ABSTRACT
A sensitive, precise and accurate quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the measurement of erythromycin A (EA) and related substances in commercial samples was developed and validated. The samples were chromatographed on a reversed-phase column with a polar endcapping and analyzed by ion trap tandem mass spectrometry in the multiple reaction monitoring (MRM) mode using positive electrospray ionization. The method showed high recovery (>or=98.82%), high sensitivity (lower limit of quantitation of 0.25 ng/mL for EA and less than 7.3 ng/mL for the related substances) and high precision (
Subject(s)
Anti-Bacterial Agents/analysis , Chromatography, High Pressure Liquid/methods , Erythromycin/analysis , Mass Spectrometry/methods , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
The discrimination between smoking of crack and other routes of cocaine application has forensic implications. The pyrolysis product anhydroecgonine methyl ester (AEME, methylecgonidine) has been found to be a marker for smoked cocaine. An improved method for the determination of AEME in serum was developed, consisting of mixed phase solid-phase extraction and GC-MS. Special care was taken for the volatility of AEME and tert.-butyldimethylsilylation was used for derivatization. Thus AEME could be determined for the first time in 13 serum samples from living subjects. The concentrations found were in a range of 3 to 34 ng/ml, a correlation with the storage time of the samples or with benzoylecgonine concentrations could not be found.