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Metrological Characteristics of the Potentiometric Assay Developed for Determining the Antioxidant Activity of Ascorbic Acid
The potentiometric assay for determining the antioxidant activity of ascorbic acid has been developed and validated according to the following parameters: specificity, linearity, accuracy, repeatability, intermediate precision. The linearity was in the concentration range of 0.002 – 0.02 mol L–1 (r2 = 0.9993). The percentage of recovery was found to be in the range from 95.38 to 105.00 %. The values of %RSD for repeatability and intermediate precision were 1.86 and 1.95 %, respectively. The method is accurate and reliable, with the relative standard deviation of less than 2 %. It has been proven that the method developed is express, rapid, highly sensitive, accurate and sufficiently reliable.
Validation of the alkalimetry method for the quantitative determination of free organic acids in raspberry leaves
Organic acids are a large group of biologically active compounds that perform important functions in the plant organism. Moreover, all plants, regardless of the species and family, contain organic acids to a small or large extent as organic acids belong to intermediate metabolites arising from the oxidation of proteins and amino acids, fats and carbohydrates.
Aim. To validate the method of alkalimetry proposed with potentiometric detection of the end-point for the quantitative determination of free organic acids in raspberry leaves.
Results and discussion. The method proposed was validated according to the International Conference on Harmonization (ICH) guidelines. The linearity was in the concentration range of 40 – 200 % (r2 = 0.9991). The percentage of recovery was found to be in the range of 98.77 – 102.48 %. The repeatability and intermediate precision were 1.58 % and 1.74 %, respectively. The method is accurate and reliable, with the relative standard deviation of less than 2 %.
Experimental part. Leaves of raspberry were collected in the Kharkiv region during the period of full ripening. A Hanna 2550 pH-meter with a HI 1131P potentiometric electrode was used for alkalimetric titration of free organic acids. The titration was carried out using a microburette with Class A accuracy.
Conclusions. The alkalimetry method for the quantitative determination of free organic acids in raspberry leaves has been proposed and validated according to the following parameters: specifcity, linearity, accuracy, repeatability, intermediate precision, robustness. It has been confrmed that the method is simple, reliable, accurate and cost-effective.
Key words: raspberry; leaves; free organic acids; alkalimetry; validation
Development and validation of the HPLC-procedure for the quantitative determination of isosorbide dinitrate in matrix granules
Isosorbide dinitrate is a universally recognized drug for the relief of angina attacks. Today, prolonged forms of isosorbide dinitrate are of great interest due to their high antianginal efficacy and lower frequency of side effects that are characteristic for drugs with immediate release.
Aim. To develop the procedure for the quantitative determination of isosorbide dinitrate in matrix granules using high performance liquid chromatography and validate it.
Results. To determine isosorbide dinitrate by the method of high performance liquid chromatography with UV-detection the optimal chromatographic conditions were selected taking into account the effect of excipients in the composition of the medicine. To prove the possibility of applying the procedure proposed in the further analysis of matrix granules of isosorbide dinitrate its validation was carried out. Such validation parameters as specificity, linearity, repeatability, accuracy, intermediate precision, limit of detection and limit of quantification, robustness were assessed using model solutions.
Experimental part. The chromatographic researches were performed using liquid chromatograph Shimadzu LC-20AD XR with diode-array detector under the following conditions: chromatographic column – Supelco Discovery C18 (150 × 4.6 мм, 5 мкм); mobile phase – water R – buffer solution with (pH 4.7) – methanol R2 (35:10:55); elution mode – isocratic; flow rate of the mobile phase – 1.0 mL/min.; detection wavelength –220 nm; software – LCsolution, 1.24.SP.1 version.
Conclusions. A new procedure for the quantitative determination of isosorbide dinitrate in matrix granules has been developed using high performance liquid chromatography. Its validation has been carried out, and its acceptability has been proven.
Aim. To develop the procedure for the quantitative determination of isosorbide dinitrate in matrix granules using high performance liquid chromatography and validate it.
