Kinetic Spectrophotometric Method Research Articles

Development and application of kinetic-spectrophotometric method for analysis of diflubenzuron in soil samples using SPE followed by HPLC method

The purpose of this paper is to present a new sensitive and simple kinetic-spectrophotometric method for the determination of the insecticide diflubenzuron (DFB). The kinetic method is based on the inhibition effect of DFB on the oxidation of sulfanilic acid (SA) by potassium periodate in acetate buffer in the presence of Fe(III) ion as a catalyst and 1,10-phenantroline. The reaction was monitored spectrophotometrically by measuring the increase in absorbance with time of the reaction product at 368 nm. Diflubenzuron was determined with linear calibration graph in the interval from 0.0374 to 0.374 μg/cm3 and from 0.374 to 26.18 μg/cm3. The detection limit and quantification limit of the method with 3σ criteria were 0.0039 μg/cm3 and 0.0131 μg/cm3, respectively. The relative standard deviations for five replicate determinations of 0.0374, 0.188 and 0.374 μg/cm3 DFB were 2.24, 2.11 and 1.10%, respectively. The method was successfully applied to determine DFB residues in soil samples. Solid-phase extraction (SPE) was used for extraction of DFB from soil and samples with Chromabond® (Macherey-Nagel) C18 cartridges. The HPLC method was used as a comparative method to verify the results. The results obtained by two different methods showed good agreement.

Determination of Lorazepam in Drug Formulation and Biofluids Using a Spectrophotometric Method and Response Surface Methodology

A novel, simple, sensitive, and selective kinetic spectrophotometric method has been developed for the determination of lorazepam in pharmaceutical and bioloical samples. The procedure is based on the catalytic effect of lorazepam on the Janus Green–bromate reaction system. The change in absorbance was followed spectrophotometrically at 618 nm. To obtain the maximum sensitivity, the reagents concentration, temperature, and time were optimized by one at the time method. Under optimum experimental conditions, the calibration curve was linear over the range 0.3–19.5 μg/mL of lorazepam, including two linear segments. The relative standard deviations (n = 5) for 1.0, 5.0, and 15.0 μmol/L of lorazepam were 1.09, 1.03, and 0.97%, respectively. The limit of detection was 0.08 μg/mL of lorazepam. An experimental check under these optimal conditions confirmed good agreement in the RSM results. The developed method was successfully applied for the determination of lorazepam in real samples, and the obtained results are in a good agreement with those using HPLC.

Highly sensitive kinetic spectrophotometric method for tramadol trace level detection and process optimization using response surface methodology

AbstractTramadol is a centrally acting analgesic‐anodyne agent of high oral bioavailability. The tramadol contains a weakly absorbing chromophore in its molecule and it was determined by kinetic spectrophotometric method in pharmaceutical, urine, and blood plasma. Response surface methodology and the central composite design was applied to study the influence of maximum sensitivity, reagents concentration, temperature, and time on the UV–Vis spectrophotometry analysis of tramadol. Analysis of variance showed a high coefficient of determination (R2) value for responses, confirming adjustment of the models with experimental data. The change in absorbance was followed spectrophotometrically at 478 nm. Under optimum experimental conditions, calibration curve was linear over the range 0.45–100.0 μg/L of tramadol. The limit of detection was 0.12 μg/L of tramadol. The developed method was successfully applied for the determination of tramadol in real samples.

New Sensitive Derivatization Methodology of Levofloxacin Antibiotic from its Dosage Formulations: Kinetic Spectrophotometric Methods for Determination

