There are thousands of variations of analytical methods used for natural products. Not all of them are fit for purpose, failing to meet a central requirement for dietary supplement cGMP’s.
Identity methods for botanical products are especially problematic, as demonstrated by the mass confusion set off by the NY A.G.
And manufacturers and contract labs are stuck in the middle of a supply chain that can lack an understanding of the source or processing method, which are important factors for labs to determine appropriate methods.
The slide deck at the link below is from a 2016 talk at SupplySide West that presented challenges and best practices for method selection and validation against established guidance. A process for laboratory qualification, method development and ‘red flags’ are included in these slides.