Volatile Organics in the Air: Analyzing the Air in Calvin College's Painting Studio
Author: Karen Gilliland
Date: Submitted on May 12, 1999
Course: Chem 395 Fall '98
Credit Hours: Two
Departmental Presentation: April 29, 1999
Mentor: Professor Kumar Sinniah
Overview
by Kumar Sinniah
During the fall semester, Karen Gilliland, a chemistry major, chose to analyze the air in Calvin College's painting studio as part of her independent project, which is required of all chemistry majors. She monitored the air in the painting studio at several different times with students painting and without students present. She also tested the effects of using air-scrubbers to remove VOC's from the painting studio. Data collection was further aided by weekly sampling the paint studio by the analytical chemistry students as part of a laboratory experiment introduced in the fall of '98.
In summary, Ms. Gilliland's results indicate that a large number of chemical components are present in the air when students paint, and many of these are long chain hydrocarbons released from the paint solvents. She was further able to show that the scrubbers in place in the paint studio was ineffective at removing VOC'S. Several interesting side projects have risen from her investigation. For example, we plan to monitor the rate of dissipation of the VOC's from the paint studio. Although a large number of components were identified in the air in the paint studio, there are still a significant number of components unidentified.
Another student will conduct an independent study in the fall of '99 to investigate how long it takes for the VOC's to dissipate while using complementary infrared spectroscopy methods to determine the unidentified chemical components
Volatile Organics in the air: Analyzing the air in Calvin College's painting studio
Introduction:
Interest in determining the amount of volatile organic compounds (VOCS) in the air has increased recently. In 1990, the Clean Air Act Amendments were passed requiring the monitoring of 55 VOC "ozone precursors" and 189 chemicals "hazardous air pollutants" (HAPs). Nearly 100 HAPs have vapor pressures greater than 0. I Torr and have been classified as VOCs.(1)
The purpose of this research project was twofold - to identify and quantify the concentration of VOCs that students in the painting studio were exposed to and compare them against national standards and to develop a procedure which could be used in sampling air in other locations around campus. Samples were taken between September and October of 1998. Air samples were collected on Tenax thermal desorption tubes from the painting studio at different times: with students painting, without students present, with chemical scrubbers (which were present in the room to theoretically reduce the chemicals in the air), and without the chemical scrubbers. A thermal desorption system in combination with a GC/MS was used to analyze the air samples within 24 hours of sampling.
Experimental Section
Solid Sorbent Tubes: Volatile organic compounds were collected on a single packed solid (Tenax) sorbent tube of about 12.5 cm in length. The Tenax thermal desorption tubes were purchased commercially from Alltech, Inc. The tubes were conditioned in a thermal desorption system at 225 degrees for 60 minutes while being purged with a stream of 40 ml/min Helium. Then the tubes were cooled to room temperature while still being continuously flushed with He. The tubes were stored for sample analysis after capping the tube ends with Teflon ferrules and brass end caps. Three such conditioned tubes were used at a sampling site. Two tubes were used for sampling; the other tube remained capped and was used as a blank sampling tube.
Sample Collection:
The VOC's analyzed were concentrated on the sampling tube by drawing air through the sample tube with a personal sampling pump (SKC, Inc. Model # ___) at 66.7ml/min for 60 minutes. At each site, the room temperature, relative humidity, and dew point were recorded.
Sample Analysis:
The thermal desorption tubes were analyzed by a thermal desorption gas chromatography/ mass spectrometry (TD/GC/MS). This was performed with a Dynatherm ACEM 900 thermal desorption unit interfaced with a HP 5890 series 11 GC/MS. The desorber is equipped with a focusing trap to trap volatile substances coming off the TD tubes, which then was directed to a transfer line consisting of fused silica capillary tubing (I m x 0.25 gm I.D.) The fused silica tubing was connected to the column by a glass Y split-end connector. The following conditions were used for the analysis of the TD: the sorbent tube was heated to 300 (C for 2 minutes to desorb the adsorbents off of the Tenax; the desorbed chemicals were then transferred to the focusing trap. The GC separation began immediately following the flash desorption of the focusing trap using the following temperature program: 30 OC for 3 minutes, 5 OC /min to 225 "C and held at 225 OC for ten minutes. Mass spectral data were collected between 20 and 550 mass units. Quantitation of the components found in the chromatograrns were analyzed by using external standards which were purchased from Aldrich. The standard mixture contained the following VOC'S: n-heptane, I -heptane, benzene, toluene, ethylbenzene, p-xylene, m-xylene, isopropylbenzene, and o-xylene each at a concentration of 1998 gg/mL. The external standards were injected into the back of the tube as described in the Compendium of Methods for the determination of Toxic Organic Compounds in Ambient Air.(2) The external standards were analyzed in under similar conditions as those used for the sample tubes. Sample chromatograms were then analyzed through a comparison database search of the NIST 98 mass spectrometry data base.