A modern validated kinetic spectrophotometric method with a novel coupling reagent has been described for the determination of levofloxacin (LEV) in pure and tablets. The method involves an oxidative-coupling reaction between LEV and 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH), in the presence of Ce(IV) in H2SO4 medium at 25±1°C, to gives greenish-blue product. The reaction is followed spectrophotometrically by measuring the increase in absorbance with time at 629 nm and then is stable for more than 2 hrs. The initial rate, rate constant, fixed absorbance and fixed time methods have been tested for constructing the calibration graphs, and are linear. The most suitable analytical methods were the initial rate and fixed time (at 20 min) methods for determination of LEV in the concentration ranges of 2.0-35.0 μg mL-1 and 0.65-35.0 μg mL-1 with LOD is 0.422 and 0.074 μg mL-1, respectively. Molar absorptivity for the method was found to be 1.40×104 L mol-1 cm-1. The activation energy (E ), activation enthalpy (ΔH ‡), activation entropy (ΔS ‡) and Gibbs free energy (ΔG ‡) are estimated for the reaction and found to be 9.84 KJ mol-1, 7.40 KJ mol-1, 177.04 JK-1 mol-1 and -44.48 KJ mol-1, respectively. The kinetic proposed methods were further applied to the determination of LEV in tablet formulations with no interfere from the excipients.

Kinetic-spectrophotometric approach to the modified Berthelot procedure for serum urea determination

The results of developed kinetic-spectrophotometric method for serum urea determination by modified colorimetric Berthelot procedure were presented in this paper. To obtain high sensitivity, all reaction rates were monitored spectrophotometrically by measuring the change of absorbance with time at 700 nm. A differential variant of the tangent method was used for the processing of the kinetic data based on linear dependence of absorbance on time. The method is valid over the 0.25–2.50 µg cm−3 urea concentration interval with RSD range 8.33–2.02%. The limit of detection was calculated as 0.09 µg cm−3. The interference effects of some metal ions, anions, antibiotics, and other molecules were investigated to access the method selectivity. The method was successfully applied for the determination of urea in human quality control blood serum.

Adsorptive removal of bis(2-ethylhexyl) phthalate using an imprinted polymer: isotherm and kinetic modelling

ABSTRACT An adsorbent material specifically designed to capture bis(2-ethylhexyl) phthalate (DEHP) was successfully prepared by molecular imprinting technology. The molecularly imprinted polymer (MIP) was fabricated using methacrylic acid as a functional monomer and was crosslinked by ethylene glycol dimethacrylate via a bulk polymerisation method. The corresponding nonimprinted polymer (NIP) was synthesised as a control sample. The polymers were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, and porosity analysis by N2 adsorption–desorption. The binding performances of the MIP and NIP were evaluated through rebinding of DEHP in prepared solutions. The experiment was conducted by quantifying the amount of unbound template via the kinetic spectrophotometric method performed with a UV–Vis spectrophotometer. The effects of the initial concentration of the template and the adsorption time were revealed through an adsorption isotherm study. The obtained MIP showed a greater efficiency towards the removal of DEHP from solution (92%) than the NIP (34%). Therefore, the MIP exhibited preferential adsorption of DEHP molecules. The adsorption isotherm experiments showed good linearity and higher correlation coefficients for the Freundlich isotherm model than for the Langmuir model, and the pseudo-second-order equation provided the best fit describing the kinetic sorption behaviour of the polymers. Under optimised conditions, the MIP exhibited high selectivity towards DEHP over a competitive molecule; in addition, good recovery was achieved, resulting in a high distribution coefficient.

Kinetic spectrophotometric analysis of naftidrofuryl oxalate and vincamine in pharmaceutical preparations using alkaline potassium permanganate

A simple, rapid and sensitive kinetic spectrophotometric method is described for the analysis of naftidrofuryl oxalate (NF) and vincamine (VN) in pure form and in their pharmaceutical preparations. The procedure was based on the kinetic investigation of the oxidation of the studied drugs with alkaline potassium permanganate and the absorbance of the produced manganate species was measured at 610 nm. Variables affecting the color development were investigated and the conditions were optimized. The concentration of the studied drugs was calculated using the regression equations for the fixed-time method. The determination of the two drugs by fixed absorbance and rate constant methods was possible but the fixed time method was more applicable. The reliability and analytical performance of the proposed method including linearity, ranges, precision, accuracy, detection and quantification limits were statistically validated. Calibration graphs are linear over the concentration ranges of 3-15 μg/mL and 4-14 μg/mL for NF and VN, respectively. The proposed method was satisfactorily applied for analysis of pharmaceutical preparations containing the studied drugs. A proposal of the reaction pathway was postulated.

