New ISO standards for electrochemical gas generation
Spantech products and ACD are proud to be
associated with the new ISO standards for electrochemical gas generation of
toxic gases which were announced at the recent NEN conference in Holland. The
abstract of the paper presented follows
A NEW STANDARD FOR THE PREPARATION OF GAS MIXTURES USED
FOR THE CALIBRATION OF ENVIRONMENTAL GAS ANALYSERS
John Scawin and Krish Narain*
The International Standardisation Organisation (ISO),
Technical committee 158 “Analysis of Gas” has provided standards for the
preparation of calibration gas mixtures. These standards are used by National
bodies to provide primary gas mixtures to calibrate traceable environmental
instrumentation. The ISO 6145 series are methods for the preparation of a
continuous flow of a corrosive or reactive calibration gas mixture at low
concentration values. Present standards include permeation, saturation,
diffusion and other methods. These methods have the disadvantage that they
depend on stable temperature environments, continuous flow operation and long
time periods to establish and maintain equilibrium conditions.
A method which overcomes these requirements is now in
preparation. DIS 6145-11 provides an electrochemical method for the generation
of a stable calibration gas mixture almost immediately. The method can be easily
transferred from one laboratory to another for comparison purposes or used in
the field. Alteration of the gas flow through the cell electrolyte, or the
current supplied to the electrodes, will change the composition of the generated
gas and can then be used as a single point or extended to obtain a complete
calibration curve for an environmental analyser. Gas flow through the cell is
achieved with a thermal mass flow controller. Gases that can be produced by
electrochemical generation are oxygen, hydrogen, nitrogen, hydrogen cyanide,
hydrogen sulphide, chlorine, bromine, ammonia, nitric oxide, carbon dioxide,
phosphine, arsine and ozone. The chosen complementary gas should prevent any
reaction with any generated component.
The relative expanded uncertainty of measurement, U,
obtained by multiplying the relative combined standard uncertainties for this
method by a coverage factor ,2, is not greater than 5%.
A full description of electrochemical gas generation will
be given highlighting its abilities and limitations in providing portable,
intrinsically safe, toxic calibration gas generators.
*Spantech Products Ltd,
Lagham Road, South Godstone, Surrey RH9 8HB
Tel: +44 (0) 794 647 6962,
krish@spantech.co.uk, www.spantech.co.uk
The full poster from AIHA 2004 and NEN 2004
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For More Information Contact:
Spantech Products Ltd
Spantech House, Lagham Road, South Gdstone, Surrey RH9 8HB
Tel: + 44 (0) 1342 893239
FAX: +44 (0) 1342 892584
Internet:
spantech-acd@tiscali.co.uk
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