Two new simple, precise, rapid and extraction-free spectrophotometric methods are proposed for the determination of raloxifene hydrochloride (RLX) using bromate-bromide mixture and two dyes, methylene blue and rhodamine B, as reagents. The methods entail the addition of a known excess of bromatebromide mixture to RLX in hydrochloric acid medium followed by determination of residual bromine by reacting with a fixed amount of either methylene blue and measuring the absorbance at 665 nm (Method A) or rhodamine B and measuring the absorbance at 555 nm (Method B). The amount of bromate reacted corresponds to the amount of RLX. In both the methods, the absorbance is found to increase linearly with the concentration of RLX. Under the optimum conditions, RLX could be assayed in the concentration ranges 0.5-5.0 and 0.1-2.0 µg mL-1 from method A and method B, respectively. The apparent molar absorptivities are calculated to be 7.0 x10 4 and 1.1x10 5 L mol-1 cm-1 for method A and method B, respectively, and the corresponding Sandell sensitivity values are 0.0073 and 0.0048 µg cm-2. The limits of detection and quantification have also been reported for both the spectrophotometric methods. The overall reproducibility of the methods was excellent and recoveries were 98.3-102.5% and 98.2-103.2% for method A and method B, respectively. The proposed methods can be readily utilized for bulk drug and in pharmaceutical formulations.

Raloxifene hydrochloride (RLX) is a selective estrogen receptor modulator that belongs to the benzothiophene class of compounds ( Fig. 1) A rapid, sensitive and selective method for the determination of raloxifene hydrochloride (RLX) in pure drug and in tablets was developed using gradient high performance liquid chromatography (HPLC). The devised method involved separation of RLX on a reversed phase Hypersil ODS column and determination with UV detection at 284 nm. The standard curve was linear (R = 0.999) over the concentration range of 50-600 mg mL -1 with a detection limit of 0.04 mg mL -1 and a quantification limit of 0.16 mg mL -1 . Intra-day and inter-day precision and accuracy of the method were established according to the current ICH guidelines. Intra-day RSD values at three QC levels (250, 450 and 550 mg mL -1 ) were 0.2-0.5%, based on the peak area. The intra-day relative error (e r ) was between 0.2 and 0.5%. The developed method was successfully applied to the determination of RLX in tablets and the results were statistically compared with those obtained by a literature method. Accuracy, evaluated by means of the spike recovery method, was the excellent with percent recovery in the range 97.7-103.2 with precision in the range 1.6-2.2%. No interference was observed from the coformulated substances. The method was economical in terms of the time taken and the amount of solvent used.

Abstract:Two new sensitive spectrophotometric methods are proposed for the determination of raloxifene hydrochloride (RLX) using bromate-bromide mixture and two dyes, methyl orange and indigocarmine, as reagents. The methods entail the addition of a known excess of bromate-bromide mixture to RLX in hydrochloric acid medium followed by determination of residual bromine by reacting with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (Method A) or indigo carmine and measuring the absorbance at 610 nm (Method B). In both methods, the amount of bromine reacted corresponds to the amount of RLX. The absorbance is found to increase linearly with concentration of RLX. Under the optimum conditions, RLX could be assayed in the concentration range 0.1-2.0 and 0.5-6.0 µg mL -1 by method A and method B, respectively. The apparent molar absorptivities are calculated to be 1.9x10 5 and 4.5x10 4 L mol -1 cm -1 for method A and method B, respectively, and the corresponding Sandell sensitivity values are 0.003 and 0.011 µg cm -2 . The limits of detection and quantification are also reported for both methods. Intra-day and inter-day precision and accuracy of the developed methods were evaluated as per the current ICH guidelines. The methods were successfully applied to the assay of RLX in its tablet formulation and the results were compared with those of a reference method by calculating the Student's t-value and F-value. No interference was observed from common tablet adjuvants. The accuracy and reliability of the methods were further ascertained by recovery experiments via standard-addition procedure.

Two spectrophotometric methods are proposed for the assay of lansoprazole (LPZ) in bulk drug and in dosage forms using ceric ammonium sulphate (CAS) and two dyes, methyl orange and indigo carmine, as reagents. The methods involve addition of a known excess of CAS to LPZ in acid medium, followed by determination of residual CAS by reacting with a fixed amount of either methyl orange, measuring the absorbance at 520 nm (method A), or indigo carmine, measuring the absorbance at 610 nm (method B). In both methods, the amount of CAS reacted corresponds to the amount of LPZ and the measured absorbance was found to increase linearly with the concentration of LPZ, which is corroborated by the correlation coefficients of 0.9979 and 0.9954 for methods A and B, respectively. The systems obey Beer's law for 0.5-7.0 mg mL -1 and 0.25-3.0 mg mL -1 for methods A and B, respectively. The apparent molar absorptivities were calculated to be 3.0 x 10 4 and 4.4 x 10 4 L mol -1 cm -1 for methods A and B, respectively. The limits of detection (LOD) and quantification (LOQ) were calculated to be 0.08 and 0.25 mg mL -1 for method A, and 0.09 and 0.27 mg mL -1 for method B, respectively. The intra-day and inter-day precision and accuracy of the methods were evaluated according to the current ICH guidelines. Both methods were of comparable accuracy (e r £ 2 %). Also, both methods are equally precise as shown by the relative standard deviation values < 1.5%. No interference was observed from common pharmaceutical adjuvants. The accuracy of the methods was further ascertained by performing recovery studies using the standard addition method. The methods were successfully applied to the assay of LPZ in capsule preparations and the results were statistically compared with those of the literature UV-spectrophotometric method by applying Student's t-test and F-test.

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