Analytical methods for measuring urea in pharmaceutical formulations

Knorst, Miriam Teresinha; Neubert, Reinhard H.H.; Wohlrab, W

doi:10.1016/s0731-7085(96)01978-4

Cited by 99 publications

(52 citation statements)

References 10 publications

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“…Other chemicals and solvents were of analytical grade. Urea was determined after the addition of 4-dimethylaminobenzaldehyde by measuring the optical absorbance at 420 nm (25). The analysis of EC was carried out on a GC-2010 gas chromatograph (GC) (Shimadzu, Kyoto, Japan) equipped with a GCMS-QP2010 plus mass spectrometer (MS) (Shimadzu, Kyoto, Japan).…”

Section: Methodsmentioning

confidence: 99%

Metabolic Engineering of the Regulators in Nitrogen Catabolite Repression To Reduce the Production of Ethyl Carbamate in a Model Rice Wine System

Zhao

Zhang

et al. 2014

Appl Environ Microbiol

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Rice wine has been one of the most popular traditional alcoholic drinks in China. However, the presence of potentially carcinogenic ethyl carbamate (EC) in rice wine has raised a series of food safety issues. During rice wine production, the key reason for EC formation is urea accumulation, which occurs because of nitrogen catabolite repression (NCR) in Saccharomyces cerevisiae. NCR represses urea utilization by retaining Gln3p in the cytoplasm when preferred nitrogen sources are present. In order to increase the nuclear localization of Gln3p, some possible phosphorylation sites on the nuclear localization signal were mutated and the nuclear localization regulation signal was truncated, and the disruption of URE2 provided an additional method of reducing urea accumulation. By combining these strategies, the genes involved in urea utilization (DUR1,2 and DUR3) could be significantly activated in the presence of glutamine. During shake flask fermentations of the genetically modified strains, very little urea accumulated in the medium. Furthermore, the concentrations of urea and EC were reduced by 63% and 72%, respectively, in a model rice wine system. Examination of the normal nutrients in rice wine indicated that there were few differences in fermentation characteristics between the wild-type strain and the genetically modified strain. These results show that metabolic engineering of the NCR regulators has great potential as a method for eliminating EC during rice wine production.

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Section: Methodsmentioning

confidence: 99%

Metabolic Engineering of the Regulators in Nitrogen Catabolite Repression To Reduce the Production of Ethyl Carbamate in a Model Rice Wine System

Zhao

Zhang

et al. 2014

Appl Environ Microbiol

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“…Urea was measured by an adaptation of the spectrophotometric method reported by Knorst et al (1997). Briefly, a filtered sample (1 mL) containing urea was reacted with 0.25 mL of an ethanolic solution of p-dimethylaminobenzaldehyde (4% w/v) and sulfuric acid (4% w/v).…”

Section: Measurement Of Ureamentioning

confidence: 99%

Strontium incorporation into calcite generated by bacterial ureolysis

Fujita

Redden

Ingram

et al. 2004

Geochimica et Cosmochimica Acta

214

141

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Abstract-Strontium incorporation into calcite generated by bacterial ureolysis was investigated as part of an assessment of a proposed remediation approach for 90 Sr contamination in groundwater. Urea hydrolysis produces ammonium and carbonate and elevates pH, resulting in the promotion of calcium carbonate precipitation. Urea hydrolysis by the bacterium Bacillus pasteurii in a medium designed to mimic the chemistry of the Snake River Plain Aquifer in Idaho resulted in a pH rise from 7.5 to 9.1. Measured average distribution coefficients (D EX ) for Sr in the calcite produced by ureolysis (0.5) were up to an order of magnitude higher than values reported in the literature for natural and synthetic calcites (0.02-0.4). They were also higher than values for calcite produced abiotically by ammonium carbonate addition (0.3). The precipitation of calcite in these experiments was verified by X-ray diffraction. Time-of-flight secondary ion mass spectrometry (ToF SIMS) depth profiling (up to 350 nm) suggested that the Sr was not merely sorbed on the surface, but was present at depth within the particles. X-ray absorption near edge spectra showed that Sr was present in the calcite samples as a solid solution. The extent of Sr incorporation appeared to be driven primarily by the overall rate of calcite precipitation, where faster precipitation was associated with greater Sr uptake into the solid. The presence of bacterial surfaces as potential nucleation sites in the ammonium carbonate precipitation treatment did not enhance overall precipitation or the Sr distribution coefficient. Because bacterial ureolysis can generate high rates of calcite precipitation, the application of this approach is promising for remediation of 90 Sr contamination in environments where calcite is stable over the long term.

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“…1.0 and 5.0 lM urea were determined six times, with RSD of 3.5 and 2.6%, respectively. This method had good selectivity and sensitivity comparing with the reported method (Table 1) [1][2][3][4][5][21][22][23][24] and was one of the most sensitive methods for urea.…”

Section: Working Curvementioning

confidence: 83%

“…Detection of urea in biological samples has important significance for pathophysiology and the renal function test, and the serum urea is widely used as an indicator of glomerular filtrating function [1]. At present, several methods have been reported to detect urea, such as colorimetry, flow injection analysis, enzyme electrode, and electrochemical methods [1][2][3][4][5]. These methods have their own advantages and analytical application fields.…”

Section: Introductionmentioning

confidence: 99%

A novel and sensitive resonance scattering assay for detection of urea in serum coupled urease catalytic reaction and NH4 + associated particle reaction

Liang

Qin

Zhang

et al. 2011

Bioprocess Biosyst Eng

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In the pH 6.6 Na2HPO4-NaH2PO4 buffer solutions and in the presence of urease catalyst, urea can be decomposed to form NH4+. The NH4+ reacted with sodium tetraphenyl boron (NaTPB) to form the association particles that exhibited a resonance scattering (RS) peak at 474 nm. When the urea concentration increased, NH4+ increased, and RS intensity at 474 nm enhanced linearly. Under the chosen conditions, the increased RS intensity (ΔI (474 nm)) had a linear response to the urea concentration in the range of 0.125-15 μM, with a detection limit of 0.058 μM urea, and a regression equation of ΔI (474 nm) = 31.6C + 2.1, a correlation coefficient of 0.9986. This catalytic RS method was applied for the detection of urea in human serum sample, with good selectivity and sensitivity, and the results were consistent with the reference method.

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Analytical methods for measuring urea in pharmaceutical formulations

Cited by 99 publications

References 10 publications

Metabolic Engineering of the Regulators in Nitrogen Catabolite Repression To Reduce the Production of Ethyl Carbamate in a Model Rice Wine System

Metabolic Engineering of the Regulators in Nitrogen Catabolite Repression To Reduce the Production of Ethyl Carbamate in a Model Rice Wine System

Strontium incorporation into calcite generated by bacterial ureolysis

A novel and sensitive resonance scattering assay for detection of urea in serum coupled urease catalytic reaction and NH4 + associated particle reaction

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