Total dissolved nitrogen determination

Soldrzano, L., and Sharp, J. H. (1980a). Determination of total dissolved nitrogen in natural waters. Limnol. Oceanogr. 25,751-754. 

Analytical Methods for Determination of Total Dissolved Nitrogen and Particulate Nitrogen... 

Merriam J., McDowell W.H., and Currie W.S. 1996. A high-temperature catalytic oxidation technique for determining total dissolved nitrogen. /. Soil Sci. Soc. Am. 60 1050-1055. 

Shepherd R.J. and Davies I.M. 1981. A semiautomatic alkaline peroxodisulphate method for the routine determination of total dissolved nitrogen in seawater. Anal. Chim. Acta 130 55-63. 

Shepherd and Davies [26] have described a semiautomated version of the alkaline peroxodisulfate procedure for the determination of total dissolved organic nitrogen in seawater. These workers carried out experiments on a range of contaminated and clean seawaters using a version [27] of Koroleff s [24] alkaline peroxodisulfate oxidation technique. 

Although the process to determine KlA and K is possible with a spread sheet, it is cumbersome for commercial specifications. The guidehne for the testing of commercial aeration devices has been well developed and is generally available (American Society of Civil Engineers, 1992). There is no requirement to measure total dissolved gas pressure or estimate dissolved nitrogen concentration, and an... 

Optical (Specific) Rotation Transfer an accurately weighed amount of sample, equivalent to about 100 mg of total tocoph-erols, into a separator, and dissolve it in 50 mL of ether. Add 20 mL of a 10% solution of potassium ferricyanide in a 1 125 sodium hydroxide solution, and shake for 3 min. Wash the ether solution with four 50-mL portions of water, discard the washings, and dry over anhydrous sodium sulfate. Evaporate the dried ether solution on a water bath under reduced pressure or in an atmosphere of nitrogen until about 7 or 8 mL remains, and then complete the evaporation, removing the last traces of ether without the application of heat. Immediately dissolve the residue in 5.0 mL of isooctane, and determine the optical rotation. Calculate the optical rotation [see Optical (Specific) Rotation, Appendix HB], using as c the concentration expressed as the number of grams of total tocopherols, as determined in the Assay (above), in 100 mL of the solution. 

Weiss, R. F., and Craig, H. (1973). Precise shipboard determination of dissolved nitrogen, oxygen, argon, and total inorganic carbon by gas chromatography. Deep-Sea R S. 20, 291-303. 

PN is included in the TON, if unfiltered samples are digested by these analytical methods, and it might be determined as difference between TON and DON. However, a more accurate determination of PN requires the analysis of the particulate collected by filtration independently with respect to the determination of dissolved nitrogen forms, as PN often constitutes only a small fraction of the total nitrogen in the natural waters. The digestion of PN collected on filters can be achieved by KD and PO methods, but the most important technique used for this analysis is the HTO method (Figure 14.1). 

PO method for analysis of total nitrogen in water samples was introduced by Koroleff [120] and subsequently revised and improved in several studies during the following years [106,121-127], imtil to become a reference methodology. Similar to the other techniques, this method was also applied to the determination of total (dissolved) organic carbon and phosphorus in water samples. 

The reaction was carried out at 100°C for about two hours until the theoretical isocyanate content, as determined by the di-n-butylamine titration method (27), was reached. The PU prepolymer with or without tertiary amine nitrogen groups was dissolved in dry MEK to obtain a prepolymer solution of 30-40% solids. It was then mixed with a mixture of 1,4-BD/TMP (4 1 by equiv. ratio) at an NCO/OH = 1.05/1.0 ratio in the presence of T-12 catalyst (0.05% based on total weight). The reaction mixture was cast in a metal mold treated with a release agent at ambient temperature. After standing 3-5 hours at room temperature, the mold was placed in an oven and post-cured at 100°C for 16 hours. The samples were then conditioned in a desiccator for one week before testing. 

---