i am trying to develop a hplc method of analysis for cr picolinate
my mobile phase is 80buffer 20 methanol
buffer is 0.005m kh2po4
flow rate is1.0ml/min
wavelength is 215
ph of buffer is 3.0 with h3po4
i am gettig a pick at 10 minute
is this a peak of picolinic acid or cr-picolinate complex how to confirm this , i can inject a picolinic acid , but if it comes at same time then what should be the conclusion.
cr-picolinate or picolinic acid can come at same rt or at different rt

Although I have not done this particular separation myself, I have a fair amount experience with this compound. In the first place, chrome is used in the synthesis of the picolinic acid so unless you go to great lengths, even your picolinic acid standard should contain some of the chrome complex. The complex is violet whereas purified picolinic acid is colorless and concentrated solutions of picolinic acid usually have a pale violet color. Second, the kinetics of formation and disassociation are extremely slow with this complex, so you should be able to separate the complex in its intact form provided the pH isn't too low. Third, pH three is in a range where the complex would be marginally stable. If you want to perform a separation of picolinic acid and the chromium complex, increase the pH to 4-5. Most likely the coelution you mentioned above is due to the on column dissociation of the complex at pH 3.

i have analysed my sample at this ph , as my sample contains, other ingridinets, its very diffuclut for me to bring the ph to 4 to 5 .my sample contains 100mcg of chromium = chromium picolinate i used chromicum picolinate as a std and igot my values above 98%. so practically it shows not probleam to me in analysing this sample by this method , as std and sample had been prepared in same media.

I have done some work with this complex. Try a column such as the Phenomenex Synergi hydro-rp or the Restek Ultra-aqueous C18 with a mobile phase of 50/50 DI/MeOH. I used the Restek column and had a RT of ~4min, with no interference with picolinic acid. Perform a DI extraction and filter with a 0.45 µm PVDF syringe filter. For more background info, here is a citation:
"Composition and Biological Activity of Chromium-Pyridine Carboxylate Complexes", Evans, G.W. and Pouchnik, D.J. Journal of Inorganic Biochem., 49, 177-187, 1993