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May-2011

Gases and gas handling for the lab environment

Over the past decade, manufacturing and process plants across the full spectrum of industry have advanced exponentially to meet the growing and evolving demands of the markets.

Stephen Harrison, Linde Gas
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Article Summary
Over the past decade, manufacturing and process plants across the full spectrum of industry have advanced exponentially to meet the growing and evolving demands of the markets they serve. In turn, the design and function of the laboratories which support these plants have had to respond to these changes. Accordingly, the gases and gas technologies used in testing, analysis and measurement, and the associated gas equipment and supply systems have advanced in quantum leaps.

Pure gases today come in various purities from ‘industrial’ or ‘technical’ grades to several high purity ‘specialty gases’ grades. Within the pure specialty grades, purity can vary from the 4.6 grade – being 99.996% pure - to the 7.0 grade at 99.99999% purity. Higher purity means fewer and lower levels of the impurities that cause problems with instrumentation and analytical measurement.

High purity gases keep instruments running at optimum levels. These include helium, hydrogen, argon and nitrogen as ‘carrier’ gases and ‘purge’ gases for gas and liquid chromatography and spectrometry. These are required for sample measurement in the gas, liquid or solid phase. High purity gases, such as nitrogen, and gas mixtures are also used for instrument span calibration and to set the zero reading: they are especially required for sample measurement in the gas phase.

Quality is therefore a critical requirement in the supply of pure gas. Pure gas cylinders are provided on the basis of supplier quality assurance, or with a certificate to validate the cylinder contents. Increasingly, quality conscious customers and stringent industrial quality systems are demanding individual certification of analysis for each cylinder supplied.

Gas mixtures also involve a range of quality levels and require different types of certificate. The most basic mixtures — such as welding gas mixtures — are filled using mass production techniques to keep cost and price low, while specialty gas mixtures are filled in more controlled environments. Mixtures for process applications, such as food packaging or laser gas mixtures, are often supplied based on the manufacturers’ quality systems. However, calibration gas mixtures always require a certificate of analysis so that the reported values can be used by the customer to precisely calibrate their instrument.

Various certificate types exist in the quest to achieve increasing levels of accuracy, traceability and accreditation. The most sophisticated of these are validated by independent organisations such as NIM (china), NATA (Australia), UKAS (UK) or DAP (Germany) to international standards such as ISO17025 or ISO Guide 34.

Calibration gases
The characteristics of gases used to calibrate instruments have also made huge strides. Today’s specialty gases for calibrating and measuring gases and for measuring liquids and solids are on the cutting edge of technology.

In a significant leap forward in the supply of calibration gases, Linde Gases including their UK business, BOC last year launched its groundbreaking HiQ® 60 calibration gases, a range of gases, including pure gases and gas mixtures, with an extended 5 year shelf life and flat-line guarantee, allowing for greater reliability in the accuracy of instrument measurement and longer term usability of gas.

“Previously, gas suppliers across the market offered product expiration guarantees generally limited to 36 months, with many products available with only 12 or 24 months of shelf life,” says the Linde Group’s Steve Harrison, Head of Specialty Gases and Specialty Equipment. “Gas products with a more limited shelf life can impact measurement accuracy, as gas stability in terms of consistency and quality can change over time. Where consistency or purity of the gas has been compromised, this can result in expensive system re-calibration procedures, additional cylinder changeovers and wasted human resource time.  

“The most important requirement of any gas used for calibration purposes, is that it can accurately and repeatedly report values of the instrument being measured. HiQ® 60 gas products alleviate concerns associated with quality or reliability issues for a period of up to 5 years and give customers peace of mind.”

Equipment and distribution systems
Sound analytical protocols are at the heart of work taking place at laboratories every day and in environmental analysis and testing, a range of sophisticated instruments and next generation gas chromatography and mass spectrometry techniques play a vital role in the identification and qualification of environmental pollutants. Both techniques and equipment require high quality specialty gases for instrument operation and/or calibration, in addition to dedicated high purity gas distribution systems.

Since the reliability of analysis is only as good as the quality of gas being used, distribution systems and equipment for high-purity and specialty gas mixtures must be able to meet increasing demands for high standards of performance and new analysing methods. Impurities occurring in as low concentrations as parts per billion (ppb) can have serious consequences.

Complementing its HiQ® solutions, Linde Gases’ REDLINE® gas supply equipment for high-purity gases and specialty gases is a high-tech, precision designed range of products, modularly designed to slot into central gas supply systems, containing gas panels, valves, points-of-use and cylinder regulators suitable for purities up to 6.0 (99,9999%). Some of the most specialised REDLINE® regulators also have the capability for vacuum dosage and high precision low pressure adjustments. For corrosive mixtures there are models available with the relevant purge assemblies.   Additionally, Linde’s BASELINE® gas equipment range can provide customers with an entry level range of specialty gases cylinder regulators which are appropriate for more flexible systems or short term project work where requirements change from time to time – for example, in universities and R&D labs.
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