DD ISO TS 17193-2011 pdf download Milk — Determination of the lactoperoxidase activity — Photometric method (Reference method)
4.2 Hydrogen peroxide solution.
WARNING — Hydrogen peroxide is corrosive and should not be brought in contact with metals orreadily flammable organic substances to prevent explosive mixtures forming.
Pipette 0,1 ml of 30 % mass fraction H202 into a 100 ml one-mark volumetric flask (5.6).Make up to the markwith water and mix.
Prepare the hydrogen peroxide solution immediately before use (see 4.3).4.3ABTSreagentsolution,2 mmol/lsolutionofthe
Weigh 55 mg of the di-ammonium salt of ABTS into a 50 ml volumetric flask(5.6). Add about 30 ml of buffersolution (4.1) to dissolve the salt. Then add 1,0 ml of hydrogen peroxide solution (4.2). Make up to the 50 mlmark with the buffer solution and mix.
Prepare a fresh reagent solution every day.
Usual laboratory equipment and, in particular, the following.
5.1 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg.5.2pH-meter, capable of measuring 0,1 unit of pH, with a readability of 0,01 unit.
5.3Spectrophotometer，capable of measuring absorbance at 420 nm，with a temperature-controlledcuvette holder capable of maintaining a temperature of 25 ℃0,5 C.
5.4 Plastic cuvette, of pathlength 1,0 cm, provided with a lid.
NOTE The use of glass or quartz cuvettes can give results that are too low due to adsorption losses.
5.5 Air-displacement pipettes or piston-operated pipettes, ISO 8655-2, of nominal capacities 0,05 ml, 0,1ml,1,0 ml, and 2,0 ml.
5.6One-mark volumetric flasks， of nominal capacities 5 ml， 10 ml，25 ml,50 ml,100 ml and 500 ml.ISO 1042, class A.
5.7Water bath or dry bath, capable of maintaining a temperature of 25 °℃0,5°℃.
Sampling is not part of the method specified in this International Standard. A recommended sampling methodis given in lsO 707 IDF 50.
lt is important the laboratory receive a truly representative sample which has not been damaged or changedduring transport or storage.