My question isn't really related to LC/GC troubleshooting, but I would appreciate any suggestions that you might have. We use wet chemistry/titration method for determination of % purity. Does this method need to be validated?
If so, what parameters need to be validated? Thank you. Marina

Validation in principle simply means demonstrating that the method does what it says it does. As a matter of practice, the amount of effort expended on validation can vary from none (for a "quick and dirty" determination that is unlikely to be repeated) to extensive (for "regulatory" assays of something like pharmaceuticals. The amount of validation (and the specific parameters) will usually be dictated by regulatory considerations (pharmaceutical, ag chemical, or environmental) or by customer requirements (chemical manufacturing, etc.).

-- Tom Jupille / LC Resources Inc.

You should convince yourself that the method is providing accurate results. This can be done with matrix spikes. The best situation would be with NIST standards if such are available.

USP23 contains a general chapter on validation that provides a table detailing which elements of validation are needed based on the type of test to be validated.

By %purity are you referring to concentration of your major analyte (active ingredient?) or impurity content? If you your referring to potency, I would suggest you use the guidelines in ICH Q2A and Q2B for method validation which will become the USP Guidelines in USP 24. Usually titrimetric procedures lack specificity for the analyte of interest in the presence of related compounds, but accuracy (recovery) of analyte from matrix, linearity and repeatability of potentiometric response, limit of detection (if low level), stability of titrant, stability of sample solution, interim precision (ruggedness) and possibly robustness, could be assessed.

Bob Kirsch, Ph.D.