Technical paper describes a technique for easy, direct automated elemental analysis of material retained on filter membranes used in water filtration and air monitoring applications
Exeter Analytical's technical paper provides useful background information on standard sampling procedures, filter preparation, optimising instrument operation and quality assurance for laboratories seeking to precisely determine the carbon, hydrogen and nitrogen content of samples retained on filters.
Further discussion illustrates how direct determination of total CHN retained on a filter is more sensitive, precise and cost-effective than making measurements on pre- and post-filtered samples and calculating the difference.
The described technique, using an Exeter Analytical model CE440 CHN elemental analyser, requires a minimum of sample preparation and may be automated.
The CE440 is a static combustion system, with a unique horizontal furnace design, which enables easy removal of filter and sample ash between each analysis.
Consequently one combustion tube will analyse in excess of 1000 samples without the need for removal and cleaning.
In addition the CE440 provides the capacity to process filters up to 47mm in diameter in one analytical cycle.
By comparison, elemental analysers employing vertical furnace designs need cleaning after as little as 20 samples, and larger filters have to be sub sampled several times and then corrective calculations made to enable analysis.
Effectively eliminating troublesome residue build-up, the gas flow characteristics of the CE440 analyser are constant - providing long-term calibration stability and enhanced accuracy and precision for measured sample data, says the company.
The model CE440 provides complete control over combustion parameters enabling the analysis of filters without the need for expensive tin capsules.
