Sediments digestion methods

A rapid method for determination of total phosphorus in water samples by digestion with persulphate was introduced by Koroleff [83], but this method has not been widely used for sediment samples. Preliminary measurements of phosphorus in lake sediments using the persulphate digestion method gave considerably lower values than the perchloric acid method [84],... 

A method [62] has been described for the determination of down to 2.5pg kg-1 alkylmercury compounds and inorganic mercury in river sediments. This method uses steam distillation to separate methylmercury in the distillate and inorganic mercury in the residue. The methylmercury is then determined by flameless atomic absorption spectrophotometry and the inorganic mercury by the same technique after wet digestion with nitric acid and potassium permanganate [63]. The well known adsorptive properties of clays for alkylmercury compounds does not cause a problem in the above method. The presence of humic acid in the sediment did not depress the recovery of alkylmercury compounds by more than 20%. In the presence of metallic sulphides in the sediment sample the recovery of alkylmercury compounds decreased when more than lmg of sulphur was present in the distillate. The addition of 4M hydrochloric acid, instead of 2M hydrochloric acid before distillation completely, eliminated this effect giving a recovery of 90-100%. 

The particulate material from the sediment traps was digested in aqua regia in a microwave digestion unit. Fe, Mn, Zn, Ca, Cr, and Cu were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) P was determined by the molybdate spectrophotometric method (28). A sediment standard (NBS No. 1645) was used regularly to check the accuracy of the sediment digestion procedure. 

Pinho, J., J. Canario, R. Cesario, and C. Vale. 2005. A rapid acid digestion method with ICP-MS detection for the determination of selenium in dry sediments. Anal. Chim. Acta 551 207-212. 

Schramel, P., Lill, G., Seif, R. A complete HF digestion method for element and trace element determination in soils, sediments, sludges and other similar samples using a closed system. Fresenius Z. Anal. Chem. 326, 135-138 (1987)... 

Fig. 12.4a. Youden plot of the determination of Al in marine sediments expressed as z-scores. The plot shows clear systematic differences due to the method of sample digestion. The group of lower (left) results was obtained by digestion methods which did not include any HF treatment e.g. nitric acid or aqua regia. The upper (right) group used an HF treatment or non-destructive methods e.g. XRF.

DIN 19734 (1999) German standard method Soil Quality - Determination of chromium(VI) of water, wastewater and sludge. Sludge and sediments. Digestion using aqua regia for subsequent determination of acid-soluble portion of metals. Deutsche Norm, DIN 38414, Part 7. 

The optimum conditions for roasting the clay and the optimum strength (30—60%) of the sulfuric acid used depend on the particular raw material. Finely ground bauxite or roasted clay is digested with sulfuric acid near the boiling point of the solution (100—120°C). The clay or bauxite-to-acid ratio is adjusted to produce either acidic or basic alum as desired and soHds are removed by sedimentation. If necessary, the solution can be treated to remove iron. However, few, if any, of the many methods claimed to be useful for iron removal have been used industrially (29). Instead, most alum producers prefer to use raw materials that are naturally low in iron and potassium. 

Method 3050B. Acid Digestion of Sediments, Sludges, and Soils. Available at http // www.epa.gov/epawaste/hazard/testmethods/sw846. 2012. Accessed June 3,2013. 

Jensen et al. [45] applied the method described in section 9.1.2.1 for the determination of DDT and polychlorobiphenyls in sulphur containing sediments to the analysis of sludges. The results in Fig. 9.7 show the beneficial effects of pretreatment of the sewage with tetrabutyl ammonium sulphate-sodium sulphite reagent on the recovery of DDT and polychlorobiphenyls from a digested sewage sludge sample. 

Aspila et al. [60] have described a semi-automated method for the determination of inorganic, organic and total phosphorus in river and lake sediments. Total phosphorus is extracted from sediments with 1M hydrochloric acid after ignition at a high temperature (550°C) (method 1) or by digestion with sulphuric acid-potassium persulphate at 135°C in a sealed PTFE-lined Parr bomb (method 2). 

Dobolyi and Bidlo [76] have described methods for the determination of phosphorus in lake sediments. Shulka et al. [75] investigated the interference by arsenic in the perchloric acid digestion procedure of Murphy and Riley [85] for the determination of phosphorus in sediments. Arsenite concentrations up to 20pg did not interfere but arsenate interfered. Between 1 and 45 pg arsenic g"1 was extracted from a lake sediment and in all cases the error in the determination of phosphorus due to the presence of arsenic was less than 1%. 

Siu and Berman [163] determined selenium in marine sediments in amounts down to 0.2pg (or 20ng g 1 of sediment) with a precision of 7%. This method is based on the fact that 1,2 diaminobenzene (o-phenylene diamine) and its derivatives react selectively and quantitatively with selenium IV (average accuracy 94 5%) to form piazselenols that are both volatile and stable. Piazselenols can be determined by electron capture gas chromatography. The sediments were digested as follows. A 0.5g sample was placed in a poly(tetrafluoroethylene) pressure decomposition vessel. A... 

In this method a 0.5 pg portion of sediment was decomposed by acid digestion in a PTFE bomb according to the procedure described by Siu and Berman [163] and diluted to 50mL in 1M hydrochloric acid. Total selenium was determined by using 500pL aliquots delivered into the hydride cell containing 5mL of 0.5M hydrochloric acid. 

Earlier work on the determination of total mercury in river sediments also include that of Iskander et al. [41], Iskander applied flameless atomic absorption to a sulphuric acid nitric acid digest of the sample following reduction with potassium permanganate, potassium persulphate and stannous chloride. A detection limit of one part in 109 is claimed for this somewhat laborious method. 

Jurka and Carter [50] have described an automated determination of down to O.lpg L 1 mercury in river sediment samples. This method is based on the automated procedure of El-Awady [51] for the determination of total mercury in waters and waste waters in which potassium persulphate and sulphuric acid were used to digest samples for analysis by the cold vapour technique. These workers proved that the use of potassium permanganate as an additional oxidizing agent was unnecessary. 

In this method approximately 19 samples of marine sediment were oven dried at 110°C then digested with nitric acid-perchloric acid and hydrofluoric acid-hydrochloric acid. The digested solution is made up to 50ml of an equal volume mixture of 6M hydrochloric acid and 2M nitric acid. 0.1ml or less of the digest was pipetted into the hydride generator, followed by 1ml 2M acetic acid, diluted to 100ml with double distilled water and reacted with sodium borohydride. 

---