Rational behind the WL selection

[vijayak]

Hi,
In general UV transmittance for drug product solution is measured at 650nm and Color values measured at 430 nm. Does any one know what is rational behind choosing only these particular Wavelength?

Appreciate the answers

Thanks
Vijayak

[danko]

Regarding the colour measurements, it’s because the most common coloration – f. x. in stability is orange, brownish, yellowish – i.e. at about 580 nm. In order to obtain an optimal measurement it has to be measured utilizing the complimentary wavelength at about 430 nm.

Best Regards

[danko]

I forgot to address the transmittance part.

Perhaps because I don’t know the answer to that.

Anyway I think it’s a huge compromise as to what is relevant and I suspect the explanation is to be found back in time when the spectrophotometers were of the filter based kind and were not up to scanning options.
My personal idea of how it should be done – both for the transmittance and coloration determinations - is a scan over the whole visual range and then empirical based decision of what is relevant following a stability study.

Best Regards