Clean gases deliver clean analyses, faster and cheaper

Clean gases deliver clean analyses, faster and cheaper

By Paul Tripp
Agilent Product Manager, Gas Management Supplies

Contaminants in gases can significantly affect your analysis. Moisture (Figure 1), oxygen (Figure 2), and hydrocarbons (Figure 3) contribute to loss of sensitivity, undermine the accuracy of the GC, and ultimately damage your column. Impurities activate glass wool in liners and accelerate septa degradation, causing high background signals and ghost peaks, which lead to time-consuming troubleshooting. Oxygen in supply gas for ICP-OES or ICP-MS can cause plasma shutdown and loss of sensitivity. Plus carbon dioxide in supply gas for TOC analyzers leads to elevated baselines and loss of sensitivity and accuracy.
Supply gases can pick up contaminants from every part of the gas line, so you need a gas filter system even if your supply gas is of the highest quality. It is not economical to buy expensive, high purity gases if their quality is downgraded by impurities in the gas line.

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Figure 1. This figure shows the difference in bleed levels of two GC columns due to moisture exposure, with and without a filter when running a temperature program (50 °C to 350 °C, 20 °C/min). When no filter is used, an extreme rise in the bleed profile is clearly visible due to moisture in the carrier gas. Agilent’s Gas Clean Filters remove all moisture in the carrier gas to provide a normal bleed profile.

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Figure 2. The lower chromatogram is a normal SimDist high temperature analysis. The upper chromatogram shows the first injection on a new column; the baseline does not return to zero. The higher signal at the end of the chromatogram is caused by the high bleed from the column, due to a leak in the system after the column was installed in the GC.

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Figure 3. The charcoal filter greatly reduces the effects of hydrocarbons in the gas stream (nitrogen 4.5 ppm, hydrocarbons < 5 ppm).

The right filter for every gas

Improvements to the absorbance materials in the GC/MS and moisture filter means they stabilize more quickly to reduce downtime and improve productivity. Agilent has also introduced a High Flow Connection Unit that handles flow rates up to 20 L/min for collision gas applications, supply gas for ICP and ICP-MS, or any application where you need high flows – expanding the range of applications you can run. For operations requiring flows above 10 L/min, you can save money by using cheaper gas and/or eliminating contaminants. All of Agilent’s gas filters are compatible with the high flow and standard connection units.
All GC applications benefit from the use of gas filters, whether your GC is connected to a FID or MS, or any other type of detector such as flame photometric, thermal conductivity, electron capture, nitrogen-phosphorous, or thermionic. Table 1 shows some of the benefits you can expect from using filters to clean your analyses gases.

Technique	Filter type	Benefit
GC/MS	GC/MS	Higher data accuracy and less maintenance
GC column	Moisture and oxygen	Longer lifetime
GC, ECD detector	Moisture and oxygen	Greater sensitivity
GC, TCD detector	Moisture and oxygen	Greater sensitivity and less maintenance
GC, Process	Process moisture	Greater sensitivity
GC, FID detector	Two charcoal filters (for air and nitrogen)	Greater sensitivity
GC, PID detector	Oxygen and charcoal	Greater sensitivity
GC, PFPD or FDP detector	Charcoal, carbon dioxide, and moisture	Greater sensitivity
GC, TSD or NPD detector	Charcoal, carbon dioxide, and moisture	Greater sensitivity
Total organic carbon	Carbon dioxide and moisture	Greater sensitivity
Zero-air generator	Carbon dioxide and moisture	Greater sensitivity
ICP-OES, ICP-MS	High flow connector with two oxygen filters	Greater sensitivity

Table 1. Chose the filter that meets your needs.

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Figure 4. Use the Agilent GC/MS filter to save on gas, and the moisture filter to improve productivity.

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Figure 5. This figure shows how much you can save by using Agilent Gas Clean Filters and 4.6 grade helium rather than 6.0 grade helium.

Faster stabilization reduces gas consumption

The Agilent GC/MS filter delivers faster stabilization times (Figure 4) so you use less gas. This single combination filter is optimized to remove oxygen, moisture and hydrocarbons from GC/MS carrier gas. Increased GC/MS sensitivity provides more accurate data, prevents column damage and reduces instrument downtime.

Use gas clean filters and save money

The Agilent Gas Clean Filter System lets you use 99.996% (4.6) pure helium instead of the more expensive 99.999% (5.0) or 99.9999% (6.0) grade, while still yielding high quality analytical results. Figure 5 compares the costs of carrier gas with the use of helium 4.6 and 5.0. The expected cost savings are 30%.
The filter system, in combination with 4.6 grade helium, delivers at least the same quality gas to your GC and GC/MS as when using 6.0 grade helium, with respect to oxygen and water. This presents considerable savings over the use of higher quality helium.
You can see how the Agilent Gas Clean Filter System delivers clean gases, reducing the risks of column damage, sensitivity loss and instrument downtime, and saving money.