Application of Capillary Electrophoresis for Determination of Inorganic Analytes in Waters

Aside from HPLC and GC, capillary electrophoresis (CE) is one of the most important techniques for high-performance separations in modern analytical chemistry. Its main advantages are the possibility of using different detection techniques, the possibility of in-capillary sample processing for preconcentration or derivatization, and ease of instrumental miniaturization down to the microfluidic scale. Those features are utilized in the separation of macromolecules in biochemistry and in genetic investigations, but they can be also used in determinations of inorganic ions in water analysis. This review, based on about 100 original research works, presents applications of CE methods in water analysis reported in recent decade, mostly regarding conductivity detection or indirect UV detection. The developed applications include analysis of high salinity sea waters, as well as analysis of other surface waters and drinking waters.

A new method for the determination of ammonium in the vitreous humour based on capillary electrophoresis and its preliminary application in thanatochemistry

Background Although the post-mortem increase of ammonium in biological fluids is well known, ammonium analysis in vitreous humour has never been used in recent times for the determination of the post-mortem interval. The present work represents a new application of capillary electrophoresis with indirect UV detection in the field of forensic analysis. Methods The electrophoretic separation was carried out in a running buffer made of 5 mM imidazole, 5 mM 18-crown-6 ether and 6 mM d,l-α-hydroxybutyric acid (HIBA). To overcome the lack of optical absorption of ammonium, indirect UV detection was applied. The used wavelength was 214 nm. Results The method showed good linearity in the concentration range from 0.16 to 5.0 mM. The limit of detection, 0.039 mmol/L, was established on the basis of the linearity curve. Precision and bias studies carried out on the pure ammonium solutions and in real biological samples, revealed %RSDs well below 20%. A preliminary application to real cases where the death time was precisely known (14 bodies) was carried out plotting vitreous humour ammonium vs. post-mortem interval with a resulting good linear correlation until 100 h post-mortem. Conclusions After validation in real cases, the present method can become a powerful tool to unravel one of the most challenging issues of forensic investigation: determination of the time of death.

RP-HPLC method with indirect UV detection for determination of sodium ibandronate in pharmaceuticals

Ibandronate sodium (IBN) [(1-hydroxy-3- (methyl pentyl amino) propylidene bisphosphonic acid monosodium monohydrate)] is the sodium salt of ibandronic acid, a synthetic nitrogen-containing bisphosphonate drug. The aim of this study was to develop a sensitive and accurate RP-HPLC method with indirect UV detection for determination of IBN in pharmaceutical formulations. Chromatographic separation was performed on a Waters Bridge C18 reversed-phase column (250 x 4.6 mm I.D.; particle size 5 µm), in an isocratic mode with a mobile phase constituted of 90% buffer: 10% acetonitrile (V/V). The buffer was made using 1.5 mL ortho-phosphoric acid, 990 mg 1-Hexanesulfonic acid sodium salt 98%, 140 mg EDTA in 1000 mL flask diluted with HPLC grade water. The elution was carried out at a flow rate of 1.0 mL minˉ1. A diode array detector measured the UV absorbance at 198 nm, in inverse mode. The method was validated for specificity/selectivity, linearity, LOD, LOQ, accuracy, precision and robustness according to ICH validation guidelines. The limits of detection and quantification were calculated at 0.0163 µg/mL and 0.0495 µg/mL, respectively. The method was effectively used for determination of IBN from commercial tablets and provided good results without any interference from commonly used excipients. Keywords: RP-HPLC with indirect UV detection, Ibandronate sodium, validation, pharmaceuticals

Development of a Micellar Electrokinetic Chromatographic Method with Indirect UV Detection for Pregabalin Determination in Serum Samples

Background: A micellar electrokinetic chromatographic (MEKC)/ indirect UV detection method with hydrodynamic and electrokinetic injection has been developed for the determination of pregabalin in the serum samples. Methods: Separation of the drug was achieved on Agilent capillary electrophorese in less than 5 min using a 50 cm × 75 μm i.d. uncoated fused-silica capillary and a background electrolyte (BGE) consisting of 5-aminosalicylic acid (5-ASA, 10 mmol L-1), cetyl trimethylammonium bromide (CTAB, 1 mmol L-1) and tri-sodium citrate (4% w/v). The influence of various parameters on the separation such as separation voltage, injection time, cassette temperature, pH of BGE and organic modifier was investigated. Results: Method validation shown good linearity (R2> 0.999) in the range of 1.5-100 µg mL-1 of pregabalin. A limit of detection (LOD) of 0.8 μg mL-1 and a limit of quantitation (LOQ) of 2.6 μg mL-1 were reported for pregabalin. Conclusion: The proposed method was found to be suitable and accurate for the determination of pregabalin in serum samples.