Article

Detection of Melamine in Milk Products by Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry

Department of Applied Chemistry, East China Institute of Technology, Fuzhou, 344000 PR China.
Analytical Chemistry (Impact Factor: 5.83). 05/2009; 81(7):2426-36. DOI: 10.1021/ac900063u
Source: PubMed

ABSTRACT Without any sample pretreatment, trace amounts of melamine in various milk products were rapidly detected noting the characteristic fragments (i.e., m/z 110, 85, and 60) in the MS/MS spectrum of protonated melamine molecules (m/z 127) recorded by using surface desorption atmospheric pressure chemical ionization mass spectrometry. Signal responses of the most abundant ionic fragment (m/z 85) of protonated melamine were well correlated with the amounts of melaime in milk products, showing a dynamic range about 5 orders of magnitude. The limit of detection (LOD) was found to be 3.4 x 10(-15) g/mm(2) (S/N = 3) for the detection of pure melamine deposited on the paper surface, which was much lower than that for detection of melamine in powdered milk (1.6 x 10(-11) g/mm(2), S/N = 3) or liquid milk (1.3 x 10(-12) g/mm(2), S/N = 3). The significant difference in LOD was ascribed to the relatively strong molecular interactions between melamine and the matrix such as proteins in the milk products. As demonstrated using desorption electrospray ionization (DESI) for melamine detection, weakening the molecular interaction between analytes and proteins is proposed as a general strategy to improve the sensitivity of ambient mass spectrometry for direct detection of analytes bound in protein matrixes. The relative standard deviation (RSD) and the recovery of this method were found to be 5.2 approximately 11.9% and 87 approximately 113%, respectively, for the detection of melamine in milk products. A single sample analysis was completed within a few seconds, providing a particularly convenient way to rapidly screen melamine presence in milk products.

Full-text

Available from: Bin Hu, Nov 11, 2014
1 Follower
 · 
250 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Natural fluorescence of melamine Milk adulteration UHT whole bovine milk HPLC-Fluorescence detection a b s t r a c t A method of high performance liquid chromatography with fluorescence detection (HPLC-Fluo), based on previous studies of the natural fluorescence emission of melamine (250/365 nm), was developed and validated for melamine determination as an adulterant of bovine UHT whole milk. The clean up treatment of milk samples by deproteinization was thoroughly optimized. No matrix effect was observed and a linear range from 0.05 to 10.0 mg mL À1 was obtained, with a value of R 2 equal to 0.9998. The limits of detection and quantification of melamine were 0.0081 and 0.027 mg mL À1 respectively, or 0.023 and 0.076 mg g À1 of milk, respectively, considering the sample dilution during extraction. Extracts of milk samples fortified with melamine at three concentration levels, two of which corresponded to the levels established by WHO for melamine in foods, led to an overall mean recovery of 95.4 ± 1.2% (n ¼ 9). This recovery value satisfies the performance criteria established by the Codex Alimentarius for analytical methods suitable for determination of food residues, demonstrating the usefulness and effectiveness of the proposed method.
    Food Control 01/2015; 51:402. DOI:10.1016/j.foodcont.2014.12.001 · 2.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Silver/carbon (Ag/C) core-shell nanowires with different thickness of shell were synthesized by a hydrothermal method and used as templates for fabricating gold nanoparticle-decorated Ag/C (Ag/C/AuNPs) nanowires. The Ag/C/AuNPs nanowires were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). It was found that the number density and particle size of Au nanoparticles can be tuned by varying the concentration of Au precursor. Surface-enhanced Raman scattering (SERS) measurements showed that single Ag/C/AuNPs nanowire exhibited strong SERS effect. Rhodamine 6G (R6G) molecules, with an extremely low concentration (1.0 × 10−11 M), were readily detected using single Ag/C/AuNPs nanowires. Detection of melamine molecules at concentrations as low as 1.0 × 10−7 M was used as an example to show the possible application of such Ag/C/AuNPs nanowires. In addition, the effect of benzoic acid on the detection of melamine was also investigated. It was found that the SERS spectrum profile and intensity of melamine is very sensitive to the presence of benzoic acid.
    RSC Advances 01/2013; 3(48):26102. DOI:10.1039/c3ra45397a · 3.71 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56×10(-6)M (0.7mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90×10(-7)M to 3.97×10(-6)M with a correlation coefficient of 0.9685. The detection limit (3σ) obtained by UV-vis spectrum was as low as 2.38×10(-7)M (i.e., 0.03mg/kg). Copyright © 2014 Elsevier Ltd. All rights reserved.
    Food Chemistry 05/2015; 174:473-9. DOI:10.1016/j.foodchem.2014.11.098 · 3.26 Impact Factor