Digestion method

Ovens that do not have the facility to monitor and control the sample temperature may need to be calibrated, so that different ovens can be used with similar results. It is not sufficient simply to set the power fraction and make a correction for the difference in wattage of the ovens. The easiest way to calibrate a microwave oven is to measure the temperature rise of 1 L of water at various power settings and times and compare these between ovens. 

In a comparison study of acid digestion in the open and using the micro- 

In the interests of efficiency and reduction of laboratory waste solvents, 

Matrix Analyte Mean (hg/g) S.D. Number of Replicates Certified Value Ref. 

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Evaluate whether the microwave digestion method yields acceptable results in comparison with the standard digestion method. 

Methods for iodine deterrnination in foods using colorimetry (95,96), ion-selective electrodes (94,97), micro acid digestion methods (98), and gas chromatography (99) suffer some limitations such as potential interferences, possibHity of contamination, and loss during analysis. More recendy neutron activation analysis, which is probably the most sensitive analytical technique for determining iodine, has also been used (100—102). 

Comparative studies were performed to evaluate microwave digestion with conventional sample destmction procedures. These included the analysis of shellfish, meats, rocks, and sods. Generally, comparable accuracy at much shorter digestion time was found for the MAE vs the classical digestion method (39). 

Elemental analysis of organie and inorganie samples requires partial or total dissolution of the sample prior to speetrometrie analysis. Mierowave-assisted extraetion (MAE) provides an alternative to traditional digestion methods and it is reeognized as one of the most effieient methods for the dissolution of soil samples. 

In the in vitro digestion method, the compound of interest is transferred from the food matrix to a bile salt micelle suspension that simulates the in vivo digestion process. This in vitro digestion procedure was first developed to estimate iron availability from meals and since then has been modified and applied to studying carotenoid bioaccessibility from various food matrices. This approach assesses the bioaccessibility of the compound from a certain meal before it is presented to and taken up by intestinal cells. 

Garrett, D.A., Failla, M.L., and Samara, R.J., Development of an in vitro digestion method to assess carotenoid bioavailability from meals, J. Agric. Food Chem., 47, 4301, 1999. 

Hedren, F., Diaz, V., and Svanberg, U., Estimation of carotenoid accessibility from carrots determined by an in vitro digestion method, Eur. J. Clin. Nutr, 56, 425, 2002. 

Spectrophotometry X-ray diffraction Combustion methods Wet digestion methods Miscellaneous... 

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

Spectro- photometry Atomic absorption spectro- metry Inductively coupled plasma atomic emission spectrometry X-ray methods Ion selective electrodes Wet digestion methods Miscellaneous... 

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],... 

Landers et al. [97] and others [98] have described a wet digestion method for the determination of total sulphur in soils. In this method the sample (1.50-500mg) is placed in a digestion flask and heated in a sand bath to dryness at 250°C with 3ml of sodium hypobromite solution. The residue is resuspended with water, neutralized with formic acid, and then hydriodic acid reduction of the sample is followed to quantitatively recover the inorganic sulphate formed by wet oxidation. 

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