Ashwinee Kumar Shrestha

A sensitive spectrophotometric method for the determination of sulfonamides in pharmaceutical preparations

A sensitive spectrophotometric method for the determination of sulfonamides in pharmaceutical preparations A new, simple and sensitive spectrophotometric method for the determination of some sulfonamide drugs has been developed. The method is based on the diazotization of sulfacetamide, sulfadiazine, sulfaguanidine, sulfamerazine, sulfamethazine, sulfamethoxazole, and their coupling with 8-hydroxyquinoline in alkaline media to yield red coloured products with absorption maxima at 500 nm. Beers law is obeyed from 0.1--7.0 μg mL-1. The limits of quantification and limits of detection were 0.11--0.18 and 0.03--0.05 μg mL-1, respectively. Intraday precision (RSD 0.1--0.5%) and accuracy (recovery 97.3--100.8%) of the developed method were evaluated. No interference was observed from common adjuvants. The method has been successfully applied to the assay of sulpha drug in pharmaceutical formulations. Osjetljiva spektrofotometrijska metoda za određivanje sulfonamida u farmaceutskim pripravcima U radu je opisana nova, jednostavna i osjetljiva spektrofotometrijska metoda za određivanje sulfonamida. Metoda se temelji na prevođenju sulfacetamida, sulfadiazina, sulfagvanidina, sulfamerazina, sulfometazina i sulfametoksazola u diazoderivate koji kondenzacijom s 8-hidroksikinolinom u alkalnom mediju daju crveno obojene produkte s maksimumom apsorpcije pri 500 nm. Beerov zakon vrijedi u koncentracijskom rasponu 0,1--7,0 μg mL-1. Granice kvantifikacije i granice detekcije su 0,11--0,18, odnosno 0,03--0,5 μg mL-1. Za predloženu metodu procijenjena je intermedijarska preciznost (RSD 0,1--0,5%) i točnost (analitički povrat 97,3--100,8). Uobičanjene pomoćne tvari u tabletama ne interferiraju tijekom određivanja. Metoda je uspješno primijenjena za analizu sulfonamida u farmaceutskim pripravcima.

Quantification of hydrogen peroxide and glucose using 3-methyl-2-benzothiazolinonehydrazone hydrochloride with 10,11-dihydro-5H-benz(b,f)azepine as chromogenic probe

A sensitive, selective, and rapid enzymatic method is proposed for the quantification of hydrogen peroxide (H(2)O(2)) using 3-methyl-2-benzothiazolinonehydrazone hydrochloride (MBTH) and 10,11-dihydro-5H-benz(b,f)azepine (DBZ) as chromogenic cosubstrates catalyzed by horseradish peroxidase (HRP) enzyme. MBTH traps free radical released during oxidation of H(2)O(2) by HRP and gets oxidized to electrophilic cation, which couples with DBZ to give an intense blue-colored product with maximum absorbance at 620 nm. The linear response for H(2)O(2) is found between 5x10(-6) and 45x10(-6) mol L(-1) at pH 4.0 and a temperature of 25 degrees C. Catalytic efficiency and catalytic power of the commercial peroxidase were found to be 0.415x10(6) M(-1) min(-1) and 9.81x10(-4) min(-1), respectively. The catalytic constant (k(cat)) and specificity constant (k(cat)/K(m)) at saturated concentration of the cosubstrates were 163.2 min(-1) and 4.156x10(6) L mol(-1) min(-1), respectively. This method can be incorporated into biochemical analysis where H(2)O(2) undergoes catalytic oxidation by oxidase. Its applicability in the biological samples was tested for glucose quantification in human serum.

Use of N,N-diethyl-p-phenylenediamine sulphate for the spectrophotometric determination of some phenolic and amine drugs

