1,4-Dioxane Chemistry, Uses, and Occurrence - Environmental Investigation and Remediation - page 84

In the 1960s, landi lls serving universities that performed biological research involving liquid
scintillation counting were highly likely to have been contaminated with 1,4-dioxane. At Duke
University in North Carolina, the campus landi ll predates hazardous waste regulations. Laboratory
wastes were buried in the landi ll in the 1960s, and releases of 1,4-dioxane to groundwater at prob-
lematic levels have been reported (University of North Carolina, 2002). In 1964, the University
of Kansas began operating a landi ll for disposal of low-level radioactive wastes, including radio-
nuclides contained in toluene and 1,4-dioxane; the landi ll produced 1,4-dioxane contamination in
off-site groundwater (Shamberg, 2002). The University of Michigan Landi ll, the University of
Nebraska Landi ll, and the Gloucester Landi ll located south of Ottawa in Ontario, Canada, are addi-
tional examples where liquid scintillation wastes have caused 1,4-dioxane contamination in ground-
water. Municipal landi lls receiving hospital wastes and commercial medical and veterinary laboratory
wastes may also be sources of 1,4-dioxane contamination. As discussed in Section 2.7 , landi lls of all
types have been found to be sources of 1,4-dioxane, though most landi ll groundwater-monitoring
programs do not analyze groundwater, landi ll gas, or landi ll gas condensate for 1,4-dioxane.
2.3.3 T ISSUE P RESERVATIVE IN H ISTOLOGY AND O THER L ABORATORY M ICROSCOPY M ETHODS
1,4-Dioxane has been used as a laboratory solvent for a variety of purposes, including study of tissue
samples, as a carrier for biocides to eliminate biodegradation of analytes in water samples, for analy-
sis of plant and wood samples, for purii cation/isolation of DNA elements, and for drying soil samples
prior to analysis. Human and animal tissue samples are prepared as thin sections on microscope
slides for examination by medical technologists and research scientists. A wide variety of methods
are used, depending on the purpose for which the slide is prepared. Dehydration and staining are
common steps in preparing tissue slides. 1,4-Dioxane has been used as a dehydrating agent for tissues
in the preparation of histological slides since the 1930s (Mossman, 1937). It is also used by biologists
to impregnate tissue sections with parafi n, and it has advantages in the preparation of histological
slides for electron microscopy (Shearer and Hunsicker, 1980). 1,4-Dioxane is preferred over ethanol
and xylene for dehydrating tissues because it removes water without causing substantial shrinkage or
hardening in the tissue (Ralph, 1938).
1,4-Dioxane is also useful for dissolving and removing mercuric chloride, a biocide formerly used
to preserve tissue samples. Tissue slides are also treated with stains or i xatives including dichromate
(orange) and chromium trioxide (sometimes called “chromic acid”—red). When treated with a 70%
1,4-dioxane solution, both chrome-based i xatives reduce to chromic oxide, which is green-brown (Winsor,
2006). Because 1,4-dioxane is an expensive reagent (about $75/L for histological grade in 2006), some
laboratories reclaim it by drying the 1,4-dioxane solution over a layer of calcium oxide or anhydrous
cupric sulfate or by freezing the 1,4-dioxane with water in a spark-proof refrigerator (Winsor, 2006).
1,4-Dioxane is used for extraction and analysis of plant material, for example, lignin in wood
samples. Analysis of wood samples involves hydrolyzing lignins and cellulose with a 1,4-dioxane
solution. Some procedures use 100% 1,4-dioxane for lignin extraction (Agarwal and Ralph, 1997).
The study of soil samples by x-ray diffraction and other applications requires drying. Drying can
be accomplished by introducing a hydrophilic solvent such as acetone or 1,4-dioxane. In some pro-
cedures, 1,4-dioxane is used to displace water; the 1,4-dioxane is subsequently displaced with a
resin to allow study of friable soil structures. 1,4-Dioxane is preferred for soil drying because it
preserves the soil structure better than acetone (Venediktova and Rudnyi, 1965; Moran et al., 1986,
1989; Chartres et al., 1989).
Preparation of water samples for the analysis of biodegradable analytes by ion-selective elec-
trodes may involve treating with a biocide carried by 1,4-dioxane. One recommended protocol uses
phenyl mercuric acetate as a biological inhibitor to treat water samples; 0.1 g is added to 20 mL of
1,4-dioxane, which is then diluted with deionized water to 100 mL of solution. A few drops of this
solution are added to the sample prior to storage and analysis (NICO2000, Ltd., 2006). 1,4-Dioxane
has been used as a reagent in various laboratory analytical methods, including detection of iodide