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

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.

Membrane Sampling with Microdialysis Coupled to HPLC/UV for On-line Simultaneous Determination of Melamine and Cyanuric Acid in Non-dairy Coffee Creamer

“…Several authors have proposed the direct analysis of MM in milk or pet food using various analytical methodologies. [15][16][17][18][19][20] The LOD for MM in the present study, after considering the 10-fold dilution of the samples, was rather low when compared with those from studies that did not involve prior sample preparation. Rambla-Alegre et al reported a direct injection method for the analysis of MM using HPLC-UV; they obtained an LOD (5 ppb) similar to ours.…”

“…[15][16][17][18][19][20] These methods include HPLC-UV, 15 Raman spectroscopy 16 direct-analysis-in-real-time mass spectrometry (DART-MS), 17 ultrasound-assisted extractive electrospray ionization mass spectroscopy (EESI-MS), 18 surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS), 19 and low-temperature plasma/tandem mass spectrometry (LTP-MS-MS). 20 Notably, most of the instruments used in these methodologies are very expensive; in addition, the limits of detection (LODs) of these methods are variable because of the intense noise caused by the matrix.…”

Rapid detection of melamine with 4-mercaptopyridine-modified gold nanoparticles by surface-enhanced Raman scattering

“…Currently, various methods-including thin-layer chromatography [6], gas chromatography (GC) [7,8], high-performance liquid chromatography [9][10][11][12], enzyme-linked immunosorbent assay technology [13], matrix-assisted laser desorption/ ionization mass spectrometry (MALDI-MS) [14], and surface desorption atmospheric pressure chemical ionization mass spectrometry [15]-have been used to detect melamine in food. However, these methods usually suffer from drawbacks, such as the need for a complicated sample preparation process, clean-up steps, and a time-consuming determination process, so they cannot fulfill the requirement for fast in situ detection.…”

Detection of trace levels of lead in aqueous liquids using extractive electrospray ionization tandem mass spectrometry

“…Recently, breakthrough of mass [36,37]. After DESI, more than 20 ambient ionization techniques were further developed, including direct analysis in real time (DART) [38,39], surface desorption atmospheric pressure chemical ionization (DAPCI) [40,41], extractive electrospray ionization (EESI) [42], low temperature plasma (LTP) [43,44], and easy ambient sonic ionization (EASI) [45]. Two major advantages of ambient mass spectrometry are minimal sample pre-treatment and high-throughput MS analysis [46][47][48].…”