DEHP

Di-2-EthylhexylPhthalate. In Western Europe, di-2-ethylhexyl phthalate [117-81-7] (DEHP), also known as dioctyl phthalate (DOP), accounts for about 50% of all plasticizer usage and as such is generally considered as the industry standard. The reason for this is that it is in the mid-range of plasticizer properties. DEHP (or DOP) is the phthalate ester of 2-ethyIhexanol, which is normally manufactured by the dimerization of butyraldehyde (eq. 2), the butyraldehyde itself being synthesized from propylene (see Butyraldehydes). 

The widespread sales of this plasticizer are a redection of its all-around plasticizing performance and its provision of adequate properties for a great many standard products. It possesses reasonable plasticizing efficiency, fusion rate, and viscosity which, coupled with the normally competitive price, go a long way to explaining the popularity of this plasticizer. Some concerns have been periodically raised as to the possible toxicity of this material, but it can be said that these concerns are often related to the vast and widespread study of the toxicity of DEHP. 

The and C q iso-phthalates (DINP and DIDP) generally compete with DEHP as commodity general-purpose plasticizers. Other iso-phthalates are available at opposite ends of the carbon number range (eg, diisoheptyl phthalate (DIHP), C, and diisotridecyl phthalate (DTDP), but these serve more speciaUty markets. The Cg iso-phthalate, diisooctyl phthalate (DIOP), has also had traditional sales ia the commodity plasticizer markets where it is seen as an equivalent to DEHP. 

The Specialty Plasticizers. Eor the purpose of this article, the term specialty plasticizer refers to any plasticizer other than DEHP (DOP), DIOP, DINP, or DIDP. 

Nylon. The high degree of crystallinity in nylon means that plasticization can occur only at very low levels. Plasticizers are used in nylon but are usually sulfonamide based since these are generally more compatible than phthalates. DEHP is 25 phr compatible other phthalates less so. Sulfonamides are compatible up to 50 phr. 

Numerous toxicological studies have been conducted on a variety of plasticizers. However, because di-(2-ethylhexyl) phthalate (DEHP) is the most widely used plasticizer and is a well-defined single substance, it is the plasticizer that has been most thoroughly investigated in terms of its toxicology and has often been considered as a model for the other phthalates (36). 

Liver Effects. In 1980 a 2-year feeding study carried out as part of the NTP/NCI Bioassay Program in the United States (38,39) indicated that DEHP causes increased incidence of Hver tumors in rats and mice and that DEHA had a similar effect in mice but not rats. In these studies the levels of plasticizers fed were very high, this being possible only because of thek low acute toxicity. 

On the basis of these differences in species response it was concluded that phthalates do not pose a significant health hazard to humans. This view is home out by the EU Commission decision of July 25, 1990 which states that DEHP shall not be classified or labeled as a carcinogenic or an irritant substance (42). This has been reaffirmed in a comprehensive review (43) which concludes that "peroxisome proliferators constitute a discrete class of nongenotoxic rodent hepatocarcinogens and that the relevance of thek hepatocarcinogenic effects for human hazard assessment is considered to be negligible."... 

The International Agency for Research on Cancer (lARC) has classified DEHP (44) as "an agent possibly carcinogenic to humans." However this classification is based only on the rodent studies and does not take into account the more recent understanding of the underlying mechanisms. 

Phthalates in Air. Atmospheric levels of phthalates in general are very low. They vary, for DEHP, from nondetectable to 132 ng/m (50). The latter value, measured in 1977, is the concentration found in an urban area adsorbed on airborne particulate matter and hence the biological avaUabUity is uncertain. More recent measurements (52) in both industrial and remote areas of Sweden showed DEHP concentrations varying from 0.3 to 77 ng/m with a median value of 2 ng/m. ... 

Atmospheric photodegradation of DEHP and DBP has been shown to be rapid (51,53) with half-life times of less than 2 days, hence a large proportion of phthalate emissions to the air are broken down by photodegradation. 

In the most recent and comprehensive study, 230 measurements from 11 sampling points along 225 km of the Rhine and adjoining rivers were made over a period of one year (1991—1992). The concentration of DEHP found varied from 0.11 to 10.3 )-lg/L the latter value is unusually high as evidenced by the mean concentration of only 0.82 )-lg/L (55). 

