percent recovery of organic acids

[chandra]

I work on GCMS , many time i get the % recovery of more than 100. Is it ok to get such higher value or i have to go for < or = 100.

Please give me the direction.

Chandra

[James_Ball]

It is possible to have the matrix enhance the signal for certain compounds or to depress the signal. If you are making a standard in DI Water and your sample is not in DI Water then there can be a difference in how well your analytes will respond to the detector.

How do you prepare the calibration standard and also the samples?

What is the sample matrix?

More information can help us better evaluate your problem

[chandra]

I made the standard in DI water and my sample matrix is urine which is extracted by ethylacetate as solvent.

[kubowicz.tomasz]

Hello

Recovery calculations is just mathematics.
Recovery higher than 100% indicates that the measured value for a matrix were higher than the nominal value of the spike.

Regards

Tomasz Kubowicz

[James_Ball]

I made the standard in DI water and my sample matrix is urine which is extracted by ethylacetate as solvent.

Do you extract the DI water standard with ethyl acetate before injection?

I think you may also be able to obtain a synthetic urine matrix that is free of target analytes to be used as a similar matrix to make standards so that they are matched.

It is probably easier though to calibrate using a water standard passed through the same extraction, then spike a sample with a known amount and evaluate the recovery of the spiked amount as a control to verify if there are either positive or negative interferences present in the sample matrix.