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(2) Purification method
At present, the literature reports that the purification methods of β-lactam drugs in animal tissues mainly include: liquid-liquid partition (LLP), solid phase extraction (SPE) and matrix solid phase dispersion technology (MSPD)
.
1) Liquid-liquid partition (liquidliquidpartition, LLP)
In the early sample purification methods, LLP was mainly used to achieve sample purification
.
After the sample has been extracted, it contains many impurities, and the initial extract cannot be directly analyzed by the instrument, and another step of purification is required to remove interfering substances
Lihl et al.
detected 5 penicillins in cattle muscle tissue, extracted with acetonitrile -phosphate solution, and purified with dichloromethane LLP
.
However, this method is not suitable for the extraction of amphoteric β-lactam drugs, especially penicillin G.
2) Solid phase extraction (solidphase extraction, SPE)
SPE does not require a large amount of organic solvents and is not easy to produce emulsification.
It is not only more effective, but also easier to achieve automatic and rapid extraction of trace drugs remaining in animal-derived foods
.
Marazuela et al.
A.
HLB column
During reverse-phase SPE purification, the organic solvent in the loading solution may increase the elution strength, which is not conducive to the retention of the target compound.
Therefore, it is necessary to concentrate and remove the organic solvent before performing the SPE purification
.
Becker et al.
D used acetonitrile-water to extract 15 kinds of β-lactam antibiotics from milk, beef and cattle kidneys, rotary evaporation to remove organic solvents, and reconstituted with pH 8.
5 phosphate buffer for use as a hydrophilic-lipophilic balance material (Divinylbenzene-co-N-vinylpyrrolidone polymer) as the adsorption matrix Oasis HLB column purification, acetonitrile-water (1+1, v/v) as the eluent, the recovery rate is 71% ~ 116%
.
Sorensen et al.
B.
C 18 column
CisSPE columns are also widely used in the detection of β-lactam drug residues
.
Terada et al.
used Sep-Pak C18 column to purify penicillin G in seafood
.
Sep-PakC 18 column is first washed with 20mL methanol, 20mL water, 2mL 2% sodium chloride solution, the extract is passed through the column at a speed of 2mL/min, and then 10mL 2% sodium chloride solution and 10mL methanol-water are used in sequence .
C.
Anion exchange column
The anion exchange SPE column can effectively retain the organic weak acid β-lactam drugs
.
Meetsehen et al.
used gas chromatography (GC) to determine the residues of 7 PENs in animal-derived foods (beef, bovine liver, bovine kidney, adipose tissue and milk)
.
The sample was extracted with acetonitrile under acidic conditions, and then sodium chloride and dichloromethane were added for LLP purification, followed by purification with an anion exchange column
Related links: Maximum allowable residue limits for β-lactam drugs
