Environmental Analysis 35 Gas Chromatographs for Online Environmental Monitoring
When it is determined that a gas chromatograph (GC) is required for online environmental monitoring, often you will look to the laboratory for guidance. However, the requirements for an online GC are significantly more demanding than in the lab. Where the online measurement needs to be made is not the clean temperature controlled environment of a lab. The online measurement needs to be fast so that the results can be directly fed into the process control strategy to avoid excursions, rather than just record them. Finally, field personnel are often not familiar with the complex nature of chromatography.
The Emerson series of gas chromatographs have a long history of installations in tough environments and have a reputation of extreme reliability. Almost all of the GCs made by Emerson undergo rigorous testing in an environmental chamber that confirms the unit will work as specified in ambient temperatures between -15°C and 55°C. The ability to reliably perform your analysis throughout this temperature range means you can install the GC without expensive climate controlled buildings that can triple the cost of installations. Applications are customised for your measurement using a variety of technologies and can include parallel chromatography to shorten analysis times. Additionally, the diagnostic software is custom designed for field installations making it easy to learn and use when compared to complicated laboratory software that has been re-engineered for online GC’s.
Reader Reply Card No. 112
Standards Compared in Moisture Measurement at Leading Institutes
When four of the world’s leading national metrology labs took the bold step of comparing their primary moisture standards, the tool of choice --a Tiger Optics LaserTrace --performed admirably. Measurements deviated less than 2 percent over the course of the three-year, multinational inter-comparison, thereby permitting the facilities to establish a much-needed baseline for future work. The groundbreaking study --undertaken by the European Association of National Metrology Institutes (EURAMET) --relied solely upon the company’s LaserTrace, along with a back-up compact HALO instrument, also from Tiger Optics (USA).
The performance of the Tiger Optics instruments permitted scientists to compare standard generation facilities by shipping the analytical instruments --in lieu of cumbersome standards --to the participants in the United Kingdom (National Physical Laboratory), the United States (National Institute of Standards and Technology), Japan (National Metrology Institute of Japan), and Germany (Physikalisch-Technische Bundesanstalt).
The measurement of trace amounts of moisture contamination is of utmost importance to a number of manufacturers and suppliers of purge and process gases. The semiconductor industry, for example, regards moisture as one of the most difficult impurities to measure and to control. As manufacturers develop moisture analysers to detect ever-smaller amounts of contaminants, there is an equally pressing need for traceable calibration. Hence, EURAMET’s desire to compare facilities and quantify the variability among the standards and their accuracy at fraction amounts.
Until this study, an inter-comparison of such facilities was untenable, due to the characteristics of trace water-vapour standards. Such standards are produced via a dynamic method, for example; gravimetrically, or a frost-point generation, involving large, weighty, and
complex pieces of equipment that are not readily brought together for comparison purposes. To resolve that problem, EURAMET elected to transport instruments, rather than standards.
The study was designed to compare the performance of each of the national metrology institute’s facilities over the range of 10 ppb to 2000 ppb. For the first time, participating laboratories were able to quantify the comparability of their trace water-vapour standard generation facilities, which proved to be excellent across the full range of measured amount fractions, as the graph illustrates.
“While we learned that such studies take considerably longer than anticipated, the chance to support the noble aim of achieving a comparable moisture standard worldwide was well worth it,” said Lisa Bergson, Tiger Optics’ founder and chief executive, adding, “Beyond that, we are proud of our analysers’ precision and robust performance. It’s great to be in a position to offer them to our friends in the institute community.”
Reader Reply Card No. 113
Agilent Technologies Replaces Signal-to-Noise Spec with Instrument Detection Limit for Triple Quadrupole GC/MS
Agilent Technologies (USA) announces that it is replacing the signal-to-noise specification with a new instrument detection limit specification for its 7000B triple quadrupole gas chromatography/mass spectrometry system.
“Twenty or even 10 years ago, signal-to- noise was a reasonable indicator of GC/MS performance,” said Terry Sheehan, Ph.D., Agilent GC/MS marketing manager, “ but GC/MS/MS baseline noise for simple standards is often too low and too inconsistent to be meaningful. Selection of different baseline segments can change the signal-to-noise ratio by five or even tenfold. Our new specification, the instrument detection limit, is based on the system’s precision, and precision directly correlates with ion count – the real measure of MS sensitivity.”
Agilent considers IDL a better measure of GC/MS/MS performance because it follows the guidelines of the International Union of Pure and Applied Chemistry, the United States Environmental Protection Agency and many other organisations.
IDL calculates typical performance from a series of automated injections for an accurate view of system performance. The well-established Student’s t-test is applied to eight consecutive injections of 100 fg OFN using a 99 percent confidence interval. Additionally, the IDL specification confirms the performance of every component in the GC/MS/MS system, from the autosampler through the detector.....
Reader Reply Card No. 114 Reader Reply Card No. 115
www.envirotech-online.com AET Annual Buyers’ Guide 2012
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