A chemometric model for the quantitative determination of isotopic impurities in d3-methylamine hydrochloride by Fourier-transform infrared spectroscopy.

Abstract Deuterated drug molecules are of increasing interest to the pharmaceutical industry due to their capacity to slow metabolism and the potential for improved pharmacokinetics or improved pharmacodynamics they may offer over their non-deuterated counterparts. The desired level of deuteration or isotopic purity is a critical quality attribute for these compounds that can be essential for drug efficacy or patient safety. Deuterated reagents are often used to introduce a deuterated moiety into the drug substance; as such, isotopic impurities in these deuterated input materials need to be tightly controlled. A novel Fourier-transform infrared (FTIR) spectroscopic method was developed and evaluated as a fast and straightforward technique to quantify low-level isotopic impurities in the deuterated reagent d3-methylamine hydrochloride. Using data acquired through LC-MS analysis, the resulting chemometric model was validated according to ICH Q2(R1) guidelines achieving limits of quantitation of 0.31, 0.31, and 0.34 wt% for d0-, d1- and d2-methylamine hydrochloride impurities respectively.