ISO 23293-2020 pdf download.Milk-based infant formula powders 一 Quantification of whey protein content by sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE).
7.2.6 Perform the electrophoresis at constant voltage with applied field strength of —497 V/cm and a capillary thermostatted to 25 °C using recirculating liquid coolant.
7.2.7 The generated current should be approximately 27 pA.
7.2.8 To avoid reagent depletion, programme the system to increment the vial position of all reagents every eight cycles.
7.3 Electropherogram processing
7.3.1 Electropherograrn integration
Automatically integrate the electropherograms from the valley located at 0.5 mm to I mm before the 10 kDa internal protein standard peak (include any peak immediately adjacent to the 10 kDa internal protein standard) to the valley between the end of K-casein peak and the peak of Ig H and BSA (no negative peaks should be generated by the integration). Then, perform a manual integration from the valley before the peak of Ig H and BSA until the end of the last peak in the electropherogram (integrate all peaks including those after the peak of Ig H and BSA if present). Examples of electropherograms including the automated and manual integration regions are given in Figures A.2 and A.,3 for SMP and infant formulas, respectively. Examples of integration parameters are listed In Table.A.1.
7.3.2 IdentifIcation of the casein region
In SMP, the casein integration area starts just before the -casemn peak (the highest peak of the electropherogram) and stops at the valley between the end of the )c-casein peak and the peak of Ig H and I3SA. For infant formulas, identify the -casemn peak and the valley by comparison with the SMP electropherogram.
8 System suitability
8.1 General
Test the system suitability using the 10 kDa internal protein standard (5.6) and the SDS-MW size standard (5.7). Define the migration time of the 10 kDa internal protein standard for each combination of instrument, capillary and reagents beforehand. The acceptance criteria for the system suitability are as follows.
8.2 The migration time of the 10 kDa internal protein standard should correspond to the value initially
established ±5 %. The seven MW markers (10 kDa, 20 kDa, 35 kDa, 50 kDa, 100 kDa, 150 kDa and
225 kDa) should be completely separated (see Figure A.4).
EXAMPLE Using a beckman Coulter/Sciex instrument, capillaries and reagents2), the migration time of the 10 kDa internal protein standard is 12.3 mm ± 0,5 mm and the seven MW markers are completely separated within 30 mm (see Figure A.4),
8.3 The acceptance criteria for the separation cycles are:
— the migration time of the 10 kDa internal protein standard should correspond to the value initially established ±5 %;
— the degree of baseline drop from the internal standard until the valley between the end of ic-casein and the peaks of lg H and BSA should not exceed 25 % of the height of the internal protein standard in the sample.ISO 23293 pdf download.