BS ISO 7725:2020 pdf download.Rubber and rubber products — Determination of chlorine and bromine content.
6.1.7 Eluent solution, capable of eluting chloride ion and bromide ion to a proper retention time in selected column. Follow the column manufacturer’s instructions.
NOTE Some examples of eluent are provided in Annex D.
6.2 Apparatus
6.2.1 Ion chromatograph, consisting of a pump to supply eluent, a sample injector, a column and a conductivity detector specified as follows:
— pump: capable of delivering a constant flow within the range of 0,1 ml/min to 2,0 ml/min;
— sample injector: capable of injecting a constant volume of solution;
— column: filled with anion exchange resin suitable for resolving chloride ion and bromide ion from other inorganic anions;
— suppressor: used for reducing the conductivity of high ionic eluent;
— detector: for detecting conductivity.
NOTE Some examples of commercially available column are provided in Annex D.
An ion chromatograph fitted with a suppressor as Figure 1 is suitable for sensitive analysis. The
suppressor is attached between a column and a detector.
An ion chromatograph without a suppressor as Figure 2 may also be selected.
6.3 Determination
6.3.1 Setting up the ion chromatograph
Set up the ion chromatograph in accordance with the manufacturer’s instructions.
6.3.2 Preparation of the calibration curve
Inject the calibration solutions in increasing order of concentration and measure the conductivity of chloride ion and bromide ion peak area in each solution. Determine the correlation formula (calibration curve) by plotting the peak area as a function of concentration by means of linear regression.
6.3.3 Measuring blank solutions and sample solutions
Inject the blank solution and sample solutions (created in 5.2) to measure the peak areas in sequence. Then determine the chloride ion and bromide ion concentration of the blank (C B1 and C B2 , respectively) as well as the concentration of the individual sample solution (C S1 and C S2 , respectively) by using the calibration curve determined in 6.3.2.
7 Method B — Potentiometric titration
7.1 Reagents
7.1.1 Water, of grade 1 or higher. It shall be as specified in ISO 3696.
7.1.2 Nitric acid, concentrated, ρ = 1,42 g/cm 3 .
7.1.3 0,5mol/l Nitric acid, c(HNO 3 ) = 0,5 mol/l, obtained by diluting 30 ml of concentrated nitric acid (7.1.2) to 1 000 ml with water (7.1.1).
NOTE Commercially available 0,5 mol/l nitric acid can be used.
7.1.7 Ethanol, of analytical reagent grade.
Alternatively, 2-propanol may be substituted wherever ethanol is specified.
7.2 Apparatus
7.2.1 Electronic balance, capable of weighing to the nearest 0,01 mg.
7.2.2 Magnetic stirrer and a stirring bar.
7.2.3 Automatic titrator.
7.2.4 Silver electrode, to be used as a measuring electrode.
7.2.5 Reference electrode, of the salt bridge type.
NOTE It is possible to use a combined electrode instead of the silver electrode and the reference electrode.BS ISO 7725 pdf download.