Cleanup sediment samples

Analysis of methyl parathion in sediments, soils, foods, and plant and animal tissues poses problems with extraction from the sample matrix, cleanup of samples, and selective detection. Sediments and soils have been analyzed primarily by GC/ECD or GC/FPD. Food, plant, and animal tissues have been analyzed primarily by GC/thermionic detector or GC/FPD, the recommended methods of the Association of Official Analytical Chemists (AOAC). Various extraction and cleanup methods (AOAC 1984 Belisle and Swineford 1988 Capriel et al. 1986 Kadoum 1968) and separation and detection techniques (Alak and Vo-Dinh 1987 Betowski and Jones 1988 Clark et al. 1985 Gillespie and Walters 1986 Koen and Huber 1970 Stan 1989 Stan and Mrowetz 1983 Udaya and Nanda 1981) have been used in an attempt to simplify sample preparation and improve sensitivity, reliability, and selectivity. A detection limit in the low-ppb range and recoveries of 100% were achieved in soil and plant and animal tissue by Kadoum (1968). GC/ECD analysis following extraction, cleanup, and partitioning with a hexane-acetonitrile system was used. 

Phase 2. In the seeond phase of the study, the partieipants were asked to analyze three extraeted and cleaned sediment samples using the DR CALUX bioassay. Sediments used for extraetion and cleanup were freshwater sediments from the Western Seheldt, The Netherlands. The sediment extracts were prepared by the Royal Institute for Fishery Research (RIVODLO), IJmuiden, The Netherlands, aeeording to the protoeol given here. Dilutions of the supplied sediment extracts were prepared by the partieipants in DMSO and tested for dioxin and/or dioxinlike content. On each 96-well mierotiter plate, a 2,3,7,8-TCDD standard ealibration curve was analyzed. Raw data as well as eonverted data were used for statistieal evaluation. 

Cleanup of sediment samples. The extracted sediment samples were cleaned up using a multilayer column. The multilayer glass column consisted of the following materials (from top to bottom) 1 cm water-free sodium sulfate, 1 g silica, 7 g 44% sulfuric acid on silica, 1 g silica, 2 g 33% sodium hydroxide on silica, 1 g silica, 1.5 g 10% silver nitrate on silica, and a small piece of silanized glass wool. After addition of each layer, the column was compacted by tapping... 

The interlaboratory results obtained from the analysis of defined standard solutions, but also from the analysis of sediment extracts prepared either by the coordinator of the study or by the participants themselves, also provide a measure of the variation between laboratories. The results show that the interlaboratory reproducibility ranges from 6.5% for the defined dioxin sample to 27.9% for the sediment sample extracted by the participants themselves. As was mentioned before, the reproducibility for this last sample is relatively high and most presumably due to the introduction of extra handlings (extraction and cleanup) to the total procedure. In addition, the fact that not all the participants had prior experience with the extraction protocol to be used could have added to the increase in variability of the process. Furthermore, the dilution factor was not dictated. This also introduces a certain degree of variation. For the reproducibility of the DR CALUX bioassay itself and not caused by differences in operating extraction conditions, the maximum variation between laboratories was observed to be 18.0%. The results for the sediment extract samples can also be used to estimate the method variability for extracts, that is, based on samples of unknown composition. Again, given the intra-as well as the interlaboratory variations observed in this study, it appears justified to conclude that the standard deviation of the means provides a reasonable estimate of the method variability, based on the overall aver-... 

Sulfur is found in many industrial wastes, marine algae, and sediment samples. Sulfur may mask the region of chromatogram, overlapping with peaks of interest. For example, in pesticides analysis, sulfur can mask over many pesticides such as lindane, aldrin, and heptachlor. Sulfur has a solubility similar to the organochlorine and organophosphorus pesticides and it cannot be separated by Florisil cleanup method. 

As analytical capabilities improve, multiple procedures are linked together in series to effect analyses. Procedures combined in this manner are called hyphenated techniques. Ferrer and Furlong [124] combined multiple techniques—accelerated solvent extraction (ASE) followed by online SPE coupled to ion trap HPLC/MS/MS—to determine benzalkonium chlorides in sediment samples. Online SPE, especially coupled to HPLC, is being used more routinely. This approach allowed online cleanup of the ASE extract prior to introduction to the analytical column. 

Nam KS, Kapila S, Yanders AF, Puri RK (1990), Chemosphere 20 873-880.. .Supercritical fluid extraction and cleanup procedures for determination of xenobiotics in biological samples" Onuska FI, Terry KA (1989), HRC CC12 357-361.. .Supercritical fluid extraction of 2,3,7,8-tetrachlorodibenzo-p-dioxin from sediment samples"... 

