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My internal standard results are not consistent at all

Question asked by steffanj on Aug 10, 2020
Latest reply on Aug 11, 2020 by james_jenkins

Hi All,

 

I am running a method to determine the amount of smoke taint in grapes, but upon trying to run my calibration standards, my internal standard results are completely all over the place. The 5975 GCMS system i am running on has just had its PM and my other calibrated method which uses the same D6 phenol internal standard has working perfectly fine with the ISTD coming out at ~100k. I am following a previously written method that has been working in the past. Is there any reason as to why my Internal standard response values are varying so wildly? Anything that i may be missing? Again the system has just had a PM last thursday and my other method is working fine. I have also checked in with another GC user who we have been offloading samples to while our method is down and the standards i have given to them are running perfectly with concordant ISTD results.

 

Please see the results below.

 

 GuiacolO-CrM-CrP-Cr4MGSyringol4MSISTD (D6)
Blank2893315826442990298815102659355211
BlankB2035181614671573145010432111360409
BlankC18151125108310906228321471376732
STD2A167521938714960143201091246147167784276
STD2B26346270262270221887186977787105181071980
STD2C171871957515227145541119648746840847326
STD10A113301913615542137111203539274479165709
STD10B2539844392403383542429185977210736657128
STD10C107582230117997157721197042045686196638
STD50A563931156449778583317649691162018774198125
STD50B1000021926651694651488991255252943740464316038
STD50C6421613410711268997263782341612023429227006
STD100A370816694856612956555956473628106560161036579840
STD100B476587861664769014705797613466143837216579715439
STD100C442632810946710793653360569309128082202454682433
STD500A10809871965549177453716498491467918343682515927323319
STD500B12335772235313202504518786961677007390903581164361583
STD500C11391922047923184124817249981544767365565559326340474

If anyone has any advice that would be great.

 

Kind regards,

 

Steffan

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