Soxhlet extractions determinations

The first step for the determination of PAHs is removal from the matrix by solvent extraction, which preferably is performed with boiling toluene or benzene (hot solvent extraction by refluxing see Jacob and Grimmer 1994), although other solvents (e.g. tol-uene/acetone, acetone, and dichloromethane) and other extraction procedures (ultrasonic treatment, Soxhlet extraction, and accelerated solvent extraction) can also be applied. 

Soxhlet extraction followed by liquid chromatography/photodiode-array detection (LC/PAD) is used for the trace determination of propanil and its major metabolite, 3,4-dichloroaniline, in soil. A 10-g soil sample is extracted with methanol in a Soxhlet system for 8 h. After the extracts have been concentrated to dryness, the residue is dissolved in 500 pL of n-hexane. °... 

The recoveries of clomeprop and its metabolite DMPA in soil after extraction with acetonitrile-water (4 1, v/v) by HPLC/UV (234 nm) are >90% The recoveries of propanil and its metabolite, 3,4-dichloroaniline, in soil are 95 and 76%, respectively, by Soxhlet extraction and LC/PAD determination. Diflufenican is added to soil in the range 0.002-0.008 mg kg to validate the method developed by Conte et al. The average recovery from the soil by this method is 92 5%. 

Standardisation of EPDM characterisation tests (molecular composition, stabiliser and oil content) for QC and specification purposes was reported [64,65]. Infrared spectroscopy (rather than HPLC or photometry) is recommended for the determination of the stabiliser content (hindered phenol type) of EP(D)M [65]. Determination of the oil content of oil-extended EPDM is best carried out by Soxhlet extraction using MEK as a solvent [66], A round robin test was reported that evaluated the various techniques currently used in the investigation of unknown rubber compounds (passenger tyre tread stock formulations) [67]. 

Applications The determination and quantification of oligomers from PET has been carried out using various techniques Soxhlet extraction followed by gravimetric analysis with identification by HPLC-DAD, selective precipitation of the polymer (from a trifluoroacetic acid solution), and chloroform extraction under pressure in a sealed Parr bomb [112]. Heating of a 1 g sample in 20 mL chloroform at 100 °C for 2h allows a precision of 5 %. 

Oligomers in HDPE are readily determined gravi-metrically by using the so-called cyclohexane extracta-bles test. In this method, a small quantity of PE resin is Soxhlet extracted with cyclohexane and determined gravimetrically after drying. The test does not give the MW(D) of the extracted species. 

An important QC analysis in the fibre and textile industry is the surface finish determination by Soxhlet extraction (AATCC Test Method 94-1992). Solvent extraction is used on textile materials to determine naturally occurring oily and waxy materials that have not been completely removed from the fibres (ASTM Method D 2257-96). Meanwhile, environmental, safety... 

Applications The method is in use for the determination of water extractable organics in PA6 and PA4.6, and for alkane extraction of waxes from HDPE (in nitrogen atmosphere to prevent oxidation) [156]. Ethylene-bis-stearamide (EBA) can be extracted from ABS in 30 min using intermittent extraction in this case quantitative Soxhlet extraction was not possible. Nelissen [157] has used intermittent extraction with MTBE for the analysis of the flame retarder system of Tribit 1500 GN30. 

Soxhlet extraction is well established, and generally exhaustively extracts all additives. The selection of extraction solvent can make large differences to the extraction time. The generally long extraction times followed by concentration steps may determine losses of volatile or thermally labile components. Because this form of extraction is one of the oldest and still widely used in industry, it is the standard to which many of the newer extraction technologies (which are likely to determine future applications) are referred. However, it should be realised that extraction mechanisms may be different, and thus comparisons are sometimes irrelevant. 

Chromatographic methods were developed for the systematic determination of five classes of additives in PE for food packaging [170]. In Soxhlet extractions phenolic AOs and acid amides were determined by HPLC and CGC, respectively. Thiodipropionic acid esters were determined by HRGC as higher alcohols obtained after saponification of the extracts with KOH. Glycerol fatty acid esters and stearates were determined... 

Normal-phase chromatography is still widely used for the determination of nonpolar additives in a variety of commercial products and pharmaceutical formulations, e.g. the separation of nonpolar components in the nonionic surfactant Triton X-100. Most of the NPLC analyses of polymer additives have been performed in isocratic mode [576]. However, isocratic HPLC methods are incapable of separating a substantial number of industrially used additives [605,608,612-616], Normal-phase chromatography of Irgafos 168, Irganox 1010/1076/3114 was shown [240]. NPLC-UV has been used for quantitative analysis of additives in PP/(Irganox 1010/1076, Irgafos 168) after Soxhlet extraction (88%... 

NMR spectroscopy is most effective in qualitative analysis when the samples examinated are substantially pure compounds and has been used to confirm the theoretically predicted low-energy conformations of the Af-acylated hindered amine light stabiliser Tinuvin 440 [210]. Trace amounts of PDMS (quantification limit 0.1 ppm) in plastic additives, dyes and pigments were determined by 111 NMR after Soxhlet extraction [211]. ll NMR was also used for the detection of octadecanol, an impurity in Irganox PS 802 (3,3 -dioctadecyl thiodipropionate). NMR has identified the nature of a supposedly UV stabiliser of empirical formula C17H18N3CIO [44] (Scheme 5.2). 

