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9.
It is suitable for the determination of zearalenol, zearalenone, diethylstilbestrol, diethylstilbestrol and diethylstilbestrol residues in milk and milk powder by liquid chromatography-tandem mass spectrometry
9.
Milk and milk powder zeranol , Zearalanone , diethylstilbestrol , hexoestrol , dienes female phenol residue with acetonitrile extraction and extraction agent as protein precipitation, anionic solid phase extraction column for purification by liquid Chromatography-tandem mass spectrometer determination, internal standard method quantification
9.
Methanol, acetonitrile: chromatographically pure; ammonia, formic acid , sodium hydroxide : analytically pure
5mol/L sodium hydroxide solution: Weigh 200g of sodium hydroxide and dilute the volume to 1L with distilled water
Eluent: ammonia-water (1+19, v/v); eluent: formic acid-methanol (1+19, v/v)
Hormone and metabolite standard substances: Zearalenol (including α-zearalenol and β-zearalenol, 50% each) purity ≥97%; zearalenone, purity ≥97%; Diethylstilbestrol, purity ≥99 %; Hexestrol, purity ≥98%; Diethylstilbestrol, purity ≥98%
Standard solution: accurately weigh appropriate amounts of zearalenol, zearalenone, diethylstilbestrol, diethylstilbestrol and hexestrol standard substances, and prepare 1mg/mL standard stock solution with methanol
Internal standard standard material: a-zearalenol-4 deuterated, purity ≥99%; diethylstilbestrol-8, purity ≥98%
Internal standard standard solution: Accurately weigh appropriate amounts of zearalenol-4 deuterated and diethylstilbestrol-8 deuterated standard materials, and prepare 1mg/mL standard stock solutions with methanol
Matrix standard working solution: mix the standard working solution and the internal standard working solution and blow-dry it in a nitrogen blower, dissolve it with the matrix extract, and vortex for 30 seconds to become the matrix standard working solution
Oasis MAX anion solid phase extraction column or equivalent: 60mg, 3mL
9.
Liquid chromatography-tandem mass spectrometer: equipped with electrospray ionization source; automatic solid phase extraction or solid phase extraction device; nitrogen drying device; vortex oscillator; centrifuge: speed greater than 3500r/min; high-speed centrifuge : The speed is greater than 9000r/min, and the temperature can be controlled at 4°C
9.
2.
4.
5 Sample preparation
(1) Sample preparation
Milk: Take 50mL of fresh or thawed milk and mix well, centrifuge at 3500r/min for 5min, and remove the lower layer; Milk powder: Take 12.
5g of milk powder in a beaker, add an appropriate amount of water at 35~50℃ to dissolve it slowly, and transfer to a 100mL volumetric flask , After cooling to room temperature, dilute to volume with water and mix well
.
Take 50mL, centrifuge at 3500r/min for 5min, and remove the lower layer
.
(2) Sample measurement
In a 50mL centrifuge tube, add different amounts of mixed standard working solution to make the concentration of each tested component zearalenol, zearalenone, hexestrol, diethylstilbestrol and diethylstilbestrol 2.
5ng/mL, 5.
0ng/mL, 10ng/mL, 25ng/mL, 50ng/mL
.
Then add an appropriate amount of internal standard standard working solution to make the concentration all 10ng/mL, and blow dry in a water bath at 40°C on a nitrogen blowing instrument
.
Take 5 negative samples, each sample is 5mL, put them in the above centrifuge tube and vortex to mix, add 10mL acetonitrile, vortex for 3min, centrifuge at 3500r/min for 10min, take the supernatant in the centrifuge tube, and then add the sample Add 5 mL of acetonitrile to it, the same operations as before, combine the extracts, and blow nitrogen at 50°C until the volume is less than 0.
1 mL
.
Add 10mL of water, adjust the pH to 11.
0 with 5mol/L NaOH, centrifuge at 9000r/min for 5min at 4°C, and set aside
.
(3) Extraction and purification
Solid-phase extraction purification conditions: first activate the column with 2mL methanol and 2mL water at a flow rate of 4mL/min
.
The sample supernatant was applied to the column with a flow rate of 1 mL/min, followed by elution with 1 mL of eluent and 0.
5 mL of methanol at a rate of 3 mL/min, and 20 mL of air was blown through the OasismAX column at a rate of 4 mL/min
.
Elute with 4 mL of eluent at a flow rate of 1 mL/min.
Add 30 mL of air and blow through the OasismAX column at a rate of 6 mL/min to collect the eluent
.
The eluate was blown dry in a 40°C water bath on a nitrogen blower, 1 mL of mobile phase was added, and vortexed for 30 seconds to dissolve
.
After the solution passes through a 0.
2μm filter membrane, it is used for liquid chromatography-tandem mass spectrometry
.
(4) Matrix extract
For the blank sample, except that the standard working solution and internal standard working solution are not added, the other operations are the same as the solution obtained after the above steps
.
(5) Preparation of measured sample solution
Take 5mL of the sample to be tested in a 50mL centrifuge tube, add an appropriate amount of internal standard standard working solution to make the final constant volume concentration of 10ng/mL follow the above steps
.
(6) Preparation of blank matrix solution
Take 5mL of the negative sample in a 50mL centrifuge tube and follow the steps above
.
Related links: Determination of linear range and detection limit of zearalenol, zearalenone, diethylstilbestrol, hexestrol, and diethylstilbestrol residues in puffer fish, eels and grilled eels