N, O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) or N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) to the indirubin solution and leaving for 1 hr at 60°C, the color remained red. Indirubin could be measured by GC/MS after replacing the active hydrogen on the amino group with -Si(CH3)3 or -Si(CH3)2C2H5 groups. However, peak tailing was observed and the quantitative and detection limits were not sensitive enough for practical use. Indirubin silylated at four sites was observed under the reaction conditions as follows; solvent dichloromethane: acetone (8 : 2), 90°C reaction temperature, 1 hr reaction time, BSTFA derivative, pyridine catalyst. The color of the solution changed from red to colorless. Retention time appeared to be faster and the peak shape improved. Under these conditions, the quantitative and detection limits of indirubin were 5 ppb and 0.1 ppb, respectively.
