Avishek Mandal
In this study, the effects of some of the important parameters in foam fractionation (such as gas velocity, pH of feed solution, collector-colligend ratio, colligend concentration, feed volume, column height and aliphatic chain length of the collector) on the recovery of captopril were determined. Captopril (gifted by Wockhardt limited, Mumbai) was used throughout this research and Tablet Aceten (25 mg.) was purchased from local medicine shop. Tetradecyl trimethyl ammonium bromide (TDTMAB)(E. Merck India Limited), and hexadecyl trimethyl ammonium bromide (HDTMAB)(Loba Chemie, Bombay) were used as collectors. Other chemicals and reagents used were analytical reagent grade. For all experiments, double-distilled water was used. A schematic diagram of the apparatus used for batch process is shown in figure 1. A foam fractionation apparatus was uniquely designed and set up with glass works from glass blowing and supplements such as a gas cylinder for nitrogen supply and a flowmeter purchased from suppliers. Samples of the initial feed solution, of the foamate, as well as of the residual solution (for controlling purposes) were taken to determine the concentration of the drug. It was measured by the titrimetric assay method using starch solution as indicator. The results indicate that the percentage recovery of captopril in formulation was lower as compared to captopril in pure form from aqueous solution at ϕ = 4. This is probably because of the presence of other soluble ingredients, which decreases the enrichment of captopril in formulation. As it is shown in Table V percentage recovery of captopril in pure form with TDTMAB (MW=336.40) was higher as compare to HDTMAB (MW = 364.46) at ϕ = 4. Since the tendency of the collector to adsorb on the interface depends on the length of its aliphatic chain, investigation were carried out with quaternary ammonia salts, RMe3NBr, where the aliphatic chain R consists of 14 and 16C- atoms. The longer the alkyl residue R, the lower the captopril concentration in the foam liquid. The results indicate that the lower the molecular weight of the surface-active agent gives higher percentage recovery.It is concluded that the experimental variables of SGV = 0.0541 cm/s, pH = 3.75, ϕ = 4, Ci = 0.5 mM/L, column height = 65cm gives highest percentage recovery of captopril from an aqueous solution by the foam fractionation method.
