Dissolved inorganic carbon in seawater with infrared detection (AIRICA)

The AIRICA (Automated Infra Red Inorganic Carbon Analyzer) is based on the IR-detection of CO₂ purged from an acidified sample and is also suited for smaller sample size.

A high precision syringe pump is used to deliver the sea water sample into the stripper. The CO₂ is liberated after acidification and transferred to the non-dispersive Infra Red analyzer and the signal is integrated. Depending on number of replicates and rinsing procedures, less than 10 ml of sample is required.

The gas stream is dried with a combination of chemical absorbers (optional), permeation tubes (Nafion^TM) and Peltier cooler. A modified control PC is integrated in the system. The software is written in a graphical programming language (LabVIEW^TM).

The AIRICA works with LI-COR models 7000, 6262, 6252. Unfortunately, all of these are not available any more. The smaller detectors 850, 840, 830 or 820 can be used with lower precision. Precision of 1.5 - 2 µmol/kg can be reached (depending on the LI-COR model). Though generally higher precision can be obtained with larger volumes and coulometric methods (VINDTA 3C, VINDTA 3D, SOMMA), the IR method is ideal, where required precision is lower due to higher gradients (e.g. coastal ocean), sample volume is limited (e.g. pore water, sub-samples from culture experiments) and higher sample throughput is desired (analysis time is 5-10 minutes/sample).

features:

• determines dissolved inorganic from small sample volumes
• high sample throughput (6-10 samples/hour)
• easily transportable and sea-going
• precision typically ± 1.5 µmol/kg
• no hazardous chemicals required (compared coulometric methods)
• user friendly software interface using LabVIEW^TM
• control PC with integrated hardware and with all software and drivers installed

Additional hardware required or recommended:
LI-COR infra-red-analyzer, model 7000, 6262, 6252. With lower precision: 850, 840, 830, 820.
carrier gas supply (nitrogen or dry and CO₂-free air)