ISO 23075:2021 Vulcanized rubbers — Determination of antidegradants by high-performance liquid chromatography

ISO 23075:2021 Vulcanized rubbers — Determination of antidegradants by high-performance liquid chromatography. 5 Materials 5.1 Eluent A: a 1:1 (by volume) mixture of methanol (HPLC grade) and a 0,01 mol/l aqueous solution of ammonium acetate (AR grade). 5.2 Eluent B: methanol (HPLC grade). 5.3 Extraction solvent: a 2:1 (by volume) mixture of isopropanol (HPLC grade) and dichloromethane (HPLC grade) or any suitable solvents. 5.4? Single? use? PTFE? filters: 25 mm diameter, 0,45 µm porosity. 6 Apparatus 6.1 HPLC apparatus, with gradient elution capability, a 10 µl fixed-loop injector, a variable-wavelength ultraviolet-visible (UV-VIS) detector and a recording-integrator data system. 6.2 HPLC column, reverse-phase type. Different columns may be used provided that a good separation of antidegradant component peaks from other extracted components is obtained. The method has been tested using a 5 µm particle size column. A column RP C18 (150 mm × 4,6 mm) is usually appropriate. However, the elution programme may need to be modified when columns different from the ones described in this document are used. 6.3 Ultrasonic bath, typically of about 2 l capacity, operating at a frequency of 47,6 kHz ± 10 %. An ultrasonic bath of different capacity and operating frequency may be used provided that extraction of the antidegradant is complete. 6.4 Analytical balance, capable of weighing to 0,01 mg. 7 Chromatographic conditions 7.1 Pump A: Eluent A (5.1). 7.2 Pump B: Eluent B (5.2). 7.3 Flow rate: 1,0 ml/min. 7.4 Column oven temperature: 40 °C. 7.5 Injection volume: 10 µl. 8 Procedure 8.1 Preparation of the calibration curve Prepare standard solutions, for example from 2 × 10 −4 mol/l to 10 −3 mol/l (see Table B.1). The concentration range shall be adapted depending on the requested quantification limit. The calibration curve is obtained by plotting the peak area against the initial concentration of the antidegradant (see examples in Figures B.1 and B.2). Check that the calibration curve is linear and the determination coefficient r 2 is greater than 0,99. Repeat the injections twice and report the average of the two values. NOTE Combination of antidegradants calibration can be used. ISO 23075 pdf download.