Posted 30 June 2012 - 12:25 AM
Posted 02 July 2012 - 07:25 AM
we measured inorganic phosphate using a method modified from chen, et al, anal. chem., 28: 1756-58 (1956). it is more sensitive than fiske-subbarow.
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Posted 24 December 2014 - 07:20 AM
Determination of inorganic phosphorus in biological fluids
Starting by "Chen P.S. et al.(1956). Microdetermination of phoshorus. Analyt. Chemistry 28:1756-58", I modified it can be placed on board to several automatic chemical instruments.
Molybdate solution pH 1.0 : dissolve 0.5 g (0.4 mM) of ammonium molybdate [(NH4)6Mo7O24-4H2O] in 1 liter of 0.21 M H2SO4 (pipet 12.0 ml of reagent grade d. 1.8 g/ml, 95% purity H2SO4 into 500 ml H2O. cool to room temperature and dilute to 1 liter), stable indefinitely if stored at 4-25 °C.
Detergent : dilute 25 ml of Triton X-100 to 100 ml with H2O. Stable for 2 years if stored at 4 °C.
Working solution : 24 hrs before to use mix 100 ml of molybdate solution with 0.9 ml (0.225% final concentration) of detergent. Stable 6 months at 2-8 °C.
Label three tubes "reagent blank" (RB), "standard" (ST - KH2PO4), and "sample" (S), add 1.0 ml of working solution and the dispense 10 ul of standard/calibrator in ST e 10 ul of serum/plasma or 1:20 dilute urine(*) in S. Mix and incubate for 5 min. at 25-37 °C. Measure Abs at 340 nm (334-365) of ST and sample against RB within 60 min. and multiply for ST concentration.
(*) For urine collect for 24 hrs in collection bottle containing 10 ml of 10% (v/v) HCl to avoid phosphate precipitation. Mix well contained bottle and dilute urine 1:20 with dH2O and multiply the result by 20.
In the phosphorus determination advisable devoted glassworks use it. Carefully goes washed with ho diluted (6 mol/L^-1) hydrochloric acid, rinsed with deionized water and preserved, filled with water, up to the moment of the use. Wash polyethylene stoppers in 6 mol(L^-1 HCl, rinse with demineralized water, then wash in 8 mol/L^-1 nitric acid and again rinse with demineralized water. Pleonastic is cannot use detergents containing phosphate.
Edited by Zagami Francesco, 24 December 2014 - 09:08 AM.