Soxhlet extraction resin cleanup

Sample Extraction and Cleanup. The sample extraction method has been described previously (27, 28). Prior to extraction, 100 pL of a dio-fluoranthene surrogate standard solution (0.82 ng/pL) was added to each sample. The XAD-2 resin was extracted for 24 h in a Soxhlet apparatus with -350 mL hexane/acetone (50/50 v/v). The extract volume was then reduced to -100 pL using rotary evaporation followed by evaporation... 

Figure 1 shows that the final XAD-2 and XAD-8 resin Soxhlet extraction by ether contains 46 and 17 GC peaks, respectively. Of these GC peaks, 33 (XAD-2) and 12 (XAD-8) were observed within the first third of the chromatograms. The number of GC peaks in the final cleanup step was felt to be too many for broad spectrum sampling and analysis because the concentrates of the sample extracts are at least 200-fold more concentrated. 

Table II. XAD Resin Cleanup by Soxhlet Extractions GC-MS Tentative Identifications by Computer Search...

Figure 2. Capillary GC profiles of resin cleanup blanks and after Soxhlet extraction and sample elution quality control blanks. Y-axis 1 E-2 to 1 E2 = 0.6 to 600 ng/L. Resin blanks solvent blank (bottle blank) XAD-2 cleanup 900 mL of etherZ700 mL of resin XAD-8 cleanup 900 mL of ether/700 mL of resin fourth elution solvent 100-mL elutions after 150 mL, 2 X 100-mL elution with...

Figure 3. Capillary GC profile comparison of resin cleanup procedures by ultrasonic bath and Soxhlet extraction. Y-axis 1E2 — 0.005 ng/L to 1 E4 = 0.5 ng/L. The resin was extracted with methanol, acetonitrile, and methylene chloride. Fifty milliliters of resin was placed in a column and eluted with 2 bed volumes (50 mL) of methylene chloride. The third bed volume was concentrated to 1 mL, and 2.5 pL was injected into the GC. This sample represents a sample elution quality assurance control blank.

Table V lists the common solvents used for cleaning XAD resins and their respective solubility parameters. Methanol and acetonitrile [which are used in the cleanup procedure of Junk et. al. (5)] have very different total solubility parameters than the compounds listed in Table IV. Thus, they should be less efficient for eluting the resin contaminants from the resin polymers. This situation explains the GC profile results, which show large numbers and high concentrations of contaminants after the successive 24-h Soxhlet extractions using methanol, acetonitrile, and ethyl ether (Figure 2).

The resin cleanup procedure employed during this project used Soxhlet extraction with the same solvents used for elution. This method assured that any impurities were eluted prior to the actual adsorbent studies. Combining the best recommendations from previous studies, the following purification procedure was used in our laboratory ... 

The XAD-4 quaternary resin was cleaned by Soxhlet extraction and kept wet under water to minimize artifacts from the resin. An oily, yellow residue observed during concentration of the acidic eluants required an additional cleanup step. On the basis of the results of the resin blank experiments, it was necessary to clean the XAD-4 quaternary resin by batch process with saturated HCl/methanol prior to Soxhlet cleaning with solvents. Artifacts such as benzoic acid were found in the resin blank experiments, but, in general, the mass of each artifact (per dry weight of resin) was negligible. 

Filtration only filter washed with MeOH Soxhlet extraction with MeOH SPE on anion exchanger (elution with 95 5 MeOH/con HCl) derivatization further cleanup with alumina, silica, copper SPE on graphitized carbon black (elution with 9 1 CH2Cl2/MeOH,0.01 M in tetra-methylammonium hydroxide) derivatization further cleanup with alumina SPE on graphitized carbon black (elution with 9 1 CH2Cl2/MeOH, 0.02 M in tetra-butylammonium bisulfate) butyl esters formed in GC injection port Liquids. SPE on Cm resin for the lower concentrations and Cm disks for the higher solids MeOH extraction extracts were cleaned up by anion exchange and additional SPE on Cm... 

Atmosphere adsorption on polyurethane foam (desorption by Soxhlet extraction with petroleum ether) alumina fractionation (elution with 2 1 MeOH/ CH2CI2) water. SPE on XAD-2 resin Matrix solid phase dispersion extraction with Cijj (MeOH elution) AI2O3 cleanup of MeOH eluate SPE on poly(styrene/divinylbenzene) disk (elution with acetone, MeCl2, hexane) NP-HPLC fractionation Water. SPE on Cig (acetone elution) sediment and algae Soxhlet extraction with hexane cleanup by SPE NH2 media (elution with 75 25 hexane/acetone)... 

A resin to be cleaned was packed into a 3-L capacity addition funnel and washed first with two volumes of high-purity water. The MSC-1 resin was then washed sequentially with 2 bed volumes of 2.0 N HC1, 5 bed volumes of high-purity water, 2 bed volumes of 1.5 N NaOH, and 5 bed volumes of high-purity water these HC1, water, NaOH, and water washes were then repeated. The same procedure was carried out with A-162, except that the order of acid and base was reversed. The resins were then extracted for at least 16 h in methanol in a Soxhlet apparatus. The final cleanup steps for MSC-1 consisted of a sequential elution with 2 bed volumes of methanol, 1 bed volume of 1.0 N NH3 in 122 methanol/882 methylene chloride (made as described later), 2 bed volumes of 122 methanol/882 methylene chloride (solvent 1), and 3 bed volumes of methanol. The same steps were used with A-162 except that HC1 replaced NH3 in the second wash. The resins were considered to be clean at this point, and they were stored in methanol. 

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