GB 5413.5-2010National food safety standard - Determination of lactose and sucrose in foods for infants and young children, milk and milk products (English PDF)

4.1 Acetonitrile.

4.2 Acetonitrile. chromatographically pure.

4.3 Standard solutions

4.3.1 Lactose standard stock solution (20 mg/mL). WEIGH 2 g (accurate to 0.1

mg) of the lactose standard sample dried in an oven at 94 °C±2 °C for 2 h;

DISSOLVE in water; USE water to dilute to a 100 mL volumetric flask. PLACE

4.3.4 Sucrose standard working solutions. separately PIPETTE 0 mL, 1 mL, 2

mL, 3 mL, 4 mL, 5 mL of sucrose standard solution (4.3.3) in 10 mL volumetric

flasks; USE acetonitrile (4.1) to dilute to mark. The series of sucrose standard

working solutions are prepared, at concentrations of 0 mg/mL, 1 mg/mL, 2

mg/mL, 3 mg/mL, 4 mg/mL, 5 mg/mL respectively.

5.1 Balance. The sensitivity is 0.1 mg.

5.3 Ultrasonic oscillator.

6.1 Sample processing

WEIGH 1 g of solid sample or 2.5 g (accurate to 0.1 mg) of liquid sample into a

6.2 Determination

6.2.1 Reference chromatographic conditions

Chromatographic column. Amino column 4.6 mm×250 mm, 5 µm, or column

with equivalent performance;

6.2.2 Making of standard curve

The series of standard working solutions is separately injected into the high

performance liquid chromatograph. The corresponding peak area or peak

height is determined.

10.1 Lead acetate.

10.2 Potassium oxalate.

10.3 Disodium hydrogen phosphate.

10.7 Potassium sodium tartrate.

10.8 Sodium hydroxide.

10.9 Phenolphthalein.

10.10 Ethanol.

10.11 Methylene blue.

10.12 Lead acetate solution (200 g/L). WEIGH 200 g of lead acetate;

DISSOLVE in water and dilute to 1000 mL.

10.13 Potassium oxalate-disodium hydrogen phosphate solution. WEIGH 30 g

of potassium oxalate, 70 g of disodium hydrogen phosphate; DISSOLVE in

water and dilute to 1000 mL.

10.14 Hydrochloric acid (1+1). 1 volume of hydrochloric acid is mixed with 1

volume of water.

10.17 Phenolphthalein solution (5 g/L). WEIGH 0.5 g of phenolphthalein in 100

mL of ethanol with a volume fraction of 95%.

10.18 Methylene blue solution (10 g/L). WEIGH 1 g of methylene blue in 100

mL of water.

11.1 Balance. The sensitivity is 0.1 mg.

12.1 Calibration of Fehling's solution

12.1.1 USE lactose to calibrate

12.1.1.1 WEIGH about 0.75 g (accurate to 0.1 mg) of the lactose standard

sample pre-dried in an oven at 94 °C±2 °C for 2 h; USE water to dissolve and

dilute to 250 mL. Inject the lactose solution into a 50 mL burette for titration.

12.2 Determination of lactose

12.2.1 Sample processing

12.2.1.1 WEIGH 2 g of infant food or skim powder, 2.5 g of whole sugared

powder or whole powder, 1 g of whey powder, accurate to 0.1 mg. USE 100 mL

of water to dissolve several times and WASH into a 250 mL volumetric flask.

12.2.2 Titration

12.2.2.1 Pre-titration. The operation is the same as 12.1.1.2.

12.2.2.2 Precise titration. The operation is the same as 12.1.1.3.

12.3 Determination of sucrose

13.1 Lactose

The content X of lactose in the sample shall be calculated according to formula

(6)

13.3 If the ratio of sucrose to lactose in the sample exceeds 3.1, when

calculating the lactose, the corrected value in Table 2 shall be added to the

titration volume and then Table 1 is referred.