Speciality gases: essential for research, production and quality control

Stephen Harrison, Linde Gas

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Article Summary

Laboratories all around the world stand or fall by their reputation for accuracy and quality control. Pivotal to this performance is the quality, purity and composition of the spectrum of gases harnessed every day to accomplish laboratory tasks. Rapid advancements in production processes across all industry sectors, as well as healthcare, have obliged laboratories to keep up with these changes, while remaining flexible and making allowances for future requirements. Against this background, a variety of role-specific specialised laboratory types have emerged, each addressing specific industry needs.

Commercial contract laboratories
Independent commercial laboratories, for instance, serve companies that do not have these capabilities in-house or require independent external analysis to support and confirm internal findings. Services might include forensics, environmental, food chemical or medical sample analysis and automotive engine emission testing. The focus in these laboratories is on productivity and repeatability of work standards. These laboratories generally comprise multiple workstations harnessing a broad range of analytical equipment in flexible configurations and are staffed by several lab technicians. In this environment, time is money and the broad range of methods used on a daily basis requires a diversity of speciality gases.

Instrument-grade pure gases such as argon, synthetic air, helium, hydrogen or nitrogen are used as carrier and detector fuel gas, and to zero or purge analytical equipment such as GC-FID and HPLC. High-purity gases are also used, for example, in Inductively Coupled Plasma (ICP) analysis and atomic absorption spectroscopy (AAS) measurements. Speciality gas supply equipment in a fixed installation for repeatable use is used in many areas to control gas cylinder pressures and to deliver gases to the point of use while ensuring purity is not compromised. For the sake of convenience and safety, laboratory gas generators for hydrogen, nitrogen and purified air have become ever more popular in this type of laboratory. Alternatively, a selection of large cylinders is stored outside the laboratory in a central gas compound and the gases piped through to the point of use.

Environmental measurements for atmospheric air, water and ground pollution use a number of individual calibration standards to measure nitric oxides, sulphur compounds, VOC and hydrocarbon emissions. The requirement here is for low-level reactive calibration gas mixtures with flatline stability, as well as other environmental mixtures produced to meet the requirements of regulatory agencies around the world. Within all areas of automotive emissions or environmental monitoring, many local governments require that the instrument and sensor calibration gases used be certified to ISO 17025. This is to ensure data is traceable to a national standard and that overall uncertainties for pollution data are within specified limits.

A wide range of speciality gas mixtures is applied to calibrate the analytical equipment and to ensure its correct operation. Normally, these mixtures are supplied in high-pressure or disposable gas cylinders. Depending on the consumption and the required mobility, the size of the cylinders varies from 0.2 to up to 50 litres.

R&D laboratories
Flexibility is particularly important for R&D labs that operate on a project basis, either in-house or via an outsource agreement. Their projects can be quite diverse, often requiring the lab to tool up for each new project, and it is seldom possible to predict the nature and requirements of the next project coming through. In the past, an R&D programme might have been set up for five years, but the accelerated pace of industrial progress has meant that today, with faster turnaround times and more information readily available to researchers, the focus of an R&D lab must now be able to shift far more quickly.

Speciality gases and speciality equipment are required in many areas of a laboratory for successful R&D, where sophisticated equipment such as GC-MS and LC-MS are commonly used. In addition to the instrumentation gases required in the contract laboratory environment, many speciality gases are used as raw materials for bench or pilot-scale chemical synthesis research. Speciality gas supply equipment used in these laboratories is often of a flexible configuration; for example, multiple cylinder regulators to enable rapid changes in application between one research project and another.

The gas mixtures used to calibrate analytical equipment are generally supplied in high-pressure or disposable gas cylinders. Depending on the consumption and the required mobility, the size of the cylinders varies up to 50 litres. However, given the short-term nature of many R&D projects, small cylinders in the size range 0.2 to 10 litres are often used and cylinders are stored inside the laboratory close to the research station. Both independent contract and R&D laboratories require a very high degree of accuracy to be able to have certainty in their results, as well as traceability to ISO and other international standards.

Distributed laboratories
Distributed process control laboratories, such as those found in petrochemical production complexes, are unmanned fixed installations primed to collect and monitor samples and feed information to the central quality control or production laboratory within the complex. Their role is dedicated and inflexible, with repeatability being the primary requirement. Individual process instruments or CEM systems installed within a production environment area can also be regarded as laboratories at the extreme end of the scale. In these cases, the sample is not taken to the instrument; instead, the instrument operates in the sample’s environment. In these distributed laboratories, the speciality equipment is designed to serve the important function of ensuring continuity of gas supply in these unmanned remote environments. This is often achieved using two gas cylinders connected to a gas supply manifold, with one of the cylinders being in use and the other in reserve as backup. The manifold is designed to automatically switch to the reserve cylinder when the in-use cylinder contents are depleted. Sophisticated systems will often trigger an alarm to the instrument engineering team, central lab or process control room to signal a change of cylinder.