A sub-minute electrophoretic method for simultaneous determination of naphazoline and zinc

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.

A green TLC densitometric method for the simultaneous detection and quantification of naphazoline HCl, pheniramine maleate along with three official impurities

Impurity profiling of a pharmaceutical compound is now taking great attention during quality assessment of pharmaceuticals, as presence of small amount of impurities may affect safety and efficacy. In this work, a novel TLC chromatographic method coupled with densitometric detection was established for the simultaneous quantification of naphazoline HCl, pheniramine maleate and three of their official impurities, namely; naphazoline impurity B, pheniramine impurities; A & B. Chromatographic separation was carried out on TLC aluminum silica plates F254, as a stationary phase, using methanol: ethyl acetate: 33.0% ammonia (2.0: 8.0: 1.0, by volume), as a mobile phase. Plates were examined at 260.0 nm and International Council for Harmonisation (ICH) guidelines were followed for method’s validation. Important factors, such as; composition of mobile phase and detection wavelengths were optimized. Linearity was achieved over the ranges of 2.0–50.0 µg band⁻¹ for naphazoline, 10.0–110.0 µg band⁻¹ for pheniramine, 0.1–10.0 µg band⁻¹ for naphazoline impurity B and 2.0–50.0 µg band⁻¹ for both pheniramine impurities. The proposed method was assessed in terms of accuracy, precision and robustness where satisfactory results (recovery % ≈ 100% and RSD < 2) were obtained. The method was also applied for the simultaneous determination of naphazoline HCl and pheniramine maleate, in Naphcon-A^® eye drops, with respective recoveries of 101.36% and 100.94%. Method greenness was evaluated and compared to the reported HPLC one via environmental, health and safety tool. The developed method has much potential over the reported one of being simple, selective, economic and time saving for the analysis of the five cited compounds.

Ultra-rapid capillary zone electrophoresis method for simultaneous determination of arginine and ibuprofen

The combination of arginine and ibuprofen is widely used for pain relief with a faster onset of action than conventional ibuprofen. Therefore, the determination of both compounds in a single run is highly desirable for rapid quality control applications. This paper reports an ultra-fast method (100 injections/h) for simultaneous determination of arginine and ibuprofen using capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation of arginine as cation and ibuprofen as anion was achieved using a background electrolyte composed by an equimolar mixture of 10 mmol/L of 2-(cyclohexylamino) ethanesulfonic acid and boric acid with pH adjusted to 8.4 using potassium hydroxide. The limits of detections were 5.3 and 10.0 μmol/L for arginine and ibuprofen, respectively. The proposed method is simple, fast (one analysis every 35 s), environmentally friendly (minimal waste generation) and accurate (recovery values between 95 and 98%).

Determination of naphazoline HCl, pheniramine maleate and their official impurities in eye drops and biological fluid rabbit aqueous humor by a validated LC-DAD method

A simple RP-HPLC-DAD method was developed and validated, as per the ICH guidelines, for simultaneous determination of naphazoline HCl (NPZ) & pheniramine maleate (PHN) along with three of their official impurities. Chromatographic separation was performed on a hypersil ODS column (5 mm, 250-4.6 mm i.d.) with isocratic elution using phosphate buffer pH 6.0: acetonitrile (70 : 30, v/v) as mobile phase, at a flow rate of 1.0 mL min-1 and UV detection at 260.0 nm. The developed method was found to be linear over the concentration ranges of 5.00-45.00 μg mL-1 for NPZ and NPZ impurity B and 10.00-110.00 μg mL-1, 10-70 μg mL-1 and 10-120 μg mL-1 for PHN, and PHN impurity A and B, respectively, with correlation coefficient values <0.999 for the five cited compounds. The method was confirmed to be accurate, robust and precise with RSD >2.0%. LOD and LOQ values for the five cited compounds were calculated. Moreover, the method was also validated in rabbit aqueous humor as per the US food and drug administration (FDA) bioanalytical validation guidelines. Finally, the proposed method was applied for the analysis of the two drugs along with their impurities in dosage form and spiked aqueous humor samples.

Contactless conductivity detection for analytical techniques: Developments from 2016 to 2018

The publications concerning capacitively coupled contactless conductivity detection for the 2-year period from mid-2016 to mid-2018 are covered in this update to the earlier reviews of the series. Relatively few reports on fundamental investigations or new designs have appeared in the literature in this time interval, but the development of new applications with the detection method has continued strongly. Most often, contactless conductivity measurements have been employed for the detection of inorganic or small organic ions in conventional capillary electrophoresis, less often in microchip electrophoresis. A number of other uses, such as detection in chromatography or the gauging of bubbles in streams have also been reported.

Ultrafast capillary electrophoresis method for the simultaneous determination of ammonium and diphenhydramine in pharmaceutical samples

Ammonium and diphenhydramine are active ingredients commonly found in the same pharmaceutical preparations. We report, for the first time, a sub-minute method for the simultaneous determination of ammonium and diphenhydramine. The method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection. Both analytes can be quantified in a single run (∼80 injections/h) using 30 mmol/L 2-(N-morpholino)ethanesulfonic acid and 15 mmol/L lithium hydroxide (pH 6.0) as background electrolyte. The separation by capillary electrophoresis was achieved on a fused-silica capillary (50 cm total length, 10 cm effective length, and 50 μm inside diameter). The limits of detection were 0.04 and 0.02 mmol/L for ammonium and diphenhydramine, respectively. The proposed method also provided adequate recovery values for spiked samples (100-106 and 97-104% for ammonium and diphenhydramine, respectively). The results obtained with the new capillary electrophoresis method were compared with those of the high-performance liquid chromatography method for diphenhydramine and the Kjeldahl method for ammonium and no statistically significant differences were found (95% confidence level).