Chromatography Forum

Hai,


I am having a problem analyzing D.I water. The D.I water in the lab when analyzed gives phosphate peak. My experiments are related to phosphate analysis involving dilution with D.I water. Is there anyway, i can find the problem why i am getting this peak inspite of thoroughly cleaning the system?

replies will be appreciated.

Thanks

First, are you certain that it is phosphate and not something else? If it really is phosphate, then the problem is either contamination or adsorption/carryover. Since it is a peak, it is coming in with the injection.

What kind of IC system do you have?

First, are you certain that it is phosphate and not something else? If it really is phosphate, then the problem is either contamination or adsorption/carryover. Since it is a peak, it is coming in with the injection.

What kind of IC system do you have?

Thanks for the reply,

i am pretty sure it is phosphate peak . do you think its contamination of column or glassware or detector or CR-ATC column? If possible can you explain any general method for washing the entire system? by the way it is ics-2000.

Thanks

What column and eluent are you using? Which autosampler, if any, do you use? I can suggest some experiments to isolate the problem when I know more about your setup.

The operator's manuals that come on the Dionex CD will describe all the recommended cleaning and maintenance procedures. There is too much to list here.

What column and eluent are you using? Which autosampler, if any, do you use? I can suggest some experiments to isolate the problem when I know more about your setup.

The operator's manuals that come on the Dionex CD will describe all the recommended cleaning and maintenance procedures. There is too much to list here.

Autosampler is simply AS. Columns: guard (AG11) and analytical (AS11) and the eleunt is KOH ( Eleunt catridge) + D.I water( Eleunt) . KOH is given by the manufacturer which has a 44 % life remaining and D.I water is from our lab which we generally change everyday.

Usually i read the operators manual. can u exactly tell me where in the manuals i can get the cleaning and maintenance procedure to isolate this problem?

Thanks for your time.

The AS-11 manual, Appendix A, p. 43, lists the recommended cleaning procedures for your column. While the AS and ICS-2000 manuals don't list specific advice on cleaning, the column cleaning will also clean the flow path of your system. You should also replace the wash liquids in the pump and AS. Two other (more remote) possibilities: the inject valve is worn and leaky, and that can result in carryover. The other is the protective coating on the needle is worn through; exposed and corroded steel surfaces trap phosphate and release it slowly. There are replacement/upgrade kits for both.

You should also talk to your local Dionex service rep.

I presume you create your own DI water in the lab? Are you taking DI water from a big container in the lab or direct from the source? Fill a vial with DI water direct from the unit that produces the DIW and run 5 replicates of it. If the peak disappears then it's glassware/container contamination, if the peak is still there then it's column/instrument contamination... Hopefully it should decrease in size over the 5 replicates.

Always prep IC samples/curves/standards/eluants using DI water direct from the source, not using containers/autodiluters etc that the rest of the lab uses.