Results
Figure 1.1
Figure 1.1 shows our VOC standard run. The first peak is an air peak while peaks 2 through 8 are compounds from the standard while peak 9 may be the solvent peak.
Peaks 2-8 were identified as:
2 - Benzene
3- 1-Heptene
4- n-Heptane
5- Toluene
6- Ethyl Benzene
7- p-xylene
8 - isopropyl benzene
To quantify the chemicals in the air that is attributed to the paintings by the students, samples were taken when students were painting and at a time when no students were present. Figure 1.2 shows the results with students while figure 1.3 shows the chromatogram from when no students were present.
Figure 1.2
(figure 1.3 not available)
From the above two diagrams it is quite evident that the background VOC's present in the painting studio is far less than the VOC's present during the times when students paint. The major compounds in figure 1.2 are CS - CIO hydrocarbons typically found in petroleum based products like paint. The three main peaks in figure 1.3 were identified as (1) Hexane 3-methyl, (2) Heptane, and (3) Heptane 2,2,3,5 tetramethyl. Since these peaks do not show up in large quantities when students are present, it must be concluded that either the chemicals are from the vent system and dissipate quickly when students are present or the chemical scrubbers may not have been present on the day we took the sample and the chemicals would normally be absorbed by the scrubbers.
The art department uses chemical scrubbers in the painting studio to reduce the amount of volatile chemicals present in the air when students paint. The scrubber is a Nox-Out Molecular Adsorber containing alkali, alumina, silcate, and sodium. Samples were taken in the painting studio with and without the chemical scrubbers. Figure 1.4 shows the results of these runs.
Figure 1.4
Comparison of Air with scrubbers vs. without scrubbers
A quick glance at the chromatograms with the presence and absence of scrubbers suggest that the scrubbers are ineffective at removing much of the VOC'S. The one major peak to dissapear, which is the peak around 8 minutes in the chromatogram without scrubbers was identified as toluene. The peaks without the scrubber are slightly less in number and much broader suggesting overlapping of peaks.
Table 1 gives the values for some of the chemicals that were analyzed. A comparison of values when scrubbers were present and when they were not shows that the scrubbers do remove some of the hydrocarbons as well as some lower molecular weight components.
Conclusion:
Though many chemicals were found in the painting studio, the concentrations of any one chemical did not come close to exceeding its legal limits. It could not be determined if the combination of chemicals could cause problems such as headaches or dizziness. Some chemicals such as decane or undecane do not have legal limits that have been found yet; however, they contain warnings such as "fumes may cause eye, nose, or mucus irritation." The results showed little difference in the chemical makeup of the air with or without the chemical scrubbers. The chemical scrubbers were effective in absorbing low molecular weight compounds such as butanone or toluene. High molecular weight compounds were found in slightly lower concentrations when chemical scrubbers were used, but the differences are not significant. The next step in the project is to determine how long it takes for the chemicals to dissipate.
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Pankow, James, Wentai Lou, Lorne Isabelle, David Bender, and Ronald Baker. "Determination of a Wide Range of Volatile Organic Compounds in Ambient Air Using Multisorbent Adsorption/Thermal Desorption and Gas Chromatography/Mass Spectrometry". Analytical ChemiLta. Dec. 15, 1998: 5213-5220
Center for Environmental Research Information Office of Research and Development. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air. 2nd ed. January 1997