Lab Processes and Analytical Standards
Chemical processing and analysis are fueling a resurgence of interest in highly purified specialty gases. Novel gas-phase chemical reactions reduce the number of unit operations and side products while eliminating the disposal of toxic solvents. Ultrapure supercritical carbon dioxide is experiencing a renaissance of its own, both in processing (mainly through extraction) and in analytics. Several vendors are pushing supercritical fluid chromatography as a mainstream analysis tool, especially for chiral compounds, with Waters (Milford, MA) adapting supercritical fluid analysis to its ACQUITY platform.
Energy-related applications of specialty gases are not limited to analysis. Manufacturers use low-conducting gases like argon as insulation between glass panes in energy-efficient windows.
One normally thinks of specialty gases as components of processes (as above for chemical synthesis) or laboratory operations (GC carrier gases, sparging of liquids). But Tony Reccek, director of business development for specialty gases at Airgas (Radnor, PA), notes the importance of high-purity specialty gases as analytical standards.
Automotive emissions are one critical application. “The EPA is tightening emissions specs. As emission controls get tighter and more components are added to the list, manufacturers must demonstrate compliance,” Reccek tells Lab Manager.
Recent additions to air emission standards, including mercury and hydrochloric acid to part-per-billion levels, apply to traditionally “dirty” industries such as power plants and cement making. In addition to maintaining those species in an analysis-friendly state, companies must demonstrate compliance with evolving regulations based on methods that utilize NISTtraceable standards. Specialty gas manufacturers have become go-to sources for those standards.
NIST-traceable standards are the buzzword in natural gas analysis, as energy companies explore more and varied sources. “Natural gas varies significantly based on where it’s from,” Reccek explains.
The need for pure standards trickles down to the point of use as well. For example, natural gas-powered vehicles are tuned for specific gas compositions and vetted based on their emissions profiles. Designers must therefore determine the precise composition of both their fuel and what emerges from the tailpipe. Both data sets rely on precise analytical standards.
“If you’re a chemist in a laboratory charged with keeping a product within spec, or a company that must demonstrate compliance, the first thing you’re wondering is whether you’re right,” Reccek says. “Your instrument says you are, but the only way you can be sure is by incorporating in your analysis NIST-traceable standards that all governments and regulators accept.”
Standard gas mixtures are common reference tools in analytical laboratories, both for quality control and for environmental applications. Calibration gas mixtures contain as few as two gases or as many as 160. Lucie Prost, vice president, metal fabrication at Air Liquide Canada (Montreal, Quebec, Canada), notes that these mixtures are used for testing, analysis, and quality control in environmental, energy, food, and manufacturing industries.
For energy customers, Air Liquide provides custom-formulated mixtures that reflect the customer’s product. Mixes contain the range of expected hydrocarbons—ten to 15 molecules are typical—at their anticipated concentrations. ALC offers pure gases at two purity standards, ALPHAGAZ 1 and ALPHAGAZ 2.
Standard hydrocarbon gases assist in calibrating the response of gas chromatographs or other testing/ monitoring equipment to actual samples. In GC this is the idea of “response ratio”—the ratio of detector response to the quantity of an analyte known to produce a signal. For monitors and sensors, the gases provide calibration.
For additional resources on specialty gases, including useful articles and a list of manufacturers, visit www.labmanager.com/specialty-gas
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