An Evaluation of the Preparation of Resin Samplers for Broad

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Downloaded by UNIV OF TEXAS EL PASO on August 18, 2014 | http://pubs.acs.org Publication Date: December 15, 1986 | doi: 10.1021/ba-1987-0214.ch012

An Evaluation of the Preparation of Resin Samplers for Broad Spectrum Analysis of Large-Volume Samples J. Gibs , L. Brenner, L. Cognet , and I. H . Suffet 1

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Environmental Studies Institute, Drexel University, Philadelphia, PA 19104 XAD resin cleaning by exhaustive extraction with a series of solvents was studied to observe if the resin cleaned in this manner was acceptable for use in broad spectrum capillary gas chromatographic (GC) analysis. Resin artifacts were always found in distilled water blanks after cleaning and after recleaning and reuse of the resin. The artifacts were identified by GC-mass spectrometry and compared to artifacts previously reported. Variations in artifacts were found between production lots. Several hypotheses are proposed for the existence of the resin artifacts after cleaning. Recommendations are given for storage, cleaning, blanking, and reusing resins for broad spectrum analysis of environmental samples.

^R.ESIN SAMPLERS are used to isolate nanogram to microgram amounts of organic compounds from samples of natural and treated waters. Sampling of waters by this method can be categorized as either lowvolume sampling (10 L). Table I indicates the sampling methods used during past environmental studies (1-25). Low-volume sampling is typically used for quantitative analysis for specific compounds, such as pesticides, polychlorobiphenyls (PCBs), and organic acids. Large-volume sampling is used to simultaneously Current address: U.S. Geological Survey, Water Resources Division, Trenton, NJ 08628 Permanent address: Lyonnaise des Eaux, Central Laboratory, 38 rue de Président Wilson, 78239 Le Pecq, France 1

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0065-2393/87/0214/0267$07.75/0 © 1987 American Chemical Society

In Organic Pollutants in Water; Suffet, I., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1986.


8-h sequential Soxhlet extraction with methanol, acetonitrile, and ethyl ether

110 Model compounds (10 L)

(A) 6-8X wash with ethyl ether (Β) 6-8X wash with methanol (A) 25 mL of methanol (B) 3 X 15 mL of water (A) wash with distilled water (B) 2 X 18-h Soxhlet extraction with acetonitrile (C) 10 bed volumes of distilled water

Cleanup

Broad spectrum analysis of drinking water (>10 L) Raw and treated drinking water « 1 0 L) Chlorinated pesticides in seawater (>10 L)

Model compounds and drinking water (10 L)

Sample Size and Compounds Studied

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(1) 1 X 4 bed volumes of acetonitrile or ethyl ether (2) 1 X 500 mL of water (3) combine 1 and 2 (4) extract 3 with 2 X 50 mL of n-hexane (1) 2 X 10 mL of ethyl ether (10 min) (2) 5 mL of ethyl ether (10 min) (3) 30 mL of methanol (4) store in methanol (1) wash with 2 L of distilled water (2) 8-h Soxhlet extraction with mixture of 150 mL of methanol and 100 mL of water

(1) 20 mL of 0.05 M NaHC0 (2) 20 mL of 0.05 M NaOH (3) 100 mL of methanol alternate method: (1) 100 mL of 1 M HC1 (2) 100 mL of 0.05 M HC1 (3) 100 mL of 0.05 M NaOH (4) 15 mL of ethyl ether 15-100 mL of ethyl ether (one elution) 20 mL of ethyl ether

Elution

Table I. Resin Cleanup and Elution Procedures for Resin Sampling


4

3

2

1

Ref


(A) wash with tap water (B) Soxhlet extraction: water (8 h), methylene chloride (24 h) (C) store in methanol

Model compounds in distilled water « 1 0 L)

13 Model compounds « 1 0 L and >10 L)

Organic acids « 1 0 L)

(A) wash with 1 L of water (B) 8-h sequential Soxhlet extraction with water, methanol, and 2X methylene chloride alternate method: (A) rinse with 20 L of water (B) continuous extractor (20-40 mL/min) with methanol (10-20 h), then methylene chloride (10-20 h) (A) wash 5X with 0.1 M NaOH (B) 24-h sequential Soxhlet extraction with methanol, acetonitrile, and ethyl ether wash successively (A) 1.5 L of acetone (B) 1.5 L of methanol (C) 1.5 L of methylene chloride or chloroform

see ref 5

EPA cleanup procedure for resin

Model pesticides and well water « 1 0 L and >10 L)

9

10

0.1 Ν NaOH

(1) 10 mL of acetone (2) 40 mL of chloroform (3) combine 1 and 2 alternate method: (1) 15 mL of acetone (2) 40 mL of chloroform (3) combine 1 and 2 continuous extractor: methylene chloride alternate method: Soxhlet extraction using methylene chloride or methanol (24 h)

Continued on next page.