While all planar aromatic PLACs and RPCBBs of interest were persistent against sulfuric acid, the cleanup of the evaporated extract in hexane was started by sulfuric acid shaking or with sulfuric acid impregnated on a silica column [43,56]. For sediment samples, elemental sulfur interference was eliminated using copper activated with HC1 [43, 57]. Further cleanup of PLACs was done according to Scheme 1 [43]. 

Plutonium Purification. The same purification approach is used for plutonium separated from sediments or seawater. In case reduction may have occurred, the plutonium is oxidized to the quadrivalent state with either hydrogen peroxide or sodium nitrite and adsorbed on an anion exchange resin from 8M nitric acid as the nitrate complex. Americium, curium, transcurium elements, and lanthanides pass through this column unadsorbed and are collected for subsequent radiochemical purification. Thorium is also adsorbed on this column and is eluted with 12M hydrochloric acid. Plutonium is then eluted from the column with 12M hydrochloric acid containing ammonium iodide to reduce plutonium to the non-adsorbed tervalent state. For seawater samples, adequate cleanup from natural-series isotopes is obtained with this single column step so the plutonium fraction is electroplated on a stainless steel plate and stored for a-spectrometry measurement. Further purification, especially from thorium, is usually needed for sediment samples. Two additional column cycles of this type using fresh resin are usually required to reduce the thorium content of the separated plutonium fraction to insignificant levels. 

These results therefore suggest a careful evaluation of the pros and cons of supercritical fluids. Another study that included PCBs showed good agreement between Soxhlet extraction and dynamic supercritical fluid extraction of soil samples with the added advantage that no cleanup step was needed with the latter (van der Velde et al. 1992). A combined extraction using C02 and acetylation with acetic anhydride and triethylamine has been used for the analysis of chlorophenolic compounds in soil (Lee et al. 1992) and air-dried sediment samples (Lee et al. 1993). This is both rapid and gives results comparable to those using conventional methods of steam distillation. 

The procedure for extraction is the same as that described for sediment samples i.e. soxhlet extraction, except for the preparation of the material. The amount of material extracted depends upon the lipid content because the more the fatty material in the tissue the more pre-injection cleanup is required. Thus, for a fish liver sample, about 2g of material is extracted. For muscle tissue, which contains less fatty material, the sample weight can be increased to about 5g. The lipid content is determined on a separate amount of sample by extracting with petroleum ether and evaporating the extract to constant weight over a steam bath. 

Concentration using aCi8 SPE Continuous-flow (methanol), high-temperature (65°C), sonicated extraction system to isolate APEO metabolites from sediment samples (low-power ultrasonic energy) sediment extraction was complete after 7 min with a total solvent consumption of 3.5 ml/sample two-step cleanup, normal-phase SPE, reversed-phase... 

The sample was submitted to MAE using acetone-n-hexane (1 1, v/v) mixture for sediment samples and methanol 112 or methanolic 1 M KOH for biological samples. Extract solution was centrifuged and evaporated just to dryness. Residues were dissolved in 1 ml of n-hexane. Cleanup was performed on a Si02/Al203. PCBs were eluted with n-hexane... 

Relatively simple cleanup steps have been used in some analytical methods for BFRs. For example, in determination of PBDEs in human mUk, the dominating PCB congeners in the LEE extract were removed by passage through a sihca column. A similar method was used for PBDEs, toxaphene, and chlordane compounds in seal blubber extracts. The hquid extracts after treatment with sulphuric acids in hexane were purified twice by silica gel column, and after elution of PCBs with hexane the analytes were eluted with a mixture of hexane and diethyl ether. PBBs and DeBDE have also been eluted from sihca gel with isooctane, and other PBDEs with diethyl ether isooctane, as was done with Soxhlet extracts of various marine mammals after treatment of the extract with sulphuric acid." Alumina columns have been used in a similar manner for Soxhlet extracts of sediment samples in the determination of PBDEs. Concentrated acetone hexane extract was passed through an alumina column and BFRs were eluted with hexane. ... 