Results. To determine isosorbide dinitrate by the method of high performance liquid chromatography with UV-detection the optimal chromatographic conditions were selected taking into account the effect of excipients in the composition of the medicine. To prove the possibility of applying the procedure proposed in the further analysis of matrix granules of isosorbide dinitrate its validation was carried out. Such validation parameters as specificity, linearity, repeatability, accuracy, intermediate precision, limit of detection and limit of quantification, robustness were assessed using model solutions.
Experimental part. The chromatographic researches were performed using liquid chromatograph Shimadzu LC-20AD XR with diode-array detector under the following conditions: chromatographic column – Supelco Discovery C18 (150 × 4.6 мм, 5 мкм); mobile phase – water R – buffer solution with (pH 4.7) – methanol R2 (35:10:55); elution mode – isocratic; flow rate of the mobile phase – 1.0 mL/min.; detection wavelength –220 nm; software – LCsolution, 1.24.SP.1 version.
Conclusions. A new procedure for the quantitative determination of isosorbide dinitrate in matrix granules has been developed using high performance liquid chromatography. Its validation has been carried out, and its acceptability has been proven.
Development and validation of GLC/MS-procedure of doxylamine quantitative determination
Doxylamine is a hypnotic medicine used for treatment of minor sleep disorders and is a frequent cause of poisoning.
Aim. To develop GLC/MS-procedure of doxylamine quantification and carry out step-by-step validation of
the developed procedure in the variants of the method of calibration curve, method of standard and method of additions.
Results. The chromatographic conditions have been chosen for doxylamine determination by the method of GLC with mass-spectrometry detection with temperature program changing during the analysis from 70 °C to 320 °C. Retention time for doxylamine is 14.53 min. To prove the possibility of the proposed procedure application in further analysis its validation has been carried out in the variants of the method of calibration curve, method of standard and method of additions. Such validation parameters as in process stability, linearity, accuracy, precision and limit of determination have been estimated by model solutions.
Experimental part. Conditions of chromatographic analysis: Agilent 6890N/5973N/7683; НР-5MS ∅0.25 mm × 30 m, 0.25 μm; DB-17MS ∅0.25 mm × 30 m, 0.15 μm; columns are connected sequentially through Deans switch; thermostat – 70 CºС (2 min), 45 ºС/min to 210 ºС, 6 ºС/min to 320 ºС (12.56 min); transfer line – 280 ºС; ion source – 230 ºС; quadrupole – 150 ºС; electron impact, 70eV; 40 – 750 m/z; injector – 250 ºС; splitless mode; inlet carrier gas (helium) pressure: 1st column – 26.06 psi, 2nd column – 19.30 psi.
Conclusions. New procedure of doxylamine quantitative determination by the method of GLC/MS has been developed. Its validation has been carried out and acceptability for application has been shown.
Development and validation of the enzymatic kinetic photometric procedure for determination of residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment
Aim. To develop and validate the new enzymatic kinetic photometric procedure for analysis of dequalinium chloride based on application of enzymatic acetylcholine hydrolysis to determine the residual quantities of dequalinium chloride while monitoring the completeness of cleaning of the pharmaceutical equipment.
Results and discussion. The optimal conditions for the enzymatic reaction course were determined – the order of mixing and the concentration of acetylcholine (0.05 mg/mL), cholinesterase (0.4 mg/mL), hydrogen peroxide (10 %) and p-phenetedine (1 %), the time of the reaction mixture maintaining (20 min), pH (8.35), the effect of the nature of the buffer solution. Validation of the procedure developed was carried out – the application range of the procedure was proposed (40–160 % in the normalized coordinates, the maximum acceptable concentration of dequalinium chloride in washes from the pharmaceutical equipment хcrit = 0.5 μg/mL), the number of concentration levels (n = 7); the order of their location within the application range, taking these data into account the maximum acceptable uncertainty of the procedure (maxΔx = 3.05 %) and the acceptability criteria for linear dependence parameters, systematic and random errors were calculated. The validation characteristics of the procedure developed were shown to correspond to the acceptability criteria calculated. The degree of extraction of dequalinium chloride from swabs with flushing from the pharmaceutical equipment was determined.