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8

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(3) extract methanol-water mixture with 3 X 25 mL of n-hexane 3 X 15 mL of ethyl ether, 10 min between elutions, or 1 X 25 mL of ethyl ether, 10 min -



Chlorinated pesticides and PCB model compounds and natural water samples Broad spectrum analysis of drinking water « 1 0 L)

Model compounds and drinking water (>10 L)

Model compounds « 1 0 L and >10 L) Model pesticides and river water « 1 0 L and >10 L) Broad spectrum analysis of chlorinated river and seawater (>10 L)

Mutagens in natural samples « 1 0 L) Mutagens in natural waters (>10 L)

Sample Size and Compounds Studied

sequential Soxhlet extraction with methanol, acetonitrile, and ethyl ether

sequential Soxhlet extraction with methanol, pyridine, and ethyl ether, 8 h each see ref 5

see ref 5

(A) washed and Soxhlet extracted with acetone (16 h ) (Β) stored in acetone

Soxhlet extraction

Cleanup

Table I. Continued

1 X 25 to 30 mL of ethyl ether

ethyl ether or 10% acetone/90% ethyl ether (1) 125 mL of ethyl ether (2) concentrate and dissolve in benzene (3) fractionate by liquid chromatography see ref 5 and 7

XAD-2 with benzene XAD-7 with petroleum ether (1) washed with 3 bed volumes of distilled water (2) residual water blown out with dry nitrogen (3) elution with 4 bed volumes acetone (140 mL) 30 mL of ethyl ether

Elution


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17

16

15

14

13

12

Ref


Organic bases (10 L) Dissolved organic carbon in natural seawater (>10 L and 10 L)

9 Model compounds (10 L)

(A)rinseXAD-2 with water until free of chloride (B) sequential Soxhlet extraction with acetone, methanol, and water (24 h each) or (A) XAD-8 soaked in 0.1 M NaOH solution for 5 days, then same procedure as for XAD-2 Soxhlet extract: methanol, tetrahydrofuran, acetonitrile, acetone, ethyl ether, (10 h each), then dried at 50 °C overnight

(A) 250 mL of water (B) 250 mL of n-hexane ( C ) 250 mL of acetone (D) 250 mL of n-hexane (E) analyze by GC (F) if not clean, repeat D and Ε until clean (A) sequential Soxhlet extraction with methanol and ethyl ether (6 h) (B) 20 mL of ethyl ether (C) analyze Β by GC (D) repeat Β and C until clean (E) store in methanol sequential Soxhlet (4 h each) acetone, ethyl ether, and methanol Soxhlet extraction with methanol and acetone

22 ethyl ether at 0.8 bed volumes/min for 2 bed volumes

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25

(1) ammonium hydroxide solution (2) methanol, then ammonium hydroxide in methanol

15% methanol and 85% ethyl ether

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(1) 20 mL of ethyl ether (2) ethyl ether (10 min) (3) 2 X 20 mL of methanol

1 X 250 mL of n-hexane



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ORGANIC POLLUTANTS IN WATER

isolate f r o m a large sample as many trace organic compounds as possible. The extract f r o m the large-volume sample can then be (1) chemically analyzed for as many compounds as possible (broad spectrum analysis) or (2) used as a m e d i u m for bioassay studies such as the Ames test. Artifacts f r o m the resin can interfere with the chromatographic analysis of the X A D resin extract. F o r example, the artifact may be a pollutant being studied, or coelution of the resin artifacts and compounds of interest may occur during capillary gas chromatographic ( G C ) analysis. Artifacts can also take part in competitive adsorption during sampling. This situation can cause sample breakthrough because certain compounds are preferentially collected. Furthermore, many bioassay procedures can be affected synergistically or antagonistically b y artifacts. In current practice, chemists use various solvents to clean the resin as completely as possible, run a resin blank, and chromatographically analyze the blank sample. Rarely are the artifacts identified. This procedure does not help the biologist who requires a blank that does not show a positive response in the bioassay test of the blank. Biologists usually clean the resin as the chemists do and complete a blank for the bioassay. Artifacts should be identified to assure that the bioassay results are in response to the compounds under study and not the artifacts in combination with the sample. F o r these reasons, artifacts must be limited as part of a quality assurance program. As defined b y the American Chemical Society Committee on Environmental Improvement (26), "the objective of a quality assurance program is to reduce measurement errors to agreed upon limits and to assure that the results have a high probability of being acceptable quality." Cleaning and blanking procedures, therefore, must be carefully evaluated to assure reliable results f r o m broad spectrum analyses of large volumes of water. M a n y questions arise about the reliability of present methods because researchers have based large-volume sampling procedures on results f r o m low-volume procedures. Early studies using resins for isolation and analysis of trace organics, such as pesticides, P C B s , and organic acids, f r o m small volumes of water showed excellent recovery and the potential of easy application to environmental samples. Isotherm studies in distilled water were used to define the sampling parameters for quantitative analysis of these compounds. Later, studies using resin samplers for large-volume environmental samples were extrapolated f r o m the early low-volume resin work of Junk et al. (5,14) and Thurman et al. (27) (see Table I). The cleaning and blanking of early large-volume samplers of Bean et al. (16), Harvey (4), M c N e i l et al. (20), and Osterroht (6) d i d not undergo quality assurance; observations and results from low-volume



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GIBS ET AL.

273

Preparation of Resin Samplers

samplers were considered sufficient. In some cases, such as V a n Rossum and W e b b (JO), a low-volume sampler was used to design a highvolume sampler. The objective of this chapter is to evaluate and recommend procedures for cleaning, blanking, and reusing X A D resin samplers for broad spectrum analysis. Experimental studies were done to develop a methodology to minimize artifacts occurring after each procedure. T h e artifacts identified that reoccur during sampling processes are described. This work w i l l help develop quality assurance procedures for largevolume X A D resin sampling programs.

Chemical and Physical Properties of XAD Resins X A D - 2 resin is a styrene-divinylbenzene copolymer that has a highly aromatic structure. It has a surface area of about 300 m V g , an average pore diameter of 90 Â, and a maximum pore diameter of 290 Â. X A D - 8 resin is a methyl methacrylate copolymer and has a slightly more hydrophilic surface than X A D - 2 . It has a surface area of about 140 m /g, an average pore diameter of 250 Â, and a maximum pore diameter of 375-840 Â. E a c h exhibits different adsorption characteristics because of structural and surface chemistry differences. Both X A D resins have a significant number of micropores

An Evaluation of the Preparation of Resin Samplers for Broad

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