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Sorption of Parabens by Flexible Tubings

Flexible tubings are extensively used in pharmaceuticals, food industry, and in hospitals. This study was undertaken to compare various flexible tubings to determine their sorption characteristics, using methyl and propyl parabens. After 24 h, some tubings showed 100% sorption of propylparaben and over 40% for methylparaben. Significant losses were observed within a few hours using several tubings. For methylparaben, the losses were in the following decreasing order of sorption: Tygon®, Clearflo®, silicone, Nylotube®, and Newtex®. For propylparaben, the losses were in the following order: Tygon®, Clearflo®, silicone, Newtex®, and Nylotube®. Teflon®, Zelite®, and Vitube® showed little to no losses of methyl and propylparaben over 120 h of study. The silicone tubing, refilled after 120 h with fresh methylparaben or propylparaben solutions, again showed significant losses within a few hours. The tubings show slow desorption when filled with the buffer vehicle. For Silastic® tubing, increase in temperature from 25 to 40°C, increase in pH from 3.5 to 6.5, tubing lot to lot variation, or curing with peroxide or platinum had little or no effect on paraben sorption. As expected, the sorption of parabens increased with increasing surface area of Silastic® tubing. Results provided can be used to select the best tubings and to minimize paraben losses during production and filling of liquid pharmaceuticals and food products containing these antimicrobial preservatives.