Determination of Certain Drugs in Multicomponent Formulations by First Derivative Ultraviolet Spectrophotometry

Application of derivative spectrophotometry under orthogonal polynomial at unequal intervals: determination of metronidazole and nystatin in their pharmaceutical mixture

This paper discusses a general method for the use of orthogonal polynomials for unequal intervals (OPUI) to eliminate interferences in two-component spectrophotometric analysis. In this paper, a new approach was developed by using first derivative D1 curve instead of absorbance curve to be convoluted using OPUI method for the determination of metronidazole (MTR) and nystatin (NYS) in their mixture. After applying derivative treatment of the absorption data many maxima and minima points appeared giving characteristic shape for each drug allowing the selection of different number of points for the OPUI method for each drug. This allows the specific and selective determination of each drug in presence of the other and in presence of any matrix interference. The method is particularly useful when the two absorption spectra have considerable overlap. The results obtained are encouraging and suggest that the method can be widely applied to similar problems.

Non-parametric linear regression of discrete Fourier transform convoluted densitometric peak responses

The manuscript discusses the application of chemometrics to the handling of TLC response time data. Derivative treatment of chromatographic response data followed by convolution of the resulting derivative curves using 8-points sinx(i) polynomials (discrete Fourier functions) was found to be beneficial in eliminating the interference due to background noise in TLC-densitometric measurements. It also compares the application of Theil's method, a non-parametric regression method, in handling the response data, with the least squares parametric regression method, which is considered the de facto standard method used for regression. Theil's method was found to be superior to the method of least squares as it assumes that errors could occur in both x- and y-directions and they might not be normally distributed. In addition, it could effectively circumvent any outlier data points.

HPLC and chemometric assisted spectrophotometric methods for simultaneous determination of diprophylline, phenobarbitone and papaverine hydrochloride

Three methods are developed for the simultaneous determination of diprophylline (DP), phenobarbitone (PH) and papaverine hydrochloride (PP). The chromatographic method depends on a high performance liquid chromatographic (HPLC) separation on a reversed-phase C18 column with a mobile phase consisting of 0.02 M potassium dihydrogen phosphate, pH 3.5--acetonitrile (55:45 v/v). Quantitation was achieved with UV detection at 210 nm based on peak area. The other two chemometric methods applied were principal component regression (PCR) and partial least squares (PLS-1). These approaches were successfully applied to quantify the three drugs in the mixture using the information included in the UV absorption spectra of appropriate solutions in the range 215-245 nm with the intervals Delta lambda = 0.2 nm. The calibration PCR and PLS-1 models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over laboratory-prepared mixtures and pharmaceutical preparations. The PCR and PLS-1 methods require neither any separation step, nor any priori graphical treatment of the overlapping spectra of the three drugs in a mixture. The results of PCR and PLS-1 methods were compared with HPLC method obtained in pharmaceutical formulation and a good agreement was found.

Determination of prednisolone and the most important associated compounds in ocular and cutaneous pharmaceutical preparations by micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatographic method to separate prednisolone, prednisolone acetate, naphazoline, Zn-bacitracin, sulfacetamide and phenylefrine is described. The separation was carried out by using a fused-silica capillary (57 cmx75 micrometer I.D.) at 25 degrees C and 30 kV, using a 5 mM phosphate-5 mM borate buffer adjusted to pH 8.2, 50 mM sodium dodecyl sulfate (SDS) and 10% methanol-water (v/v) as background electrolyte. Under these conditions, the run time was 8 min and the limits of quantification were about 1.0 mg/l for every component. The method was applied to pharmaceutical preparations and the results provided recoveries close to 100% and the method gave good results when compared with a reference multivariate calibration spectrophotometric method.