A New Sensitive Method for Quantitative Determination of Cisplatin in Biological Samples by Kinetic Spectrophotometry.

This study describes a kinetic spectrophotometric method for accurate, sensitive and rapid determination of cisplatin in biofluids. The developed method is based on the inhibitory effect of cisplatin on the oxidization of Janus Green by bromate in acidic media. The change in absorbance as the criteria of the oxidation reaction was followed spectrophotometrically. To obtain the highest rate of sensitivity, efficient reaction parameters were optimized. Under optimum experimental conditions, a calibration graph was obtained linearly over the range 10.0 - 5750.0 μg L-1 and the limit of detection (3sb/m) was 4.2 μg L-1 of cisplatin. The interfering effect of diverse species was investigated. The developed method was used for the quantification of cisplatin in bio fluids of patients treated with cisplatin, spiked bio fluids and pharmaceutical samples and yielded satisfactory results.

Effect of lansoprazole on DNA integrity of human spermatozoa and activity of seminal creatine kinase.

Although lansoprazole (brand name Prevacid) is a commonly used dug to manage various acid-related gastrointestinal diseases, little is known about its effects on human semen quality and sperm parameters. Here, we aimed to investigate the effect of lansoprazole on DNA integrity of human spermatozoa and activity of seminal creatine kinase. DNA integrity of human spermatozoa was assessed by the Apo-Direct™ kit followed by flow cytometry. The activity of creatine kinase was measured by kinetic spectrophotometric method using commercially available kits following the International Federation of Clinical Chemistry recommendations. Lansoprazole at 3µg/ml, after 1-hr incubation period, did not show any significant increase in fluorescein isothiocyanate fluorescence (p>.05) and hence on the content of DNA breaks of human spermatozoa. In addition, there was no significant change (p=.8113) in the activity of seminal creatine kinase by the effect of lansoprazole. In conclusion, lansoprazole at 3µg/ml did not alter DNA integrity of human spermatozoa or activity of seminal creatine kinase after 1-hr incubation period.

A batch and cloud point extraction kinetic spectrophotometric method for determining trace and ultra trace amounts of Benzodiazepine drugs (Clonazepam and Nitrazepam) in pure and pharmaceutical preparations

Abstract Utilizing the batch Diazotization coupling reaction and the cloud point extraction kinetic spectrophotometric method, trace and Ultra trace amounts from reducing Nitrazepam and Clonazepam were evaluated by way of using 2,5-dimethoxyaniline as a new Chromogenic reagent to give colored products (red) in acidic medium which have a maximum absorption at 500 and 502 nm, respectively. In the work, the analytical data of batch and cloud point for Nitrazepam and Clonazepam depended on initial rate and fixation time. This involved concentrations of (0,3-9), (0.05-1.2), (0.5-10) and (0.025-1) µg mL−1, as well as molar absorptivity of (3.8×104), (3.1×105) (3.39×104) and (3.47×105) L mol−1 cm−1. According to our results, Sandall’s sensitivity were (0.0074), (0.0009), (0.0092) and (0.0009) µg cm−2, while detection limits were (0.055) and (0.069) µg mL−1, (8.4) and (8.5) ng mL−1. In addition, the measurements enrichment factors were (33.33) and (50), while preconcentration factors were (8) and (9.9), respectively. The reaction of Nitrazepam and Clonazepam with 2,5-dimethoxyaniline were a pseudo first order according to kinetic studies. The proposed methods are not affected by existence of excipients so the methods can be applied successfully for determination of Nitrazepam and Clonazepam in pharmaceutical preparations.

