Simultaneous quantitation of meperidine, normeperidine, tramadol, propoxyphene and norpropoxyphene in human plasma using solid-phase extraction and gas chromatography/mass spectrometry: Method validation and application to cardiovascular safety of therapeutic doses

Analysis of low-abundance molecules in complex matrices by quadrupole-linear ion trap mass spectrometry using a simultaneous fragmentation and accumulation strategy

RATIONALE

Fast and sensitive analysis of low-abundance molecules in complex matrices has always been a challenge in chemical and biological applications. Mass spectrometry (MS) has been widely used in the fields of chemical and biological analysis due to its unparalleled specificity and sensitivity. However, the MS signals consistently deteriorate in the presence of matrices. Demands for more sensitive and efficient methods to analyze those low-abundance molecules in chemical and biological systems are in urgent need.

METHODS

Based on a home-made quadrupole-linear ion trap (Q-LIT) mass spectrometer, a simultaneous fragmentation and accumulation strategy was developed to improve the sensitivity of the analysis for the low-abundance molecules in complex matrices. Ions were filtered by the quadrupole into the LIT. The precursor ions were fragmented and the product ions were isolated and accumulated in the LIT simultaneously. The fragmentation, isolation and accumulation processes were conducted at the same time. The accumulation time could be controlled to accumulate sufficient product ions.

RESULTS

With this strategy, the signal intensity of targeted molecules could be increased by 2-8 times and by increasing the accumulation time, this could be further enhanced. Those interferences induced by isomers and matrices can be reduced by using our method. We further applied our method to the quantification and analysis of biological samples. Tryptic digested peptides of myoglobin (Mb) were successfully detected by our method.

CONCLUSIONS

We have established a new method with great advantages in the detection of molecules in complex matrices. The application of this method promises better results in the bioanalytical area, especially for the analysis of substances in complex matrices in the future.

HPLC-UV assay of tramadol and O-desmethyltramadol in human plasma containing other drugs potentially co-administered to participants in a paediatric population pharmacokinetic study

Multimodal analgesia is employed in paediatric pain management to maximise analgesia and minimise side effects. Tramadol is dosed at 1-1.5 mg/kg to treat severe pain in children but the assay for tramadol in plasma samples for pharmacokinetic and toxicology studies does not often consider concurrently administered medications. In this study we developed and validated an HPLC-UV method to quantify tramadol and its main metabolite (O-desmethyltramadol) in human plasma in the presence of seven potentially interfering drugs. Sample preparation method was developed by combining liquid-liquid extraction and protein precipitation. Chromatographic separation was achieved on a BDS-Hypersil-C18 column (5 µm, 250 × 4.6 mm) using a double gradient method. The limit of quantification was 6.7 ng/ml for both tramadol and ODT. The precision and accuracy were in compliance with ICH guidelines. This method was successfully employed to analyse the blood samples of 137 paediatric participants in a tramadol pharmacokinetic trial.