Spectrophotometric determination of phenylephrine HCl and orphenadrine citrate in pure and in dosage forms

A simple and rapid spectrophotometric methods have been estimated for the microdetermination of phenylephrine HCl (I) and orphenadrine citrate (II). The proposed methods are based on the formation of ion-pair complexes between the examined drugs with alizarine (Aliz), alizarine red S (ARS), alizarine yellow G (AYG) or quinalizarine (Qaliz), which can be measured at the optimum lambda(max). The optimization of the reaction conditions is investigated. Beer's law is obeyed in the concentration ranges 2-36 microgram ml(-1), whereas optimum concentration as adopted from Ringbom plots was 3.5-33 microgram ml(-1). The molar absorptivity, Sandell sensitivity, and detection limit are also calculated. The correlation coefficient was >/=0.9988 (n=6) with a relative standard deviation of </=1.7, for six determinations of 20 microgram ml(-1). The proposed methods are successfully applied to the determination of drugs I and II in their dosage forms using the standard addition technique.

Quantitative determination of acrivastine and pseudoephedrine hydrochloride in pharmaceutical formulation by high performance liquid chromatography and derivative spectrophotometry

In this study, fourth derivative spectrophotometry and high performance liquid chromatography (HPLC) have been used and described for the quantitative determination of acrivastine (I) and pseudoephedrine hydrochloride (II) in their pharmaceutical capsules form (Duact). In the former method, d4A/d gamma 4 values were measured in methanol at 315 and 269 nm for (I) and (II) respectively. The relative standard deviations (RSD) for the method were found to be 1.16% for (I) and 0.94% for (II). The latter method based on reversed phase HPLC system using LiChrosorb C18 analytical column. The mobile phase used for separation of (I), (II) and internal standard (p-hydroxymethylbenzoate) were the water/acetonitrile/methanol/perchloric acid/n-octylamine (500:130:25:13:0.3 v/v) and the detection of the compounds in the capsules were at 260 nm using UV detector. The RSD for the HPLC method were determined to be 0.79 and 0.88% for (I) and (II) respectively. The proposed methods, which give thoroughly comparable data, are simple, rapid, and allow precise and accurate results and could be used for commercial formulations containing acrivastine and pseudoephedrine hydrochloride in combination.

Spectrofluorimetric and derivative absorption spectrophotometric techniques for the determination of loperamide hydrochloride in pharmaceutical formulations

Simple, sensitive and rapid spectrofluorimetric and derivative absorption spectrophotometric procedures are described for the accurate determination of loperamide hydrochloride. The spectrofluorimetric method involves the measurement of the fluorescence of the compound in an ethanol-sulphuric acid mixture (90:10, v/v) using either the direct or the synchronous modes of measurement. Optimum conditions for maximum fluorescence are described. The derivative spectrophotometric method involves the measurement of either the second derivative peak amplitude (crest to trough, i.e. maximum to minimum) between 258 and 263 nm or the second derivative peak height (i.e. maximum to zero line) at 224 nm of an ethanolic solution of the drug. The proposed methods have been used for the determination of loperamide in pharmaceutical formulations. Compared to the pharmacopoeial method, the proposed methods give equally accurate (t-test) and precise (f-test) results. The proposed methods have the advantages of being highly sensitive for the determination of small concentrations of loperamide, a weak UV-absorbing compound prescribed in low doses.

Determination of dissociation constants of some pharmaceutical compounds using derivative spectrophotometry

Derivative spectrophotometry is applied to the determination of the dissociation constants (pKa) of some weakly dissociating compounds. The pKa value(s) can be calculated by measuring the amplitude of derivative maxima (D) at the selected wavelengths for the dissociated, undissociated and partially dissociated forms of the compound. A graphical technique, based on plotting the derivative spectrophotometric titration curves and interpolating pKa at D1/2 is also presented. Both methods are applied to pharmaceutical compounds with single and double dissociation constants. The results are in good agreement with the reported pKa values of the investigated compounds.

First-derivative spectrophotometric determination of salbutamol in pharmaceutical preparations

The development of a first-order derivative spectrophotometric assay of salbutamol as a single-component and in combination with beclomethasone dipropionate in pharmaceutical formulations is described. The method eliminates the interference of tablet excipients and allows the determination of both components without their previous separation. The precision of the method for the assay of salbutamol in tablets was 1.0% with an average recovery of 98.8%. In the assay of the two-component preparation, the precision was 1.1%, with average recoveries for salbutamol of 99.3% and for beclomethasone dipropionate of 99.4%.