A Method to Separate Two Main Antioxidants from Lepidium latifolium L. Extracts Using Online Medium Pressure Chromatography Tower and Two-Dimensional Inversion/Hydrophobic Interaction Chromatography Based on Online HPLC-DPPH Assay

Free radicals, including 1,1-diphenyl-2-picrylhydrazyl, mediate oxidative stress to cause many chronic diseases (including cardiovascular diseases, diabetes and cancer). The extract of traditional Tibetan medicine Lepidium latifolium L. (L. latifolium) was reported to have free radical inhibition ability. Therefore, a system method was established to separate the ethanol extract of L. latifolium to prepare two main antioxidant compounds. First of all, silica gel and a medium-pressure liquid chromatography tower were used for pre-treatment of the ethanol extract of L. latifolium to obtain the main antioxidant active component fraction 4 through online high-performance liquid chromatography-1,1-diphenyl-2-picrylhydrazyl (HPLC-DPPH) assay. Then, fraction 4-1 was obtained by one-dimensional preparation using Megres C18 chromatographic column, and two active compounds with IC50 values 59.9 and 71.3 μg/mL were obtained by two-dimensional preparation using Click XIon chromatographic column. Through the study of the chemical components and separation methods of L. latifolium, the combination of HPLC-DPPH assay and two-dimensional preparative liquid chromatography was realized, providing a reference for the separation of active compounds from L. latifolium.

LC-MS/MS Determination of 21 Non-Steroidal Anti-Inflammatory Drugs Residues in Animal Milk and Muscles

The presented procedure combines experience from two LC-MS/MS methods previously developed by our team for NSAIDs determination in meat and milk. The novelty was a modification of sample preparation and combining LC-MS/MS method for milk and muscle. The clean-up procedure was investigated, leading to a change from SPE to dSPE with C18 bulk sorbent. Unlike most of the existing methods, chromatographic separation was achieved on a C8 chromatographic column. This method was developed and validated under European Commission Decision 2002/657/EC. Recovery for milk samples values between 86.3% to 108%, with the coefficient of variation, varied from 5.51% to 16.2%. The recovery for muscle was calculated to be between 85.0% and 109%, and the coefficient of variation was—4.73% to 16.6%. The validation results prove that the method is suitable for confirmatory purposes in milk and muscle. Of 452 samples tested in 2019 and 2020, two have been identified as non-compliant.

Influence of the nature of organic solvents on the process of separation of antioxidative additive in a transformer oil by a gas-chromatographic method

THE PURPUSE. The paper considers the influence of the nature of organic solvents on the process of separation of an antioxidant additive added to transformer oil at a concentration of up to 0.40% by weight, and organic solvents used as selective extractants. Based on the analysis of literature data, it is shown that mineral transformer oil is a complex hydrocarbon composition that undergoes oxidative degradation during operation, leading to aging of transformer oil and deterioration of technical conditions of operation of transformer electrical equipment. As a result of this process, peroxide compounds appear in transformer oil, which affect its color, oxidation stability, aging resistance, compatibility with structural parts of equipment, etc. Gas -liquid chromatography was used to determine the "Ionol" antioxidant additive and organic extractants in transformer oil. Experiments were performed on a chromatograph of Chromosomes GC -1000 with a flame ionization detector and a quartz capillary column 30 m long, 0.32 mm in diamet er, filled with a fixed liquid phase Valko Bond VB-WAX P/n with a film thickness of 0.5 microns. The sample was dosed into the gas-liquid chromatograph injector using an automatic liquid dispenser DAZH-23, designed for entering up to twenty-three samples of sorbates and controlled by a computer with the appropriate software.METHODS. Aliphatic alcohols from C1 to C5 were studied as extractants of the antioxidant additive, which are well separated from the ionol both under isothermal conditions and in the mode of linear programming of the column temperature from 40 to 220 °C. Under these conditions the chromatogram of the separation of antioxidant additives, and aliphatic alcohols, which are used to calculate their relative retained volumes, the asymmetry of chromatographic peaks and the column efficiency, which depends on the physico -chemical nature of the solutes to be analyzed and the conditions of the chromatographic experiment.RESULTS. The dependence of the relative volume of retention of aliphatic alcohols on their permittivity, which has a nonlinear form, is established. At the same time, with a decrease in the chain length of alkyl substituents in the aliphatic alcohol molecule, there is a tendency to increase their permittivity. The dependence of the relative retained volume of aliphatic alcohols on the selectivity coefficient of separation with Ionol is linear. In this case, the most optimal separation selectivity, approaching one, is characteristic of the Ionol – Butanol-1 pair. It is shown that the dependence of the logarithm of the retention time of aliphatic alcohols on their boiling points is linear both at a low temperature of the chromatographic column (40 °C) and at a higher temperature (more than 100 °C). CONCLUSION. At the same time, the angle of inclination of the corresponding lines changes in the boiling point of organic solvents, which is associated with a change in the sorption mechanism in a capillary chromatographic column filled with a polar stationary phase.

