A method for the simultaneous determination of phosphate and silicate based on spectrophotometric
measurement at 385 nm of a single peak using aflow injection system with two component calibration
is described. In the system, a stream of sample containing both analytes is merged with a stream of
ammonium molybdate to form (at 1opHo2) molybdophosphoric and molybdosilicic acids. Total
absorbance of the compounds is registered in a form of a constant signal. Simultaneously, oxalic acid
solution is injected into a carrier stream (H2SO4) and then merged with the stream of sample containing
the mixture of heteropolyacids. A characteristic peak is registered as a result of selective decomposition
of molybdophosphoric acid by oxalic acid. The area (or the absorbance measured at the constant signal)
and the absorbance measured at the minimum of the peak can be used as measures corresponding to the
phosphate and silicate concentrations, respectively. The time of the peak registration is about 3 min.
Two-component calibration with the use of four standard solutions of the phosphate/silicate concentra-tions established in accordance with 2
2
factorial design was applied. Phosphate and silicate can be
determined within the concentration ranges of 0.20–15.00 and 0.20–20.00 mg L
1
, with precision less
than 2.7 and 0.9% (RSD), respectively and accuracy better than 6.2% (RE). The detection limit is 0.054 and
0.092 mg L
1
for phosphate and silicate, respectively. The method was applied to determination of the
analytes in certified reference materials of groundwater, wastewater, and river water giving results
consistent with the certified values.
&2014 Elsevier B.V. All rights reserved
A method for the simultaneous determination of phosphate and silicate based on spectrophotometricmeasurement at 385 nm of a single peak using aflow injection system with two component calibrationis described. In the system, a stream of sample containing both analytes is merged with a stream ofammonium molybdate to form (at 1opHo2) molybdophosphoric and molybdosilicic acids. Totalabsorbance of the compounds is registered in a form of a constant signal. Simultaneously, oxalic acidsolution is injected into a carrier stream (H2SO4) and then merged with the stream of sample containingthe mixture of heteropolyacids. A characteristic peak is registered as a result of selective decompositionof molybdophosphoric acid by oxalic acid. The area (or the absorbance measured at the constant signal)and the absorbance measured at the minimum of the peak can be used as measures corresponding to thephosphate and silicate concentrations, respectively. The time of the peak registration is about 3 min.Two-component calibration with the use of four standard solutions of the phosphate/silicate concentra-tions established in accordance with 22factorial design was applied. Phosphate and silicate can bedetermined within the concentration ranges of 0.20–15.00 and 0.20–20.00 mg L1, with precision lessthan 2.7 and 0.9% (RSD), respectively and accuracy better than 6.2% (RE). The detection limit is 0.054 and0.092 mg L
1
for phosphate and silicate, respectively. The method was applied to determination of the
analytes in certified reference materials of groundwater, wastewater, and river water giving results
consistent with the certified values.
&2014 Elsevier B.V. All rights reserved
การแปล กรุณารอสักครู่..
