Air and interfering

[just me]

hello
I have read that common solvents and air can cause interfering peaks during HPLC UV analysis especially at low wavelengths. Can air really absorb uv light to cause interfering peaks

[Mark Tracy]

Oxygen does absorb UV starting around 200 nm. It elutes very early next to the void. The other thing that oxygen does is quench fluorescence; this is a known problem for PAH analysis.

[HW Mueller]

You may take a look at the other chain touching on this.

[just me]

Thanks for the reply Mark i didnt realise oxygen absorbs uv light.
HW Mueller which post are you talking about ???

[tom jupille]

HW Mueller which post are you talking about ???

Hans has a very good memory! There are a number of threads on dissolved oxygen in the archives (pre-2004). I located these:

http://www.lcresources.com/discus/messa ... 20040256pm
http://www.lcresources.com/discus/messa ... 20020537am
http://www.lcresources.com/discus/messa ... 19990355pm

[HW Mueller]

Thanks Tom, maybe you could tell us a little about archive searches, I usually have great problems with it, maybe my key words are bad choices?
(This is generally speaking, I didn´t try it in this instance, thanks to you).

[HW Mueller]

Now I took a little time and found a printout of still another chain, copied the address into my browswer: didn´t get it (error message, instead). After several search trials I finally found it and pasted the (somewhat different) address here:

http://www.sepsci.com/chromforum/viewto ... ium+degass

Wonder whether it works?

[tom jupille]

The link works just fine!

The search functions in the "current" Forum and the archives are different. Both are supposedly "full text" searches; the key, as you pointed out, is to use the correct words.

If you use multiple keywords, the current Forum defaults to an "or" search (i.e., it returns posts which have any of the keywords), but you can click on a button to force an "and" search (posts which contain all of the keywords).

The Archives search is a bit of a "kludge" (I don't know how that would translate into German!). The software which ran the original Forum was so out-of-date that we couldn't even upgrade it. Fortunately, each post was contained in a single small html file, so we ended up simply using a Google search bar, which defaults to "and" search. The trick is that you have to include the four-digit "code" for the area along with the keywords. So, for example, to search for all LC posts regarding air and baseline, the Google seach would be [5133 air baseline] (without the square brackets, of course).

[DR]

Without having looked at the links, I can offer memories of Beckman 166 detectors having little barbs on them for the purpose of sparging the optical bench with nitrogen. They recommended doing so at very low wavelengths (<205nm or something like that).

[HW Mueller]

Thanks, Tom, copied that for the future (wouldn´t remember that, the copy will be placed so that I have to remember). I experienced kludge, so I should know what it means.

Dr.,
dissolved and nondissolved gases in the liquid cause the problem (scattering, refractive index changes....).