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.

Download full-text

Full-text

Available from: Bin Hu, Nov 11, 2014
1 Follower
 · 
252 Views
  • Source
    • "Several analytical methods were developed to detect and quantify melamine and its analogs in food since its first detection in China (Liu, Todd, Zhang, Shi, & Liu, 2012). Mass spectrometry based methods, including DAPCI-MS (Yang et al., 2009), EESI-MS (Zhu, Gamez, Chen, Chingin, & Zenobi, 2009) and LC-MS/MS (Smoker & Krynitsky, 2008; Turnipseed, Casey, Nochetto, & Heller, 2008) have been used as confirmatory and/or screening for melamine, due to their high selectivity and low detection limits. However, the main limitations of mass spectrometry techniques rely on its high cost and complexity. "
    [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
  • Source
    • "c o m / l o c a t e / f o o d c h e m melamine is a potential adulterant because of its high nitrogen content (66% by mass). In fact, many different methods including LC–MS/MS, APCI-MS and ESI-MS have been developed for detection of melamine in milk products (Turnipseed, Casey, Nochetto, & Heller, 2008; Zhu, Gamez, Chen, Chingin, & Zenobi, 2009; Yang et al., 2009) in parallel with the principal analytical method proposed by the US Food and Drug Administration (FDA, Smoker & Krynitsky, 2008). However, the high cost instrumentation, staff training and infrastructure associated with MS techniques limit their widespread use. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The Kjeldahl method and four classic spectrophotometric methods (Biuret, Lowry, Bradford and Markwell) were applied to evaluate the protein content of samples of UHT whole milk deliberately adulterated with melamine, ammonium sulphate or urea, which can be used to defraud milk protein and whey contents. Compared with the Kjeldahl method, the response of the spectrophotometric methods was unaffected by the addition of the nitrogen compounds to milk or whey. The methods of Bradford and Markwell were most robust and did not exhibit interference subject to composition. However, the simultaneous interpretation of results obtained using these methods with those obtained using the Kjeldahl method indicated the addition of nitrogen-rich compounds to milk and/or whey. Therefore, this work suggests a combination of results of Kjeldahl and spectrophotometric methods should be used to screen for milk adulteration by these compounds.
    Food Chemistry 12/2013; 141(4):3649-55. DOI:10.1016/j.foodchem.2013.06.046 · 3.26 Impact Factor
  • Source
    • "Detecting and thus visualizing the tiny differences require high sensitivity of analytical tools. As reported previously [20] [38] [43] , DAPCI shows high sensitivity for detection of small concentrations of analytes on surfaces without sample pretreatment. This makes DAPCI an attractive tool to determine slight differences between signatures prepared by the same person at different times. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Molecular images of documents were obtained by sequentially scanning the surface of the document using desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS), which was operated in either a gasless, solvent-free or methanol vapor-assisted mode. The decay process of the ink used for handwriting was monitored by following the signal intensities recorded by DAPCI-MS. Handwritings made using four types of inks on four kinds of paper surfaces were tested. By studying the dynamic decay of the inks, DAPCI-MS imaging differentiated a 10-min old from two 4 h old samples. Non-destructive forensic analysis of forged signatures either handwritten or computer-assisted was achieved according to the difference of the contour in DAPCI images, which was attributed to the strength personalized by different writers. Distinction of the order of writing/stamping on documents and detection of illegal printings were accomplished with a spatial resolution of about 140 µm. A Matlab® written program was developed to facilitate the visualization of the similarity between signature images obtained by DAPCI-MS. The experimental results show that DAPCI-MS imaging provides rich information at the molecular level and thus can be used for the reliable document analysis in forensic applications. © 2013 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons, Ltd.
    Journal of Mass Spectrometry 09/2013; 48(9):1042-9. DOI:10.1002/jms.3250 · 2.71 Impact Factor
Show more