Chromatography Forum

Hi,

We are planning to buy a GC-MS or LC-MS for confirmation of our semiquantitative testing of drugs of abuse (DAU) in urine. Is GC-MS or LC-MS have some advantages over each other in routine confirmation of DAU. Which one would you prefer and why?

And my second question is what is the difference between LC/MS and LC/MS/MS. If we buy an LC/MS can we use the methods which are developed for LC/MS/MS?

Thanks in advance,

--cem

Hi

Although it was a long time ago I did some DAU in my early"medtech" days before switching to more analytical/organic pharma chemistry, I would spontanously say GC/MS.

A GC/MS with a DB-5ms type of column allows you to see great number of different drugs, just browse a column catalog and you will see, unless you have some specific requirements.

Any +/- or disadvantages with regard to sample cleanup and other +/- with LC/MS vs GC/MS I will leave to other more experianced users.

Good luck sounds exciting.

Thank you krickos, much appreciated. DB-5ms column is noted.,

Since we will try to implement GC-MS or LC-MS in a routine use, I am also wondering if sample pretreatment (extraction, derivatization etc.) would be easier in any of two compared to the other.

Hi

Although it was a long time ago I did some DAU in my early"medtech" days before switching to more analytical/organic pharma chemistry, I would spontanously say GC/MS.

A GC/MS with a DB-5ms type of column allows you to see great number of different drugs, just browse a column catalog and you will see, unless you have some specific requirements.

Any +/- or disadvantages with regard to sample cleanup and other +/- with LC/MS vs GC/MS I will leave to other more experianced users.

Good luck sounds exciting.

LC/MS allows for the use of simpler extraction procedures. It is also more amenable to a greater percentage of compounds, i.e. thermally unstable compounds, compounds that are more polar, etc. Many drugs simply don't "GC/MS" well.

For drugs of abuse, therapeutic drugs, etc. I would choose LC/MS/MS over GC/MS any hour and any day of the week...provided you have the money to spend. If you don't have the budget, GC/MS is fine, but you'll have to do some more sample pretreatment.

Thank you very much Stryder08. It will be really important for us to have simpler extraction procedures. I had a short experience in an analytical toxicology lab with GC-MS and observed that many compounds need serious pretreatments.

The only obstacle for us may be the budget then.

Thanks again,

--cem

LC/MS allows for the use of simpler extraction procedures. It is also more amenable to a greater percentage of compounds, i.e. thermally unstable compounds, compounds that are more polar, etc. Many drugs simply don't "GC/MS" well.

For drugs of abuse, therapeutic drugs, etc. I would choose LC/MS/MS over GC/MS any hour and any day of the week...provided you have the money to spend. If you don't have the budget, GC/MS is fine, but you'll have to do some more sample pretreatment.

If you are doing drugs of abuse, especially in a biological matrix, by LC you must use MS\MS. A simple LC-MS system will not give an unabiguous identification, you need the fragmentation of the MS\MS to get a positive identification of the compounds.

GC-MS is generally much less expensive, but for some drugs the sample preparation is more involved than with LC-MS. In many cases the decision will depend on what drugs you want to analyze.

Thank you very much for your input Ron. I am now beginning to understand as I am reading the analysis principles of MS and you guys' advices. Since I am an MD I haven't been deeply interested in these area before, but it seems that I will have to.

Generally we are thinking to confirm the urine immunoassay results of opioids, cannabis, cocaine, benzodiazepines and amphetamine. We may also want to analyze vitamin D or any other drug at some point, but currently our priority is the 5 drugs listed above.

Thanks again,

--cem

If you are doing drugs of abuse, especially in a biological matrix, by LC you must use MS\MS. A simple LC-MS system will not give an unabiguous identification, you need the fragmentation of the MS\MS to get a positive identification of the compounds.

GC-MS is generally much less expensive, but for some drugs the sample preparation is more involved than with LC-MS. In many cases the decision will depend on what drugs you want to analyze.