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The Mandatory Guidelines for Federal Workplace Drug Testing Programs provide criteria for specimen validity testing, including urine pH cut-offs, to report a urine specimen as adulterated or invalid. Since the urine pH criteria for invalid classifications, ≥ 3 and < 4.5 or ≥ 9 and < 11, became effective in November 2004, a number of specimens with results within the upper invalid limits, typically in the range of 9.1 to 9.3, have been reported with no evidence of adulteration. This study evaluated the hypothesis that these pH findings were the result of exposure to increased environmental temperatures during specimen standing and transport. Indeed, increased storage temperatures were associated with increased urine pH, with the magnitude of the change related to both storage time and temperature. The pH values of specimens stored at −20°C are relatively stable, whereas pH results > 9 are achieved at storage temperatures of room temperature or higher. It is noteworthy that no condition(s) produced a specimen with a pH > 9.5. Degradation of nitrogenous urine analytes is most likely responsible for the noted increases in pH. These findings are intended to supplement information used by the Medical Review Officers who are responsible for interpreting such marginally invalid pH results.
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... However, the precipitates yielded in R 2 and R 3 were no significant difference. Since the R 3 reactor is temperaturecontrolled in an airtight environment, bacterial growth is mostly inhibited, urea hydrolysis happens gradually; as a result, phosphate and calcium did not precipitate much and remain in the solution [29]. Spontaneous formation of struvite is reported to be dependent on the pH of the solution, the solution supersaturation, and on the presence of impurities [30]. ...
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... However, the precipitates yielded in R 2 and R 3 were no significant difference. Since the R 3 reactor is temperaturecontrolled in an airtight environment, bacterial growth is mostly inhibited, urea hydrolysis happens gradually; as a result, phosphate and calcium did not precipitate much and remain in the solution [29]. Spontaneous formation of struvite is reported to be dependent on the pH of the solution, the solution supersaturation, and on the presence of impurities [30]. ...
Article
Phosphorus (P) is an essential yet non-renewable nutrient, so recovering it from urine is getting more attention since it has a high concentration of nutrients. This study aimed to investigate the impacts of temperature, storage condition on urine's characteristics, and the effects of pH, Mg:P ratio, and calcium (Ca) ion on yielded magnesium phosphate hydrate (Mg3(PO4)2•xH2O) crystallization from fresh urine. The results indicated that the urine stored at 4 °C in a sealed environment created less spontaneous precipitation. The findings showed that the favorable condition for Mg3(PO4)2•xH2O recovery was at pH 10.5 and Mg:P of 1.3. The XRD analysis confirmed that P was crystallized as Mg3(PO4)2•xH2O phase with an average particle size of 0.5 mm. Furthermore, SEM-EDS images suggested the Ca and K might co-precipitate with Mg3(PO4)2•xH2O. These findings indicate that the potential of P recovery from nutrient-rich wastewater can both reduce environmental pollution and profit from phosphate fertilizers.
... 18,19 . Yet, few studies, outside the medical and veterinary fields in which urine samples need to be preserved for analysis, rather than further use/experimentation [20][21][22] , have investigated the best preparation and storage methods for animal urine for use in experiments. A common method of urine preservation is by acidification with sulphuric (H 2 SO 4 ) or hydrochloric (HCl) acid to prevent bacterial constituent degradation and NH 3 volatilisation e.g. ...
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Chapter
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