Problem in negative ionistion in Quottro Micro LCMSMS

[Davidantony]

We have a problem with our waters Quottro Micro LCMSMS.we have operating in ESI mode.We have not getting peeks of negative ionisation componds in multimode ionisation modes.We have tried in single ionisation mode with only negative ionisation also but we have not getting peeks of negative ionisation compounds.What is the cause of this?

[bisnettrj2]

Has this analysis worked before? What specific compounds are you looking for in both positive and negative ionization? What is your mobile phase? By your limited description, I take it you also have compounds that respond with positive ionization, and they are responding properly?

[Davidantony]

yes this analysis is worked nicely earlier.we have this problem starting one week earlier.We analysing compounds like chloramphenicol,TFNA,fipronil etc in -ive ionisation.The positve ionisation componds are ok.

[bisnettrj2]

OK, what mobile phase are you using?

[Davidantony]

we are using acetonitrile and water in single iomisation mode for chloramphenicol and 5mm Ammonium formate in water and Methanol for Mixmode ionisation.

[bisnettrj2]

Have you done the usual - re-make your mobile phases, purge the LC and degasser of the old mobile phase, and re-make your chloramphenicol standard? Did anything occur a week ago, like running a different analysis, or maintenance?

[carras]

Hi Davidantony,

As I wrote in a previous thread regarding loss of sensitivity in a QMicro it could be due to a dirty first quadrupole.

[Davidantony]

we have cleaned the source and 1 st quadrapole.Then make some adjustments. now the response of the ngative and positive compounds is good.