VALIDATED KINETIC SPECTROPHOTOMETRIC DETERMINATION OF PITAVASTATIN CALCIUM USING ACIDIC PERMANGANATE OXIDATION

Objective: Development and validation of a sensitive, indirect spectrophotometric kinetic method, based on oxidation-reduction reaction, using potassium permanganate, for the quantitative assay of pitavastatin calcium, a cardiovascular drug used for the treatment of hyperlipidemia.
 Methods: The developed spectrophotometric kinetic method is based on the ability of potassium permanganate to oxidize Pitavastatin, where, the drug solution is treated with a fixed concentration of permanganate in acidic medium, and after a specified time, the unreacted permanganate is measured at 525 nm. All variables affecting the color development have been investigated and the conditions were optimized. Different kinetic methods, including initial rate, rate constant, fixed time and fixed concentration, were applied for the determination Pitavastatin.
 Results: During the course of the reaction, the absorbance values, at 525 nm, related to KMnO4, decreased linearly with increasing the concentration of the drug. The reaction rate obeyed was found to be pseudo-first-order and the kinetic method used was the fixed-time method. The assay of PITA in the concentration range of 16-80 μg/ml, using the fixed time method was successfully determined with a correlation coefficient value of 0.9999. The applicability of the developed method was also demonstrated by the determination of pitavastatin in its pure form and in its pharmaceutical formulation, where, the effect of excipients has also been studied and found to have no effect.
 Conclusion: The developed indirect spectrophotometric kinetic method, using the fixed time method, was used for the determination of Pitavastatin in pharmaceutical tablets. This method was simple, accurate and easy to apply for routine assay and in quality control laboratories.

Kinetics Spectrophotometric determination of Ranitidine based on its Inhibitory effect on the Oxidation Rate of Malachite green by N-bromosuccinide

A simple and sensitive kinetic spectrophotometric method is described for the determination of ranitidine. The method is based on the inhibiting effect of ranitidine on the rate of oxidation of malachite green (MG+ ) with N-bromosuccinimide (NBS) The oxidation reaction was followed spectrophotometrically by measuring the rate of change of the absorbance of malachite green with time at λ=617nm in the presence of different concentrations of ranitidine using the recommended procedure. Ranitidine can be determined from 0.08 to 2.40 g ml-1 with a linear calibration graph and detection limit of 0.026 g ml-1 . The method was successfully applied for the determination of ranitidine in pure ranitidine samples and in ranitidine tablets. The recovery of the analyzed samples were 97-100% with relative standard deviation, sr (%) =1.14 x 10-4 indicating high accuracy and precision of the suggested method. The interference of various cations and anions in the determination of ranitidine was studied

Kinetic Spectrophotometric Method for 4-nitrophenol Determination in Drinking Water

This paper describes a rapid, highly sensitive and simple kinetic spectrophotometric method for determination of p-nitrophenol (p-NP) based on its activating effect on sulfanilic acid oxidation by hydrogen peroxide in basic media in the presence of Co2+ as catalyst. Coloration of sulfanilic acid is used to monitor the reaction spectrophotometrically at 368 nm. p-Nitrophenol can be determined in the ranges of 40‒200 and 200‒400 ng/mL under optimal conditions. The detection limit of the method according to 3σ criteria is 8 ng/mL. The RSD is 4.8‒0.8% for concentration interval 40‒200 ng/mL. The kinetic parameters of the reaction are reported, and the rate equations are suggested. The developed procedure was successfully applied to the rapid determination of p-NP in water samples using solid phase extraction for phenol preconcentration and removing interferences. The HPLC method was used as comparative method to verify results.

The kinetic spectrophotometric method for the determination of azlocillin in solutions

Aim. To develop the method for the quantitative determination of azlocillin.Materials and methods. The study object was Securopen® – a powder of azlocillin (Azl) sodium in vials for preparation of the solution for injections (Azlocillin, 1.0 g). Peroxomonosulfate acid as triple potassium salt 2КНSO5 ∙ КНSO4 ∙ K2SO4 (Oxone®) of “extra pure” qualification was used as an oxidant.Results and discussion. The kinetics of the conjugated reactions of S-oxidation and perhydrolysis of Azlocillin (Azl) with potassium peroxomonosulfate in the alkaline medium has been studied by the increase of the forming product light absorbance at 275 nm. The conditions have been optimized, and the procedure of the quantitative analysis of Azl by the kinetic spectrophotometric method has been developed using potassium peroxomonosulfate as a reagent. RSD = 2.02 %.Conclusions. The results of the drug analysis obtained by the developed and standard methods are in good agreement with each other; δ = +0.49 %.

