Spectrophotometric Determination of Various Drugs Using Chloranilic Acid as Chromogenic Reagent-II

Simple, accurate and reproducible visible spectrophotometric method for the assay of drugs such as pyrilamine and fluvoxamine as maleates was established based on the formation of charge-transfer complex and redox reaction between the corresponding drug and substituted p-benzoquinone (chloranilic acid). The optical characteristics such as Beer’s law limits, molar absorptivity and Sandell’s sensitivity are reported. Regression analysis using the method of least squares was made to evaluate the slope (b), intercept (a) and correlation coefficient (r) and standard error of estimation (Se) for each drug.


Introduction
Fluvoxamine 1 (as maleate FXA) is a selective serotonin reuptake inhibitor (SSRI) used to treat obsessive -compulsive disorder (OCD).It may also be used to treat depression and other conditions.It belongs to a new chemical series of 2 amino ethyl oxime ethers.The mechanism of action of fluvoxamine maleate in obsessive compulsive disorder is presumed to be linked to its specific serotonin reuptake inhibition in brain neurons.In preclinical studies, it was found that fluvoximine inhibited neuronal uptake of serotonin.Pyrilamine 1 (as maleate PYRA) is an antihistamine with a low incidence of side effects.It is effective for use in perennial and seasonal allergic rhinitis, vasomotor rhinitis, allergic conjunctivitis due to inherent allergens and foods, mild uncomplicated allergic skin manifestations of urticarea and angiodesma, angioedema, demo graphism and aneceoratum of reactions of blood or plasma.It is an antagonizing agent that competes for receptor sites with natural histamine, a biogenic amine present in most body cells and tissues.
A very few physicochemical methods appeared in the literature for the assay of the proposed drug samples in biological fluids and pharmaceutical formulations.Most of them are based on visible spectrophotometric methods 2,3 , HPLC [4][5][6] , GC 7,8 , fluorimetry [9][10][11] , LC-MS 12 ,GC-MS [13][14][15] &TLC 16 ,Mass 17 .Existing analytical methods reveal that relatively little attention was paid in developing visible spectrophotometric methods by exploiting the analytically useful functional groups.Hence there is a need to develop sensitive and flexible visible spectrophotometric methods which prompted the author to carry out in this accord.

Experimental
An Elico, UV-Visible digital spectrophotometer with 1 cm matched quartz cells were used for the spectral and absorbance measurements.An Elico LI-120 digital pH meter was used for pH measurements.
All the chemicals and reagents used were of analytical grade and solutions were prepared in triply distilled water.A 1 mg/mL solution was prepared by dissolving 100 mg of pure drug sample in 100 mL of 0.1N HCl and this stock solution was diluted step wise with distilled water to get the working standard solutions of concentration 200 µg/mL.
Chloranilic acid solution was (Sd-fine; 0.1%, 4.785x10 -3 M) prepared by dissolving 100 mg of p-chloranilic acid initially in 20 mL of isopropyl alcohol followed by dilution to 100 mL with chloroform.
Into a series of 10 mL calibrated tubes containing aliquots of standard drug solution (0.5-3.0 mL, 200 µg.mL - ), 2.0 mL (4.785x10 -3 M) of chloranilic acid was added and kept aside for 30 min at lab temperature.The volume in each tube was made up to the mark with chloroform.The absorbance of the colored species was measured at 540 nm against a reagent blank.The amount of the drug was calculated from Beer's law plot.
About 100 mg of formulated drug sample was transferred into a 100 mL volumetric flask, 80 mL of warm ethyl alcohol was added and shaken well for 20 min.The contents were diluted with ethyl alcohol up to the mark and mixed thoroughly.The solution was filtered and the filtrate was evaporated to dryness and analyzed.

Results and Discussion
In order to ascertain the optimum wavelength of maximum absorption (λ max ) of the coloured species formed in the above methods, specified amounts of drug samples were taken and colors were developed separately by following the above procedures.The absorption spectra were scanned on a spectrophotometer in the wave length region of 340 to 900 nm against a similar reagent blank or distilled water.The reagent blank absorption spectrum of each method was also recorded against distilled water.
The optimum conditions for the color development were established by varying the parameters one at a time, keeping the others fixed and observing the effect produced on the absorbance of the colored species.The following experiments were conducted for this purpose and the conditions so obtained were incorporated in recommended procedures.
FXA possesses aliphatic primary amine group which functions as an electron donor, participates in charge transfer interaction with DHQ.The colour species formation in the method appears to be due to the formation of radical anion.The optical characteristics such as Beers law limits, molar absorptivity and Sandell's sensitivity, regression analysis using the method of least squares was made to evaluate the slope (b), intercept (a) and correlation coefficient (r) and standard error of estimation (Se) for the samples are given Table 1.
The similarity of the results is obvious evidence that during the application of these methods, the excipients are usually present in pharmaceutical formulations (Table 2 & 3) do not interfere in the assay of proposed methods.The accuracy of the methods was ascertained statistically by the t-and F-tests.As an additional check of accuracy of the proposed methods, recovery experiments were carried out.The recovery of the added amounts of standard drug was studied at 3 different levels.From the amount of drug found, the % recovery was calculated (Table 4).

Conclusion
The proposed method exploits the various functional groups in drug samples.The concomitants which do not contain the functional groups chosen in the present investigation do not interfere in the color development by proposed method.Thus the proposed method is simple, sensitive or selective with reasonable precision and accuracy and constitute better alternative to the reported ones in the assay of FXA and PYRA in bulk form and pharmaceutical formulations.
of the presence of aliphatic tertiary amino group functions as an electron donor and participates in charge-transfer interaction with electron acceptor DHQ.The colour species formation appears to be due to the formation of radical anion.

Table 1 .
Optical and regression characteristics, precision and accuracy of the proposed drug samples.

Table 3 .
Commercially available formulations for pyrilamine maleate.

Table 4 .
Assay of proposed drug samples in pharmaceutical formulations.