Determination of carbon, phosphorus, nitrogen and silicon species in waters

Sampling, sample treatment and quality assurance issues for the determination of phosphorus species in natural waters and soils

“…Traditional methods of digestion for natural water samples include fusion, dry ashing, perchloric acid, sulphuric acid-nitric acid and boiling on a hot plate, with more recent methods generally using autoclaving, UV photooxidation and microwave heating [75]. UV photo-oxidation can be used for organic phosphorus compounds in marine and freshwaters [47,76,77] but condensed polyphosphates present in the sample will not be broken down by UV photooxidation alone [2,3,78,79] and also need to be heated to 90-120 • C in the presence of acid [75]. To ensure that all polyphosphates present in the sample are decomposed, either boiling with HCl or potassium peroxydisulfate after UV irradiation is therefore recommended [80].…”

“…For accurate measurements, knowledge of phosphorus speciation is required as environmental behaviour is often critically dependent on its physico-chemical form. In aquatic systems, for example, phosphorus species are found in "dissolved", "colloidal" and "particulate" fractions, as inorganic and organic compounds and in biotic and abiotic particles [2]. The common operationally defined aquatic forms of phosphorus and the various terms used to describe them are shown schematically in Fig.…”

“…Ascorbic acid on its own however has the major disadvantage of slow colour development [8], but the addition of antimony as a catalyst increases the rate of reduction of the complex [4]. Using tin(II) chloride generates a product with a wavelength maximum at 690-700 nm as compared with 882 nm for ascorbic acid [2]. This allows greater sensitivity when a solid state detector (using a red light emitting diode light source) is used [9].…”

High Sensitive and Selective Hydrogen Phosphate ISFET Based on Polyvinyl Chloride Membrane

“…The importance of monitoring phosphate concentration levels spans all areas of science and technology. A system that can continuously and selectively detect phosphate levels in aqueous solutions will find numerous applications such as environmental monitoring [1,2], where the problem is caused in part by the leaching of inorganic phosphate from agricultural land into waterways. Since phosphorus is an essential mineral for the human body and all other living organisms, where the majority of phosphorous exists as phosphate monohydrogen or dihydrogen phosphate [3], it was well studied in biomedical research, clinical chemistry and pharmacology.…”

Spectrophotometric Determination of Phosphate Anion Based on the Formation of Molybdophosphate in Ethylene Glycol-Water Mixed Solution

“…2 Conventional molybdenum blue method is based on the formation of blue metal-substituted-molybdophosphate anions in aqueous solution. [3][4][5] The formation equilibria in the aqueous medium are quite complex, 6,7 so that the phosphate determination must be done under carefully controlled conditions. Although the addition of water-miscible organic solvent (O) can stabilize the blue molybdophosphate species to improve the spectrophotometric response, 8 it is not easy to apply the method to the phosphate determination in complicated matrix.…”