Forensic Applications for 1,4-Dioxane and Solvent Stabilizers - Environmental Investigation and Remediation - page 445

TABLE 9.10
Stabilizers and Impurities in Pre-1986 Technical Grade
Methyl Chloroform

Concentration

Stabilizers
1,4-Dioxane 3.8 wt%

1,2-Epoxybutane 0.47 wt%

Nitromethane 0.27 wt%

n -Methyl pyrrole

<0.0001 wt%

Impurities
Chloroform

100 ppm

Carbon tetrachloride 250 ppm

Trichloroethylene 200 ppm

1,2-Dichloroethane 2300 ppm

1,1-Dichloroethylene 398 ppm

1,2,3-Trichloroethane 41.8 ppm

trans -1,2-Dichloroethylene 50 ppm

Tetrachloroethylene 475 ppm

Source: After Maltoni, C., et al., 1986, Acta Oncology 7: 101-117.

• Analytical methods are available to detect the marker stabilizer

• Stabilizer compound intended to serve as a unique marker of the solvent is not commonly

used in other applications that might be released in neighboring industrial operations

The combined occurrence of these circumstances is unlikely because stabilizers generally com-
pose only a small percentage of the solvent mixture. The following examples proi le the potential
for solvent stabilizers to serve as marker chemicals.

9.4.1 PCE AS A D IELECTRIC F LUID
As described in Chapter 1, PCE is stable up to 150°C in the presence of air and moisture, and in the
sealed environment of an electrical transformer, but in the absence of catalysts, PCE may be stable
up to 500°C. The desired characteristics of a dielectric l uid include long-term resistance to decom-
position at high temperatures in the presence of oxygen to prevent formation of electrically conduc-
tive or corrosive materials. PCE was used in transformers as a replacement for the more toxic class
of dielectric l uids containing PCB compounds. Commercial grades of PCE may contain manufac-
turing impurities including any of the chlorinated ethanes at levels up to 0.3 wt% (Borror and Rowe,
1981). When PCE is used as a dielectric l uid in an electrical transformer, any chlorinated ethanes
present can be expected to undergo dehydrochlorination, producing hydrochloric acid and causing
corrosion. To function well as a dielectric l uid, PCE must have less than 50 ppm total chloroethanes
(Borror and Rowe, 1981). In particular, dichloroethane, methyl chloroform, symmetrical tetrachlo-
roethane, pentachloroethane, and hexachloroethane should not be present in PCE used as a dielec-
tric l uid at masses totaling more than 10 ppm by weight, and unsymmetrical tetrachloroethane
should not exceed 30 ppm by weight. Even small amounts of chloroethanes present as impurities
will react with aluminum chloride or other catalysts and form acid, which will in turn begin to
attack PCE. PCE destined to be used as a dielectric l uid was subjected to extra rei ning, including