Desorption of Residual Ethylene Oxide from Fumigated Library Materials
Experimental Description
Materials
Carboxide™ gas, which is 10 percent ethylene oxide in carbon dioxide, was obtained from Linde Specialty Gases, a division of Union Carbide Company.
The fine wood pulp book paper used in this study is Springhill™ Offset paper, which had been obtained one year prior to its use from the International Paper Company as a single roll from which 8 1/2"xll" sheets were cut for this experiment. This is an alum-rosin-sized paper with a pH value of 5.5 units. The newsprint paper was also obtained as a single roll from the US Government Printing Office about 15 years prior to its use in this work. The newsprint paper has a pH value of 4.8, and was cut into 8"x10" sheets for this work. Leather scraps were an uncharacterized mix of several different kinds of leather from the Library's Book Conservation Section.
The vinyl audio records were typical 33 RPM long-play records from the Library's collection. They were fumigated without their covers.
Two different photographic films were used in these experiments. One was a 35 mm roll of black and white motion picture film on a cellulose acetate safety base, while the other was a 35 mm roll of color motion picture film on a polyester base.
For each of the materials selected for this study, exactly 1.4 Kg of the material was weighed out for treatment.
Experimental Setup
A 33-liter cylindrical, round-bottomed heavy-gauge glass chamber with an open top was used to contain the materials during exposure to Carboxide™ gas. This chamber was fitted with an air-tight half-inch thick Plexiglas™ (acrylic) cover with four openings. These openings were joined with air-tight fittings to (1) a Carboxide™ gas cylinder, (2) a Welch Duo-Seal Model 1400 vacuum pump through a trap and valve, (3) a Matheson pressure gauge through a valve, and (4) a flexible tubing that extended to the bottom of the chamber on one end and was equipped at the other end, outside the chamber with a needle valve.
This tubing at the fourth opening served as an inlet for air and also as an outlet for sampling and analysis of the air within the chamber. Air samples could also be withdrawn through a septum that covered an opening in the middle of the Plexiglas™ cover. A perforated stainless steel rack sitting about an inch above the bottom of the chamber supported the objects being fumigated. To the sides of the metal rack were attached an Airguide™ relative humidity gauge and a Weston Model 4200 thermometer, both of which could be viewed plainly from outside the sealed chamber. This glass chamber was placed inside a fumehood, where all the work was carried out.
Fumigation Procedure
With the materials in place and the cover with all its fittings secured, the chamber was evacuated for 30 minutes. The pressure inside the chamber was well under 30 torr in the case of all the materials studied. The Carboxide™ gas was allowed into the chamber until the pressure was about 650 torr. The system was left undisturbed for 24 hours.
Two separate and independent procedures were followed to compare the relative affinity of library materials for ethylene oxide. In the first procedure, the air inside the chamber was changed several times, and the decreasing concentration of ethylene oxide was periodically monitored. At the end of the 24 hour fumigation period, and thereafter after every aeration step, the chamber was evacuated for 30 minutes and room air (40% RH) allowed to enter the chamber until a pressure of 650 torr was registered. The ethylene oxide concentration inside the chamber was monitored constantly at regular intervals 20 to 40 minutes apart. The total contact time between the fumigated material and fresh air varied between 3 and 16 hours (longer times were for aerations that continued overnight).
In the second procedure, the evacuation of the chamber was initiated at the end of the 24-hour fumigation period, and continued for several hours while the ethylene oxide concentration at the vacuum pump exhaust was monitored at regular intervals. For experiments that could not be completed by the end of the workday, the system was sealed off overnight and the process continued the next morning.
No attempt was made in these experiments to introduce additional moisture other than that present in the room air and that given off by the materials themselves. The relative humidity varied from 25% RH under vacuum to 45% RH in the presence of air.
Ethylene Oxide Detection and Analysis
The work area and laboratory personnel were constantly monitored by EOTrak™ badges (Chemrox, Inc.) for ethylene oxide TWA exposure dose.
Two gas chromatographs were employed at different points in this study. One of these was an HNU Systems Model 301 gas chromatograph equipped with a HayeSep D 80/100 stainless steel column (4'xl/8"), and a photoionization detector (PID) was used to measure ethylene oxide concentration inside the chamber. This gas chromatograph was equipped with a microprocessor programmed to measure the ethylene oxide concentration repeatedly over pre-determined intervals by monitoring the response of the detector at 10.565 eV, the ionization potential for ethylene oxide. This instrument was also used periodically to monitor ethylene oxide concentration in the work area. The other gas chromatograph used was a Varian Model 3700 which was equipped with an HNU Systems Model 52 PID detector. A Porapak Q column was used at 135øC. The gas chromatographs were calibrated with two standard mixtures of ethylene oxide in air (5.4 ppm and 19.1 ppm) obtained from MG Industries.
Table of Contents - Introduction - Experimental - Results and Discussion - References - Supporting Documents