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- Posts: 3475
- Joined: Mon Jan 07, 2013 8:54 pm
- Location: Western Kentucky
MSCHemist wrote:
Well If I'm fortunate to have several papers on a given method my way of developing a method is usually to look for consensus, pick out the bits and pieces of each I like and combine them with ideas of my own. However, It would be a revelation if I ever downloaded a method that was well designed and actually worked as published.
I do the same thing when working on developing methods to analyze nutraceuticles. I had a client wanting to analyze Quercetin in onion skins, we had to take several methods and combine them then use trial and error to finally come up with a reproducible, accurate method.
I tried to follow another method to analyze for Glucoraphanin in broccoli seeds, the paper and method I was given was from a very prestigious medical university that I won't name. I found my results always were 2x the results they got for the same tests. After tearing the method apart, we found that they stated how they prepared their samples, but their calculation was off because they used a different sample size in the example calculations and then transferred the correction factor for sample size verses prep volume to the final results instead of including the actual sample size and prep volume in the final calculation.
Another client sends us their methods to use, one was for Chloride by IC. In the method it calls for a calibration curve with concentrations of 0.1ppm, 0.5ppm and 1.0ppm, then calls for a check standard of 5.0ppm On top of that, the prep instructions to make the 5.0ppm check standard actually calculate out to a final concentration of 10ppm. Yet when you talk to their chemist he says they always pass when following the method as written!! We followed it and sure enough the check standard will pass, because the curve is not linear and it will quantitate the 10ppm standard as 5ppm Makes me wonder where some of these chemist got their degree.