Sample Preparation In Food Safety Of QuEChERS
At present, liquid chromatography-tandem mass spectrometry for the determination of lean meat in animal-derived foods generally uses enzymatic hydrolysis extraction and solid-phase extraction purification to process samples.
This method is time-consuming and expensive. In this study, acid extraction and enzymatic hydrolysis were used in combination with QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) purification and high-performance liquid chromatography-tandem mass spectrometry to establish terbutaline, salbutamol, and ractopamine in animal food And Clenbuterol for rapid qualitative confirmation and quantitative detection of 4 β2 receptor agonists. Enzymatic hydrolysis extraction-QuEChERS purification treatment samples.
Under electrospray ion source positive ion scanning (ESI +) and multiple reaction monitoring (MRM) modes, the four types of clenbuterol are linear and linear between 1.0 and 20.0 μg / L. The correlation coefficients were all greater than 0.999. The detection limits and quantification limits were 0.1 and 0.3 μg / kg, respectively. The recoveries of the four compounds in pork and beef samples were 78.5% to 112%, and the relative standard deviations RSD were 2.8% to 8.9%.
When the acid hydrolysis method is used instead of the enzymatic hydrolysis extraction, although the ractopamine measurement results in the sample are slightly lower, the sample pretreatment time is greatly shortened. The combination of the two extraction methods is of great significance to improve the efficiency of emergency treatment of food poisoning caused by lean meat essence.
Phase 1: Complex pre-processing methods
Sample pulverization-extraction-GPC purification-SPE cartridge purification (may require multiple purifications)-nitrogen blowing or other concentration constant volume-instrument detection , Elution, collection, etc.)
The main goal at this stage is to determine more residues in the presence of complex matrices to meet various regulatory requirements.
The challenge is: very slow.
Second stage: QuEChERS method
Crushing of the sample—single solvent extraction and separation with acetonitrile—adding salts such as MgSO4 to remove water—adding adsorbents such as ethylenediamine-N-propyl silane (PSA) to remove impurities—detection by supernatant instrument.
Advantages: fast, simple, many laboratories want to change the original pretreatment method to QuEChERS method.
The challenge is: The traditional QuEChERS method uses solid-phase adsorption materials PSA, C18, GCB, and Carbon. Its purification capacity is limited, and it can only process simple samples such as fruits and vegetables. Samples containing alkaloids and organic acids (such as green leafy vegetables, shiitake mushrooms, green onions, ginger, garlic, tea, cereals, medicinal plants, animal-derived foods) are not ideally purified.
Operation Principle of QuEChERS
There is some operative principle provided for consideration: first use a single organic solvent to extract the target in the matrix, such as pesticide residues, then add the extraction salt to the matrix to shock centrifugation, then use the dispersed solid phase extraction, use the adsorbents such as SPE, C18、Carb to purify, remove the fatty acid, pigment, carbohydrate and other interferences from the components, and finally take the upper layer clear solution for analysis after centrifugation.
Extraction Steps of QuEChERS
Specific steps are as followed: first, take a certain amount of homogenized sample in a plastic centrifuge tube, add the internal standard and acetonitrile and shake violently; second, add the extraction salt, shock centrifugation to ensure the stability of the target compound, at the same time, the moisture in the matrix is completely separated from the acetonitrile extract. Then a certain amount of supernatant was added to the purification tube, and the fatty acids, pigments, and carbohydrates were removed from the components with the adsorbent. Finally, shock, centrifugation, take the upper liquid can be analyzed.