Applicability of chemically modified capillaries in chiral capillary electrophoresis for methamphetamine profiling

An up-converting phosphor technology-based lateral flow assay for point-of-collection detection of morphine and methamphetamine in saliva

Morphine (Mop) and methamphetamine (Met) are highly addictive drugs worldwide. Point-of-collection testing (POCT) for drug-of-abuse screening is important in abuse/rehabilitation clinics and law-enforcement agencies. We established an up-converting phosphor technology-based lateral flow assay (UPT-LFA) as a point-of-collection testing (POCT) method, namely Mop-UPT-LFA and Met-UPT-LFA, for the detection of morphine and methamphetamine without complicated sample pre-treatment, respectively, in saliva. The sensitivities of the Mop-UPT-LFA and the Met-UPT-LFA were 5 and 10 ng mL-1 with accurate quantitation of 5-100 ng mL-1 and 10-250 ng mL-1 for morphine and methamphetamine, respectively, for a detection time of 15 min. In reference to the detection limits of 20 and 25 ng mL-1 for morphine and methamphetamine, respectively, in the Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) program of the European Union, the percentage test/control (T/C) ratio of the UPT-LFA between 2 and 15 min reached 101% and 86%, and the UPT-LFA produced accurate qualitative results in 2 min for 100 simulated-saliva samples with the exception of a few weakly positive samples. The sample and sample treating buffer were mixed and added to the test strip, and the test was conducted 15 min later. Although we found no significant difference between the UPT-LFA quantitative test and the liquid chromatography tandem mass spectrometry (LC-MS) test, compared with the latter, the UPT-LFA was substantially faster and had higher detection efficiency. The UPT-LFA showed more accurate qualitative results than the LC-MS for 50 simulated-saliva samples. The ease of operation, high sensitivity, and accuracy of the UPT-LFA make it a valid candidate POCT method for drug-of-abuse screening.

Sodium deoxycholate/TRIS-based hydrogels for multipurpose solute delivery vehicles: Ambient release, drug release, and enantiopreferential release

Herein, we report the investigation of sodium deoxycholate (NaDC)/TRIS-based hydrogels as delivery vehicles for a broad range of applications. Three hydrogel formulations were chosen for unique rheological behaviors that suggest a change in internal hydrogel structure with the application of a shear force. In this work, we compare solute release from sheared and non-sheared hydrogels in order to explore the effect of shear force on structure and release kinetics. It was found that the application of a shear force, in addition to changes in temperature, drug solubility, drug concentration, and hydrogel formulation each affected the amount of solute ultimately released from a hydrogel system. Moreover, the use of the inherent chirality of the hydrogel network for enantio-preferential drug release was also explored. We show significant enantio-preference in the release of model drugs tryptophan and ibuprofen from the hydrogel network. Furthermore, hydrophobic domains within the hydrogel network were exploited to enable ibuprofen loading at ten times the maximum water solubility. Retention of enantio-preference was observed at this higher ibuprofen concentration. Cyclodextrin modification to the hydrogel matrix allowed for enantio-preferential inversion which is an unprecedented observation.

Improving repeatability of capillary electrophoresis-a critical comparison of ten different capillary inner surfaces and three criteria of peak identification

A poor repeatability of migration times caused by the fluctuations of electroosmotic flow (EOF) is an inherent weakness of capillary electrophoresis. Most researchers endeavor to prevent this problem using relative migration times or various capillary coatings which are expensive and not easy in comparison. Herein, we present an original approach to this problem: we apply a model sample designed to induce significant EOF instability, in order to critically compare ten capillary types with different physicochemical characteristics. Moreover, we accompany capillary modification with the evaluation of various criteria of peak identification: migration time, migration times ratio, and electrophoretic mobility. Our results show a great effectiveness of a dynamic coating in the stabilization of migration times, with the average RSD(%) value reduced from 3.5% (bare silica capillary) down to 0.5%. The good outcomes were also obtained for the surfactant-modified silica and amine capillaries. For the capillaries exhibiting significant instability of EOF, electrophoretic mobility turned out to be a more universal and reliable criterion of peak identification than relative migration time. It can be explained by an intrinsic dependency of migration times ratio on EOF change, which should always be considered during the selection of an internal standard.

Capillary coating as an important factor in optimization of the off-line and on-line MEKC assays of the highly hydrophobic enzyme chlorophyllase

The choice between bare and coated capillaries is a key decision in the development and use of any methods based on capillary electrophoresis. In this work several permanently and dynamically coated capillaries were successfully implemented in a previously developed micellar electrokinetic chromatography (MEKC) assay of the plant membrane enzyme chlorophyllase. The results obtained demonstrate the rationale behind the use of capillary coating, which is crucial for successful optimization of both the off-line mode and the on-line/electrophoretically mediated microanalysis assay mode. The application of an amine permanently coated capillary (eCAP) is a simple way to significantly increase the repeatability of migration times and peak areas, and to ensure a strong electroosmotic flow that considerably decreases the overall analysis time. A dynamic coating (CEofix) allows one to apply an on-line incubation to control the reaction progress inside the capillary, and to increase the signal-to-noise ratio and peak efficiency. The dynamic coating is possible with use of both the normally applied uncoated silica capillary and the precoated amine capillary, which ensures more repeatable migration times. The strong points of the uncoated silica capillary are its attractive price and wide range of pH that can be applied. The characteristics presented may simplify the choice of capillary modification, especially in the case of hydrophobic analytes, MEKC-based separations, and other enzymatic assays.

A validated gas chromatography mass spectrometry method for simultaneous determination of cathinone related drug enantiomers in urine and plasma

A sensitive and selective method for detection and quantitation of 31 synthetic cathinones using GC-MS has been developed and validated. They were separated into their optical enantiomers after derivatization with L-TPC and nikethamide was used as IS.

Cyclodextrins in capillary electrophoresis: recent developments and new trends

Despite the fact that extensive research in the field of separations by capillary electrophoresis (CE) has been carried out and many reviews have been published in the last years, a specific review on the use and future potential of cyclodextrins (CDs) in CE is not available. This review focuses the attention in the CD-CE topic over the January 2013-February 2014 period (not covered by previous more general CE-reviews). Recent contributions (reviews and research articles) including practical uses (e.g. solute-CD binding constant estimation and further potentials; 19% of publications), developments and applications (mainly chiral and achiral analysis; 38 and 24% of publications, respectively) are summarized in nine comprehensive tables and are commented. Statistics and predictions related to the CD-CE publications are highlighted in order to infer the current and expected research interests. Finally, trends and initiatives on CD-CE attending to real needs or practical criteria are outlined.