Automated Handling Techniques for the Analysis of Elevated Volatile Organic Compound (VOC) Concentrations in Soils Utilizing the Atomx Concentrator/Multimatrix Autosampler

Anne Jurek, Teledyne Tekmar

In U.S. EPA Method 5035 there are two collection options for samples containing high levels of volatile organic compounds (VOCs). The first involves collecting a bulk soil sample in the field. In the lab, the bulk soil is dispersed in a water miscible solvent. Next, an aliquot of the solution is added to 5 mL of water and finally, the sample is purged. The second option is to collect a 5 g soil sample and add it to a pre-weighed vial containing a prescribed amount of water miscible solvent. An aliquot is then purged. Both of these processes are time consuming and have the potential to introduce human error both in the field and in the laboratory.

In order to automate this time consuming extraction process, Teledyne Tekmar developed a new combination purge and trap concentrator/multimatrix autosampler, the Atomx. This article evaluates the efficiency and accuracy of the Atomx extractions as compared to a manual extraction.

Experimental-Instrument Conditions

The Atomx with Tekmar's proprietary #9 trap was connected to an Agilent GC–MS system, and J&W Scientific 20 m × 0.180 mm × 1.0 μm column was used for the analysis. The temperature profile was 35 °C to 210 °C. The MS scanned in the full scan mode from 35–300 m/z at 5.19 scans/s.

Calibration

Calibration standards were prepared over the range of 1.0–200 μg/mL. Each calibration standard was spiked with 1 mL of methanol to accurately mimic the final volume of methanol that would occur with the extracted samples. The internal standard was delivered to the samples using the standards vessel on the Atomx in order to hold a constant concentration of 25 ppb.

The relative response factors of all of the analytes were evaluated for response and linearity. The %RSD for all of the Gasoline Range Organic (GRO) compounds are listed in Table I.

Table I: Extraction Study Results

Carryover Evaluation

When dealing with high level waste samples, system carryover and contamination can be a major concern. Following a 20 ppm extraction, the Atomx reduced carryover to less than 0.4% in the first blank. This achievement is possible due to the system's methanol rinsing function. The system is capable of rinsing the entire sample pathway with clean extraction solvent (patent pending) in between analyses. The results are listed in Table I.

Reproducibility Study

In order to demonstrate the precision and accuracy of the methanol extraction option on the Atomx, a reproducibility study was performed. Ten replicate extractions were prepared either manually or by the Atomx so as to evaluate the three key functions of the process; the efficiency of the extraction, the accuracy of the dilution, and the reproducibility of the analysis. The results of the study indicate that the precision and accuracy of both the manual and the Atomx extractions are comparable. The results are listed in Table I.

Conclusions

The new Atomx offers the best of both worlds, combining the Purge &Trap and Autosampler into one system resulting in shorter sample pathway, improved temperature uniformity, and decreased carryover. The concentrator is equipped with Teledyne Tekmar's U-shaped proprietary #9 adsorbent trap, which is ideal for the removal of water and for handling increased volumes of methanol. The system displayed precision and accuracy in sample extraction for Gasoline Range Organics. The Atomx's versatility makes it ideal to run waters, soils, and automated sample extractions. Automating sample extraction allows you to save time and labor, thus, increasing lab productivity.

Teledyne Tekmar

4736 Socialville Foster Road, Mason, OH 45040

tel. (800)874-2004, fax (513)229-7050

Website: www.teledynetekmar.com