Most USP reference standards for nitrosamines are supplied in liquid form, whereas other suppliers are predominantly provided as powder. Could you please advise if there is a specific rationale for USP offering these standards in liquid form? For instance, is this related to improved stability or reduced susceptibility to degradation in the liquid state? Is there any other reason that I may not be aware of? Could the reference standards from other suppliers be considered reliable? For reference, I have included example links to the relevant USP standards below.
Thank you for your time and consideration. I look forward to your guidance.
I think the most probable cause is laboratory safety.
With solutions, you donāt have to handle pure nitrosamine substances.
I would prefer preādissolved solutions over pure nitrosamines any day.
Different suppliers can definitely be considered reliable, but always check the COA for detailed analytical data (NMR, etc.) to make sure it is really the correct analyte youāre looking for.
I attended a USP webinar today. One of the USP nitrosamine impurity standards is in an acetonitrile solution, while the others are in methanol solutions. A large amount of data is published for USP impurity standards. For example, take a look at the information sheet for N-nitroso sertraline.
The data are publicly available free of charge. It includes chromatograms, MS spectra, and even E/Z ratios. According to the presentation, if identification by MS is not possible, they introduce Ā¹āµN and confirm the NāNO bond using Ā¹āµN NMR to ensure that the standard has been correctly synthesized. They seem to be confident in the quality of their products.