Advancing accuracy in gas analysis

As environmental legislation continues to tighten, emissions testing and monitoring certainly doesn’t get any easier and demand for accurate gas analysis has never been greater. But how is the gas industry responding to the challenge to improve accuracy?

The drive for accuracy is driven by the growing demands of environmental legislation. Industry is currently required to comply with a highly complex set of legislative emissions limits and targets, reporting their data at national and international levels. At the same time, the number of pollutants facing scrutiny is growing and advanced methods of gas analysis are increasingly required in order to measure multiple components at low concentrations.

This legislative change is continuing and 2010 is set to be a pivotal year. The last few legislative stages of the new EU Industrial Emissions Directive are due to be completed this year – effectively bundling together the many pieces of European environmental legislation that currently exist into a single directive. This legislation has come about as a result of some European member states failing to meet emissions reduction targets. As a sign of its disapproval, in October 2009 the EU confirmed its intention to take legal action against six member states for failing to ensure that valid Integrated Pollution Prevention and Control (IPPC) permits were in place at more than 1,500 industrial installations.

The details of the EU’s Emissions Trading System (ETS) will also be finalised this year and could include pollutants such as mercury, nitrous oxide and methane. Last but certainly not least, REACH (Registration, Evaluation and Authorisation of Chemicals) legislation is continuing its roll out and registration of test data, which must be completed before 30 November 2010.

The emissions testing industry realises that it cannot afford to watch and wait for these legislative developments to take shape. Demand for highly accurate and reliable measurements is ongoing and this has already led to developments in the world of specialty gases.

One of the most interesting developments to take place recently is a move to extend the shelf-life of the gas mixtures, which are commonly used in analytical calibration. Until recently, gas mixtures – some of which may contain up to 100 components – had an industry-wide maximum shelf-life limit of five years. Developments by Air Products in advanced cylinder treatments and in the way these mixtures are produced have now allowed this limit to be doubled to ten years, which means laboratory analysts can store and use them for longer, with total confidence of their stability.

Analytical calibrations typically use small quantities of gas for each calibration and the extended shelf life is especially beneficial to lower volume users performing less frequent calibrations. However, all analysts will benefit from the increased peace of mind that comes from purchasing calibration mixtures that stay stable for considerably longer.

As well as increasing the shelf-life of gas mixtures, the specialty gas industry has

expanded its range of top grade calibration mixtures. These mixtures provide an assurance of accuracy in the even the most demanding analytical applications and come with ISO 17025 certification, fulfilling UKAS and other equivalent European standards. The extended range includes mixtures with components commonly used in emissions monitoring applications – nitrogen oxides, sulphur oxides or carbon monoxides – at ultra low concentrations down to part per billion levels in air or in nitrogen, in order to achieve the most accurate calibration possible.

Choosing the right gas mixture for each analytical calibration can sometimes be difficult. Gas analysts need to ensure that the components that make up the mixture are high quality, as this will minimise uncertainties and ensure that the measurements taken are of the highest accuracy. With this in mind, an easy-to-use online tool has been developed, which enables the user to select bespoke mixtures comprising only the highest quality gases, which come with quality certificates and are fully traceable. All the analyst needs to do is specify some simple data including the preferred cylinder size, mixture type and composition. This kind of tool is increasingly vital in the fast-moving world of emissions monitoring and control, where fast and accurate analysis across a range of emissions is required.

Today’s emissions monitoring systems are capable of making accurate analyses for all emissions regardless of their reactivity or their concentrations. Their improved accuracy is in part due to improved access to top grade calibration gas mixtures that stay stable for longer. In the field of emissions monitoring, it is now possible to achieve precise analyses for reactive gases such as hydrogen chloride emissions, against average daily values of 10mg/m3, as specified in Annex V of the Waste Emissions Directive.

In the drive to improve accuracy in the field of gas analysis, there is always room for further improvement. For example, care is needed when selecting the right equipment. While expert advice is sometimes needed to make the right choice, analysts can now use an online tool to browse and select the equipment they need. By completing the online criteria – requesting details of a variety of variables about the specific application – the analyst can select the right equipment and eliminate any possibility of error.

For example, it may be necessary to maintain a precise outlet pressure throughout the use of the cylinder, even when inlet pressure varies. Taking account of such criteria is vital and can have a significant effect on the accuracy of the calibration and therefore of the measurements given. The right choice of material can also be crucial; for safety, purity or compatibility reasons. When using corrosive gases, for example, only stainless steel equipment should be used and when oxygen or oxidising gas mixtures are being used, brass equipment is preferred.

Of course, it can be easy to overlook one or more of the variables involved in equipment selection. Among the most common errors made when choosing equipment is failing to recognise that a double-stage regulator is needed or specifying equipment which will provide the wrong outlet pressure. Using the new online equipment selector, all the thinking is done in advance, so all the user needs to do is answer a simple set of questions and a recommendation for the best equipment model is made.

Such smart solutions are performing an increasingly important role in improving the accuracy and reliability of gas analysis and they will continue to do so in the future.