Determination of iodine content in Fijian foods using spectrophotometric kinetic method

The spectrophotometric kinetic method was validated for the determination of iodine in different food samples. The method is based on the iodide catalysed reduction of Ce4+ to Ce3+ by As3+. The absorbance of the kinetic indicator reaction was measured at 370 nm for exactly 1 min at 37 °C. The change in absorbance per min, as a measure of initial rate, was plotted against the different iodine concentrations to achieve a linear calibration equation with the R2 value of 0.9998 which showed excellent reproducibility. The limit of detection (LOD) was 1.54 ng/mL and the limit of quantification (LOQ) was 4.90 ng/mL. The incineration of the food organic matter was achieved by ashing the food samples at 600 °C using KOH and ZnSO4 in steps for 3 h. Trace levels of iodine (ng) were determined successfully using the validated spectrophotometric kinetic method for the 9 food samples (36 sub-samples). The Fiji seaweeds, lumiwawa (brown seaweed) showed the highest iodine content being 6373.30 ± 0.39 ng/g followed by sea grapes (green seaweed) 1162.81 ± 0.61 ng/g, lettuce 114.81 ± 0.08 ng/g, English cabbage 108.40 ± 0.06 ng/g, Chinese cabbage 104.01 ± 0.06 ng/g, pumpkin 101.24 ± 0.08 ng/g, long bean 97.61 ± 0.10 ng/g, banana 76.18 ± 0.10 ng/g and tomato 40.32 ± 0.04 ng/g. The coefficient of variation for the sample analysis was <5.31% with a mean and standard deviation of 2.55 ± 0.17% for the food samples analysed. The recovery analysis of iodine from standard samples ranged from 99.84 ± 0.91% to 100.24 ± 5.92% with an excellent average recovery of 100.06 ± 3.16%. The analytical coefficient of variation was calculated to be 0.34% for the food samples analysed. This shows exceptional system analytical stability of the method used in this study.

Serum Neutrophil Gelatinase-associated Lipocalin in children with septicemia

Neutrophil gelatinase-associated lipocalin (NGAL) is a rapidly emerging biomarker for early detection of acute kidney injury (AKI). The aim of the study is to evaluate the impact of sepsis on serum NGAL in critically ill children and to investigate whether the presence of sepsis affects the ability of serum NGAL to predict AKI. Sixty-eight patients, who met criteria of sepsis and related syndromes, were classified into two groups (septic shock and severe sepsis). They were reclassified regarding who developed AKI into AKI and non- AKI groups. Twenty sex and age-matched healthy subjects served as a control group. Serum NGAL was assayed using Enzyme-linked Immunosorbent Assay (ELISA), and serum creatinine was measured using the kinetic spectrophotometric method. Serum NGAL levels were significantly high in critically ill septic patients compared to healthy controls (median: 100.4ng/ml vs. 47.1 ng/ml, P>0.0001), and were significantly higher in septic shock (median 105.1ng/ml) than in severe sepsis (median 96ng/ml) with P values of 0.005. However, there was no significant difference in the levels of serum NGAL between AKI patients and non- AKI patients (P=0.3). Receiver operating characteristic (ROC) curve analysis of serum NGAL for prediction of AKI in critically ill septic children showed an area under the curve (AUC) was 0.56 (95% C.I. =0.42-0.70) with an optimal cutoff value of 102.5ng/ml, sensitivity=56.2%, specificity 55.6%, PPV =52.9%, NPV =58.8%, and accuracy=55.9%. For serum creatinine, the AUC was 0.97 (95% C.I. =0.94- 1.00) with an optimal cutoff value of 0.6 mg/dl, sensitivity= 90.6%, specificity 91.7%, PPV=90.6%, NPV=91.7% and accuracy=91.2%. In conclusion, serum NGAL is raised in critically ill septic children and is a marker of bacterial infection and systemic inflammation. However, in AKI associated with sepsis, serum NGAL is not a specific biomarker for the prediction of AKI and it loses its early predictive property. In such patients, serum creatinine is more specific than serum NGAL.

