Whilst the basic components of a modern gas chromatograph (GC) haven’t changed since its introduction by Martin and James in 1952, continued refinement of the instrumentation has matched the demands for faster and more sensitive separation of complex samples.
Over the last 20 years there have been significant steps forward in detector development and the lowering of detection limits. This same time period has also seen considerable improvements on the stationary phase.
Sensitivity is defined in terms of the signal to noise ratio. Improving sensitivity can be achieved by either increasing the signal strength or by reducing signal noise. Impurities in your carrier gas are one of the factors that can contribute significantly to baseline noise. The push for greater sensitivity is making carrier gas impurity levels more critical than ever. Levels that were previously acceptable are now seen to be affecting baseline noise and accelerating degradation of modern stationary phase columns.
How do impurities enter the system? There are a number of potential sources of impurities; a typical example is every time the gas line is broken to replace a cylinder for instance. At this point, there is the opportunity for atmospheric impurities (in the form of moisture and oxygen) to enter the gas lines. This is another example, and one which is less obvious when inline purifies are used. When changes of these purifiers are required (due to saturation), this can open your gas line up to the very types of impurities that you are looking to avoid.
When it comes to choosing a carrier gas, most chromatographers carefully select a high purity gas. However, even in gases with a purity of 99.9999% (6.0 Grade), the other 0.0001% can contain levels of oxygen, moisture and hydrocarbons that are significant enough to have a negative impact on your results.
Fortunately, technology has moved forward to help gas chromatographers. High purity gases are available in specially modified cylinders that are able to filter out impurities before they leave the cylinder. The modification within these cylinders is referred to as BIP® technology and have proven beneficial to users, baseline noise is noticeably reduced, peak separation improved, and column life extended as a result of less critical impurities within the carrier gas. The BIP® technology cylinder is exclusively available from Air Products and is available with high purity argon, helium, hydrogen and nitrogen.
Switching to a high purity gases with BIP® technology couldn’t be easier, just order BIP® gases in place of your normal carrier gas and see the benefits immediately.