Simultaneous determination of vitamin B6 and magnesium using capillary electrophoresis coupled with contactless conductivity detection: Method development, validation, and application to pharmaceutical and nutraceutical samples.

Vitamins and minerals are usually incorporated in pharmaceutical and nutraceutical products, but a simple, rapid, and inexpensive analytical method for their simultaneous determination is still lacking. In this study, we developed a quantification method for pyridoxine (vitamin B6) and magnesium (Mg) by using purpose-made capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) instrument. Main analytical conditions include: fused silica capillary (total length 55 cm, effective length 40 cm, inner diameter 50 µm); background electrolyte consisted of 10 mM L-arginine/acetic acid (pH 5) with 20% acetonitrile; separation voltage + 20 kV; hydrodynamic injection (siphoning at 20 cm in 25 s). Detection limits of vitamin B6 and Mg were 1 and 0.1 mg/L, respectively. Good linearity (R2 > 0.999) was observed for vitamin B6 and Mg calibration curves over concentration ranges of 3-100 and 0.3-200 mg/L, respectively. The method was applied to analyze vitamin B6 and Mg in several pharmaceutical and nutraceutical samples. The analytical results obtained by our method were in good agreement with reference methods (i.e., HPLC for vitamin B6 and ICP-OES for Mg). High-efficient and low-cost CE-C4D method can accordingly serve as a promising tool for concurrent analysis of inorganic and organic species in pharmaceutical and nutraceutical analysis.

Antibody-free detection of amyloid beta peptides biomarkers in cerebrospinal fluid using capillary isotachophoresis coupled with mass spectrometry.

This study reports a capillary isotachophoresis (ITP) - electrospray ionization mass spectrometry (ESI-MS) method for the determination of several amyloid ß (Aß) peptides, which are biomarkers of Alzheimer's disease (AD) in cerebrospinal fluids (CSF). For the first time, these peptides have been detected directly from CSF by MS without recourse to an immunocapture-based sample pre-treatment. The antibody-free approach is based on the marriage between capillary ITP, a powerful on-line electrokinetic preconcentration technique, and MS for simultaneous detection of different Aß peptides. To ensure a good performance, the ITP process of fluorescently labelled Aß peptides was for the first time implemented and verified with laser induced fluorescent detection, prior to methodology transfer to MS detection. Better detection sensitivity was achieved with labelled Aß peptides for both detection modes. Using hydroxyl ions as the terminating and acetate as the leading ions, our method allows efficient ITP preconcentration under alkaline conditions of the slowly migrating Aß peptides to reach quantifiable concentration down to 50 pM. The developed ITP-MS approach allows reliable quantification of different fluorescently derivatized Aß peptides, i.e. Aß 1-42, Aß 1-40 and Aß 1-38 down to sub nM ranges in CSF samples from AD and non-demented (healthy control) patients. Good agreement (<20% deviation) for the determination of Aß 1-42/Aß 1-40 ratio in CSF was achieved between results obtained with this new ITP-MS and our recently developed method based on large volume sample stacking coupled to CE. Discrimination of one AD patient from two healthy controls was successfully made with the Aß 1-42/Aß 1-40 ratio obtained by the developed ITP-MS method for the tested cerebrospinal fluid samples.

Concurrent determination of anions and cations in consumer fireworks with a portable dual-capillary electrophoresis system.

A new automated portable dual-channel capillary electrophoresis instrument was built and applied to the concurrent determination of cations and anions. The system uses a single buffer and hydrodynamic injection of the sample is performed autonomously. A novel engraved flow-cell interface is used at the injection ends of the capillaries allowing the autonomous operation of the system. The engraved flow-cell replaces traditionally used split injectors in purpose made capillary electrophoresis systems and makes the system design easier. A new software package with graphical user interface was employed to control the system, making its operation simple and increasing its versatility. The electrophoretic method was optimized to allow the baseline separation of 12 cations and anions commonly found in fireworks. The system was proven to be useful for the analysis of consumer fireworks, saving time and expenses compared to separate analyses for anions and cations. This is the first time that cationic and anionic compositions of fireworks are investigated together. The analysis of samples revealed several inaccuracies between the declared compositions for the fireworks and the obtained results, which could be attributed to cross-contamination during their manufacture or to a transfer between other components of the pyrotechnic item. The presence of certain unexpected peaks, however, had no apparent reason and might represent an irregularity in the manufacture of some devices.