Soil cadmium column

Soil cadmium column

Cadmium column reduction device (determination of nitrate and nitrite in food and dairy products)

【 Material 】glass

Instructions for Use:

1 【Introduction to the device】

Cadmium column reduction device used in foodnitriteandnitrateThe determination of nitrate is in accordance with GB 5009.33-2010. The cadmium column reduction device used for nitrate determination by cadmium column method includes a storage funnel with capillary tube, a connecting plug, a cadmium column, and a cadmium column glass tube. The lower end of the cadmium column glass tube has a J-shaped liquid outlet capillary tube, characterized in that there is at least one reinforced connecting column between the outer wall of the cadmium column glass tube and the outer wall parallel to the J-shaped liquid outlet capillary tube. Due to the reinforcement of the connecting column, the device is not easily broken and has a long service life.

II 【principle】

Determination of Nitrite by Cadmium Column Reduction Method and Naphthalene Ethylenediamine Hydrochloride Method

After precipitation of protein and removal of fat, the sample was diazotized with nitrite and p-aminobenzenesulfonic acid under weak acid conditions, and then reacted with naphthylethyl hydrochloride

Diamine coupling forms a purple red dye, and the nitrite content is measured by external standard method. Using a cadmium column to reduce nitrate to nitrite, nitrite was measured

The total amount of salt is subtracted from the nitrite content to obtain the nitrate content in the sample.

III 【Usage】

Preparation of sponge like cadmium: Add enough zinc skin or zinc rod into 500 mL of cadmium sulfate solution (200 g/L), and after 3-4 hours, when

After all the cadmium is replaced by zinc, gently scrape off with a glass rod, remove the residual zinc rod, let the cadmium sink to the bottom, pour out the upper clear liquid, and pour it with water

Wash the metal particles multiple times, then transfer them to a tissue grinder, add 500 mL of water, crush for about 2 seconds, and wash the metal particles onto a standard sieve with water

The part between 20 and 40 mesh.

Loading of 2 cadmium columns: as shown in Figure 2. Fill the cadmium column glass tube with water and place a 2cm high glass wool pad as a cushion, pressing the glass wool towards the bottom of the column

At that time, all the air contained in it should be expelled, and sponge like cadmium should be added under gentle tapping to a height of 8 cm to 10 cm, with a height of 1 cm on top

Cover with glass wool, place a storage funnel on top, and tightly connect the end to the cadmium column glass tube through a rubber stopper.

If there is no cadmium column glass tube mentioned above, a 25 mL acid burette can be used as a substitute, but attention should be paid to always keeping the liquid level above the cadmium layer when passing through the column.

After filling the cadmium column, wash it with 25 mL hydrochloric acid (0.1 mol/L) first, and then wash it twice with water, each time with 25 mL of water. When the cadmium column is not in use, use water

Cover, always keep the horizontal plane above the cadmium layer, and do not allow bubbles to be trapped in the cadmium layer.

4 【Determination of Reduction Efficiency of Cadmium Column】

Take 20 mL of standard sodium nitrate solution, add 5 mL of diluted ammonia buffer solution, mix well, and inject

Enter the storage funnel and let it flow through the cadmium column for reduction. Collect the effluent in the original beaker. After the sample liquid in the storage funnel has flowed out, add 5 mL of water for replacement

The sample liquid retained in the column. Take 10.0 mL of reduced solution (equivalent to 10 μ g of sodium nitrite) and transfer it to a 50 mL colorimetric tube. Follow 11.4 steps below

Operate according to the standard curve starting from "suction 0.00 mL, 0.20 mL, 0.40 mL, 0.60 mL, 0.80 mL, 1.00 mL..."

The calculated results should be consistent with the addition amount *, and the reduction efficiency should be greater than 98% to meet the requirements.