Walker O. Smith
University of Tennessee

POC-PON Method:

Sampling Samples are collected in 1 or 2 liter polypropylene bottles. Water is filtered onto precombusted (450 degrees C, 3 hours) 25mm Whatman GF/F filters (nominal pour size 0.7 micron). Just prior to end of filtration, filter is rinsed with a weak HCl (0.01 N in filtered sea water) to remove inorganic carbonates. Filter is removed, placed in a precombusted (525 degrees C, 2 hours) shell vial, and vial is capped with precombusted (525 degrees C, 2 hours) aluminum foil. Samples are stored in a 60 degree C oven until processed Procedure Sample Analysis 1. Prior to analysis, the filters are kept dry in a 60 degree oven, in precombusted (525 degree C, 2 hours) vials. 2. The samples are placed in tin capsules and analyzed on a Carla Erba EA1108-Elemental Analyzer. One conditioning sample, two tin blank samples, three standard samples, and three standard samples run as unknowns are run to test the machines calibration each day. An average of twenty to twenty-five POC/PON samples can be analyzed each day. A standard is run after approximately five POC/PON samples for calibration. Standardization and blank determination Acetanilide standards and tin blanks (empty tin sleeves) are measured prior to each batch of samples. The standard is weighed in tin capsules on a Sartorius XM 1000 P balance for calibration runs and test runs, usually measuring between 90 and 250 micrograms. Acetanilide is run as an ordinary sample (test run) to test the accuracy of the calibration of the machine each day. Blanks are combusted 25mm Whatman GF/F filters soaked in surface sea water and treated in exactly the same manner. Data are collected and stored by a microcomputer.