OR/14/067 Setting up resin column

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Lapworth, D J, Surridge, B, Williams, P J, Heaton, T H E, and Gooddy, D C. 2014. Method for analysing phosphate 18O/16O ratios for waters with high C:P ratios. British Geological Survey Internal Report, OR/14/067.

For each sample, a column was prepared comprising two 60 ml capacity syringes loaded with resin, the first syringe containing Dax-8 resin to remove organic compounds and the second containing Dowex anion exchange resin to collect the phosphate and other anions. The 60 ml plastic syringes were prepared with a ‘frit’ made up of a triple layer of Whatman glass microfiber prefilters at the nozzle end of the syringe. The syringe plungers had a small hole drilled through them to allow tubing (1/4” external diameter, 1/8” internal diameter and flexible/soft) to be connected. Making sure that the nozzle of the syringe was sealed, resin slurry was then poured into the syringe and allowed to settle so that the resin comprised 50 ml of the syringe volume with Ultrapure water the top 10 ml. These proportions can be achieved exactly by adjusting with a small dropping pipette and any air voids in the resin removed at the same time. When all the syringes are filled, a second frit is placed at the top of the resin, and the plungers attached. The Ultrapure water at the top of the syringe backfills into the tubing attached to the plunger as they are inserted. Once assembled, a rubber band was stretched around each syringe to prevent any possibility of internal pressure disconnecting the plunger.

Plate 1 Syringes containing amber coloured Dowex anion exchange resin.
Plate 2 Syringes containing white Dax-8 resin.

A Watson Marlow 205U peristaltic pump was used to pump the samples through the resin columns. Pump tubes (purple-white colour code) with an internal diameter of 2.79 mm were used to allow adequate pumping speeds. The assembly from the sample to the pump and the resin column was connected throughout with Tygon flexible tubing (1/4” external diameter, 1/8” internal dimater). The column was drained to a sink.

The pump speed was set at 4 ml/min which allowed 1 litre of sample to be pumped through the resin column every 4 hours and 10 minutes.

Plate 3 Samples being pumped through the resin column by a peristaltic pump.