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The knowledge and experience Linde has with an extensive range of applications gives us a clear picture of the most widely requested and relevant gas mixtures for each application. This helps us effectively speed up your selection procedures. As many of our gas mixtures and high purity gases gomeasuring and analysis instruments, our standard products are designed to be suitable for these applications. Examples are: direct showing analyzers, general instruments like gas chromatographs and threshold monitors.
High Quality Gas Mixtures - Different mixture types
Specific instrument calibration mixtures:
An instrument is called specific because it measures one specific substance and cannot be used for others. Specific instruments are normally calibrated with a zero gas and a span gas. Zero gas is normally a pure gas not containing the component to be measured, and as similar to the matrix of the measured sample as possible. Normally this is synthetic air or nitrogen. The span gas is optimal a mixture of 90% of measured value of component in matrix (if measuring 50 ppm span calibration point will be 0.9 x 50=45 ppm.) Therefore our standard mixtures have concentrations correlating to 90% of typical measuring values.
General instrument calibration mixtures:
An instrument is called general when the instrument can be used to analyze a wide variety of chemical substances. General instruments like gas chromatographs (GC) are often calibrated by creating a calibration line or curve covering the intended measuring area. Therefore our standard products are points at such a line or curve. In addition to this many of the points represent 90% of full scale for a substance specific instrument.
Threshold monitor mixtures:
To avoid and warn for occupational or fire hazards special monitors are used. These are specific instruments that are set to alarm when a pre-set concentration of the substance monitored is reached. High quality gas mixtures for these types of applications have typically half and full time weighted threshold limit value concentration for the substance in air (if this is not possible nitrogen is used,) or for flammable products typical concentrations are 20, 40, 50, and 60% of Lower Explotion Limit (LEL.)
Most liquefied hydrocarbon mixtures are supplied with additional head space pressurization using a high purity inert gas such as helium to prevent the lighter hydrocarbon components from separating after final production. To maintain composition during use, the mixture may supplied in a cylinder using a dual port valve to allow additional pressure to be introduced as required to keep the head space pressure consistent.
Of course is it possible to order any kind of gas mixtures. The limiting factors are as always chemical and physical properties coupled to our commitment to your and everybody else's safety.