Chromatography Forum

Is it necessary to use internal standards in LC-MS/MS analysis??

It depends! If you are working in an environment where there are regulatory issues and methods must be properly validated, and you require good accuracy, and you're using samples where ionization is likely to be affected by other components of your matrix/sample (cosuppression) then you will probably need to use internal standards. If you are trying to measure something obscure for which no suitable internal standard is commercially available, and you're doing it in the context of biological research, you will probably be forgiven for not using an internal standard, provided you make reasonable efforts to show that your measurements are fair. (For example, if you're worried about suppression of ionization, you can spike a sample that contains very little analyte, and check that you get the expected size of peak back; if you don't, it might mean that the sample does contain analyte, but also contains something preventing its ionization).
Having said all the above, a bad internal standard is worse than no internal standard. Using some random unrelated chemical, or something that gives a fuzzy, unreliable peak, will only introduce errors into your data.

EPA Method 544 for Microcystins is performed without an internal standard while EPA Method 545 for Anatoxin/Cylindrospermopsin does include internal standards. It just depends as stated above if there are suitable compounds available to be used for the internal standard.

I also have an in house method for analyzing Picrate in water samples by LCMSMS that does not include an internal standard and works just fine, but most samples are clean waters, soils will give interferences as evidenced when we to matrix spikes.