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-------- Crayfish food safety testing (1)
As the summer approached, crayfish began to flourish on the table. However, there are also news reports that someone in a certain area suspected that crayfish was being taken to the hospital. There are all kinds of sayings, and watching them is really scary. Can the crayfish be eaten in the end? Are some people worried about heavy metals, veterinary drugs, bleaching, etc.?
A physical and chemical testing center recently conducted a large test on a number of "net red" lobster shops. So what is the result? Today, Xiaobian will take you to the field to test it.
Sample preparation: 4 samples of crayfish samples purchased randomly: A physical and chemical testing center test items:
Detection of heavy metals: lead and cadmium detection of veterinary drug residues: malachite green nitrofuran detection bleaching anti-corrosion: sulfur dioxide detection illegal addition: papaverine five
Four crayfish samples were sent to a laboratory at a physical and chemical testing center. The experimenters began sampling and sample preparation, and tested four crayfish according to the heavy metal, veterinary drug antibiotic residue, bleaching and antiseptic, and illegal addition.
A week later, the results of four crayfish tests were finally released. (This experiment is only responsible for the sample being sent)
First, let's look at the results of heavy metal testing. This indicator mainly reflects whether the growth environment of crayfish is contaminated. Test reports showed that lead was not detected in four crayfish samples, but cadmium was detected in all four samples.
According to the national standard, the requirement for heavy metal cadmium in crustaceous aquatic products is 0.5mg/kg. The highest cadmium in the four samples is 0.22mg/kg, which is Meet the national requirements for heavy metal cadmium."
It seems that the first level of crayfish food safety testing: the detection of heavy metals, passed smoothly. The quality is still reassuring.
Then we will look down and see how crayfish food testing is done~~
Heavy metal refers to metals with a density greater than 5g/cm3, including 45 elements such as gold, silver, copper, lead, zinc, nickel, cobalt, cadmium, chromium and mercury. Heavy metal pollution refers to pollution caused by heavy metals and their compounds, mainly It refers to pollution caused by heavy metals such as mercury (mercury), cadmium, lead, chromium and metalloid arsenic and their compounds. Because heavy metals cannot be biodegraded, they can be enriched thousands of times under the biomagnification of the food chain and finally enter the human body. Moreover, heavy metals can interact strongly with proteins and enzymes in the human body, making them inactive, and may accumulate in certain organs of the human body, causing chronic poisoning. In recent years, the harm of heavy metal elements in food to the human body has gradually become recognized. Countries around the world have established strict limits for heavy metals in foods, which puts high demands on the accuracy, selectivity, sensitivity and analytical efficiency of trace analysis methods for heavy metals in different types of foods.
The content of heavy metal elements in food is extremely small, generally only in the order of μg/g or ng/g. It is difficult to detect. At present, atomic absorption spectroscopy (AAS) and hydride generation-atomic fluorescence spectroscopy (HG-AFS) are mainly used. ), inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and the combination of these methods with chromatography.
Today, Xiaobian mainly introduces absorption spectroscopy (AAS). 
Principle <br> After the sample is ashed or acid digested, a certain amount of sample digestive solution is injected into the atomic absorption spectrophotometer graphite furnace. After electrothermal atomization, the 228.8nm resonance line is absorbed, and the absorbance value is within a certain concentration range. It is proportional to the cadmium content and is quantified using the standard curve method.
Instruments and Equipment <br> Atomic Absorption Spectrophotometer with graphite furnace.
Cadmium hollow cathode lamp.
Electronic balance: The sensitivities are 0.1 mg and 1 mg.
Muffle furnace.
Analysis step
1. Sample preparation Dry sample: grain, beans, remove impurities; nuts to impurities, shelling; ground into a uniform sample, the particle size is not more than 0.425mm. Store in a clean plastic bottle and mark it for storage at room temperature or under sample storage conditions.
Fresh (wet) samples: vegetables, fruits, meat, fish and eggs, etc., homogenized or ground into a homogenate by a food processor, stored in a clean plastic bottle, marked with a mark, in - Store in a refrigerator at 16 °C ~ -18 °C.
Liquid sample: Stored in the sample storage conditions for use. Gas samples should be degassed before use. 
2. Sample digestion dry ashing: Weigh 0.3g ~ 0.5g dry sample (accurate to 0.0001g), fresh (wet) sample 1g ~ 2g (accurate to 0.001g), liquid sample 1g ~ 2g (accurate to 0.001g) in porcelain crucible, first small fire on the adjustable electric furnace carbonized to smokeless, moved into the muffle furnace 500 °C ashing 6h ~ 8h, cooling. If the individual samples are not completely ashed, add 1 mL of mixed acid to heat on a small adjustable electric furnace, dilute the mixed acid, and then transfer to a muffle furnace at 500 °C for ashing for 1 h to 2 h until the sample is completely digested. , grayish white or light gray. Let it cool, dissolve the ash with nitric acid solution (1%), transfer the sample digest solution to a 10mL or 25mL volumetric flask, wash the porcelain crucible 3 times with a small amount of nitric acid solution (1%), and mix the washing solution in a volumetric flask with nitric acid. The solution (1%) was adjusted to the mark and used; and the reagent blank test was performed at the same time.
Ohaus Analytical Balance can be selected in the experiment <br> Ohaus Adventurer® AX Analytical Balance, 320x 0.1mg Large scale one ten thousandth balance, suitable for any sample. The AX balance is very easy to clean for testing meat samples. The small size of the balance helps the lab save space on the console. Very helpful for complicated laboratory testing! Below, Xiaobian will take you to see the official announcement of AX~~
Impeccable! Ohaus continues to make progress in weighing performance, design and balance application functions, and has developed the new Adventure AX series of electronic balances. The Adventurer AX series is equipped with a color touch display that complies with GLP/GMP regulations. The front U disk reading interface, the overall space saving hood design, fully meet all the weighing needs of the laboratory. The Adventurer AX series is the best choice for your balance. 
The first test results of crayfish are reassuring, and there are other tests, so stay tuned~
If you want to know more about the balance series or other products of Ohaus, or are looking for more professional and detailed selection guide, please call 4008-217-188, or click to read the original text and leave relevant information. Our professional engineers will serve you wholeheartedly!
Reference: "Measured! Can the "Net Red" crayfish be safe to eat? This set of data tells you the truth! 》
Laboratory method for detecting the metal content of "Net Red" crayfish
Can the "Net Red" crayfish be safe to eat? This set of data tells you the truth!