We are currently using a wavelength accuracy procedure for HPLC detector qualification that uses Holmium Oxide with a range from 239nm to 365nm.

Does anyone have any suggestions as what to use for wavelength accuracy below 239nm. We seem to have an increasing amount of methods that we are running below 239nm ie the lowest being 210nm
and want to calibrate our detectors through the range of use.

ASTM has a standard practice for testing UV detectors (ASTM 1657-96). You can order a copy via their web site: www.astm.org.

It doesn't specify particular test probes, just something whose absorbance maximum wavelength is known. It makes the point that variable wavelength UV detectors have a broad bandpass anyway so that wavelength accuracy is not that big a deal. PDA's, where you would be looking for both spectral and chromatographic informatio, are another story.

-- Tom Jupille / LC Resources Inc.

Please read the following reference, Chromatographia Vol 26 (1988) 321-323. In there you will find a test solution which lets you check wavelength accuracy at 218.5nm, this test is universally applicable. Also, in the same reference you will an alternate solution to check upper wavelengths at at least three different points in the UV-Vis region.

Both tests are very simple and quite accurate.

The compuond with maxima at 218.5nm and several others at higher wevelenths is Terbium perchlorate. It can be obtained as 50% H2O solution from Alpha Aesar (Stock No. 40573). However, if your detector has a bandpass greater than 5nm, those nerrow spikes may be hard to find.