Phthalate ester, separation

The Separation of Some Phthalate Esters by Exclusion Chromatography on Styrene-Divinyl Benzene Based Gel... 

Phthalate esters C(H (COOR)2 are well-characterised, aoderately polar liquid phases [8]. As might be expected, the polarity of the phases declines as the alkyl (R) group increases in size, while their volatility decreases. Hi volatility compared to other available liquid phases has reduced their importance in recent years. Tetraunsaturated hydrocarbons and aromatic hydrocarbons (electron-donor solutes) Iqf... 

Figure 4.2 Separation of phthalate esters according to EPA methods 606 and 8060 by (a) fast temperature programming and (b) conventional CGC. Reproduced by permission of Thermedics Detection Inc.

C12 to C20, primarily Ci6 to ( is), used as surface lubricants in the manufacture of food-contact articles. The method, which uses ethyl palmitate (Eastman Chemicals No. 1575 Red Label) as an internal standard, has been validated at 200 ppm total FAME [185]. Other FAME standards (methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate) are available (Applied Science Laboratories) [116], Worked out examples of additive determinations are given in the Food Additives Analytical Manual [116], which also describes a great many of indirect food additives, such as BHA, BHT, TBHQ, l-chloro-2-propanol, DLTDP, fatty acid methyl esters, w-heptyl-p-hydroxybenzoate, propyl-gallate, sodium benzoate, sodium stearoyl-2-lactylate, sorbitol and phenolic antioxidants. EPA methods 606 and 8060 describe the CGC separation of phthalate esters (direct injection) (cf. Figure 4.2). 

The main features of PC are low cost, need for small sample amount, high level of resolution, ease of detection and quantitation, simplicity of apparatus and use, difficult reproducibility (because of variation in fibres) and susceptibility to chemical attack. Identification of the separated components is facilitated by the reproducible Rj values. Detection methods in PC have been reviewed [368]. Fluorescence has been used for many years as a means of locating the components of a mixture separated by PC or TLC. However, also ATR-IR and SERS are useful. Preparative PC is unsuitable for trace analysis because filter paper inevitably contains contaminants (e.g. phthalate esters, plasticisers) [369]. For that purpose an acceptable substitute is glass-fibre paper [28]. 

The different classes of compounds that have been successfully separated by MEKC include, among others, phenols [932,933], antioxidants [930,934], vitamins [935], phthalate esters [931,936] (Figure 4.26) and charged and neutral dyestuffs, including some dispersive dyes [937-939]. The separation of various priority... 

More problems are encountered with plasticisers because most extracts from polymer compositions are mixtures and, when separated by TLC, the amount of the individual fractions is often too small for convenient examination by 1H 1-NMR spectroscopy. Moreover, the original plasticisers themselves are often mixtures. For example, tricresyl (tritolyl)phosphate is based on mixed cresols, while most of the higher phthalate esters are based on complex mixtures of alcohols. 

This technique was used by Delmas et al. [404] to separate lipid extracts in seawater into various classes. Lipid classes that have been eluted away from the point of application may be burnt off the rod in a partial scan, allowing those lipids remaining near the origin to be developed into the place that has just been simultaneously scanned and reactivated. By analysis of complex mixtures of neutral lipids in this stepwise manner it is possible to be more selective about lipid class separations as well as to be more confident about assigning identities to peaks obtained from a seawater sample. In addition, this approach also reduces the possibility of peak contamination by impurities which would normally coelute with marine lipid classes (e.g., phthalate esters [403]). 

Although the metabolism of several phthalate esters has been studied in vitro, essentially all of the in vivo studies have involved DEHP. A summary of these experiments which involved exposure offish to aqueous - C-DEHP is presented in Table IV (11,12). Tissue C was isolated and separated into parent and the various metabolites by preparative thin layer chromatography on silica gel. Metabolites were hydrolyzed where appropriate and identified by gas chromatography-mass spectroscopy. In whole catfish, whole fathead minnow and trout muscle, the major metabolite was the monoester while in trout bile the major metabolite was the monoester glucuronide. The fact that in all cases the major metabolite was monoester or monoester glucuronide despite the differences in species, exposure level and duration, etc. represented by these data, suggests that hydrolysis of DEHP to monoester is important in the biotransformation of DEHP by fish. 