Use of N, N-diethyl-p-phenylenediamine sulphate for the spectrophotometric determination of some phenolic and amine drugs Spectrophotometric methods are proposed for the determination of drugs containing a phenol group [salbutamol sulphate (SLB), ritodrine hydrochloride (RTD), isoxsuprine hydrochloride (IXP)] and drugs containing an aromatic amine group [dapsone hydrochloride (DAP), sulfamethoxazole (SFM), and sulfadiazine (SFD)] in pharmaceutical dosage forms. The methods are based on coupling of N, N-diethyl-p-phenylenediamine sulphate with the drugs in the presence of KIO4 to give a green colored product (λmax at 670 nm) and a red colored product (λmax at 550 nm), respectively. Linear relationships with good correlation coefficients (0.9986-0.9996) were found between absorbance and the corresponding concentration of drugs in the range 1-7, 2-22, 1-17, 1.5-12, 2-25, and 2-21 μg mL-1 for SLB, RTD, IXP, DAP, SFM and SFD, respectively. Variable parameters such as temperature, reaction time and concentration of the reactants have been analyzed and optimized. The RSD of intra-day and inter-day studies was in the range of 0.2-1.0 and 0.4-1.0%, respectively. No interference was observed from common pharmaceutical adjuvants. The reliability and performance of the proposed methods was validated statistically; the percentage recovery ranged from 99.5 ± 0.1 to 99.9 ± 0.3%. Limits of detection were 0.14, 0.21, 0.51, 0.44, 0.33 and 0.37 μg mL-1 for SLB, RTD, IXP, DAP, SFM, and SFD, respectively. Upotreba N, N-dietil-p-fenilenediamin sulfata za spektrofotometrijsko određivanje lijekova iz skupine fenola i amina U radu je predložena spektrofotometrijska metoda za određivanje lijekova s fenolnom skupinom [salbutamol sulfat (SLB), ritodrin hidroklorid (RTD), izoksuprin hidroklorid (IXP)] i lijekova s aromatskom amino skupinom [dapson hidroklorid (DAP), sulfametoksazol (SFM) i sulfadiazin (SFD)] u farmaceutskim dozirnim pripravcima. Metode se temelje na reakciji ljekovitih tvari s N, N-dietil-p-fenilendiamin sulfatom u prisutnosti KIO4, pri čemu nastaje zeleni (λmax pri 670 nm), odnosno crveni produkt (λmax pri 550 nm). Apsorbancije linerano ovise o koncentrancijama lijekova uz visok koeficijent korelacije (0,9986-0,9996) u koncentracijskom području 1-7, 2-22, 1-17, 1,5-12, 2-25 i 2-21 μg mL-1 za SLB, RTD, IXP, DAP, SFM i SFD. Analizirani su i optimirani promjenjivi parametri kao što su temperatura, reakcijsko vrijeme i koncentracija reaktanata. Repetibilnost i intermedijarna preciznost iznosile su 0,2-1,0, odnosno 0,4-1,0%. Nije primjećena nikakva interferencija s uobičajenim farmaceutskim pomoćnim sredstvima. Pouzdanost i izvedbene značajke predložene metode validirane su statistički. Povrat analitičke metode bio je od 99,5 ± 0,1 do 99,9 ± 0,3%. Granice detekcije bile su 0,14, 0,21, 0,51, 0,44, 0,33 i 0,37 μg mL-1 za SLB, RTD, IXP, DAP, SFM, odnosno SFD.

Development of quantitative enzymatic method and its validation for the assay of glucose in human serum.

OBJECTIVE To develop a simple, rapid, sensitive and affordable assay method for the determination of glucose in blood samples using a novel approach. DESIGN AND METHODS A spectrophotometric method for glucose quantification in human serum samples based on self-coupling of activated 2,5-dimethoxyaniline (DMA) in the presence of peroxidase (POD)/glucose oxidase (GOD) and H(2)O(2) is described. H(2)O(2) generated in situ by catalytic reaction between GOD and glucose, activates DMA in the presence of POD to form a green-colored product, which has a strong absorption at λ(max)=740 nm at room temperature (30°C) in a 100 mmol/L acetate/acetic acid buffer of pH 4.2. RESULTS The linearity ranges for the quantification of glucose by rate and one-time detection method are 0.017-0.740 and 0.017-0.478 mmol/L, respectively. Within-day and day-to-day precision were 0.98-1.4% (n=10) and 1.33-2.89% (n=15), respectively. Glucose recoveries ranged from 96.6 to 102%, indicating minimal interference by commonly present interferants in serum samples. Accuracy results were between 90 and 102%. The detection and quantification limits of glucose were 2.376 and 7.923 μmol/L, respectively. The proposed method has good correlation coefficient of 0.999 with the enzymatic kit method. CONCLUSIONS This is a rapid and convenient method to determine serum glucose using simple spectrophotometer with excellent recovery and minimal interference by interferants in serum samples with low detection limit. Therefore, this method can be considered for adoption by the clinical diagnostic laboratories.

