EXPERIMENT

Objectives

1. Improve characterisation of suits sent to their laboratory with suspected contamination.
2. Detect compounds of interest down at suitably low concentrations.
3. Improve evaluation of the effectiveness of standard suit cleaning procedures on site.

Characterisation of Contaminated Suits

Various suits, many from fire services, had been sent back to the suit manufacturer’s laboratory for routine checking. Suits were left inside their storage bags. After taking a measurement of the background air in the laboratory, a sampling tube from an MS-200 was simply inserted into a sealed bags and after approximately 2 minutes a sample of ‘suit air’ was analysed.

• 10 suits were analysed within about two hours.
• Four of the suits were found to have positive solvent contamination. Using the mass spectral database on the MS-200, the contamination could easily be identified as acetonitrile, tetrachloroethylene, xylene and acetone respectively.
• Six suits were found to be free of any detectable contamination.

Sensitivity And Detection Limit Of The MS-200

A representative subset of chemicals from a list of commonly encountered chemicals was chosen. To perform a quantitative analysis, gaseous standards in concentrations from approximately 30 to 100 ppm were produced by injecting the liquid sample into a Tedlar® bag filled with a metered amount of nitrogen. Results acquired in a ten second analysis are shown below.

*Compared to nitrogen having a sensitivity of 1.
**Estimated from the sensitivity and the statistical noise of the background spectrum for the component of concern. Calculated as 3*s of the background noise.

Performance of the MS-200: In-Situ Analysis of suit-cleaning procedure

For this phase, an MS-200 was taken to a client in the chemical industry. This client has hundreds of suits to protect staff during work which exposes them to potentially harmful chemicals.

• The MS-200 was set up on a bench between the suit cleaning and storage area.
• Within 10 minutes the instrument was ready to take the first analysis.
• Suits were selected to cover a range of different exposure chemicals.
• As in the initial lab experiment, an air background was taken, then the sampling tube of the MS-200 was placed inside the suit.
• For some suspect suits, additional samples were taken in the sleeves, or from the outside of the suit.

In this way, 42 samples were taken from 11 suits within 3 hours of set-up. On the first two suits analysed no contamination above the background sample could be identified. The third suit showed significant mass peaks above the background. As the operator was not aware of the client’s procedures, the MS-200 result was analysed ‘blind’ using the NIST database. A library search suggested that the unknown compound could be “Limonene”. It was than confirmed that limonene is the major constituent of the cleaning agent used when decontaminating the suits. The MS-200 mass spectrum sampled can be seen below.

The result of the NIST search was feed back into the MS-200 and a ‘mixture analysis’ was performed. The MS-200 mixture analysis reported a very good fit for limonene, thus confirming the NIST search result.

Limonene residues were found on 7 out of the 11 suits analysed, at various levels. No other contamination could be identified above levels noted in the table above, confirming the effectiveness of the cleaning process, within the detection sensitivity of the instrument noted above.

Conclusions

• MS-200 has the capability of performing rapid, in-situ characterisation of protective suits, both contaminated and after cleaning.
• Detection limits for many compounds are significantly below 1ppm in a ten second analysis.
• Confirmation of the effectiveness of cleaning methods for protective suits decreases the risk to personnel from potentially harmful chemicals.
• Ease-of-use, fast analysis, identification by mass spectrometry and portability make the MS-200 an ideal tool to provide a cost-effective and flexible service in a broad range of applications.