A Room Temperature Procedure for the Manual Determination of Urea in Seawater

Estuarine, Coastal and Shelf Science (1998) 47, 415418 Article No. ec980357 A Room Temperature Procedure for the Manual Determination of Urea in Seawater L. Goeyens, N. Kindermans, M. Abu Yusuf and M. Elskens Vrije Universiteit Brussel, Laboratorium Analytische Chemie, Pleinlaan 2, B-1500 Brussels Received 10 July 1997 and accepted in rewrite form 16 March 1998 Several earlier studies corroborate the important role of dissolved organic motion and much particularly carbamide in phytoplanktonic nitrogen phthisis ?uxes. Generally, the intent of urea concentrations relies on the formation of an imidazolone-thiosemicarbizide complex, a complexation which requires very straight temperature control when carried out at high temperature. It is besides possible, however, to earn reliable results with a room temperature procedure. The measured abundances for some(prenominal) complexation at high temperature (85 C, 20 min) and at close temperature (22 C, 72 h) be closely compar able. Lower values are observed for temperatures 70 C accelerates the destruction of the red colour and the competition that complexation at close temperature yields a complex which is stable for at least(prenominal) 3 old age (Newell et al.

, 1967) led us to inquire the urea analysis at room temperature in a alike(p) way as is done for the manual determination of ammonium ion (Korole?, 1969). The chemical principles of the imidazolone formation remain unchanged. The authors followed the method of Mulvenna and Savidge (1992), but omitted the thermostatization at 85 C after addition of the reagents. Instead, the samples we re stored at close temperature (22 C 1) in ! the dark and their absorbances were measured 3 old age later. The absorbance vs time graph (Figure 1) has a curvilinear shape, showing that best colour development occurs after 72 h and throw constant for an additional 48 h at ambient temperature (22 C 1). The mean absorbance value amounted to 0·444 (SD=0·003, N=9) after 72 h and to 0·450 (SD=0·004, N=10)...If you want to get a full essay, order it on our website: OrderCustomPaper.com

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