Spectrophotometric Determination of Rosiglitazone in Pure form and in Pharmaceutical formulations

 

K. Purushotham Naidu and N.V.S. Naidu*

Dept of Chemistry, S.V. University, Tirupati, India.

*Corresponding Author E-mail: nvsn69@gmail.com

 

ABSTRACT:

Two simple, rapid and sensitive spectrophotometric methods were developed for the determination of Rosiglitazone either in raw material or in Pharmaceutical formulations. Method A is based on the extraction of Rosiglitazone by Fe3+ in acidic medium, and the subsequent interaction of iron (III) with ferricyanide to form purssian blue with the product exhibiting an absorption maxium at 728 nm. Method B is based on the oxidation of Rosiglitazone by Fe3+ in presence of orthophosphoric acid was demonstrated at 522 nm with 2, 2’- bipyridyl. The analytical parameters and their effects on the reported systems are investigated. Beer’s law was obeyed in the concentration  range 5 – 50 µg ml-1 and 2 – 20 µg ml-1 with correlation coefficient 0.995 and 0.997 for Method A and B respectively .The molar absorptivity , sandell’s sensitivity, detection and quantification limits were also calculated. The proposed methods have been applied successfully for the analysis of the studied drugs in pure and pharmaceutical formulations with percentage recoveries range from 99.30 to 100.08. The results were in good agreement with those obtained by the official methods.

 

KEYWORDS: Spectrophotometry, Potassiumferricynide, 2, 2’ – Bipyridyl, Ferric chloride, Formulations

 


 

INTRODUCTION:

Rosiglitazone (ROZ), 5- ((4-(2-(methyl – 2- pyridinylamino ethoxy) phenyl) – methyl-2, 4 – thiazolidinedione (Fig.1) is a thiazolidinedione antidiabetic agent used in the treatment of type 2diabetes mellitus. Thiazolidine dione antihyperglycemic agents exert their effect through the peroxisome proliferator activated receptor gamma (PPARγ), which facilitates the expression of genes responsible for glucose and lipid metabolism (1).

 

 

Several methods have been reported for the determination of rosiglitazone in pharmaceutical preparations such as High performance thin layer chromatograpy (2-4), high performance liquid chromatograpy (5- 10), Capillary electrophoresis (CE) (11), capillary zone electrophoresis (CZE) (12), Voltammetric (13) and UV – Visible spectrophotometry (14-20).

 

In the present investigation two simple and sensitive visible spectrophotometric analyses were developed for the analysis of rosiglitazone in tablets. The proposed methods are based on the Oxidation of drug by Fe3+ in presence of Potassium Ferricynide and 2, 2’-Bipyridyl.

 

Fig.1: Chemical structure of Rosiglitazone

 

EXPERIMENTAL:

Apparatus:

All absorption spectra were recorded using a Shimadzu model 2450 UV –Visible double beam spectrophotometer with 1cm matched quartz cells.

 

Materials and reagents:

Methanol, Potassium ferricyanide, Ferric chloride, orthophosphoric acid, Sulphuric acid, 2, 2’-Bipyridyl and chloroform. All Chemicals and materials used were of analytical grade and all solutions were freshly prepared in bidistilled water. Pharmaceutical grade Rosiglitazone pure sample was kindly supplied by Nicholas Piramal India Limited, Hyderabad, India.

Pharmaceutical formulations of rosiglitazone such as Rosinorm -2 (Micro Labs Ltd, Solan, India) were purchased from local market.

 

Ferric Chloride (0.5%): The aqueous solution of 0.5% ferric chloride (S.D.fine, Mumbai, India) was prepared by dissolving 500 mg of the Chemical in 100 ml distilled water and stored in dark bottle.

 

Potassium fericynide (0.5%): 500 mg of Potassium ferricynide (Merck, India) was dissolved in 100 ml of distilled water.

2, 2’-Bipyridyl (0.2%): was prepared by dissolving 200 mg of 2, 2’-Bipyridyl (Qaligens fine chemicals, Mumbai, India) in 100 ml of distilled water.

 

Orthophosphoric acid (0.03M): Concentrated acid (Merck, India) was appropriately diluted with distilled water to get the required concentration.

 

Sulphuric acid (5M): Required volume of concentrated sulphuric acid (Merck, India) was diluted with distilled water to get the required concentration.

 

Preparation of standard stock solution:

Stock reference solution of Rosiglitazone (1000 µg ml-1) was freshly prepared by dissolving 100 mg of pure drug in methanol, followed by dilution to 100 ml with the same solvent to obtain 1 mg ml-1 standard solution. This solution was further diluted with methanol so as to obtain a working standard solution of 100 µg ml-1 for method A and B.

