ISO 23776:2021 pdf free download – Meat and meat products一 Determination of total phosphorous content.
Dissolve in water 479,4 mg of potassium dihydrogen phosphate (KH2PO4), previously dried for 3 h at (103 ± 2) °C and allowed to cool in desiccators.
Transfer quantitatively to a 1 000 ml volumetric flask. Dilute to the mark with water and mix.
7.1.7 Phosphate standard solutions, containing between 0,05 mg and 0,30 mg of P205 per millilitre.
Transfer by pipette or burette to 100 ml volumetric flasks 10 ml, 20 ml, 30 ml, 40 ml, 50 ml and 60 ml of the phosphate stock solution (7.1.6). Add 10 ml of the nitric acid (7.1.2). Dilute to the mark with water and mix.
The range of standard curve can be adjusted according to the use of different concentrations of standard substance. Use water to dilute.
7.1.8 Blank solution.
Pipette 2 ml of the nitric acid (7.1.2) and 30 ml of the colour reagent (7.1.5) into a 100 ml volumetric flask. Dilute to the mark with water and mix.
7.2 Apparatus
IMPORTANT — All glassware shall be thoroughly cleaned using a phosphate-free detergent and then rinsed with water.
The usual laboratory apparatus and, in particular, the following shall be used.
7.2.1 Mechanical or electrical equipment capable of homogenizing the laboratory sample, including a high speed rotational cutter or a mincer fitted with a plate with holes not exceeding 4,5 mm in diameter.
7.2.2 Water bath, capable of being maintained at 100 °C.
7.2.3 Fluted filter paper, of diameter 15 cm, phosphate free.
7.2.4 Spectrometer, capable of being used at a wavelength of (430 ± 2) nm, or a photo-electric colorimeter with an interference filter with absorption maximum of (430 ± 2) nm.
7.2.5 Glass cells, of 10 mm optical path length.
7.2.6 Analytical balance, capable of weighing to an accuracy of ±0,001 g.
7.2.7 One-mark volumetric flasks, of capacities (100 ± 0,10) ml and (1 000 ± 0,40) ml.
7.2.8 Muffle furnace, with adjustable temperature control, temperature (550 ± 25) °C.
7.2.9 Electric hot plate, with adjustable temperature control.
7.2.10 Porcelain crucible, with 60 mm diameter, 25 mm high inclined wall.
7.2.11 Desiccator, provided with an effective desiccant.
For details of this and other apparatus needed for the incineration procedure, see Iso 936.
7.2.12 Mechanical meat mincer, laboratory size, fitted with a plate with holes of diameter not
exceeding 4 mm.
7.3 Preparation of test sample
Homogenize the laboratory sample with the appropriate equipment (7.2.1). Take care that the temperature of the sample material does not rise above 25 °C. If a mincer is used, pass the sample at least twice through the equipment.
Fill a suitable airtight container with the prepared test sample, close the container and store in such a way that deterioration and change in composition are prevented. Analyse the test sample as soon as practicable. The storage time should be not more than 24 h.
7.4 Procedure
7.4.1 Test portion
7.4.1.1 If it is necessary to check whether the repeatability requirement (see 7.8) is met, carry out two single determinations in accordance with 7.4.1 to 7.5.
7.4.1.2 Weigh, to the nearest 0,00 1 g, about 5 g of the prepared test sample. Carry out the mineralization of the test portion by using an incinerator (7.2.8) and the method described in ISO 936. Take up the resulting ash in 10 ml of the nitric acid (7.1.2) using a stirring rod to aid dissolution. Cover the dish with a watch glass and heat for 30 mm on a boiling water bath (7.2.2). Allow to cool and transfer the liquid quantitatively to a 100 ml volumetric flask (7.2.7). Dilute to the mark with water, mix and filter through the filter paper (7.2.3), rejecting the first 5 ml to 10 ml of filtrate.