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The produced mixture quality is reached both by inspection in the production phase (checking of the amount of added ingredients) and by the final mixture composition analysis.
The end checking is made by measuring of all components in one cylinder filled in one batch at standard mixtures which are used as industrial gases in different technologies,. This procedure documents that the mixture composition reaches a blend tolerance Impurities content is checked at standard mixtures as well.
Each filled cylinder of calibration gas mixture is measured . Analytical results of all components concentration and uncertainty of measurement is a basic information printed on an analytical certificate that is attached to each filled cylinder.
Various analytical methods suitable for measurement of required components in given concentration range are used in laboratories of Linde Gas:
- Gas chromatography with different detectors;
- Optical methods (FTIR, IR, UV-VIS);
- Specific systems for oxygen and humidity contents measurement;
- Mass spectrometry;
- Atomic absorption;
- Spectrophotometry with inductively coupled plasma (ICP);
- Ionic chromatography;
- The absolute chemical methods - volumetric analysis.
To ensure a quality of results following procedures are applied:
- Own, specifically prepared calibration mixtures – i.e. primary reference materials – directly traceable to the mass etalon;
- International reference materials (BAM, NIST, NMi, NPL);
- Absolute chemical methods, i.e. volumetric analysis according to DIN/VDI;
- Interlaboratory comparison within Linde Group or between Linde Gas and external companies
Calibration gases are supplied with the relevant analytical certificate. The certificate contain all data required by valid standards, as, for example following:
- Mixture composition;
- Measured concentration including a measurement uncertainty;
- Technical information related to the cylinder
- Storage condition;
- Filling date, stability.
The original certificate is attached to each calibration gas cylinder.
Accreditation of the laboratory
The accreditation of the laboratory represents the formal acknowledgement of the working place in the accredited calibration activities. By obtaining the accreditation, the laboratory complies with its customers’ requirements. The professional laboratory staff confirmed their qualification and continue in their professional development. The laboratory declares its neutrality, objectivity, and independence. The laboratory manager is responsible for the following of valid standards. The planned internal audits and systematic archiving, reporting and implementation of preventative action ensure the continuous laboratory working quality enhancement.
The accredited measurement methods include the application of the gas chromatography (FID and TCD detection) and the analysers using FID detection, IR spectrometry, chemiluminiscence, magnetic permeability, and electrochemical methods.
For selected calibration gas mixtures, the analysis according to the ČSN EN ISO/IEC 17025:2005 standard may be carried out and the relevant analytical certificate may be issued.