Reverse Phase HPLC Method for the Simultaneous Determination of Cetirizine, Verapamil/Diltiazem and Amlodipine
ANALYTICAL AND BIOANALYTICAL CHEMISTRY RESEARCH
Authors: Shamshad, Hina; Naz, Asia; Mirza, Agha Zeeshan
Determination of cetirizine, diltiazem, or verapamil and amlodipine in an active and in dosage formulations has been performed using a simple RP-HPLC method. Rosuvastatin is used in this novel RP-HPLC method as an internal standard to improve the selectivity of the method. At 230 nm, the separation was performed using a mobile phase consisting of methanol, acetonitrile, and water mixture in a ratio of 65:5:30, and pH at 2.8 allowed improved separation and faster times of analysis. ICH guidelines have pursued the validation of the method by assessing accuracy, precision (%RSD > 2), and linearity (>0.999). The retention times of diltiazem, verapamil, amlodipine, cetirizine, and rosuvastatin was found to be 2.5, 3.2, 4.1 and 6 minutes, respectively. The specificity of the proposed method was good as no interference of excipients of the tablets was observed in the analysis. The developed method could be used for routine quality control and in biological samples for the analysis of these drugs.
Interaction of squaraine dyes with proteins: Looking for more efficient fluorescent turn-on probes
DYES AND PIGMENTS
Authors: Butnarasu, Cosmin; Barbero, Nadia; Barolo, Claudia; Visentin, Sonja
Proteins are essential constituents of living organisms. The increased development of fluorescent probes with proper selectivity offers opportunities to explore the roles of proteins in physiological functions. Squaraine dyes have demonstrated to be valuable fluorescent probes given their ability to turn-on their fluorescence in response to specific proteins. Here we investigate the binding of four different squaraines with commercially available transferrin, fibrinogen, trypsin, pepsin and a generic protease. The protein-dye interaction was studied by means of UV-Vis and fluorescence spectroscopy. The association (K-A) and dissociation (K-D) constants were determined based on the turn-on response of squaraines in presence of the proteins, and the quantum yield of the complexes was measured. The protein's surface hydrophobicity seems to play an important role on the fluorescence turn-on response of the squaraines, especially for those with shorter alkyl chains.