Use a QQQ only as a GC-MS?

Hi, there is nothing necessary to turn off. Keep the collision and quench gases for the collision cell on. Simply configure the method for either MS1 Scan or MS2 Scan.

MS1 Scan is recommended as using MS2 Scan could have distortion in the spectra of some analytes due to unimolecular decay of the ion occurring as it is transmitting through Q1 and the collision cell, and then not being included in the scan abundance of the parent ion. This effect only occurs for some analytes (for example, nitrobenzene spectrum when comparing MS1 Scan and MS2 Scan will differ as mass 123 will decompose into 93 when using MS2 Scan.)

MS2 Scan does have slightly higher abundances and for some compounds a NIST spectrum comparison may actually be better with MS2 Scan. This is a VERY minor improvement and again is compound specific.. so overall, try MS1 Scan first.

When I first started using TQ I thought it would be a good idea to turn the collision gases off if I was going to operate the instrument in Scan mode but this is not correct. You will change the tuning of the instrument by changing the flow rates in the collision cell, and it simply isn't necessary.

Hi graettin,

thanks alot for your answer.

We are validating a SIM-Method for THC-Quantification and our problem is, that the Ion ratios are totaly different as our other instrument (only a GC-MS). The Quantifier (Ion 371) for THC-OH & THC-COOH is very low with the SIM-Method. What could be the reason for that?

Hi graettin,

thanks alot for your answer.

We are validating a SIM-Method for THC-Quantification and our problem is, that the Ion ratios are totaly different as our other instrument (only a GC-MS). The Quantifier (Ion 371) for THC-OH & THC-COOH is very low with the SIM-Method. What could be the reason for that?