BS EN 902:2009 pdf free download – Chemicals used for treatment of water intended for human consumption一 Hydrogen peroxide.
C.1 General principle
Arsenious acid, antimonic acid and selenious acid, the As(lll). Sb(lll) and Se(IV) oxidation states of arsenic, antimony and selenium, respectively, are instantaneously converted by sodium borohydride reagent in acid solution to their volatile hydrides. The hydrides are purged continuously by argon or nitrogen into an appropriate atomizer of an atomic absorption spectrometer and converted to the gas-phase atoms. The sodium borohydride reducing agent. by rapid generation of the elemental hydrides in an appropriate reaction cell, minimizes dilution of the hydrides by the carrier gas and provides rapid, sensitive determinations of arsenic, antimony and selenium.
The sample is digested to solubilize particulate As, Sb and Se. The digested solutions are treated separately for determination of As, Sb and Se to convert them to As(lll), Sb(lll) and Se(lV) oxidation states respectively.
C.2 Interferences
Interferences are minimized because the As, Sb and Se hydrides are removed from the solution containing most potential interfering substances. Slight response variations occur when acid matrices are varied. Control these variations by treating standards and samples in the same manner. Low concentrations of noble metals (approximately 100 pg/I /l of Ag, Au, Pt, Pd, etc.) concentrations of Cu, Ni and Pb at or greater than 1 mgil, and concentrations between 0,1 mg/I and I mg/I of hydride-forming elements (Bi, Sn and Te) can suppress the response of As. Sb and Se hydrides due to the formation of mixed metal — As-Sb or -Se compounds. The presence of As, Sb and Se in each other’s matrices can cause similar suppression. Reduced nitrogen oxides resulting from HNO3 digestion and nitrite also can suppress instrumental response for all elements. Large concentrations of iodide interfere with the Se determination by reducing Se to its elemental form. Do not use any glassware for determining Se that has been used with iodide reduction of As(V).
C.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 in accordance with EN ISO 3696.
C.3.1 Sodium tetrahydroborate (sodium borohydride)
Dissolve 8 g NaBH4 in 200 ml of NaOH, c(NaOH) = 0,1 mol/l. Prepare fresh daily.
C.3.2 Sodium iodide, prereductant solution
Dissolve 50 g Nal in 500 ml water. Prepare fresh daily.
C.3.4 Sulfuric acid, solution c(H2S04) = 1.25 mol/l.
Cautiously add 35 ml sulfuric acid, density (p) = 1,84 glml to about 400 ml water, let cool, and adjust volume to 500 ml.
C.3.5 Nitric acid, density (p) = 1.42 g/ml.
C.3.6 Perchioric acid, density (p) = 1,66 g/ml.
C.3.7 Hydrochloric acid, density (p) = 1,16 g/ml.
C.3.8 Argon (or nitrogen), commercial grade.
C.3.9 Hydrogen, commercial grade.
C.3 10 Arsenic (Ill) solutions:
— stock As(lll) solution: Dissolve 1,320 g arsenic trioxide, As203 in water containing 4 g NaOH, Transfer quantitatively to 1000 ml one-mark volumetric flask and dilute to the mark with water and mix; 1,00 ml = 1.00mg As(lll):
— intermediate As(lll) solution: Dilute into 1000 ml one-mark volumetric flask 10 ml stock As (Ill) solution to the mark with water containing 5 ml hydrochloric acid (C.3.7) and mix; 1,00 ml =10.0 pg As(lll);
— standard As(lll) solution: Dilute into 1000 ml one-mark volumetric flask 10 ml intermediate As(lll) solution to the mark with water containing the same concentration of acid used for sample preservation (2 ml to 5 ml nitric acid (C.3.5)) and mix; 1,00 ml = 0,100 ig As(lll). Prepare diluted solutions daily.
C.3.1 I Arsenic(V) solutions:
stock As(V) solution: Dissolve 1,534 g arsenic peritoxide, As205, in water containing 4 g NaOH. Transfer quantitatively to 1000 ml one-mark volumetric flask and dilute to the mark with water and mix; 1,00 ml = 1,00 mg As(V);
— intermediate As(V) solution: Pepare as for As(lll) above; 1,00 ml = 10,0 pg As(V);
— standard As(V) solution: Prepare as for As(lll) above; 1,00 ml = 0,100 pg As(V).
C.3.12 Selenium(lV) solutions:
— stock Se(lV) solution: Dissolve 2.190 g sodium selenite. Na2SeO3 in water containing 10 ml hydrochloric acid (C.3.7) arid transfer quantitatively to 1000 ml one-mark volumetric flask and dilute to the mark with water and mix; 1,00 ml = 1,00 mg Se(lV);
— intermediate Se(IV) solution: Dilute into 1000 ml one-mark volumetric flask 10 ml stock Se (IV) solution to the mark with water containing 10 ml hydrochloric acid (C.3.7) and mix; 1,00 ml = 10,0 pg Se(IV);
— standard Se(lV) solution: Dilute into 1000 ml one-mark volumetric flask 10 ml intermediate Se(IV) solution to the mark with water containing the same concentration of acid used for sample preservation (2 ml to 5 ml nitric acid (C.3.5)) and mix. Prepare solution daily when checking the equivalent of instrument response for Se(lV) and Se(Vl); 1,00 ml = 0,100 pg Se(IV).