The use of supercritical fluid extraction (SEE) as an extraction technique is related to the unique properties of the supercritical fluid. These fluids have a low viscosity, high diffusion coefficients, low toxicity, and low flammability, all clearly superior to the organic solvents used in SPE extraction. The most common fluid used is carbon dioxide. SEE extractions of sediment samples have shown recoveries of >95% for all the individual PCBs. The separation of PCDDs from PCBs and chlorinated benzenes is difficult because of their similar solubility. An interesting development is the use of fat retainers. Samples, mixed in different weight ratios with, e.g., silica/silver nitrate 10% or basic alumina, can be placed in 7 ml extraction cells. The analytes are recovered by elution with 1.5-1.8 ml of hexane. With the correct fat-silica ratios and SEE conditions, no additional cleanup procedure is necessary for GC with an electron-capture detector (ECD). One drawback of SEE may be that the methods developed are valid for a specific matrix, but as soon as, e.g., the fat content of a biota sample or the type of lipids changes, the method has to be adapted. SEE is relatively complicated compared to other extraction techniques. In addition, the cell volumes are small, which limits the sample intake, and, with that, the detection limits. Einally, some reliable types of SEE equipment have recently been withdrawn from the market. This will have a substantial negative effect on the use of SEE in the near future. 

Preparation of soil—sediment of water samples for herbicide analysis generally has consisted of solvent extraction of the sample, followed by cleanup of the extract through Uquid—Uquid or column chromatography, and finally, concentration through evaporation (285). This complex but necessary series of procedures is time-consuming and is responsible for the high cost of herbicide analyses. The advent of soUd-phase extraction techniques in which the sample is simultaneously cleaned up and concentrated has condensed these steps and thus gready simplified sample preparation (286). 

Preparative TLC may be applied to cleanup selected compound fractions separated from geochemical samples by such methods as HPLC, as Aries et al. [113] has described. To analyze phospholipids and nonphospholipids in sediments, organic matter was extracted and extracts LC-fractionated to obtain polar fractions. At the... 

For pesticide residue immunoassays, matrices may include surface or groundwater, soil, sediment and plant or animal tissue or fluids. Aqueous samples may not require preparation prior to analysis, other than concentration. For other matrices, extractions or other cleanup steps are needed and these steps require the integration of the extracting solvent with the immunoassay. When solvent extraction is required, solvent effects on the assay are determined during assay optimization. Another option is to extract in the desired solvent, then conduct a solvent exchange into a more miscible solvent. Immunoassays perform best with water-miscible solvents when solvent concentrations are below 20%. Our experience has been that nearly every matrix requires a complete validation. Various soil types and even urine samples from different animals within a species may cause enough variation that validation in only a few samples is not sufficient. 

Extraction and cleanup techniques for soil and water samples are described in other articles, and only comments specific to sediments are included here. 

A rapid and simple method for PBDE and HBCD determinations in sediment and fish samples was used. The analytical method was based in selective pressurized liquid extraction (SPLE) [21] without further cleanup step and analysis by gas chromatography coupled to mass spectrometry (GC-MS), working with negative ion chemical ionization (NCI) [22, 23],... 

PCBs in biological samples are usually extracted by a Soxhlet column and with a nonpolar solvent such as hexane. The sample is first mixed with sodium sulfate to remove moisture. The extraction of PCBs from sediments was tested with sonication, with two sonications interspersed at a 24-h quiescent interval, with steam distillation, or with Soxhlet extraction (Dunnivant and Elzerman 1988). Comparison of the recoveries of various PCB mixtures from dry and wet sediments by the four techniques and the extraction efficiency of four solvents showed that the best overall recoveries were obtained by Soxhlet extraction and the two sonication procedures. In comparisons of solvent systems of acetone, acetonitrile, acetone-hexane (1+1), and water-acetone-isooctane (5+1.5+1), recoveries of lower chlorinated congeners (dichloro- to tetrachloro-) were usually higher with acetonitrile and recoveries of higher chlorinated congeners (tetrachloro- to heptachloro-) extracted with acetone were superior (Dunnivant and Elzerman 1988). The completeness of extraction from a sample matrix does not seem to discriminate against specific isomers however, discrimination in the cleanup and fractionation process may occur and must be tested (Duinker et al. 1988b). 

Lopez-Avila et al. [59] used microwave assisted extraction to assist the extraction of polyaromatic hydrocarbons from soils. Another extraction method was described by Hartmann [60] for the recovery of polyaromatic hydrocarbons in forest soils. The method included saponification of samples in an ultrasonic bath, partitioning of polyaromatic hydrocarbons into hexane, extract cleanup by using solid-phase extraction, and gas chromatography-mass spectrometric analysis using deuterated internal standards. Polyaromatic hydrocarbons were thermally desorbed from soils and sediments without pretreatment in another investigation [61]. 

---