Primary production oxygen method

Revsbech, N.P. and 3j8rgensen, B.B., 1981. Primary production of microalgae in sediments measured by oxygen microprofile, H 1 003" fixation, and oxygen exchange methods. Limnol. Oceanogr., 26 717-730. 

Peroxide Value. Oxidation of oils is a major cause of their deterioration. Hydroperoxides are the primary products formed by the reaction between oxygen and the unsaturated fatty acids. Hydroperoxides have no flavor or odor but break down rapidly to form aldehydes, which have a strong, disagreeable flavor and odor. The peroxide concentration, usually expressed as peroxide value (PV), is a measure of oxidation or rancidity in its early stages. PV measures the concentration of substances, in terms of milliequivalents of peroxide per 1000 grams of sample, that oxidize potassium iodide to iodine. AOCS Method Cd 8-53 (103) is the official method for peroxide value determinations. 

From a mechanistic standpoint, however, the first method to be developed [22, 4] is of more interest and relied very simply on available kinetic data, which indicated that the capture of an alkyl radical by molecular oxygen is some ten thousand times faster than the competitive hydrogen atom abstraction from a thiol. Thus, the simple passage of triplet oxygen through a solution of the O-acylthiohydroxamate and a non-nucleophilic mercaptan such as fert-butanethiol leads to excellent yields of hydroperoxides (Scheme 18). Whilst these primary products can of course be iso-... 

R being the relative photosynthesis, determined empirically, for the appropriate value of surface radiation, k the extinction coefficient per metre of the water, C the amount of chlorophyll in g m, and the factor 3.7 a mean value for the assimilation number. Values estimated by this method and those determined by the oxygen technique agreed reasonably well for a number of sea areas in which primary productivity varied by an order of magnitude (Fogg, 1975). 

To sum up, it should be realised that both methods, O2 2md C method, have serious limitations. The C method is certainly the more sensitive one, but from data no respiration can be measured and therefore no net production can be calculated whereas the oxygen method gives a good estimate of assimilation and dissimilation (Golterman, 1975). The question, at one time actively debated, on whether uptake gives a measure of net or gross photosynthesis or some intermediate value, has never been resolved (Bunt, 1975). Mostly the assumption is made that nearly all fixed carbon comes from directly assimilated CO2 (and not partly from older respired carbon) and that the radiocarbon method more or less measures net primary production (De Vooys, 1979). 

In some cases, particularly with iaactive metals, electrolytic cells are the primary method of manufacture of the fluoroborate solution. The manufacture of Sn, Pb, Cu, and Ni fluoroborates by electrolytic dissolution (87,88) is patented. A typical cell for continous production consists of a polyethylene-lined tank with tin anodes at the bottom and a mercury pool (ia a porous basket) cathode near the top (88). Pluoroboric acid is added to the cell and electrolysis is begun. As tin fluoroborate is generated, differences ia specific gravity cause the product to layer at the bottom of the cell. When the desired concentration is reached ia this layer, the heavy solution is drawn from the bottom and fresh HBP is added to the top of the cell continuously. The direct reaction of tin with HBP is slow but can be accelerated by passiag air or oxygen through the solution (89). The stannic fluoroborate is reduced by reaction with mossy tin under an iaert atmosphere. In earlier procedures, HBP reacted with hydrated stannous oxide. 

Anemia is a decrease in the number of red blood cells (RBCs), a decrease in die amount of hemoglobin in RBCs, or bodi a decrease in die number of RBCs and hemoglobin. When diere is an insufficient amount of hemoglobin to deliver oxygen to die tissues, anemia exists. There are various types and causes of anemia For example, anemia can be die result of blood loss, excessive destruction of RBCs, inadequate production of RBCs, and deficits in various nutrients, such as in iron deficiency anemia Once the type and cause have been identified, die primary health care provider selects a method of treatment. 

A number of methods are available for following the oxidative behaviour of food samples. The consumption of oxygen and the ESR detection of radicals, either directly or indirectly by spin trapping, can be used to follow the initial steps during oxidation (Andersen and Skibsted, 2002). The formation of primary oxidation products, such as hydroperoxides and conjugated dienes, and secondary oxidation products (carbohydrides, carbonyl compounds and acids) in the case of lipid oxidation, can be quantified by several standard chemical and physical analytical methods (Armstrong, 1998 Horwitz, 2000). 

---