COMPARISON OF CAPTIVE AND PULSATING BUBBLE SURFACTOMETERS WITH USE OFLUNG SURFACTANTS

We compared surface tension measures of surfactants with various surfa ce activities by using a pulsating bubble surfactometer (PBS) and a ca ptive bubble surfactometer (CBS). Rabbit lung lavage surfactant (60,00 0 X average g for 60 min), bovine surfactant extract (Survanta), and a synthetic lipid surfactant mixture (dipalmitoylphosphatidylcholine-eg g phosphatidylglycerol-palmitic acid) were studied at 1.25 mg phosphol ipid/ml. The PBS was used either unmodified according to manufacturer' s instructions or with the sample chamber capillary kept dry and the s ample adsorbing at maximum bubble size (5 min). The CBS was used in a manner that imitated the unmodified PBS. We found that all three techn iques indicated low surface tension on the first cycle for 60K. For Su rvanta, the CBS and the modified PBS reported low surface tension on t he first cycle, whereas the unmodified PBS did not achieve this within 10 cycles. For the synthetic lipid surfactant mixture, only the CBS m easured low surface tension within 10 cycles. Video observations indic ate that the modified PBS performs better than the unmodified PBS beca use keeping the capillary dry prevents surface film from occupying thi s large surface during cycling, thereby allowing larger area compressi ons.