AC Coconut Shell Activated Carbon Solid Phase Extraction Column

GB5009.332025

Nitrite standard solution (5.00mg/L): Take 2.50mL of nitrite standard reserve solution into a 100mL volumetric flask and dilute with water to the mark. Ready to use and ready to use.

Nitrate standard solution (5.00mg/L): Take 2.50mL of nitrate standard reserve solution into a 100mL volumetric flask and dilute with water to the mark. Ready to use and ready to use.

material

Coconut shell activated carbon solid-phase extraction column (2g). Activate sequentially with 5mL of methanol and 5mL of water before use.

Instruments and equipment

Electronic balance: sensitivity of 0.1mg and 0.01g.

Organize crushers or grinders.

Ultrasonic cleaner.

Constant temperature drying oven: temperature control accuracy ± 2 ° C.

Thermostatic water bath.

Spectrophotometer.

Cadmium column device: The cadmium column device can be filled with commercial cadmium particles, or cadmium particles can be prepared according to the method in Appendix B. The determination of cadmium column reduction efficiency shall be carried out according to the method in Appendix C.

analysis steps

extract

Milk and dairy products, infant formula foods, and special medical formula foods: Weigh 45g-90g (accurate to 0.01g) of liquid sample and 1g~10g (accurate to 0.01g) of solid sample, place them in a 250mL conical flask with a stopper, add 12.5mL of 50g/L sodium borate solution and water at around 70 ° C in sequence to a total volume of about 160mL (for cheese samples that are not easily dispersed, they can be heated to disperse), mix well, heat in a boiling water bath for 15 minutes, take them out and cool them in a cold water bath, and place them at room temperature. Quantitatively transfer the above extraction solution to a 200mL volumetric flask, add 5.00mL of 106g/L ferrocyanide solution, shake well, and then add 5.00mL of 220g/L zinc acetate solution to precipitate the protein. Add water to the mark, shake well, and let it stand for 30 minutes (centrifuge operation can be added if necessary to clarify the filtrate), remove the upper layer of fat, filter the supernatant with filter paper, discard 30mL of the initial filtrate, and set aside the filtrate for later use.

Highly gelatinized high starch content sample: Weigh 5g (accurate to 0.01g) of the sample and place it in a 150mL stoppered conical flask. Add 0.5g of alpha amylase (the enzyme dosage can be adjusted according to the starch content), add 60mL of water, mix well, and place it in a 60 ° C water bath for 15 minutes. Then add 12.5mL of 50g/L sodium borate solution, heat it in a boiling water bath for 15 minutes, take it out and cool it in a cold water bath, and let it stand at room temperature.

Other samples: Weigh 2.5g-5g (accurate to 0.01g) of the sample and place it in a 250mL stoppered conical flask. Add 12.5mL of 50g/L sodium borate solution and approximately 150mL of water at around 70 ° C, mix well, heat in a boiling water bath for 15 minutes, remove and cool in a cold water bath, and let it stand at room temperature. Transfer the above extraction solution quantitatively to a 200mL volumetric flask.

Note: When the supernatant becomes opaque, the volume of ferrocyanide solution and zinc acetate solution can be adjusted; When the turbidity or chromaticity of the sample interferes with the detection results, the filtrate can be passed through a coconut shell activated carbon solid-phase extraction column, and the first 5mL of filtrate can be discarded to obtain the purified filtrate. If the sample has a darker color and cannot achieve the desired purification effect after one purification, it can be purified again using a coconut shell activated carbon solid-phase extraction column or a purification column with a larger column capacity can be used.