SUMMARY

The phosphate adsorption capacity (Pmax) of samples from various horizons of five Danish podzolized soils were investigated before and after organic matter removal. Removal of organic matter had no direct influence on Pmax suggesting that organic matter did not compete with phosphate for adsorption sites. In the soils investigated aluminium and iron oxides were the main phosphate adsorbents. Thus, more than 96% of the variation in Pmax could be accounted for by poorly crystalline aluminium and iron oxides (extractable by oxalate) and by well-crystallized iron oxides (taken as the difference between dithionite-citrate-bicarbonate-extractable iron and oxalate-extractable iron).



Organic matter affected phosphate adsorption indirectly by inhibiting aluminium oxide crystallization. The resulting poorly crystalline oxides had high Pmax. In contrast, the influence of organic matter on the crystallinity of the iron oxides, and therefore on their capacity to adsorb phosphate, seemed limited.

Influence of organic matter on phosphate adsorption by aluminium and iron oxides in sandy soils

Glucose oxidase (EC 1.1.3.4) is the most widly employed enzyme as analytical reagent. This is the result of (1) its utility in the determination of glucose, an analyte of wide analytical interest, and (2) its relatively low cost and good stability that make the glucose/glucose oxidase system a very convenient model for method development (particularly in the area of biosensors). This review discusses in detail enzyme structure, biocatalysis, enzymes as analytical reagents, properties of glucose oxidase (including a historical account), and the use of glucose oxidase as an analytical reagent in homogeneous systems as well as an immobilized reagent.

/pdf/glucose-oxidase-as-an-analytical-reagent-5cjtmb1wo9.pdf

Glucose Oxidase as an Analytical Reagent

Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, School of Oceanography, University ofWashington, Seattle, Washington 98195-7940, Department of Marine, Earth and Atmospheric Sciences, North Carolina State University,Raleigh, North Carolina 27695Received July 14, 2006

/pdf/chemical-sensor-networks-for-the-aquatic-environment-1sduublt1q.pdf

Chemical sensor networks for the aquatic environment

Different aluminium species react with oxine at different rates, a behaviour that we have used as the basis of an analytical method. The reaction is performed in a FIA system and is terminated by extraction of the excess oxine, together with the aluminium trioxinate formed, into chloroform. The reaction time is 2.3 sec, much shorter than that used normally. After separation, the amount of aluminium trioxinate in the organic phase is determined spectrophotometrically. The system has been validated using model substances with known complexation constants. Al3+, AlOH2+, probably Al(OH)2 +, aluminium sulphato complexes and, to some extent, some of its weakest organic complexes are included in the measured fraction, whereas fluoro complexes, citrato complexes and Al13O4(OH)7+ 24 are excluded. Complexes with fulvic and humic acid cause a reduction of the signal. The detection limit is at best about 5 μg/L (ca. 0.2 μM), and we can make 60 measurements per hour. Results from measurements made on natural ...

J. Ruzicka

Papers

Flow injection analysis, 2nd edn.