Figure 2. GPC separation of phthalate esters. Col imn Perkin-Elmer/PL gel 100 A.

Russell, D.J. McDuffie, B. (1983) Analysis for phthalate esters in environmental samples separation from PCBs and pesticides using dtral coltrrrm liqtrid chromatography. Int. J. environ, anal. Chem., 15, 165-183... 

Phthalate esters Diethyl phthalate, di-n-octyl phthalate Separated on a C-18, or C-8, reverse phase high temperature bonded silica column and UV detection at 254 nm also determined by gel permeation chromatography... 

Application of LC-MS/MS techniques to the analysis of phthalate ester metabolites in urine have also been developed. For example, Blount et al. (2000b) have developed an assay to quantify the monoester metabolites (including MEHP) of eight phthalate diesters in urine, utilizing HPLC coupled with atmospheric pressure chemical ionization and tandem mass spectrometric (APCI-MS/MS) detection techniques. Urine samples were treated with -glucuronidase to release the free phthalate monoesters followed by a two-step solid phase extraction procedure. After evaporative concentration of the eluant, the analytes in the purified samples are further separated on a phenyl reverse phase HPLC column and quantified by APCI-MS/MS, following careful optizimation of the APCI-MS/MS instrument. The limits of detection for MEHP were determined to be 1.2 ng/ml urine with recovery efficiencies of between 78 and 91%. 

Plasticiser Soften polymer, reduce Tg Separates polymer chains from each other Phthalate esters, aliphatic diesters, epoxidised oils, phosphate esters, polyesters... 

A typical Soxhlet procedure was employed by Ruminski et al. to extract DEHP from very polluted soil using hexane as the extraction solvent and changing to methanol for LC analysis. Soxhlet was also used to extract phthalate esters from dust and from airborne fallout." " In the latter case, the material was trapped in nylon nets impregnated with silicone oil (SE-30) and further cleanup processes were needed afterwards to separate the oil from the phthalate esters extracted. 

Some studies on the application of electrophoretic techniques to the separation of phthalate esters can be found in the literature.In these cases, micellar electrokinetic chromatography (MEKC) allowed the study of the migration of phthalate esters in different electrophoretic media. 

Supercritical fluid chromatography was coupled online to Proton High Field Nuclear Magnetic Resonance Spectroscopy by an specially designed pressure-proof continuous-flow probe head. Separation of phthalate esters was carried out under supercritical conditions using carbon dioxide as eluent. ... 

Zurmiihl, T., Development of a method for the determination of phthalate esters in sewage sludge including chromatographic separation from polychlorinated biphenyls, pesticides and polyaromatic hydrocarbons, Ana/yjr, 115, 1171-1175, 1990. 

Students must first optimize the separation of the esters using RP-HPLC, record and store the ultraviolet absorption spectra of the separated esters, and compare the spectrum of the unknown against the stored UV spectra. In addition, staff will be available to conduct the necessary GC-MS determination of the unknown. A hardcopy of the chromatogram and mass spectrum will be provided so that the student will have additional confirmatory data from which to make a successful identification of the unknown phthalate ester. 

First, find the mobile phase solvent strength which optimizes the separation of the four phthalate esters. Second, retrieve the UV absorption spectrum for each of the four and build a library. Third, inject the unknown sample and retrieve its UV spectrum. Fourth, make arrangements with the staff to get your unknown sample analyzed using GC-MS which is available at the Research Complex-Engineering. 

Udris [85] discusses the problem of the detection of organotin stabilisers and phthalate ester plasticisers when they are present together in solvent extracts of PVC. He points out that IR spectroscopy whilst it may show the presence of major components of such mixtures may miss the minor ones which may also be present, such as, phenol derivatives and metal carboxylates. These can be separated and identified by TLC followed by IR or UV spectroscopy. 

Also using silica gel G layers, Bbaun [4, 5] has separated numerous plasticisers with methylene dichloride, after they had been extracted from the plastic material with benzene or ether (provided the polymer itself was not soluble). Antimony(V)chloride (Rgt. No. 18) is a generally applicable spray reagent it yields brown spots with most of the plasticisers after the plate is heated to 120° C. Phthalate esters can be detected in addition with resorcinol solution (Rgt. No. 218) and phosphate esters with a diazonium salt reagent (No, 238). 

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