Development and Validation of a Single Quadrupole LC/MS Method for the Trace Analysis of Six Nitrosamine Impurities in Valsartan

The findings that nitrosamine impurities, mutagenic carcinogens, have been detected in several classes of medicines, including valsartan, have raised safety concerns; regulatory authorities responded by strengthening surveillance, creating specific guidance and risk assessment strategies. At the core of these responses are a number of highly sensitive analytical methodologies to detect and quantitate trace amounts of nitrosamines in pharmaceutical products. However, many of the issued methods rely on high resolution or other advanced mass spectrometers which may not be readily available or ideally suited for routine analysis of large sample sets for risk assessment. Here we describe our efforts to develop an alternative approach based on a LC method coupled with a single quadrupole mass spectrometer. Six nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodiisopropylamine (NDIPA), N-nitrosoethylisopropylamine (NEIPA), N-nitrosodibutylamine (NDBA), and N-nitrosomethylaminobutyric acid (NMBA) were investigated and a LC/MS method was developed for the detection and quantitation of the six nitrosamine impurities in valsartan. Two commonly used techniques, large-volume injection (LVI) and matrix precipitation for sample preparation, were incorporated to enhance sensitivity. The developed single quadrupole LC/MS method has the capacity for detection and quantitation of the six nitrosamines listed with a LOQ of 0.05 ppm relative to valsartan. Furthermore, the method was validated within a wide dynamic range (0.05 – 3.6 ppm) and applied to commercial valsartan samples.