Feature

Reduction in Analysis Time Increases Productivity

Posted on 08 February, 2010 | Tags: Analytical Solutions

Many advances have been made to the simple technique of gas chromatography. Introduction of new capillary column with narrower id results in better separations and smaller run time thus leading to significant reductions in analysyis time.

-Abhijit Pal & Vivek Dhyani

Chromatography is the most popular analytical technique with gas chromatography being the simplest and most widely used in chemical process labs. The modern gas chromatograph is very simple and easy to use instrument that is software controlled. The samples are introduced either manually or via an auto sampler. Separation takes place in the column that is considered as the heart of the chromatograph and the analytical results are automatically calculated. The results are printed together with the pertinent operating conditions in a standard format.
Initially packed columns were used in the chromatographs and there was a limitation on speed of analysis and resolution between the components. Gas chromatography is the advanced technique that has reduced the run time to 20-40 minutes now, which used to run into hours earlier. Invention of capillary columns has contributed to this achievement of reduction in analysis time and capillary columns are fast replacing the conventional packed columns. Though there have been many advances in the field of gas chromatography but still these techniques are a little time consuming in comparison with today's demand of faster analysis.
There is lot of emphasis on further improving the speed and productivity of the new capillary column. New capillary column with much narrower id has been introduced. Narrower column and smaller film thickness result in better separations and smaller run time. With the invention of narrow bore capillary column with internal diameter going down to 0.1 mm, there is demand of gas chromatograph that can perform with this type of column.
These columns require systems with high pressure rating inlets and detectors with faster data collection rates. Fast gas chromatography allows accurate and consistent analyses almost ten times faster than standard gas chromatographs.  Quicker results allow more timely decisions, lesser product wastage, increased higher value products and also reduce the time to market. Out-of-spec products can be identified and segregated immediately that further reduces liability and increases safety. More samples can be processed in a day with lesser consumption of carrier gas and electricity using less costly columns.

Low Thermal Mass (LTM) Technology Dramatically Increases Sample Throughput
The needs and demands of the users have changed considerably and demand for higher productivity is increasing fairly among the customers in many laboratory gas chromatography applications. Many users also have increasing needs for field transportable applications that require low power consumption.  Low Thermal Mass Technology by Agilent addresses these growing needs. This technology combines a fused silica capillary column with heating and temperature sensing components that are wound around it. The design heats and cools the column very efficiently for significantly shorter analytical cycle times as compared to conventional air-bath gas chromatography oven techniques involving much higher thermal mass.
The heating rate in conventional gas chromatograph is usually 10-20 degree Celsius per minute, whereas with LTM technology, the temperature programming rates may go up to 1800 degree Celsius per minute. This leads to amazingly shorter run time.
Fast cooling times in seconds aid to rapid analytical cycle times. The runs that usually take 40- 50 minutes in routine chromatography can be completed in 2-3 minutes. This results in substantial savings in time that ultimately results in significant cost saving as there is substantial reduction in consumption of costly gases, electricity and man-hours.
Though the technology uses the same GC injectors, detectors and fused silica capillary columns (up to 30 m in length), the difference is in the way a column is heated. The concept is to heat the column as compared to the complete oven in conventional gas chromatograph. The other advantage is that up to 4 LTM modules can be added to single GC system. Each LTM module can have a different oven program thus converting single GC into multiple GC that further results in better returns on investments. 
The Free Method Translation Software makes the job of the chemist much easier. The system has very good retention time and repeatability in comparison with the conventional gas chromatographs.

Capillary Flow Technology (CFT) is Another Useful Technique
This is yet another innovative approach that allows reliable, leak-free, in-oven capillary connections with ease, which can withstand extreme temperatures of a modern GC. CFT is based on a diffusion-bonded process. These inert, low mass, low-dead volume devices not only make it easy to make secure connections but also have the ability to pneumatically divert the gas flow with precision as required. This highly favorable step opens the door to highly useful techniques such as back-flushing, heart-cutting, flow splitting and Deans switching. CFT can improve analytical results as well as save time and resources.
This device can be used for Back Flushing- Its availability reduces cycle times and provides better data quality. The option of back flushing heaviers and high boilers prolongs the column life. 
Deans switch facilitates heart cutting by switching peaks to a second column of different stationary phase. Additional selectivity can provide better resolution of trace compounds in complex matrices. The purged splitter is easy to use, leak-free device to split column effluent reliably among two or three detectors. GC X GC Flow Modulator offers comprehensive multidimensional chromatography without the need for cryogen. This also provides visualization of sample components for class determination.
Quick Swap device allows column changing or inlet maintenance without the need to vent an attached mass spectrometer. Difficult analytical challenges can be addressed as the system can run up to four column modules simultaneously with different temperature programs.
Strong synergy with Capillary Flow Technology provides significant new capabilities in multidimensional gas chromatography and comprehensive gas chromatography. The feature Multimode Inlet with two inlets in one for maximum performance and flexibility is an important component of gas chromatography. This enhances the capabilities in a single inlet that typically require two or more inlets. Multimode inlet has large volume injection capabilities and can carry out multiple tasks of increasing sensitivity, analyze thermally labile compounds or inject dry samples. All this can be doe simultaneously with standard injections, performed with a split or split-less inlet. 
Agilent's 7890 and 6890 systems are loaded with all the features like fast automatic injection; split/ split less inlets, 0.1 mm capillary columns, high-speed detectors, method translation software and have the capable of fast data handling to yield faster results from gas chromatography.

Abhijit Pal is Marketing Program Manager for Chemical Analysis Solution Unit ,  Agilent Technologies
E mail :  abhijit_pal@agilent.com

 

 

Vivek Dhyani is Application Engineer with Agilent Technologies in India.
E mail vivek_dhyani@agilent.com