Alkalinity water sample should be collected in 250 mL or greater volumes in glass or polyethylene bottles. Since alkalinity is susceptible to change between the time of collection and the time of analysis, the titration should be performed within a few hours of collection. The sample must be sealed from exposure to the atmosphere. The main problem encountered when holding the sample for extended periods of time is the loss of free carbon dioxide which results in a conversion of bicarbonate ion.