Experimental part. The residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment were determined by the degree of inhibition of the enzymatic reaction assessed by the unreacted residue of the substrate of the biochemical reaction, such as acetylcholine. The residual quantities of acetylcholine in the reaction mixture was determined by the kinetic photometric method by the indicator reaction of p-phenetidine oxidation with peracetic acid (formed during the auxiliary perhydrolysis reaction when adding an excess of hydrogen peroxide to the reaction mixture) in the way of registering the light absorbance of the resulting reaction product – azoxifenetole (λmax = 358 nm) for a definite period of time.
Conclusions. The enzymatic kinetic photometric procedure has been developed to determine the residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment after its cleaning. The procedure developed has been validated by such parameters as linearity, accuracy, precision and the limit of quantification
Results and discussion. The optimal conditions for the enzymatic reaction course were determined – the order of mixing and the concentration of acetylcholine (0.05 mg/mL), cholinesterase (0.4 mg/mL), hydrogen peroxide (10 %) and p-phenetedine (1 %), the time of the reaction mixture maintaining (20 min), pH (8.35), the effect of the nature of the buffer solution. Validation of the procedure developed was carried out – the application range of the procedure was proposed (40–160 % in the normalized coordinates, the maximum acceptable concentration of dequalinium chloride in washes from the pharmaceutical equipment хcrit = 0.5 μg/mL), the number of concentration levels (n = 7); the order of their location within the application range, taking these data into account the maximum acceptable uncertainty of the procedure (maxΔx = 3.05 %) and the acceptability criteria for linear dependence parameters, systematic and random errors were calculated. The validation characteristics of the procedure developed were shown to correspond to the acceptability criteria calculated. The degree of extraction of dequalinium chloride from swabs with flushing from the pharmaceutical equipment was determined.
Experimental part. The residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment were determined by the degree of inhibition of the enzymatic reaction assessed by the unreacted residue of the substrate of the biochemical reaction, such as acetylcholine. The residual quantities of acetylcholine in the reaction mixture was determined by the kinetic photometric method by the indicator reaction of p-phenetidine oxidation with peracetic acid (formed during the auxiliary perhydrolysis reaction when adding an excess of hydrogen peroxide to the reaction mixture) in the way of registering the light absorbance of the resulting reaction product – azoxifenetole (λmax = 358 nm) for a definite period of time.
Conclusions. The enzymatic kinetic photometric procedure has been developed to determine the residual quantities of dequalinium chloride on the surface of the pharmaceutical equipment after its cleaning. The procedure developed has been validated by such parameters as linearity, accuracy, precision and the limit of quantification
Development and validation of HPLC/UV-procedures for quantification of metronidazole in the blood and urine
Metronidazole belongs to the group of antiprotozoal medicines and widely used for the treatment of infectious diseases; the medicine has a number of side effects manifested by usual symptoms of acute intoxication, especially when interacting with other drugs and alcohol.
Aim. To apply the system of MiLiChrome® A-02 HPLC-analyzer widely used in the Ukrainian laboratories of forensic toxicology for the metronidazole quantitative determination in biological fluids and carry out validation of the procedures developed.
Materials and methods. The sample preparation of blood and urine was carried out by extraction with acetonitrile and 2-propanol followed by separation of the organic layer under the conditions of the aqueous phase saturation with ammonium sulfate. Previously blood and urine were treated with acids. Isolation was carried out in the strong acid, neutral and weak alkaline medium.
Results and discussion. To find the optimal conditions of the sample preparation such validation parameters as specificity/selectivity and recovery were determined. The results of the blank samples analysis were acceptable for all variants of the sample preparation procedures. Recovery values were reproducible for all procedures of analysis studied, but efficacy of metronidazole isolation was variable – from 85% to 97 %. The results of verification of metronidazole stability showed the necessity to carry out all measurements within 12 hours after obtaining the solutions to be analyzed. The results of determination of linearity, accuracy and precision were the evidence
of acceptable systematic and random errors of the HPLC/UV-procedures studied in the variant of the method of calibration curve, method of standard and method of additions.
Conclusions. The set of HPLC/UV-procedures for the metronidazole quantitative determination in blood and urine has been developed. Validation of the procedures developed has been carried out.
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