Simple, fast, and validated UV-spectrophotometric, HPLC, and GC methods for the analysis of benzalkonium chloride in a disinfectant were developed. UV-spectrophotometric determination was based on measuring the amount of light absorption of aqueous solutions of benzalkonium chloride at 268 nm. HPLC determination was achieved with a 150 mm × 4.6 mm, 5.0 μm C18 column. The mobile phase consisted of a 0.01% water solution of triethylamine (with pH 2.5) and acetonitrile in the ratio of 40 : 60 v/v. The column temperature was kept at 30°C, and the injection volume was 10 μL. The flow rate was 1.0 mL/min, and the diode array detector was set at 215 nm. GC determination was performed using a flame ionization detector on a glass capillary column ZB-WAX plus 30 m × 0.25 mm with an inner coating thickness of 0.25 μm. It creates a gradient increase in the temperature of the furnace to the maximum of 200°C. The temperature of the injector was 250°C, 1 μl was injected, and the separation of the sample was 1 : 100. Helium was used as a carrier gas, and the gas flow rate was constant, equaling 1.6 ml/min. The temperature of the detector was 250°C, and a mixture of hydrogen, helium, and air in a ratio of 30 : 8.5 : 350 was used in the split of the detector. All proposed methods were validated according to ICH guidelines with respect to the accuracy, precision (interday, intraday, and reproducibility), linearity, the limit of detection, the limit of quantitation, and robustness. All three methods were linear (R2 = 0.997–0.999) over a concentration range of 400–600 μg/ml for UV and 80–120 μg/ml for HPLC and GC, accurate (recovery was 98.4–101.7% for all methods), precise (RSD <2%), and robust. The cost of the analysis of one sample of the disinfectant for the content of benzalkonium chloride by three methods was calculated. The comparison of the obtained results facilitates a more efficient allocation of laboratory resources, depending on the goal.
Aim of our war was to investigate the degradation of diazinon in the model mixture in comparison with the experimental preparation. Methyl alcohol was used as a basis for the manufacture of diazinon drops and the model mixture. The concentration of diazinon was determined by reversed-phase high performance liquid chromatography on the third, fourteenth and twenty-first day after preparation of the model mixture and experimental preparation when stored at room temperature. Despite the large number of publications studying the degradation of diazinon under the influence of various factors, there is a need to study this process in mixtures of a specific composition, in particular in new veterinary drugs that have not yet been studied. This article presents the results of determining the content of diazinon in 10% of the drug and the model mixture based on methyl alcohol. The analyzes were performed on a Knauer liquid chromatograph with a spectrophotometric detector equipped with a Luna® Omega Polar C 18 150 × 4.6 mm column filled with a 5 μm particle sorbent from Phenomenex with a universal C 18 pre-column 4 × 3.0 mm ID. Mobile phase: degassed mixture of acetonitrile: water in the ratio 65:35, flow rate was 1.1 ml/min, temperature of the column was ambient. Diazinone was detected at 245 nm. Injection volume was 0.050 ml and the time of one separation – 20 minutes. The appearance of an unknown peak on the 3 min chromatogram of the solution of the production experimental preparation was revealed. On the twenty-first day of storage of the experimental drug, the content of diazinon decreased to 34 % of the stated amount. On the third and twenty-first day of storage of the model mixture, a decrease in the content of diazinon by 16 % and 79%, respectively, and the appearance of an additional peak were observed. The use of methyl alcohol with other components is likely to be a factor in the breakdown of diazinon in the drug. According to the recipe of the drug, methanol is about half the content of ingredients. This composition does not provide stability of the proposed dosage form of the drug. The next step will be to study the effect of other solvents on maintaining the stated concentration of diazinon.
The aim of the study was to investigate the stability of diazinon in two model mixtures in which the active substance content is 10%. Methyl and isopropyl alcohols were used as a basis for the production of model solutions with diazinon. According to the recipe of model drugs, methyl or isopropyl alcohols make up about half of the content of drug components. The diazinon content was determined by reversed-phase high performance liquid chromatography (HPLC) on 3, 14 and 21 days for the model mixture with methyl alcohol and on 14 and 50 days for the mixture with isopropyl alcohol. A significant number of publications have been devoted to the study of the degradation of diazinon and other nonspecific organophosphorus pesticides under the influence of various factors. However, it remains relevant to study this process in mixtures of a certain composition, in particular in new veterinary drugs under development. This article presents a comparison of the results of determination the content of diazinon in model mixtures based on methyl and isopropyl alcohols. The analyzes were performed on a Knauer liquid chromatograph with a spectrophotometric detector equipped with a Luna® Omega Polar C 18 150 × 4.6 mm column filled with a 5 μm sorbent of Phenomenex particle size with a 4 × 3.0 mm universal C 18 protective column. Mobile phase: degassed mixture of acetonitrile: water in the ratio 65:35, flow rate 1.1 ml / min at a column temperature of 20 °C, detection at a wavelength of 245 nm, injection volume - 0.050 ml, time of one separation - 20 minutes. It was found that the content of diazinon on the 21st day of storage of the model mixture based on methyl alcohol is about 30 % of the applied, while on the 50th day of storage of the model mixture based on isopropyl alcohol – 97 %. As we found in previous studies, the use of methyl alcohol is a probable factor in the breakdown of diazinon in the drug. The appearance of the peak of one of the products of diazinon for 3 min of the chromatogram of solutions of the production experimental preparation and the model mixture made in the HPLC laboratory with the solvent methanol was noted. When replacing methanol with isopropanol, the chromatogram of the drug solution did not show the appearance of an additional peak, except for the peak identified as diazinon. The use of isopropyl alcohol does not reduce the concentration of diazinon in the model mixture, as in the case of methanol. The composition with isopropyl alcohol provides relative stability of the model mixture.
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