The use of liquid chromatography method for quantitative determination of active substances in Enalapril-H tablets

The aim. Combination therapy is used to treat hypertension. Strengthening the action of the ACE inhibitor enalapril is carried out in combination with the thiazide diuretic hydrochlorothiazide. On the pharmaceutical market, such combined preparations are presented by different manufacturers in various concentrations of the active ingredients of enalapril maleate and hydrochlorothiazide. Development of methods for the quantitative determination of active substances in combined drugs by liquid chromatography is topical. Materials and methods. Shimadzu Nexera X2 LC-30AD liquid chromatograph equipped with DAD SPD-M20A diode array detector, SIL-30AC autosampler and CTO-20AC column thermostat; analytical balance - UniBloc AUW120D; pH meter - Knick type 911pH; chromatographic column ACE C18, size 250 mm × 4.6 mm, packed with octadecylsilyl silica gel for chromatography with a particle size of 5 μm. Results. Based on the results of the work, a method for the quantitative determination of enalapril and hydrochlorothiazide in the presence of HPLC was proposed. The obtained validation characteristics indicate that the method for the quantitative determination of hydrochlorothiazide in Enalapril-H tablets corresponds to the following parameters: correctness, precision, linearity ( =0.70 ≤ max =1.60, d=0.22 ≤ maxd = 0.51, a=0.71 max a=2.60, r = 0.9997 min r=0.9981). In the quantitative determination of enalapril maleate in combined tablets, it was found that correctness, precision, linearity are performed ( =1.21 ≤ max =1.60, d=0.24 ≤ max d=0.51, a=1.35 max a=2.60, r = 0.9991 min r= 0.9981). Conclusions. The method of quantitative chromatographic determination of enalapril maleate and hydrochlorothiazide in an antihypertensive combination drug has been improved. The proposed parameters of the chromatographic separation of the mixture in comparison with the initial ones contribute to a decrease in the costs of monitoring, a decrease in the volume of harmful emissions and cause an extension of the life of the chromatographic column

Analysis of gallic acid and ellagic acid in leaves of Elaeagnus angustifolia L. from different habitats and times in Xinjiang by HPLC with cluster analysis

ObjectiveTo determine the levels of gallic acid and ellagic acid by using high-performance liquid chromatography (HPLC) with R software hierarchical cluster analysisin Elaeagnus angustifolia L. gathered from different locations in Xinjiang.MethodsA chromatographic column Diamonsil C18 with a size of 4.6 × 250 mm and 5 μm was used with methanol as A and 0.1% phosphoric acid aqueous solution as B as the mobile phase. The flow rate was 1 mL/min for the gradient elution and the injection volume was 5 μL. HPLC was performed with a detection wavelength of 260 nm and chromatographic column of 35 °C. In addition, R software hierarchical clustering method was used for studying the levels of gallic acid and ellagic acid in E. angustifolia L. from 10 areas.ResultsGallic acid and ellagic acid showed a good linear relationship between 7.375 and 236 μg/mL with a correlation coefficient of 0.9999, and between 3.625 and 116 μg/mL with a correlation coefficient of 0.9999 respectively. The average recovery values were 103.98 and 101.57%, and the Relative Standard Deviation (RSD) values were 1.92 and 1.47%.ConclusionDifferences in the levels of gallic acid and ellagic acid in E. angustifolia L. leaves from different areas in Xinjiang showed that both were the highest in Kuitun.

On factors affecting surface free energy of carbon black for reinforcing rubber

The surface activity of carbon black (CB) is an important factor affecting the reinforcement of rubber. The quantitative determination of the surface activity (surface free energy) of CB is of great significance. A simplified formula is obtained to determine the free energy of CB surface through theoretical analysis and mathematical derivation. The surface free energy for four kinds of industrial CBs were measured by inverse gas chromatography, and the influential factors were studied. The results showed that the aging time of the chromatographic column plays an important role in accurate measurement of the surface free energy of CB, in comparison with the influences from the inlet pressure and carrier gas flow rate of the chromatographic column filled with CB. Several kinds of industrial CB were treated at high temperature, and the surface free energy of CB had a significant increase. With the increase of surface free energy, the maximum torque was decreased significantly, the elongation at break tended to increase, the heat generation of vulcanizates was increased, and the wear resistance was decreased.