Gas analysis – the hydrogen way increases in popularity

which can contain huge numbers of componentsmany at very low concentrations. This kind of gas analysis is a critical part of the manufacture of any gas or petrochemical product and is carried out at every stage of the production process.

" Hydrogen is not new to gas chromatography and has been used extensively by the...  

Hydrogen in GC-FID applications is used to produce the flame that converts the sample into electrically-charged ions that produce the required electrical signals that generate the chromatograph.

The vast majority of GC-FID applications use hydrogen for this purpose but to date the analytical accuracy and limits of detection achieved have been limited by the purity of the hydrogen and air that is commercially available. For optimum analytical results it is important to use the highest grade of gas possiblewith a low total hydrocarbon (THC) content.

When the purity of the hydrogen or air used in the GC-FID application falls short of the quality needed for such gas analysisit results in a phenomenon known to chemists as ‘baseline noise’ – the appearance of unwanted peaks on the chromatogram. These imperfections can make it virtually impossible to measure the area beneath the peaks accurately. For the oil or gas analystthis means that it may not be possible to detect some components in the sample at allsimply because they are present at very low concentrations below the limit of detection.

In the ongoing drive for improved accuracythese imperfections are no longer acceptable and the petrochemical and natural gas industries are demanding quality gas products that are capable of producing highly accurate analyses and improved limits of detectiontime after time. Ultimatelythis focus on accuracy gives the process manager better control over the process and can help to improve overall plant efficiency.

In a bid to improve the accuracy of GC-FID applicationsAir Products has developed a new hydrogen product which uses its own BIP technology to deliver an exceptional ultra-high purity gas productwith critical impurities such as oxygenwater and hydrocarbons dramatically reduced compared to conventional hydrogen grades.

Fitted with an internal purifier and patented valve systemthe technology effectively ensures that the gas meets the highest standard of purity at the point of useevery time it is used.

This technological development has the potential to make a big difference. For the analystusing the ultra-high purity BIP hydrogen will significantly lower detection levels and provide an assurance of improved accuracy.

For some oil and gas industry customersthere could be further benefits too if they consider extending their use of pure hydrogen to other analytical applications.

A recent survey by LCGC Europe has revealed that 73percent of the problems that arise in GC analysis are due to impurities in the carrier gas. Such impurities are typically water and oxygen and they need only be present at very low levels to affect the accuracy and reliability of analyses.

In order to eliminate this problempetrochemical and natural gas industry customers are increasingly using higher purity gases and currentlythe carrier gas of choice is heliumwhich provides fast analysis combined with a high level of analytical accuracy. As a carrier gashelium compares very favourably to nitrogenwhich while lower in cost results in much slower analysis.

Howeverthe arrival of the ultra-high purity BIP hydrogen presents an opportunity for petrochemical and oil industry operators to improve efficiency by further increasing the speed of analysis in some applications.

When hydrogen is used as a carrier gasit is possible to complete each analysis with a time saving that can be as high as 35percent. There is another benefit too – when using hydrogen as a carrier gasthe analytical results produced can often be even more accurate than when using helium.

Despite the potential improvements with hydrogenhelium is likely to remain the carrier gas of choice for the petrochemical and natural gas industries mainly because it is totally inert and therefore does not react at all with any components in the sample. Howeverfor some laboratories where there is a particularly high level of usagethe efficiencies that could be attained by switching to hydrogen as a carrier gas are difficult to ignore.

In such circumstancesusing hydrogen has recently become all the more viable due to the safety features that have been introduced to modern gas chromatographssuch as flow rate monitors that will automatically shutdown the hydrogen supply if a leak is detected.

The introduction of these safety featurescombined with the availability of the
ultra-high purity BIP hydrogen gasis encouraging a growing number of analytical users to consider using hydrogen as a carrier gas for the first time.

he cumulative effect of these recent developments presents an opportunity for the petrochemical and natural gas industries as they look for ways to increase analytical accuracyimprove limits of detection and produce ever more high performancehigh-tech fuel and energy solutions for the modern age. While ideal as a fuel gas for most GC-FID applicationseven the purest form of hydrogen has its limitations and is unlikely to replace helium as the industry's preferred carrier gas.

Howeverthe new hydrogen alternative is already attracting significant interest internationally and the full potential of the efficiency benefits it is capable of delivering has yet to be fully explored.o

Gary Yates is Air Products’ European Product Manager Analytical and LaboratoriesWalton-on-ThamesSurreyEngland. www.airproducts.co.uk

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