Analytical Instrumentation 15


maintained and since peaks are twice as narrow, they are also twice as high. This enhances sensitivity and can lead to lower detection limits, but it also allows the injection of smaller sample volumes. The advantages of using hydrogen are clear, but attention must also be given to method conversion prior to implementation.


Adapting methods to hydrogen carrier gas requires some consideration of elution temperature. Changing from helium to hydrogen is relatively simple for isothermal methods; the linear velocity is increased by roughly a factor of two and 50% of the sample volume is injected using the same split ratio. This results in the same sensitivity (peak height). Injecting less sample has the additional benefit of reducing contamination, which in turn reduces the costs and time required for inlet and column maintenance. However, converting temperature-programmed methods is more complex and requires additional changes. If the same peak elution order is desired when using hydrogen, the oven temperature program rate must also be changed or the components will elute at different times and the elution order may change. In order to ensure that the target analytes elute at the same elution temperatures, a change of oven temperature program rate is needed. Roughly, when twice the linear velocity is used, the isothermal times must be cut in half and temperature programs must be multiplied by a factor of two in order to obtain the same separation in half the time. While one can calculate this, there are freeware programs available on the web that are helpful for more complex methods. Or you can use the helpdesk of companies like Restek (support@restek.com) to assist you in determining the new settings.


Summary


As the cost of helium continues to soar and its availability becomes more and more uncertain, many labs using gas chromatography are considering switching to hydrogen carrier gas.


Hydrogen can be reliably produced on demand using hydrogen generators, which are safer and more cost-effective than free-standing, high-pressure gas cylinders. In addition, using hydrogen allows efficient separations to be obtained twice as fast compared to helium, which offers clear benefits to sample throughput and overall lab productivity.


Restek Corporation


Restek is a leading developer and manufacturer of chromatography columns, standards, and accessories. We provide analysts around the world with the innovative products and services they need to monitor the quality of air, water, soil, food, pharmaceutical, chemical, and petroleum products.


www.restek.com References


[1] T. Newcomb, Time NewsFeed (August 23, 2012). http://newsfeed.time.com/2012/08/23/theres-a-helium-shortage-on-and-its-affecting-more-than- just-balloons/#the-government (accessed November 1, 2012).


New Version of Vision


FOSS NIRSystems, Inc. (USA) have introduced Vision 3.60. Vision is a software package specifically designed for use with the FOSS NIRSystems Near-Infrared (NIR) laboratory and process analysers. Vision 3.60 replaces earlier versions of Vision and offers support for the latest NIR laboratory and process hardware.


The main new features in Vision 3.60: Vision 3.60 is 64 bit compatible. Vision can now be installed and run on both 32 bit and 64 bit versions of Windows XP, Windows Vista, and Windows 7. Vision 3.60 supports the NIRS DS2500 Analyser


If you are a current user of the FOSS Vision software, please contact FOSS NIRSystems for more information and/or a complete list of new features appearing in version 3.60.


The FOSS Vision software is 21 CFR Part 11 compliant and supports PAT through numerous process analysis options and process communication capabilities. The software has an extensive security system with multiple access levels, secure data archiving and report generation as well as database and spreadsheet compatibility. Vision comes with a user-friendly electronic manual with tutorials and data for self taught hands-on method development and software operation.


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How to Select a Capillary GC Column


An optimised chromatographic


separation begins with the column. Selection of the proper capillary column for any application should be based on four significant factors: polarity of the stationary phase, column I.D., film thickness, and column length.


At Supelco (USA), the team of GC application scientists and technical experts has created a


valuable map to help you navigate through capillary column selection. Supelco’s GC Column Selection Guide meticulously escorts you through each of the deciding factors, while providing you with literature references and column selection charts grouped by industry, phase, and application. Also included is a detailed description of each Supelco capillary phase, including chiral phases, and a handy cross reference chart for comparing Supelco column chemistries to those from other manufacturers.


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Highly Accurate and Versatile Mercury Analysis Made Simple


The VM-3000 Mercury Vapour Monitor, from Mercury Instruments (Germany), performs continuous measurement of mercury concentration in gases. It is used in the laboratory or can be installed in locations where mercury has to be monitored. Industry people use the VM-3000 in industrial applications as well as university researchers or safety officers and personnel. It is the perfect tool for many different applications: work place monitoring, exhaust air monitoring, emissions monitoring in the chemical industry, ground air screening of contaminated areas, quality control of hydrogen and other gases and as a detector for laboratory applications.


The sample gas is fed into an optical cell by a maintenance-free membrane pump. A beam of UV light passes through the optical cell, a part of it is absorbed by the mercury atoms present in the sample. This method is called "atomic absorption spectroscopy" (AAS). It is extremely selective and sensitive. For mercury determination the AAS method is still ideal despite other, more contemporary methods being made available to the mercury analysis market. The VM-3000 is low in interference and does not require an amalgamation step or expensive carrier gases.


The VM-3000 uses a high-frequency driven electrode-less low pressure mercury lamp as its UV source. This lamp emits lines of an extremely narrow bandwidth which are congruent with the absorption lines of the Hg atoms. Cross-sensitivities are thus minimised. The extremely high stability of the UV source in the VM 3000 is a result of the reference beam feedback control method. Total background noise is less than 0.1 µg/m³


As with all of Mercury Instruments’ range of analysers - the use of advanced technology ensures that the VM-3000 meets the highest quality standards. Their range of instruments which includes stack emission monitors, ambient air monitors and laboratory mercury analysers comply with applicable national, European and American standards and/or regulations. These analysers are supported by a world class and worldwide network of sales and service agencies.


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New Compact Distillation Tester


Petrotest (Germany), a division of Anton Paar, offers the new ADU 4+ automatic distillation tester with a built-in cooling system, fire extinguisher and integrated computer with external flat screen monitor and ADUPro software. The compact, rugged unit performs distillation testing at atmospheric pressure of aviation fuels, gasoline, turbine fuels, fuel oils, kerosene, naphtha, solvents, special boiling point spirits and a wide variety of petroleum products.


Performing distillation testing manually, typically requires considerable operator experience to be done properly and safely. Reading a thermometer, observing the receiver, manually adjusting the heating and recording test results must all be done accurately and simultaneously. With the Petrotest ADU 4+ all of these steps are done automatically using state-of-the-art electronics, avoiding incorrect ASTM D86 measurements and eliminating operator bias.


The modular ADU 4+ provides fully automatic analysis of boiling characteristics according to ASTM D86, D850 and D1078-IP 195. The unit can also be customised to perform user-specific applications. A powerful 1200-watt heater provides sample heating up to 450 degrees C (depending on sample and stem correction mode). All distillation criteria, e.g. cooling temperature and chamber tempering, can be switched over automatically from group 1 to 4 during the distillation. The unit includes glassware set according to ASTM D86 (Group 1-4). With additional accessories, the unit is suitable for testing of aromatic hydrocarbons and volatile organic liquids according to ASTM D850 and ASTM D1078.


The ADU 4+ is designed as a complete ready-to-go system that occupies only a minimum amount of laboratory bench space. The highly versatile unit features volume detection by solid-state light barrier system, rugged high-grade stainless steel powder coated cabinet, temperature-controlled swing-out receiver chamber and digital display with membrane keys.


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