Determination of melamine in animal food by GC-MS
Spectra-Quad on-line detection of melamine content by ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry for determination of residual melamine in feed by RP-HPLC method for determination of melamine in feeds by high performance liquid chromatography-diode array method for determination of high protein foods Determination of Melamine in Feed by High Performance Liquid Chromatography (HPLC) with High Performance Liquid Chromatography-Quadrupole Mass Spectrometry[J]. Determination of Melamine Content in Feeds by Solid Phase Extraction and High Performance Liquid Chromatography for Determination of Melamine Liquid in Pet Foods Determination of melamine residues in feed by melamine liquid chromatography-tandem mass spectrometry in pet food by chromatography-tandem mass spectrometry (LC-MSMS)
Determination of melamine in animal food by GC-MS method: melamine detection method example instrument and condition high performance liquid chromatography; diode array detector (DAD), detection wavelength 240nm, column temperature: 40 °C.
(1) AgelaVenusilTM ASBC18 (4.6 x 250 mm); buffer: 10 mM citric acid, 10 mM sodium heptane sulfonate; mobile phase: buffer solution: acetonitrile = 85:15; flow rate: 1.0 mL/min.
(2) AgelaVenusilTM ASBC8 (4.6 × 250 mm); mobile phase: buffer: acetonitrile = 85:15; buffer: 10 mM citric acid, 10 mM sodium octane sulfonate, adjusted to pH 3.0; flow rate: 1.0 mL / min;
Ion exchange solid phase extraction column AgelaClearnertTMPCX
Reagents and samples Pet feed samples (provided by the Ministry of Agriculture Feed Supply Center); methanol, acetonitrile for Beijing Aijieer Technology Co., Ltd.; ammonia, lead acetate, three, are purchased from Beijing Chemical Reagent Company; melamine standard, citric acid, Sodium octane sulfonate (Sigma); methanol is chromatographically pure, others are chemically pure.
experimental method
1, sample pretreatment method
(1) Standard sample preparation:
Take 50 mg of melamine standard, dissolve to a volume of 50 mL in 20% methanol to obtain a standard solution of 1000 ppm, and when used, dilute to the desired concentration with the extract (0.1% tri).
(2) Extraction:
Weigh 5g of feed sample, add 50ml of 0.1% three extracts, mix well, add 2mL 2% lead acetate solution, and sonicate for 20min.
Then, a part of the solution was transferred to a 10 mL centrifuge tube, centrifuged at 8000 rpm/min for 10 min, and the supernatant was subjected to a 3 mL over-mixed cation exchange cartridge (PCX).
(3) Purification (PCX cartridge, 60mg/3mL):
a) Activation and balance: 3 mL of methanol, 3 mL of water
b) Loading: adding extract 3mL
c) Rinse: 3 mL of water; 3 mL of methanol; discard the eluent and drain the cartridge.
d) Elution: 5 mL of 5% ammoniated methanol (v/v) eluted. (Preparation of 5% ammoniated methanol: 5 mL ammonia water + 95 mL methanol).
e) Concentration: 50 ° C, nitrogen blow dry, 20% methanol / water to 2 mL, HPLC analysis or post-derivative GC / MS analysis.
2, melamine was filed
2.1 Melamine HPLC-UV detection method Melamine is a highly polar compound, which is poorly retained on the traditional reversed-phase C18 column. It requires ion-pair reagent chromatography to have good retention and separation. According to the US Food and Drug Administration (FDA) The melamine test method and the melamine test method announced by the Ministry of Agriculture of China use Agela ASB series hydrophilic column to obtain good separation effect:
(a) Column: Venusil ASBC 84.6 x 250 mm; standard: FDA method; mobile phase: buffer: acetonitrile = 85:15; buffer: 10 mM citric acid, 10 mM sodium octane sulfonate, adjusted to pH 3.0; 1.0 mL/min; column temperature: 40oC; wavelength: 240nm
(b) Column: Venusil ASB-C184.6×250mm; Standard: Standard method issued by the Ministry of Agriculture; Buffer: 10 mM citric acid, 10 mM sodium heptane sulfonate; Mobile phase: buffer solution: acetonitrile = 85:15; : 1.0 mL / min; column temperature: 40 ° C; wavelength: 240 nm
Blank plus level (mg / L) recovery rate 0.01116% 0.1108% 0.592%296%
2.2 Melamine LC-MS detection method Because the FDA published the HPLC-UV method, the mobile phase added ion-pairing reagent, thus limiting the use of the LC-MS method; but without the ion-pair reagent chromatography method, melamine in the traditional C18 column The retention on the surface is very poor, and good separation and quantification cannot be obtained [3].
Based on this problem, Aijieer Technology has independently developed a new method, using Agela ASB series hydrophilic column, which can effectively retain and separate without ion pair reagent. Therefore, the mobile phase of the method does not contain an ion pair reagent and can be used for mass spectrometry.
Compared with the FDA's April 2007 published "Updated FCCD evelopmental Melamine Quantitation (HPLC-UV)", this method greatly reduced the minimum detection limit (MSD: 0.5 ppm; UV: 2 ppm) and improved the detection sensitivity.
In this method, a good spectrum was obtained in ASB-C84.6×250 mmASB-C184.6×250 mm.
Buffer: 10 mM NH4AC; Mobile phase: Buffer:: ACN=95:5; Flow rate: 1.0 mL/min; Injection volume: The sample was first dissolved with 70% ACN to about 1 mg/mL, and diluted with ACN to 0.1 mg/min. mL, into 10uL; column temperature: 40 ° C; wavelength: 240 nm
Results and discussion
1. Cation exchange column (PCX)
Melamine is weakly alkaline (weak cationic compound), and the cation exchange column should generally be selected for the purification process. A mixed cation exchange column (PCX) has two types of cation exchange and reverse phase adsorption by bonding a sulfonic acid group (-SO3H) to a polar polymer polystyrene/divinylbenzene (PEP) adsorbent. Mechanism, and has the following advantages:
a) The washing of two different solutions (water/pH buffer solution and organic solvent) can make the sample cleaner and improve the sensitivity of the test.
b) Batch repeatability is good.
c) High recovery rate and good reproducibility, even if the column runs dry, it can get higher recovery rate.
2, LC-MS method advantages:
(1) The detection process is simple: without the addition of ion pair reagents, melamine can be well retained and separated, avoiding the complicated process of preparing ions to the mobile phase.
(2) Improved detection sensitivity: no ion pair reagents, can be used in mass spectrometry detectors, greatly reducing the minimum detection limit (MSD: 0.5ppm; UV: 2ppm).
(3) Reduce the cost of detection: without the use of ion-pairing reagents, it is no longer necessary to buy more expensive ion-pairing reagents, thereby reducing the cost of testing.
(4) Extends column life: avoids the use of ion-pairing reagents to reduce column life.
(5) The column used in this method is versatile: whether using the FDA method, the standard method of the Ministry of Agriculture, and the LC-MS method developed by the company, using the Agela ASB series hydrophilic column Both can get a good test result, thus providing customers with a variety of choices.
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