Determination of methadone in urine using ion trap GC/MS in positive ion chemical ionization mode

Differentiating the aromatic positional isomers of methylbuphedrones and methoxybuphedrones via chemical ionization-mass spectrometry

Discrimination of aromatic positional isomers of methylbuphedrones and methoxybuphedrones was successfully achieved. Meta isomers were discriminated by chemical ionization-tandem mass spectrometry (CI-MS/MS) using acetonitrile as a reagent gas. Furthermore, all the aromatic positional isomers were discriminated by CI-MS/MS using vinyltrimethylsilane as a reagent gas.

A critical review of microextraction by packed sorbent as a sample preparation approach in drug bioanalysis

Sample preparation is widely accepted as the most labor-intensive and error-prone part of the bioanalytical process. The recent advances in this field have been focused on the miniaturization and integration of sample preparation online with analytical instrumentation, in order to reduce laboratory workload and increase analytical performance. From this perspective, microextraction by packed sorbent (MEPS) has emerged in the last few years as a powerful sample preparation approach suitable to be easily automated with liquid and gas chromatographic systems applied in a variety of bioanalytical areas (pharmaceutical, clinical, toxicological, environmental and food research). This paper aims to provide an overview and a critical discussion of recent bioanalytical methods reported in literature based on MEPS, with special emphasis on those developed for the quantification of therapeutic drugs and/or metabolites in biological samples. The advantages and some limitations of MEPS, as well as its comparison with other extraction techniques, are also addressed herein.

Determination of free and protein-bound methadone and its major metabolite EDDP: Enantiomeric separation and quantitation by LC/MS/MS

OBJECTIVE

To measure free and protein-bound R- and S-enantiomers of methadone and its major metabolite, 2-ethylidine-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in serum.

METHODS

To determine free fraction, samples were filtered using ultrafiltration membranes with a molecular weight cut-off of 10,000 Da and extracted using liquid-liquid extraction. The solvent extract was evaporated and reconstituted in mobile phase for analysis by LC/MS/MS. Total analyte was determined by extracting unfiltered samples. Enantiomeric separation was by chiral chromatography.

RESULTS

LC conditions resulted in baseline separation of R- and S-EDDP, and 85% resolution of methadone enantiomers. Precision of spiked specimens for both R- and S-methadone and R- and S-EDDP was less than 10% at 100 nM, and did not exceed 20% at 10 nM.

CONCLUSIONS

Using minimal sample clean-up and a total instrument run-time of 10 min, a rapid, sensitive and highly specific method was developed for quantitation of free and total R- and S-enantiomers of methadone and EDDP.

Analytical chemistry of synthetic routes to psychoactive tryptamines : Part III. Characterisation of the Speeter and Anthony route to N,N-dialkylated tryptamines using CI-IT-MS-MS

Twelve symmetrically and 13 asymmetrically N,N-disubstituted glyoxalylamide precursors and their corresponding tryptamine derivatives have been characterised by gas chromatography low-pressure chemical ionisation ion trap tandem mass spectrometry (CI-IT-MS-MS) with internal (in situ) ionisation using methanol as the chemical ionisation reagent. Mass spectral differences and similarities between the investigated compounds are discussed and put into context with previous investigations. In tryptamines the formation of [CH2=N+R2R3] iminium ions after beta-cleavage appears to be the dominating process. Dissociation of the protonated molecule into [3-vinylindole]+ for example, appears to be a minor pathway when compared with electrospray triple quadrupole tandem mass spectrometry (ESI-TQ-MS-MS) where this ion transition was found to be of distinctive importance. CI-IT-MS-MS is also found to enable the differentiation between most isomeric derivatives studied.