Impregnation of sillica gel with tetraalkylammonium salts in adsorption chromatography of neutral aromatic compounds
The determination of penicillins by titrations with mercury(II) solution
A simple technique, involving two titrations with mercury(II) solutions, is described for the determination of penicillins and their degradation products. The first titration, at pH 4–5 on an untreated penicillin solution, gives the amount of degradation products; the second titration, on a hydrolysed solution at the same pH, gives the sum of the degradation products and penicillin degraded during the hydrolysis. Enzymic hydrolysis is superior to alkaline hydrolysis for penicillinase-sensitive penicillins. Enzyme-resistant penicillins should be hydrolysed with alkali at optimum conditions, e.g. for cloxacillin at pH 13.5 for 5 min. A standard deviation of less than 0.5 % was obtained for the penicillins investigated. The method is absolute; calibration with standard penicillin is not necessary.
Determination of metoprolol enantiomers in human plasma and saliva samples utilizing microextraction by packed sorbent and liquid chromatography–tandem mass spectrometry
Molecularly imprinted polymer-sol-gel tablet toward micro-solid phase extraction: I. Determination of methadone in human plasma utilizing liquid chromatographyetandem mass spectrometry
In the present work molecularly imprinted sol-gel tablet (MIP-Tablet) was prepared. The MIP-sol-gel was prepared as a thin layer on polyethylene material in a tablet form. Methadone-d9 was selected as the template and 3-(propylmethacrylate)-trimethoxysilane was used as precursor. MIP-Tablet was applied for micro-solid phase extraction (μ-SPE). The MIP-Tablet was used for the determination of methadone in human plasma samples utilizing liquid chromatography-tandem mass spectrometry; and each tablet could be used twenty times. The extraction time was 10 min while desorption time was 6 min. Factors affecting the extraction efficiency such as desorption solvents, sample pH, salt addition, extraction time, desorption time and adsorption capacity were investigated. The calibration curves were obtained within the range of 5–5000 ng/mL using methadone in human plasma samples. The coefficients of determination (r2) values were ≥0.999 for all runs and the extraction recovery was >80%. The accuracy values for quality control samples varied from +3.6 to +9.7% and the inter-day precision (RSD %) values were ranged from 5.0 to 8.0%. The limit of detection was 1.0 ng/mL and the lower limit of quantification was 5 ng/mL utilizing methadone in human plasma samples.
Saliva as an alternative specimen to plasma for drug bioanalysis. A review
Saliva provides a suitable medium for screening and determination of drugs. It is easy to collect and handle besides the non-invasive sampling. Extraction techniques such as micro extraction by packed sorbent (MEPS) and dried saliva spot (DSS) provides fast and efficient recovery of the analytes. Moreover, MEPS could be fully automated to ascertain method reproducibility and DSS provides fast simultaneous collection
and extraction of samples. Several studieswere conducted to determine drugs in saliva in correlation to plasma aiming to establish rigid evidence on the suitability of saliva in monitoring of drug levels. Only free drug could be present in salivary fluid thus protein binding of drugs affect markedly on the salivary levels of drugs. Pharmacokinetic parameters could be determined for drugs in saliva with emphasis on diffusion parameters of drugs to salivary fluid such as pH and drug lipophilicity. Screening techniques are mainly based on mass spectrometry (MS) with an emphasis on Liquid Chromatography-Mass Spectrometry (LC-MS), due to limited sample volumes and the low detection limits. Saliva could make drug testing outside laboratory environments feasible with the appropriate techniques for analysis. This review focuses on the developments and challenges in testing of drugs in saliva in correlation to plasma and application to drug analysis in saliva regarding therapeutic drug monitoring and pharmacokinetics.