Application of Electrochemically Synthesized Ferrates (VI) for the Removal of Th(IV) From Natural Water Samples

The efficiency of the application of electrochemically generated Na2FeO4, for the purpose of the elimination of Th(IV) ions from water samples as coagulating agent was investigated. Th is a radioactive element often used as a fuel for nuclear reactors. The continuous exposure to Th(IV) may cause cancer of the pancreas, bone or lung. Analyzed natural water samples spiked with Th(IV) were treated with solution of ferrates (VI) under recommended conditions of electrochemically synthesized ferrates solution and Th(IV) was quantified by established kinetic method. Removal of Th(IV) ions by ferrates (VI) was successfully confirmed by comparison of the concentration of Th(IV) before and after ferrates (VI) treatment of spiked analyzed water samples. A simple kinetic-spectrophotometric method was successfully applied to determine Th(IV) concentration, indicating the decrease in the concentration of Th(IV) in water samples applying ferrate (VI).

Development of a New Kinetic Spectrophotometric Method for the Determination of Chromium with an Optical Probe.

The aim of this work is the development, optimization, and validation of a new spectrophotometric kinetic method for the determination of dissolved chromium species in water samples with the use of the polymethine dye Astra Phloxine FF. The progress of the chemical reaction was simple, effective, and precisely monitored from the start of the reaction using an optical probe. The method is based on the impact of Cr(VI) concentration on the rate of decrease in the Astra Phloxine FF concentration. The experimental data were evaluated using four experimental data analysis methods, namely with the initial rate method, the average rate method, the fixed time method, and the absorption peak volume change method. Under the optimal reaction conditions, the best results were achieved using the method of the average rate constant for evaluating the experimental data. Using this data evaluation method for the determination of Cr(VI), the LoD was found to be 1.87 µg L-1 and RSD ( n = 6; 0.2 mg L-1 Cr) 3.59%. The presented work was used for the determination of chromium in model samples-CRM material and tap and waste water-and with the calibration line method and the standard additions method.

Kinetic-Spectrophotometric Determination of Thiocyanate in Human Saliva Based on Landolt Effect in Presence of Astrafloxine FF

In the present study a kinetic-spectrophotometric method for thiocyanate determination is described. The suggested method for the determination of thiocyanate is based on its "Landolt effect" on the reaction of bromate with hydrobromic acid, which leads to the formation of only one halogen bromine. The reaction was monitored spectrophotometrically at the maximum wavelength of astrafloxine FF light absorption at 535 nm. The absorbance of reactants mixture decreased with an increase of the reaction time. The calibration curve for thiocyanate determination was obtained in the concentration range of 0.03-2.0 μg mLμ1 under the optimal conditions (pH 1.5; CBrO3 - = 7.6 × 10-4 mol L-1; Castrafloxine FF = 1 × 10-5 mol L-1). The limit of detection was 0.01 μg mLμ1. The method was successfully applied to the determination of thiocyanate in human saliva samples with satisfactory results.

Mechanistic Study and Kinetic Determination of Cu (II) by the Catalytic Kinetic Spectrophotometric Method

A highly sensitive and selective catalytic kinetic spectrophotometric method for the determination of Cu (II) is proposed. It is based on the catalytic effect of Cu (II) on the oxidation of glutathione (GSH) by potassium hexacyanoferrate (III) in acidic medium at 25.0°C. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of oxidant at 420 nm using the fix-time method. Under the optimum conditions, the proposed method allows the determination of Cu (II) in a range of 0 - 35.0 ng mL−1 with good precision and accuracy and the limit of detection is down to 0.04 ng mL−1. The relative standard deviation (RSD) is 1.02%. The reaction orders with respect to each reagent are found to be 1, 1/2, and 1/2 for potassium hexacyanoferrate (III), glutathione and Cu (II) respectively. On the basis of these values, the rate equation is obtained and the possible mechanism is established. Moreover, few anions and cations can interfere with the determination of Cu (II). The new proposed method can be successfully used to the determination of Cu (II) in fresh water samples and seawater samples. It is found that the proposed method has fairly good selectivity, high sensitivity, good repeatability, simplicity and rapidity.