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Densitometry, video-scanning and capillary electrophoresis for determination of valsartan and amlodipine in a combined dosage form: A comparative study

Inglot T. W., Gumieniczek A., Komsta Ł., Związek R.

Acta Chromatographica

2013

Vol. 25, no. 1

47-58

Comparison of classical densitometry, video-scanning, and capillary electrophoresis was performed for determination of angiotensin II receptor antagonist, valsartan, and calcium channels blocker, amlodipine, in a combined dosage form. Thin layer chromatography was performed on RP8F254 TLC plates with a mobile phase consisting of acetonitrile-phosphate buffer at pH 9.0 (5:5, v/v) and temperature 20 °C. Densitometry was done in the reflectance mode at 217 nm for valsartan and in the absorbance mode at 370 nm for amlodipine. Video-scanning was elaborated at 254 and 366 nm for valsartan and amlodipine, respectively. For chromatographic analysis, calibration plots were constructed in the range of 0.4–2.8 μg per spot for valsartan and 0.02–0.14 μg per spot for amlodipine. Capillary electrophoresis (CE) was performed using a 75 μm × 94 cm fused silica capillary (72 cm effective length), 0.01 mol L-1 borate buffer at pH 8.0, 20 kV voltage, 30 °C temperature, hydrodynamic injection (10 mbar, 6 s) and UV detection at 237 nm. Calibration plots were constructed in the range of 0.1–0.6 mg mL-1 for valsartan and 0.005–0.03 mg mL-1 for amlodipine. All methods were validated in respect to robustness, specificity, stability, linearity, precision, and accuracy. Generally, statistical comparison between the methods did not show significant differences so all procedures are suitable for pharmaceutical analysis.

Dealing with charged-coupled device noise in thin-layer videodensitometry. Optimization of several image-denoising techniques

Komsta Ł.

Acta Chromatographica

2009

Vol. 21, no. 3

355--367

Charged-coupled device (CCD) noise can be a serious problem during videoscanning, especially when scanning dark plates with weakly fluorescent spots. The proper denoising of videoscans inside mathematical environments is a critical part of any advanced chemometric processing. The paper reports comparison and optimization of representative videoscan denoising by different techniques. Several kind of filters (averaging, circular, Gaussian, Savitzky-Golay, median, Wiener, FIR) and wavelet shrinkage (twelve mother wavelets from the Daubechies, Symmlet, and Coiflet family, five decomposition levels, and soft/hard thresholding) were optimized against noise autocorrelation or mean-squared error to the reference image. The reference image was obtained by grabbing and averaging 256 CCD frames. The median filter is the winner of the competition; other filters except Gaussian and wavelet shrinkage at high decomposition level are also sufficient and good ways of videoscan denoising. The Gaussian filter and wavelet shrinkage at low decomposition level performed worst and could not be recommended.