Over the last ten years, German legislators have issued increasingly strict environmental requirements and broader ranging information obligations that have had important implications for laboratory testing. This relates in particular to special category waste. Nowadays, before it is disposed of and in particular to ensure its correct disposal, the composition of waste must be accurately determined as well as any possible risks. Therefore, fairly costly analysis tests are required at state-approved testing laboratories. One of these laboratories is run by Lobbe GmbH, the tenth largest waste disposal company for toxic substances in Germany, at Letmathe in Iserlohn (Sauerland).

The analysis of contaminated substances and special category waste is normally a very complicated and extensive process. The more complicated the composition of the sample, the more difficult the analysis because of an interfering matrix. Therefore, to ensure reliable results, it is important that high-purity carrier gases are used in gas chromatographs (GC) and electron capture detectors (ECD).

Pure gases for improved detection

With the accuracy of analysis depending so much on the quality of the carrier and make-up gases, it is all the more important to prevent the presence of additional impurities such as moisture, oxygen, or halogenated hydrocarbons in the gas. This is particularly important at the Lobbe laboratory: "As a state-approved testing laboratory, we have to determine the composition of special category waste and contaminated substances even down to a few parts per billion. We also carry out regular comparison tests with other state-approved testing laboratories in inter-laboratory trials. We cannot allow for any unpurified carrier gases," reports laboratory manager Dr. Barbara Ziegler. "If there are too many ghost peaks or an increase in the baseline noise, the whole procedure must be repeated until all impurities are reliably identified and the composition of the sample determined. This costs the laboratory time and, especially with increased gas use, money. In addition, the contamination of carrier gases by oxygen, moisture, and halogenated hydrocarbons impairs the detector sensitivity and the life of the columns."

With this in mind, Air Products has developed the only helium and nitrogen cylinders of GC and ECD quality. Using an integrated filter, called a built-in purifier, these cylinders ensure a guaranteed 10 ppb oxygen and 20 ppb moisture in the GC gases as well as only 1 ppb halogenated hydrocarbons in the ECD gases. This unique patented process makes the gases ideal for use in gas chromatographs connected to electron capture detectors. In addition to and because of their purity, the new BIP gases also help reduce costs.

BIP Cylinder Gases (O₂ = 10 ppb; H₂O = 20 ppb)

The laboratory at Letmathe has been one of Air Products' customers since 1992. At the start, industry standards helium 5.0 and nitrogen 5.0, with a 99.999% purity level, were supplied as carrier and make-up gases for analyses. These gases have an oxygen content of less than 1 ppm helium or 3 ppm nitrogen and a water content of less than 2 ppm. To bring these 5.0 grade gases to the increased level of purity needed, an external purifier was connected between the gas cylinder and measurement apparatus. These filters, however, are expensive and require strict monitoring of the saturation level of the filter cartridges. Because of its need for even higher purity gases, the state-approved testing laboratory in Letmathe was one of the first customers to be offered the new Air Products helium GC and nitrogen GC with the built-in purifier. These gases have a guaranteed oxygen content of less than 10 ppb and a guaranteed moisture content of less than 20 ppb. These extremely low values are made possible by the built-in purifier, which is integrated into the cylinder to reliably remove substances from helium 5.0 or nitrogen 5.0 which would otherwise have a negative influence on a GC-ECD or GC-MS analysis. The technology was developed at Air Products' research labs and the company is the only supplier to offer gases with such a high purity level.

Up to 77 % savings on cost

The laboratory at Letmathe currently uses on average four cylinders of helium GC and five cylinders of nitrogen GC a month. Lobbe GmbH is very satisfied with the quality of the BIP gases and the resultant analysis results which are now more reliable and more accurate with fewer repeat procedures necessary.

The increased reliability of results is also reflected in reduced purification costs for ECD detectors. Before using the BIP gases of GC quality, the ECD detectors had to be purified four times a year. Now they need only be purified once a year. The purification costs have therefore decreased dramatically from 24,000 DM to 6,000 DM—a drop of 75 %. The need for purification cartridges, which Lobbe GmbH could not do without, has also decreased. Instead of needing to replace the cartridges on each of the two removal posts six times a year, which cost Lobbe 3240 DM, replacement is now only required once a year at a cost saving of 2500 DM or 77 %.

As a result of the cost savings, Dr. Barbara Ziegler has expanded Air Products' contract to now include all five Lobbe GmbH laboratories in Germany. "Air Products offers us excellent quality gas, a better service than the competitors, rapid delivery and leading-edge products all at a very reasonable price," explains Dr. Ziegler.