Analytical methodology for the determination of urea: current practice and future trends

Francis, Paul S.; Lewis, Simon W.; Lim, Kieran F.

doi:10.1016/s0165-9936(02)00507-1

Cited by 132 publications

(86 citation statements)

References 30 publications

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“…Although the direct method persists as the approach of choice for the analysis of urea in seawater (Francis et al 2002), the enzymatic method has been extensively used, not only in the past, but also in recent studies (e. g., McCarthy 1972; Glibert et al 1991;Cho and Azam 1995;Metzler et al 1997;Bronk et al 1998;Berg et al 2001;Dyhrman and Anderson 2003;Bode et al 2004;Lomas et al 2004). In a comparative work on these techniques, Price and Harrison (1987) demonstrated that the enzymatic method underestimated urea concentrations in seawater compared to the direct method, and the effect was largely attributed to the inhibitory effect of seawater ions on the enzyme.…”

Section: Introductionmentioning

confidence: 99%

Urea analysis in coastal waters: comparison of enzymatic and direct methods

Revilla¹,

Alexander²,

Glibert³

2005

Limnol. Oceanogr. Methods

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This study presents a comparison of two existing methods for the determination of urea concentration in seawater. These methods are referred to here as the enzymatic method, which is based on the use of the enzyme urease, and the direct method, which is based on the reaction of urea with diacetylmonoxime. A room temperature modification of the direct method was adapted for a single reagent and both the enzymatic and the direct method were tested in artificially prepared solutions and in natural samples from estuaries and shelf waters. We were particularly interested in the effects of salinity and humic acids on the accuracy of both methods. The effect of humic acids was negligible. In contrast, salinity ~34 caused a 15% to 40% underestimation in the urea concentrations measured by the enzymatic method and the degree of underestimation varied among enzyme batches. Urea concentrations corrected for the salt effect should, however, be considered estimations, as other factors also interfered with the enzymatic method in natural samples. The direct method as modified in this study presented a low detection limit (0.04 µM urea‐N) and high precision (standard deviation: 0.02 µM urea‐N; coefficient of variation: 1.1%) comparable to those of the enzymatic method. The direct method was more accurate and less salinity dependent than the enzymatic method. As urea levels could have been underestimated by the enzymatic method, our findings support previous conclusions regarding the important role of urea in the nitrogen cycle and its link with some harmful algal bloom phenomena.

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Section: Introductionmentioning

confidence: 99%

Urea analysis in coastal waters: comparison of enzymatic and direct methods

Revilla¹,

Alexander²,

Glibert³

2005

Limnol. Oceanogr. Methods

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“…Urease activity is widely found among prokaryotes, as well as in eukaryotes including fungi and plants (Blakeley & Zerner, 1984;Li, Csetenyi & Gadd, 2014). To date, the widest analytical application of urease has been for the quantification of urea in blood and urine (Francis, Lewis, & Lim, 2002). Recently, there has been a growing demand for urease in applications in other areas, such as food production (Krajewska, 2009).…”

Section: Ureasementioning

confidence: 99%

Microbially-induced Carbonate Precipitation for Immobilization of Toxic Metals

Kumari

Qian

Pan

et al. 2016

Advances in Applied Microbiology

157

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“…Urea has also many uses in chemical industries such as the manufacture of resins, medicines, cosmetics and cleaning products [1][2][3][4][5][6]. Besides, it has great biological importance, since it is the final metabolite of nitrogenous compounds in mammals [1,3,5].…”

Section: Introductionmentioning

confidence: 99%