By Barry Hicks on Sunday, May 16, 1999 - 06:49 pm:
I am trying to quantitate lactic acid in the presence of dextrose. Prior to sterilization, there are no interferences and the method performs well. Upon sterilization, a number of peaks appear, one immediately prior to lactic acid and one immediately after. Neither are baseline resolved from the lactic acid peak. When I use peak area for quantitation, recoveries are biased two to three percent high, but using peak area they are biased two to three percent low. I require a method that does not show a bias in either direction.
I am hesitant to change the method, as it has been validated for use with lactic acid and dextrose solutions, although at a higher ratio of lactic acid to dextrose. Can anybody suggest a procedure whereby dextrose can be removed from the sample prior to HPLC analysis but which will not affect the lactic acid response?
By Tom Jupille on Tuesday, May 18, 1999 - 08:13 pm:
In principle, you should be able to take out sugars using an SPE cartridge packed with a boronate gel. I have no idea what the effect would be on lactic acid. One source of cartridges is (or at least used to be) Bio Rad in Hercules, CA. You might want to call them and see if they have any pertinent applications notes.
-- Tom Jupille / LC Resources
By A Williams on Wednesday, May 26, 1999 - 05:55 pm:
Are you sure that the dextrose is causing the problem? To test for this you could inject a solution of dextrose alone to see if you can detect the interfering peaks. If you are sterilizing by 0.2 micron filtration, you could be picking up contaminants from the filters. Pre-washing the filters with the buffer used to dissolve the lactic acid should wash out the contaminants.
By Anonymous on Monday, June 14, 1999 - 07:05 am:
Sterilized dextrose can give fructose and also 5 HMF which are the 2 peaks detected
By lmadsen on Monday, September 22, 2003 - 11:05 am:
First, We look at sugars by HPLC DRI (HPX-48Ca)fast high-level (water @85C), or HPPAD (PA-1 or 10)slower, low level (200mm NaOH). Then anions, including lactate are quantified using HPIC-ECD (NaOH gradient to 1M, about 60min runtime). Good separation is achieved between the major anion participants resulting from fermentation including lactic, acetic, propionic and butyric acids; succinate is handy too. Good luck!
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