Simple identification method for adulteration of calcium hydrogen phosphate
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Common calcium hydrogen phosphate adulterants are: stone powder, bone powder, agricultural superphosphate, tricalcium phosphate, talc powder, a mixture of phosphate rock powder and phosphoric acid, and a mixture of stone powder and phosphoric acid. Some of these adulterated products contain higher levels of calcium and phosphorus, but the utilization rate of livestock and poultry is very low; some contain a large amount of fluorine, which seriously endangers the health of livestock and poultry. The following describes the method for the identification of calcium hydrogen phosphate, for reference only.
1 Appearance feed grade calcium hydrogen phosphate is a white powder with uniform fineness. Calcium hydrogen phosphate mixed with bone powder has a dull or yellowish color and a bone powder smell.
2 Phosphate ion test A small amount of sample is wetted with 5% silver nitrate solution and yellow, indicating the presence of phosphate ions, otherwise the sample is not calcium hydrogen phosphate.
3 Calcium ion test Weigh 0.1g sample, add 5ml glacial acetic acid, boil and cool, filter, add 5ml of 3% ammonium oxalate solution to the filtrate, if a white precipitate is formed, it indicates the presence of calcium ions.
4 Dissolution test Take a small amount of the sample and dissolve it with salt. If it is vigorously bubbling, a 0.3% calcium hydroxide solution (upper layer clear liquid) will be produced. If a white precipitate is produced, the sample is mixed with calcium powder such as stone powder; If it is completely insoluble, the sample may be phosphate rock powder, talcum powder, etc.; if a small amount is dissolved, the sample may be agricultural superphosphate.
5 Determination of phosphorus content In the acidic medium, the phosphate in the sample solution and the quinoline molybdate form a quinoline phosphomolybdate precipitate, the precipitate is filtered, washed, dried at 180 ° C, weighed, and the phosphorus content is calculated. The national feed standard stipulates that the phosphorus content (P) is ≥16.0%, and the normal content range is from 16.00% to 18.0%. If it is not within this range, it is a adulterated product.
6 Determination of calcium content Add excess amount of disodium edetate solution to the sample solution, complex with calcium ions, use chrome black T as indicator, titrate excess sodium disodium edetate with zinc standard solution , calculate the calcium content. The national feed standard stipulates that the calcium content is ≥21.0%-23.3%. If it is not within this range, it is a fake product.
7 Determination of fluorine content Fluorine is a trace element necessary for normal physiological activities of animals, but it is also a toxic element. Long-term intake of feed containing super-scalar fluoride in livestock and poultry can cause chronic fluorosis, which seriously affects the normal growth of livestock and poultry, so it is necessary to detect fluoride in calcium hydrogen phosphate. The detection of fluorine generally uses a fluoride ion selective electrode method. The national feed standard stipulates that the fluoride content in feed grade calcium hydrogen phosphate should not exceed 1800 mg/kg. If the measured result exceeds the standard, it is adulterated or not detoxified and cannot be used.