Peroxidase-Catalyzed Oxidative Coupling of Paraphenylenediamine with 3-Dimethylaminobenzoic Acid: Application in Crude Plant Extracts

This paper presents a novel spectrophotometric method to measure peroxidase activity using paraphenylenediamine dihydrochloride (PPDD) and 3-dimethylaminobenzoic acid (DMAB). The PPDD traps free radicals and becomes oxidized to electrophillic 1,4-diimine, which couples with DMAB to give an intense green-colored chromogenic species with maximum absorbance at 710 nm. This assay was adopted for the quantification of hydrogen peroxide between 5 and 45 microM. From the kinetic data, a two-substrate ping-pong mechanism of peroxidase was established. The catalytic efficiency and catalytic constant (k(cat)) of the proposed assay were 0.54 x 10(6) M(-1) min(-1) and 0.0436 x 10(3) min(-1), respectively. As a simple, rapid, precise, and sensitive technique, PPDD-DMAB stands as a potential replacement for the traditional guaiacol method. Application of this method in plant extracts opens its relevance in the field of biochemical analysis.

Spectrophotometric determination of catecholamine using vanadium and eriochrome cyanine r

A highly sensitive spectrophotometric method for the analysis of catecholamine drugs; L-dopa and methyldopa, is described. The analysis is based on the reaction of drug molecules with vanadium (V) which is reduced to vanadium (IV) and form complex with eriochrome cyanine R to give products having maximum absorbance (lmax) at 565 nm. Beers law is obeyed in the range 0.028-0.84 and 0.099-0.996 mg mL-1 for L-dopa and methyldopa, respectively. The statistical analysis as well as comparison with reported methods demonstrated high precision and accuracy of the proposed method. The method was successfully applied in the analysis of pharmaceutical preparations.

Spectrophotometric Method for the Determination of Drugs Containing Phenol Group by Using 2, 4- Dinitrophenylhydrazine

A spectrophotometric method has been proposed for the determination of four phenolic drugs; salbutamol, ritodrine, amoxicillin and isoxsuprine. The method is based on the oxidation of 2, 4- dinitrophenyl-hydrazine and coupling of the oxidized product with drugs to give intensely colored chromogen. Under the proposed optimum condition, beer’s law was obeyed in the concentration range of 2.5-17, 2-29, 4-33 and 5-30 μg/mL for salbutamol, ritodrine, amoxicillin and isoxsuprine respectively. The limit of detection (LOD) and limit of quantification (LOQ) were 0.2, 0.83, 0.09, 0.84 μg/mL and 0.66, 2.79, 0.3 and 2.81 μg/mL in the same order. No interference was observed from common pharmaceutical adjuvants. The ringbom plots and low relative standard deviation assert the applicability of this method. The suggested method was further applied for the determinations of drugs in commercial pharmaceutical dosage forms, which was compared statistically with reference methods by means of t- test and F- test and were found not to differ significantly at 95% confidence level. The procedure is characterized by its simplicity with accuracy and precision.

Simple and sensitive method for the quantification of total bilirubin in human serum using 3-methyl-2-benzothiazolinone hydrazone hydrochloride as a chromogenic probe

We here describe a new spectrophotometric method for measuring total bilirubin in serum. The method is based on the cleavage of bilirubin giving formaldehyde which further reacts with diazotized 3-methyl-2-benzothiazolinone hydrazone hydrochloride giving blue colored solution with maximum absorbance at 630 nm. Sensitivity of the developed method was compared with Jendrassik-Grof assay procedure and its applicability has been tested with human serum samples. Good correlation was attained between both methods giving slope of 0.994, intercept 0.015, and R(2)=0.997. Beers law obeyed in the range of 0.068-17.2 μM with good linearity, absorbance y=0.044 C(bil)+0.003. Relative standard deviation was 0.006872, within day precision ranged 0.3-1.2% and day-to-day precision ranged 1-6%. Recovery of the method varied from 97 to 102%. The proposed method has higher sensitivity with less interference. The obtained product was extracted and was spectrally characterized for structural confirmation with FT-IR, ¹H NMR.