 

Assay Procedures:

Method A:

Into a series of 10 ml calibrated flask, Rosiglitazone aliquots ranging from 0.5 – 5 ml (5-50 µg ml-1) of 100 µg ml-1 standard solution were transferred using micro burette. Then, 2 ml each of FeCl3 (0.5%) and Potassium ferricynide (0.5%) were added to each flask, kept on water bath for 10 min cooled and add 1ml of 5M Sulphuric acid for complete color development.. Then transferred the colored solution into 125 ml separating funnel. The mixture was extracted twice with 10 ml Chloroform by shaking for 2 min, and then allowed to stand for clear separation of the two phases. The absorbance of the separated chloroform layer i.e purssian blue colored complex was measured at 728 nm against a reagent blank prepared similarly.

 

Method B:

Different aliquots of working standard solution Rosiglitazone (100 µg ml-1) ranging from 0.2 to 2.0 ml (2-20 µg ml-1) were transferred in to a series of 10 ml standard flasks by means of micro burette. To each flasks 1.0 ml ferric chloride (0.5%) and 1.5 ml of 2,2’- Bipyridyl (0.2%) were added and kept in a water bath (60 ± 10C) for 15 min, then immediately cooled to room temperature using a cold water bath and 1 ml of orthophosphoric acid was added. The solutions were made up to volume with distilled water. The absorbance of each solution was measured at 522 nm against the reagent blank.

 

In both methods A and B calibration graph was then prepared by plotting the absorbance versus concentration of the drug. The concentration of the unknown was read from the calibration graph or computed from the regression equation derived using the Beer’s law data.

 

Procedure for analysis of Pharmaceutical formulations:

Twenty tablets were accurately weighed and powdered. An amount of powder equivalent to 100 mg of Rosiglitazone was accurately weighed and transferred into a 100 ml calibrated flask, 30 ml of methanol was added and the content shaken thoroughly for 15 – 20 min to extract the drug into liquid phase, the volume was finally diluted to the mark with methanol, mixed well and filtered using a whatman no 42 filter paper. Suitable aliquot of the filtrate (1000 µg/ml Rosiglitazone) was diluted stepwise to get 100 µg/ml concentrations for method A and B.

 

Optimization of variables:

Effect of reagent concentration:

The experimental variables for the formation of the stable and sensitive colored product were optimized. The results obtained showed that minimum 2.0 ml of Ferric chloride is required for maximum color development in Method A and 1.0 ml in Method B. The amount of Potassium ferricynide and 2, 2’-Bipyridyl required for optimum color development are 2.0 and 1.5ml in method A and Method B respectively. The color formed under these conditions in Method A was stable for more than 5h and more than 3h in Method B.

 

The reaction product in method A, Purssian blue was found to flocculate with in 25-30 min of color development. To delay the flocculation, acid was added after full color development and before dilution. A 1.0 ml volume of sulphuric acid was found to adequate for full color development. The presence of orthophosphoric acid was necessary to increase the stability of developed orange red color complex by maintain the desired pH in method B. One ml orthophoric acid was found adequate in method B.

 

Effect temperature and heating time:

The procedures were tried on cold conditions and it was found that Method A needed 10 min for color development and Method B required 2h for optimum color development. In Method B heating on water both at 60 ± 20C needed 15 min for optimum color development. For this reason the heating time was selected to be 15 min for Method B. further increase in the heating time does not cause any change in color intensity.

 

Sequence of addition of reagents:

The following order gave maximum absorbance and stability, due to this reason the same order of addition was followed in present investigation. In method A; Drug, Ferricynide and Iron (III) followed by sulphuric acid. In Method B; Drug, 2, 2’ – Bipyridyl and Iron (III) followed by Orthophosphoric acid

 

Selecting of the extracting solvent:

The effect of the extracting solvent used for Rosiglitazone on extraction efficiency and color intensity was examined. Chloroform, dichloromethane and 1,2-dichloroethane proved useful solvents. Chloroform was selected because of its slightly higher efficiency and considerably lower extraction ability for reagent blank.

 

RESULTS AND DISCUSSIONS:

In method A Rosiglitazone reduces ferric chloride to ferrous ions which in turn couples with reagent having divalent iron like potassium ferricyanide to from purssian blue colored potassium ferroferrous complex. The formation of the purssian blue complex was employed in the qualitative detection of Fe (II). A deep blue complex was formed from the reaction between Fe (II) and hexacynoferrate (III). The chromogenic reagent blank (Fe (III) mixed with hexacynoferrate (III) in acidic medium) did not show strong absorption in the visible region of the spectrum. However, after addition of the Rosiglitazone, the spectrum changed because of the formation of the purssian blue complex, which has a λ max of 728 nm (Fig.2)

 

Fig.2: Calibration plot of Rosiglitazone (Method A)

 

Method B is based on the formation of tris (2, 2’-Bipyridyl – iron (II) following the reaction of Rosiglitazone with Fe3+ - bipyridyl. The reaction proceeds through the reduction of Fe3+ to Fe2+ with the subsequent formation of an intense orange – red coloration attributable to the complex. The absorption spectrum of the colored complex under optimum conditions were scanned in double beam mode against a reagent blank over the range 400 – 900 nm, and recorded according to general procedures. Characteristic λ max value was obtained at 522 nm (Fig.3)

 

Method validation:

Linearity:

Under optimum conditions, linear relationship between the absorbance at λ max and the concentration of the drug was found with in the range 5-50 and 2-20 µg ml-1 for method A and B respectively. The molarabsorptivity value of method A and B was found to be 1.05x104 and 1.59x104 respectively. Sandell’s sensitivity was found to be 0.0344 and 0.023 for method A and B respectively. The fairly high value of molar absorptivity and low values of sandell’s sensitivity indicates the high sensitivity of the method. The results of optical characteristics such as Beer’s law limits, correlation coefficient, slope, intercept and absorptivity values were summarized in Table.1.

