Chromatography Forum

Hi
i want analysis desloratidine and its metabolite 3-hydroxydesloratatdine on LC-MS/MS API 4000
Can Iuse loratadine as internal standard for one of them or there is limitations

what other suggestions for good internal standards cheaper than the labeled ones for both analytes

If you are trying to develop a method for analysing biological matrix, especially of plasma, then you should not use loratadine as internal standard. Because loratadine may convert in vivo into its metabolite and that will show up on your metabilite MRM. Thus you will end up wrongly quantitating your drug. Instead try to use other drugs of same class or you can use the drug which has same Pka as of your analyte of interest.