Waters solution for simultaneous detection of dicyandiamide and melamine in dairy

Ding Juanjuan Ji Yinghua Zhao Jiayu Zhuang Shuyu Waters Technology (Shanghai) Co., Ltd.

Abstract: In 2008, Sanlu milk powder was found to be harmful to human body melamine, which shocked the country for a time. Since then, the state has been strengthening the regulation of melamine in milk powder. In early 2013, New Zealand milk and dairy products were found to contain low levels of the toxic substance dicyandiamide, and the New Zealand government has ordered the ban on the sale of milk products containing dicyandiamide.

Waters ^® has been committed to protecting the healthy lives of humans. It has developed a method for simultaneous detection of dicyandiamide and melamine in milk powder to improve the effectiveness of detection and analysis.

Dicyanamide (dicyandiamide), abbreviated DICY or DCD. It is a dimer of cyanamide and a cyano derivative of hydrazine. Chemical formula C ₂ H ₄ N ₄ . White crystal powder. It is soluble in water, alcohol, ethylene glycol and dimethylformamide, and is almost insoluble in ether and benzene.

Melamine, commonly known as melamine and protein concentrate, is a triazine-containing nitrogen-containing heterocyclic organic compound used as a chemical raw material. Slightly soluble in water, soluble in methanol, formaldehyde, acetic acid, hot glycol, glycerin, pyridine, etc., insoluble in acetone, ether, harmful to the body, not for food processing or food additives.

Analysis difficulties:
The main difficulty in the simultaneous analysis of dicyandiamide and melamine in milk powder is that although both are polar substances, HILIC chromatographic separation mode is required, but according to previous experience, melamine remains on the BEH HILIC column and peak shape is better. Well, dicyandiamide remains on the BEH Amide column and peak shape is preferred. Therefore, it is necessary to establish a unified LCMSMS method for the analysis of dicyandiamide and melamine, and to obtain better peak shape and sensitivity.

On the other hand, the traditional melamine method uses the Oasis ^® MCX reverse cation and cation exchange composite SPE mode, however this method is completely unsuitable for dicyandiamide; while the Sep-Pak ^® AC2 cartridge can be used for double Purification and enrichment of cyanamide, but still need to develop a faster pretreatment method.

experimental method:
Instrument: Waters ACQUITY UPLC ^® with Xevo ^® TQ-S
Column: ACQUITY BEH Amide column, 1.7μm, 2.1*150mm
Mobile phase A: 5 mM ammonium formate 0.1% formic acid aqueous solution mobile phase B: acetonitrile flow rate: 0.4 mL/min
Column temperature: 35 ° C
Injection volume: 5μL
Gradient curve:

Mass spectrometry parameters:
Capillary voltage: 2.5kv
Desolvation gas temperature: 500 ° desolvation gas flow rate: 8 00 L/Hr
Collision gas flow rate: 0.15mL/min

Sample preparation method:

For rapid and efficient testing purposes, the Waters DisQuE sample preparation kit was used in this experiment.
The Waters DisQuE sample preparation process is as follows:

In this experiment, the concentration of 1ppb was added to the blank matrix without adding an isotope internal standard. The average recovery of dicyandiamide was 83%, and the average recovery of melamine was 71%.

Experimental result

in conclusion:
In this paper, Waters UPLC ^® Ultra Performance Liquid Chromatography with high sensitivity triple quadrupole Xevo TQ-S, developed a simultaneous analysis method for detecting milk powder dicyandiamide and melamine, this method is based on the mechanism of HILIC column BEH Amide on. Adding 1 ppb of the analyte to the matrix, after the DisQuE matrix dispersion sample preparation kit is cleaned and injected, not only the peak shape is good, but also the matrix interference is not affected, and the sensitivity also fully meets the detection requirements.

In order to achieve rapid and efficient analysis, the DisQuE matrix dispersion sample preparation kit is used in this paper. After the sample is precipitated by simple protein, it is added to the DisQuE kit for purification, and then directly injected, without the need for dry reconstitution. The method is simple and rapid, especially for the detection of large quantities of samples, which can greatly improve the efficiency of analysis.

In the development of the LCMSMS method, the HILIC mode column of the hybrid particles played a large role. First, both analytes were polar compounds, and reversed phase chromatography could not be retained. HILIC provided a complementary choice. Secondly, in many HILIC mode columns, the BEH Amide column is a hybrid particle technology with a wide pH tolerance (pH 1-10), which provides more room for method development, and BEH Amide has more in this application. Good selectivity and peak shape.