Oxytocin is unequally distributed in a bag of normal saline--true or false?

Oxytocin infusion used in labour can sometimes be left hung on the stand for many hours. There has been no study to determine if oxytocin is equally distributed throughout the infusion bag and if the distribution stays the same with time. We postulated that there may be settling of the molecules such that oxytocin concentrates at the bottom of the infusion bag. Eight infusion bags were prepared by mixing 10 IU of oxytocin in 1 litre of normal saline. The infusion bags were hung on infusion stands for 8 hours after which 10 samples of 100 mls of the solution from each bag were taken in different containers and the concentration of oxytocin calculated using oxytocin specific Enzyme Immunoassay (EIA) in the different samples. No statistically significant correlation between the oxytocin concentration and the sample number was observed (p-value = 0.738). There was no obvious relationship between oxytocin concentration and the sample number in each bag. There was no evidence to suggest that a linear oxytocin concentration gradient develops in a bag of normal saline over an 8-hour period. In fact the distribution appears to be random and unequal.