These data together with those from wastewater treatment plants at Darmstadt, Germany Gothenburg and Stockholm, Sweden and Noord-Brabant, the Netherlands, show that the concentrations of DEHP, and in some cases total phthalates, entering wastewater treatment plants vary from 1 to 167 )-lg/L. After treatment the concentrations range from <1 to 36.8 )-lg/L. 

Atmospheric Toxicity. The only known atmospheric toxicity effect of phthalates is the phytotoxicity arising from the use of DBP plasticized glazing bars in greenhouses. However, the higher phthalates such as DEHP are not phytotoxic. General atmospheric concentrations of phthalates are extremely low and it is concluded that they pose no risk to plants or animals. 

Sediment Toxicity. Because of their low solubiUty ia water and lipophilic nature, phthalates tend to be found ia sediments. Unfortunately httle work has previously been carried out on the toxicity of phthalates to sediment dwelling organisms. Eor this reason ECPI has commissioned some sediment toxicity studies designed to measure the effect of DEHP and DIDP ia a natural river sediment on the emergence of the larvae of the midge, Chironomus riparius. 

Report prepared for CMA, Washington, D.C., Indoor DEHP Mir Concentrations Predicted after DEHP Volatilitiesfrom Vinyl Products, Environ. Corp., 1988. 

Figure 13.17 LC-GC-MS(EI) cliromatogram of a ti-eated drinking water containing 55 and 40 ng 1 , respectively, of DBF and DEHP. Reprinted from Journal of High Resolution Chromatography, 20, T. Hyotylainen et al., Reversed phase HPEC coupled on-line to GC by the vaporizer/precolumn solvent split/gas dischaige interface analysis of phthalates in water , pp. 410-416, 1997, with permission from Wiley-VCH.

Figure 13.17 shows the LC-GC-MS ehromatogram of treated drinking water eontaining 55 and 40 ng 1 of di-n-butylpthalate (DBF) and di(2-ethylhexyl)phtha-late (DEHP), respeetively. The PTV system therefore allows the LC eluent to be injeeted direetly and no ehange in the eomposition is needed. 

Contaminated solvents and glassware are a very well known problem in analysis involving extraction. The major problem in the use of solvents is contamination with plasticisers, especially DEHP. After sample extraction usually enrichment of the analytes is required prior to the analysis. 

Isolation of the products from complex matrixes (e.g. polymer and water, air, or soil) is often a demanding task. In the process of stability testing (10 days at 40 °C, 1 h at reflux temperature) of selected plastic additives (DEHA, DEHP and Irganox 1076) in EU aqueous simulants, the additive samples after exposure were simply extracted from the aqueous simulants with hexane [63]. A sonication step was necessary to ensure maximum extraction of control samples. Albertsson et al. developed several sample preparation techniques using headspace-GC-MS [64], LLE [65] and SPE [66-68]. A practical guide to LLE is available [3]. 

Work is in progress to validate the MAE method, proposed for EPA, in a multi-laboratory evaluation study. Nothing similar has been reported for additives in polymeric matrices. Dean el al. [452] have reviewed microwave-assisted solvent extraction in environmental organic analysis. Chee et al. [468] have reported MAE of phthalate esters (DMP, DEP, DAP, DBP, BBP, DEHP) from marine sediments. The focus to date has centred on extractions from solid samples. However, recent experience suggests that MAE may also be important for extractions from liquids. 

Cyclic oligomers of PA6 can be separated by PC [385,386] also PET and linear PET oligomers were separated by this technique [387]. Similarly, PC has been used for the determination of PEGs, but was limited by its insensitivity and low repeatability [388]. PC was also used in the determination of Cd, Pb and Zn salts of fatty acids [389]. ATR-IR has been used to identify the plasticisers DEHP and TEHTM separated by PC [390]. Although this combined method is inferior in sensitivity and resolution to modem hyphenated separation systems it is simple, cheap and suitable for routine analysis of components like polymer additives. However, the applicability of ATR-IR for in situ identification of components separated by PC is severely restricted by background interference. 

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