Storing soil samples

Greenhalgh, R. and Belanger, A. Persistence and uptake of carbofuran in a humic mesisol and the effects of drying and storing soil samples on residue levels, J. Agric. Food Chem., 29(2) 231-235, 1981. 

Bartlett, R. and James, B. (1980) Studying dried, stored soil samples - some pitfalls. Soil Sci. Soc. Am.J., 85, 721. 

Store soil sample in plastic container which has been sieved through 2 mm mesh to prevent drying. Analyse on the same day. 

A soil sample was taken from a field, transported back to the laboratory by road and stored for three weeks prior to analysis. The analytical procedure consisted of drying the soil in an oven at 100°C for 24 h before the analyte was extracted using 200 cm of dichloromethane. This extract was reduced in volume to 200 til and a 20 p.l aliquot then analysed by HPLC. A calibration was set up by measuring the response from a number of solutions containing known concentrations of the analyte. The resnlt obtained from the unknown , after suitable mathematical manipulation, indicated the original soil sample contained 20 0.05 mgkg of the analyte. Comment on the accuracy of this result. 

In the laboratory, soil samples collected in the held are mixed thoroughly and reduced in size to laboratory samples. The air-dried soils are passed through a 2-mm sieve in order to remove stones and roots, then the water content of the soil is calculated after drying at 105 °C for 5h. If the analytical samples cannot be analyzed immediately after drying and sieving, they should be stored at about —20 °C in glass or Teflon bottles fltted with screw-caps. 

Ultrasonication was reported for the extraction of triazines from soil, previously sieved to 2 mm and stored at -18 °C, prior to analysis using CC/NPD and CC/lTD. A 5-g soil sample was placed in a polypropylene column and extracted for 15 min with 4 mL of ethyl acetate in an ultrasonic bath at room temperature. Subsequently, the solvent was filtered and collected in a graduated tube, and the extraction was repeated for another 15-min period using a second 4-mL portion of ethyl acetate. The two extracts... 

Two soil sampling tubes were removed from each tank 2, 5, 9, 15, 27, 30, 43, and 58, and 72 days after the start of the experiment, then frozen and stored for later analyses. For analyses, the frozen soil cores were removed from the glass tubes (by brief immersion in hot water), then sectioned into four 1-cm cylinders representing 0-1, 1-2, 2-3, and 3-4 cm soil depths. Samples from each depth were shake-extracted with 100 ml ethyl acetate hexane overnight, and again with 100 ml methanol overnight. Extracts were filtered, concentrated to 20 ml and analyzed by LS and TLC as described below. 

Excavations were completed in summer 2002. The residues to be excavated were classified by on-site analytical methods, and were temporarily stored on-site for later off-site disposal. Soil sampling at the site showed that the highest level of contamination was found, as expected, in the area surrounding the former inlet of the pond. However, during excavation, a second hot spot was found with TNT concentrations of several g/kg TNT. Thus more soil had to be excavated than was initially expected. The TNT was concentrated in clayey soil. 

Sampling of the Soil. Representative soil samples were taken from conventional and no-tillage plots before planting and afterward at intervals of 1 month since April, 1985. The soil samples were placed in quart jars, frozen immediately by using dry ice, and stored at -18 °C. 

Arce et al. [39] developed a flow injection analysis (F1A) system (Fig. 5.3) for online filtration of water samples prior to CE analysis. They also constructed a pump-driven unit for extraction and filtration of soil samples combined with CE in an online mode (automated sample transfer between pre-CE sample preparation step and the CE) [40]. The method was precise and four times faster than conventional methods of sample preparation with an off-line unit. Blood samples are centrifuged immediately to remove red blood cells and the serum is stored as discussed above. Sometimes, urine samples also contain precipitates which are removed by centrifuge. 

Common to nearly all analyses is preservation with refrigeration at 2-6°C, a practice, which minimizes the volatilization of organic compounds with low boiling points and the bacterial degradation of most organic compounds. That is why we must place samples on ice immediately after they have been collected, ship them in insulated coolers with ice, and keep them refrigerated until the time of analysis. Water samples collected for metal analysis and preserved with nitric acid are an exception to this rule as they may be stored at room temperature. The addition of methanol or sodium bisulfate solution to soil collected for VOC analysis is the only chemical preservation techniques ever applied to soil samples. 

Option 5. Preserve two soil samples per either one of the four above-described options transfer the third sample into a vial with 10 ml of purge-and-trap grade methanol store at 2-6°C analyze methanol-preserved samples within 14 days of collection. 

Inexpensive disposable non-hermetic plastic soil sampling syringes are available from several manufacturers. These devices are not suitable for storing and shipping samples, only airtight coring devices are. 

The laboratory will store the containers with methanol-preserved soil at 2-6°C. The holding time for analysis is 14 days as defined by EPA Method 5035. ASTM Standard D 4547-98 indicates that methanol-preserved samples do not exhibit VOC losses for a period of time of up to two months (ASTM, 1998). The state of Alaska Department of Environmental Conservation (ADEC) Method AK101 for gasoline analysis of methanol-preserved soil samples specifies a holding time of 28 days (ADEC, 1999). 

Acidified stored water samples are generally analysed directly, or after filtration through a 0.2 or 0.4 p membrane filter. Particulates on filters are dissolved in a suitable digestion acid mixture, generally following dry ashing to destroy the membrane (see Soils, Sediments, and Rocks , below). 

All burials were located at the Elizabeth site in west-central Illinois, dated approximately to the Middle Woodland Period (100 B.c. to 400 a.d.). Soil samples were taken at 5-cm intervals from the midpoint of the shaft of each femur, in horizontal and vertical directions. Approximately 50-100 g of soil was removed with a steel trowel from a 2-cm circle surrounding the measured position. The soil samples were air-dried and stored in sealed, polyethylene-lined paper bags. 

Soil-gas samples collected on adsorbents should be stored in the same manner as soil samples to prevent drying out and loss of sulphur compounds. Samples collected in solutions or on filters are generally analysed immediately or shortly after collection. 

In geochemical exploration, soil samples, either surficial or (in arid regions) microlayer are the recommended sample medium for the collection of sulphur compounds in soil gases. Soils should be placed in plastic bags or glass containers that are as air-tight as possible. An entire study area should be sampled at one time, over a period of as few days as possible, to avoid weather-related or seasonal fluctuations in soil-gas concentrations. The soil samples should be stored in a cool place or in a freezer. All of the soil samples from a particular area should be analysed as quickly as possible after collection. They should be sieved to the same mesh size and should be of the same weight for analysis. 

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