The export of tea leaves is influenced by the content of magnetic metals and has become more and more common in recent years. The Ministry of Agriculture's Tea Quality Supervision, Inspection and Test Center examined six batches of Zhejiang tea exports. There were five batches of tea that detected magnetic substances. The CJ magnetic metal detector was the main instrument for the determination of magnetic metals. Thus, in addition to the impact of pesticide residues and heavy metal elements, China's tea exports will become a new factor in the export of tea. At present, the commonly used method for the determination of magnetic substances in tea leaves is that a magnet is used to suck back and forth several times in tea leaves, and then the adsorbed magnetic substance is collected from the magnet and weighed. There are many shortcomings of this method. For example, some tiny magnetic materials wrapped in tea cannot be adsorbed by magnets. There is a problem of incomplete collection when collecting magnets adsorbed by magnets. Inclusion of some tea powders that are absorbed by static electricity affects the accuracy of the determination of magnetic substances in tea. Scan the QR code below to watch the Top WeChat official WeChat (also WeChat search: top instrument), agricultural equipment information in real time view: Urban Bike Helmet,Urban Helmet Bicycle,Stylish Urban Helmet Bike,City Bike Helmet Dongguan Yoloon Sports Goods Co.,LtD , https://www.yoloonprotection.com
Determination of magnetic material. The grinded sample was poured into the upper container of the measuring device, the power was turned on, and the electromagnet was energized. The motor was started and the flow control plate was adjusted so that the sample flowed into the sample holding box via the seesaw. After the sample flow, cut off the power, cut off the magnet and brush off the magnetic material and put a known weight of the citrus. The sample was repeated twice according to the above method, and the magnetic materials were each brushed into a citrus vortex, and rinsed several times with carbon tetrachloride until the tea powder was removed, then dried, cooled, and weighed.
The magnetic material in tea was determined with CJ Magnetic Metal Detector. The recoveries were between 95% and 102%. The relative standard deviation (RSD) was 1.4% and the detection limit was 0.01%. The indicators of the method were all satisfactory. The requirements of the detection method and the method are simple to operate and are suitable for the inspection requirements of various companies and quality inspection departments. In the pre-treatment, the tea is smashed with a pulverizer and sieved through a 28-mesh sieve. This allows the small magnetic material trapped inside the tea to also be adsorbed. This method uses an electromagnet. When the electricity is turned off, the magnetism disappears and the magnetic material disappears. Can be all collected, to overcome the problem of incomplete collection of magnetic material on the general magnet; the final use of four described carbon rinsing can completely eliminate the adsorption of tea due to static electricity, improve the accuracy of the method. 