Sub-sampling technique for the determination of particulate-phase organic carbon in water

A procedure for determining particulate-phase organic carbon (POC) in water was developed and applied to the analysis of samples from the Laurentian Great Lakes of North America. Water samples were filtered through 0.7 mu M pore-size glass fiber filters which were sub-sampled to introduce measurable quantities of particulate matter into a Carlo Erba EA-1108 elemental analyzer The sub-sampling technique allowed quick filtration of water samples, typically I to 4 liters for open-lake locations, using 47 mm diameter filters while metering the small size requirement of the combustion chamber. The defection limit of the instantaneous combustion procedure was 2.9 mu g of carbon per sub-sample, which translates to 28 mu g/L POC for a sample volume of I liter. The precision of the sub-samples averaged 6.2% coefficient of variation (CV), which was comparable to the precision of replicate water samples (6.6% CV).