I have studied the removal of azo dyes by the polymer based hybrids, using UV Visible spectroscopy. I want to analyze the same samples (1 ppm) on HPLC. But the concentration must be high (10 - 50 ppm) to get prominent peaks. Is there any method of standard addition to concentrate my samples and what will be the calculations?
I believe a good approach will be to add your internal standard to the sample prior concentration to the sample. Then concentrate the sample 10 or 20-fold to be able to detect by UV and calculate the IS recovery that will be representative to the samples. You should get an IS similar to your peaks of interest or the labelled version (13C, 14C, D..). Hope it helps, good luck.
Best bet would be to extract your analyte from a greater amount of sample than you use to elute it with. In this way you can concentrate the sample to levels that are measurable using the HPLC UV/Vis detector. My first thought was solid phase extraction but we have found that azo dyes tend to stick to the stationary phase. Perhaps some sort of liquid liquid extraction.
hmmm I am a bit pussled, actually the HPLC method should be more sensitive than the UV spectrophotometric method, as long as You work on the same wavelength - just because You separate a bit background away and actually the peak is a dynamic signal against the static one from the UV.
May I assume You have not tried to optimise injection volumes wavelengthsand band width for the HPLC detector?
Kai Bester, sir i have concentrated the samples in 1 : 1 ratio with 50 ppm standard of dye for HPLC, and found that the peak was remarkably reduced from the initial peak of 50 ppm azo dye, following the same trend as analyzed by UV Visible spectroscopy on same wavelength.
But, now I am not able to calculate the concentration from the chromatograms.
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