By Anonymous on Friday, June 25, 2004 - 10:15 am:

Can anyone suggest a better method for analyzing excipients in Dulbecco's PBS? Specifically I need to measure Chloride and Phosphate both in the mM range. Currently I am using a Hamilton PRP-X100 column and 8mM p-hydroxybenzoic acid. The detector is conductivity. The problem I am having is that the Phosphate peak is not reproducible, barely linear and is giving poor recovery (too high - 120%). If anyone knows of a better methodology it woul be greatly appreciated. Thanks in Advance.

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By Chris Pohl on Saturday, June 26, 2004 - 03:18 pm:

The issues you describe are commonly observed when trying to analyze inorganic anions using nonsuppressed mode. Your problem is easily solved by using suppressed conductivity detection. A number of columns are suitable for your application. To get more information on suitable columns and suppressors, I suggest you visit the Dionex website (http://www1.dionex.com/en-us/index.html).

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By Markus Laeubli, Metrohm on Sunday, June 27, 2004 - 11:03 pm:

I agree partially with Chris. PRP-X 100 is not the column of choice for this application. The described issues are sometimes observed for phosphate under these conditions but by far not for the other anions.
Anyway I also would recommend to use suppressed IC. Get more information from the Metrohm website (http://www.metrohm.com) or more specific (http://products.metrohm.com/default.asp ... =ICColumns).

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By Markus Laeubli, Metrohm on Tuesday, June 29, 2004 - 01:37 am:

Sorry, I forgot to add my e-mail address.