Methyl iodide has been highlighted as a potential genotoxic impurity (PGI). A sensitive HS-GC method with ECD was developed and validated for the determination of methyl iodide impurity in Tedizolid phosphate, an active pharmaceutical ingredient. HS-GC method on DB-624,column 60m × 0.53mm, film thickness 3μm, with electron capture detector (ECD) was used. The proposed method was specific, linear, accurate, rugged and precise. The calibration curves showed good linearity over the concentration range of 0.78 μg/g to 11.7 μg/g and the correlation coefficient was 0.997. Method had very low limit of detection (LOD) and limits of quantification (LOQ) are 0.23 μg/g and 0.78 μg/g, respectively, with respect to test concentration. Accuracy was observed within the range 96.0% to 103.2%. This method is a further extended good quality control tool for low level quantitation of methyl iodide impurity in another API, alogliptin benzoate.
Methyl iodide is such a special electrophile, however, that successful alkylations with it cannot usually be used as an indication that alkylations with higher homologs or with more reactive alkylating agents such as allylic or benzylic halides, will necessarily be so rewarding.