Occasionally there is the need for simultaneous determination of MW, MWD of polymers and identifica-tion/quantilication of additives [38]. This was the case for polymer and additive analysis of SBR/(softeners, flavour agents, stabilisers) (chewing gum) [41]. The many constituents of the SBR portion of the sample were not resolved, since adjacent components were similar in size. It should be stressed, however, that the need for simultaneous determination of the molecular weight of polymers and the identification/quantification of additives is exceptional rather than the rule. The determination of molecular weight distributions by SEC has indicated that oligomer fractions analysed by dissolution and (Soxhlet) extraction methods may differ essentially [42],... 

The explosive decomposition of the solid has been studied in detail [6], The effect of moisture upon ignitibility and explosive behaviour under confinement was studied. A moisture content of 3% allowed slow burning only, and at 5% ignition did not occur [7], Thermal instability was studied using a pressure vessel test, ignition delay time, TGA and DSC, and decomposition products were identified [8], The presence of acyl chlorides renders dibenzoyl peroxide impact-sensitive [9], There is a further report of a violent explosion during purification of the peroxide by Soxhlet extraction with hot chloroform [10], Residual traces of the peroxide in a polythene feed pipe exploded when it was cut with a handsaw [11]. The heat of decomposition has been determined as 1.39 kJ/g. The recently calculated value of 69° C for critical ignition temperature coincides with that previously recorded. 

Thermal desorption mass spectrometry is a rapid technique for the determination of oil in soils and sediments [9]. This method exhibited lower analytical variance compared to Soxhlet extraction, i.e. followed by conventional analysis. The analysis time for wet soil samples was about 20min. 

Onuska and Terry [14] have described a method for the determination of chlorinated benzenes in bottom sediment deposits. Sample preparation methods using Soxhlet extraction, ultrasonic extraction or steam distillation were compared. The chlorinated benzenes were characterized by open tubular column gas chromatography with electron capture detection. In recovery studies using sediments with different organic matter contents, the steam distillation method was the most efficient. Detection limits were in the range 0.4-10pg kgy1. 

Lee [42] determined pentachlorophenol and 19 other chlorinated phenols in sediments. Acidified sediment samples were Soxhlet extracted (acetone-hexane), back extracted into potassium bicarbonate, acetylated with acetic anhydride and re-extracted into petroleum ether for gas chromatographic analysis using an electron capture or a mass spectrometric detector. Procedures were validated with spiked sediment samples at 100,10 and lng chlorophenols per g. Recoveries of monochlorophenols and polychlorophenols (including dichlorophenols) were 65-85% and 80-95%, respectively. However, chloromethyl phenols were less than 50% recovered and results for phenol itself were very variable. The estimated lower detection limit was about 0.2ng per g. 

Johnson and Van Emon [57] have described a quantitative enzyme based immunoassay procedure for the determination of polychlorinated biphenyls in soils and sediments and compared the results with those obtained by a gas chromatographic method. The soil is extracted with methanol, or Soxhlet extracted or extracted with a supercritical fluid. In the case of the latter two extractants good agreement was obtained between immunoassay and gas chromatographic methods. Spiking recoveries from soil achieved ranged from 104% (Aroclor 1248) to 107% (Aroclor 1242). Detection limits were 9pg kg-1 (Aroclor 1245) and 10.5pg kg-1 (Aroclor 1242). Chlorinated anisoles, benzenes or phenols did not interfere. 

The supercritical fluid chromatographic procedure [20] described in section 9.1.1.5 for the determination of organochlorine insecticides in soils has also been applied to river sediments. Snyder et al. [20] compared supercritical fluid extraction with classical sonication and Soxhlet extraction for selected organochlorine insecticides. Samples of sediments extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave =85% recovery of organochlorine insecticides including Dichlorvos, Diazinon, Endrin, Endrin aldehyde, decachlorobiphenyl, p,p -DDT and Mirex. 

Snyder et al. [94] compared supercritical extraction with classical sonication and Soxhlet extraction for the extraction of selected organophosphorus insecticides from soil. Samples extracted with supercritical carbon dioxide modified with 3% methanol at 350atm and 50°C gave a =85% recovery of Diazinon (diethyl-2-isopropyl-6-methyl-4-pyrimidinyl phosphorothiodate or 0,0 diethyl-0-(2-isopropyl-6-methyl-4-pyrimidyl) phosphorothioate). Ronnel (or Fenchlorphos) 0,0-dimethyl-0-2,4,5 trichlorophenol phosphorothiodate), Parathion ethyl (diethyl-p-nitrophenyl (phosphorothioate), Tetrachlorovinphos (trans,-2-chloro-l-(2,4,5 trichlorophenyl) vinyl (chlorophenyl-O-methylphenyl phosphorothioate) and Methiadathion. Supercritical fluid extraction with methanol modified carbon dioxide has been applied to the determination of organophosphorus insecticides in soil [260]. 

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