GB 5009.242-2017National food safety standard - Determination of Manganese in Food (English PDF)

3.1 Reagents

3.1.1 Nitric acid (HNO3).

3.1.2 Perchloric acid (HClO4).

3.2 Reagents preparation

3.3 Standard substance

Metal manganese standard substance (Mn). purity > 99.99%.

3.4 Preparation of standard solution

3.4.1 Manganese standard stock solution (1000mg/L). accurately take 1g (accurate

to 0.0001g) of metal manganese; add nitric acid to dissolve; transfer into 1000mL

volumetric flask; add nitric acid solution to the scale; mix evenly; store into the

polyethylene bottle at 4°C; or use the standard solution certified by the state, awarded

standard substance certificate.

3.4.2 Manganese standard working solution (10.0mg/L). accurately pipette 1.0mL of

manganese standard stock solution into the 100mL volumetric flask; use the nitric acid

solution to dilute to the scale; store into the polyethylene bottle at 4°C.

4.1 Atomic absorption spectrometer, equipped with flame atomizer, manganese

hollow cathode lamp.

4.2 Analytical balance. sensitivity is 0.1mg and 1.0mg.

4.6 Adjustable temperature-control electric hot plate.

4.7 Adjustable temperature-control electric hot furnace.

4.8 Microwave digestion instrument, equipped with Teflon digestion inner tank.

4.9 Constant-temperature drying oven.

4.10 Pressure digestion tank, equipped with Teflon digestion inner tank.

5.1 Specimen preparation

5.1.1 Solid sample

5.1.2 Liquid sample

Shake evenly the soft drinks, spices and the like samples.

5.1.3 Semi-solid sample

Stir evenly.

5.2 Sample digestion

5.2.1 Microwave digestion method

Take 0.2g~0.5g (accurate to 0.001g) of specimen into the microwave digestion inner

tank; firstly, heat the sample contained ethanol or carbon dioxide at low temperature

on the electric hot plate to remove ethanol or carbon dioxide; add 5mL~10mL of nitric

acid; cover it to stand for 1h or stay overnight; tighten the outer tank;

5.2.2 Digestion method of pressure tank

Take 0.3g~1g (accurate to 0.001g) of specimen into the Teflon pressure digestion inner

tank; firstly, heat the sample contained ethanol or carbon dioxide at low temperature

on the electric hot plat to remove the ethanol or carbon dioxide; add 5mL of nitric acid;

cover it to stand for 1h or stay overnight; tighten the outer tank;

5.2.3 Wet digestion method

Take 0.5g~5g (accurate to 0.001g) of specimen into the glass vessel or Teflon digestion

vessel; firstly, heat the sample contained ethanol or carbon dioxide at low temperature

on the electric hot plate to remove the ethanol or carbon dioxide; add 10mL of mixed

acid; cover it to stand for 1h or stay overnight; place it on the adjustable temperature-

control electric hot plate or electric hot furnace for digestion;

5.3 Instrument reference conditions

Optimize the instrument to the best conditions; major reference conditions. absorption

wavelength 279.5nm, slit width 0.2mm, lamp current 9mA, gas flow rate 1.0L/min.

5.4 Drawing of standard curve

Separately inject the standard series working solutions into the atomic absorption

spectrometer; measure their absorbance values; draw standard curve with

concentration of standard working solution as abscissa, while the absorbance value

as ordinate.

5.5 Determination of sample solution

Under the same experimental conditions for determination of the standard cure

working solution, inject the blank solution and specimen solution into the atomic

absorption spectrometer; measure the absorbance value of manganese; the

manganese concentration of the to-be-tested solution can be obtained from the

standard curve.