 

Fig.3: Calibration plot of Rosiglitazone (Method B)

 

Table.1: Optical and regression Characteristics of the proposed methods

Parameters

Method A

Method B

λ max nm

728

522

Beer’s Law limit (µg ml-1)

5-50

2-20

Molar absorptivity  (L. mol-1  cm-1)

1.05x104

1.59x104

Sandell’s sensitivity (µg.cm-2/0.001 A.U)

0.0344

0.0233

Regression equation (Y = mX + C)

 

 

Slope (m)

0.027

0.045

Intercept (C)

0.008

0.004

Correlation coefficient (r2)

0.995

0.997

% Relative Standard deviation

0.518

0.314

Color

Orange red

Purssian blue

LOD (µg ml-1)

0.80

0.30

LOQ (µg ml-1)

1.00

0.88

 

Sensitivity:

The limit of detection (LOD) and limit of quantitation (LOQ) were determine using the formula

LOD = 3s/k           and         LOQ = 10s/k

Where s is the standard deviation of five reagent blank determinations and k is the slope of the calibration curve. According to this equation LODs were found to be 0.8 and 0.3 and LOQs were 1.0 and 0.88 respectively.

 

Accuracy and Precision:

The accuracy and precision of the proposed methods (A and B) was evaluated by replicate analysis (n=5) of rosiglitazone calibration standards at two concentration levels (2.0 and 4.0 µg ml-1) for short term (Intra - day) and daily (Inter - day) precisions (Table.2). Precision and accuracy were based on the calculated relative standard deviation (RSD %) and relative error (RE %) of the found concentration compared to theoretical one, respectively.


Table.2: Evaluation of Intra-day and Inter-day accuracy and precision

Method

RSG taken µg/ml

Intra - day

Inter - day

Found µg/ml

Recovery ± RSD%

RE%

Found µg/ml

Recovery ± RSD%

RE%

A

2

1.986

99.30 ± 0.76

-0.70

1.987

99.37 ± 0.28

-0.63

4

3.977

99.40 ± 0.14

-0.55

3.978

99.50 ± 0.16

-0.54

B

2

1.988

99.44 ± 0.71

-0.56

1.987

99.36 ± 0.35

-0.64

4

3.978

99.40 ± 0.12

-0.53

3.978

99.46 ± 0.10

-0.53

 

Fig.4: Absorption Spectrums of Rosiglitazone Method A and B

 

Table.3: results of analysis of tablet formulations containing Rosiglitazone

Tablet brand name

Label claim

µg/ml

%Founda ± SD (µg/ml)

Reference method (20)

Method A

Method B

Rosinorm – 2b (2mg per tablet)

2

97.85 ± 1.10

99.75 ± 0.58

T=1.21,F=0.18

99.83 ± 0.54

T=1.05, F=0.07

a Mean value of five determinations

b Micro Labs Ltd, Solan, India. The value of t at 95 % confidence level and for four degrees of freedom is 2.45, the value of F at 95% confidence level and for four degrees of freedom are 6.94

 

 


Application in Pharmaceutical analysis:

The proposed methods were successfully applied to the determination of rosiglitazone in Rosinorm tablet and results are summarized in Table.3. The results obtained were statistically compared with those of the reference method (20). The results showed that the t- and F- values were less than the critical value, indicating that there was no significant difference between the proposed and reference method for Rosiglitazone.

 

CONCLUSIONS:

The spectrophotometric methods developed for the determination of Rosiglitazone use readily available chemicals and inexpensive chemicals compared to many reported methods. These methods are simpler, economic and more sensitive than those previously published. An additional advantage of the spectrophotometric methods is that the absorbance is measured at longer wavelength where the interference from excipients is less. Hence, recommended procedures are well suited for the assay and validation of drugs in Pharmaceutical industrial quality control.

 

ACKNOWLEDGMENTS:

Authors are thankful to Nicholas Piramal India Limited, Hyderabad, India for providing the gift sample of drug rosiglitazone and Dept of chemistry for providing lab facilities to carry out this work.

 

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Received on 04.07.2011        Modified on 02.08.2011

Accepted on 14.08.2011        © AJRC All right reserved

Asian J. Research Chem. 4(9): Sept, 2011; Page 1420-1424