HPLC data analysis compare to UV analysis

[cmfafaf]

I'm not sure this is the right forum to post. My question is:
I'm doing a dissolution study and analysis the samples with the UV spectro. analysis and HPLC method. In UV analysis a range of scan from 190 to 600nm was done and our compound (peaks appeared) both in 260nm and 325nm. The 260nm data values from UV analysis matching the HPLC analysis value in 260nm and 325nm. However the UV analysis in 325nm scan is always end up in a higher value (the % release of API). why?
Appreciate any help.
note: % recovery profile in 260nm HPLC is same as % recovery profile in 325nm HPLC analysis. % recovery profile in 260nm UV analysis is same as both scan in HPLC. % recovery profile in 325nm UV always end 20% higher!

[michaldousa]

I think that problem is one. The absorbance is additive function. There is some compound that systematically increases absorbance value at 325 nm (during UV spectro measuring and HPLC method is more selective under these conditions).

[JM]

Your plabebo may be absorbing at 325 which is interfering in UV spectro.
take a scan of your placebo ( dummy tab with out drug) and confirm.

JM

[cmfafaf]

Thanks michaldousa and JM for prompt response.

JM we already did that and there's no absorption under UV and HPLC for the placebo, so that's rule out the possibility.

michaldousa could you briefly explain more detail the situation is.

Appreciate for everybody help.

Michael