sodium butyrate by HPLC

Question

Hi guys,

I have to analyze a sample of sodium butyrate (powder from dietary supplement) in HPLC without using phosphate buffer. I've found this method but it seems it doesn't work..

mobile phases: A water 1% formic acid; B: ACN; column T 40°C; flow 0.6 ml/min; Column Zorbax SB c18

t %B

0 0

3 0

7 1

13 13

16 30

23 55

24 0

Anyone has a method to suggest me?

thanks!

Dr. Know · Accepted Answer

Hi, 
 be aware that you do not analyze sodium butyrate, it's a salt. You can only analyze butanoic acid, therefore you choose some buffer with a pH 2 units below the pKa of butanoic acid (pKa = 4.82). At the pH of <2.80 you have butanoic acid which you have to analyze. Normally you do that by GC for the smaller acids or specialty columns like Hi-Plex columns. If there is not much else present a C18 can work, but only if the pH during the analysis stay below 2.8 - adding organic modifier to a buffer increases pH! 
 Regards, 
 Norbert

sodium butyrate by HPLC

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