Analysis of Melamine Cyanurate in Urine Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Abstract

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was applied to the direct analysis of melamine cyanurate (MC). The three commonly used MALDI matrixes, namely, alpha-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA), and 2,5-dihydroxybenzoic acid (DHB), were able to desorb/ionize melamine from MC upon N(2) laser irradiation, with CHCA showing the highest detection sensitivity in the positive mode. Only DHB and SA were able to desorb/ionize cyanuric acid from MC in the negative mode but with remarkably lower sensitivity. The method is able to detect melamine unambiguously from a small amount of MC (down to 12.5 microg) spiked into urine and was successfully applied for the rapid and sensitive detection of melamine in urine stones/residues of the samples collected from patients clinically confirmed of having kidney stones associated with the consumption of melamine-tainted food products. The urine matrix resulted in interfering ion peaks and suppressed the ion intensity of melamine, while a cleanup process consisting of simply washing with water eliminated such interference and enhanced the ion intensity. The merit of the method is simplicity in sample preparation. The analytical time of the method for high-throughput analysis from the time of sample treatment to analysis is less than 7 minutes per sample, with sensitive detection of the presence of melamine in the urine stones/residues of the patient samples.

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.…”

Simultaneous determination of melamine and related compounds by hydrophilic interaction liquid chromatography–electrospray mass spectrometry

“…For the simultaneous determination of melamine and cyanuric acid, HPLC-MS [32] and MALDI-MS [33] were employed. But limited methods are suitable for the simultaneous determination of melamine, ammeline, ammelide and cyanuric acid.…”

Application of Tandem Mass Spectrometry for Analyzing Melamine

“…To eliminate the interference of 5-hydroxymethylfurfual (5-HMF) produced during heating of the milk, TOFMS with a higher resolving power has been used to distinguish MEL (m/z 127.0732) and 5-HMF (m/z 127.0395) which have very close molecular weights. Tang et al, (2009) employed MALDI-MS for direct analysis of biochemical crystals containing melamine/cyanuric acid complexes in urine samples. MEL can be desorbed/ionized upon N 2 laser irradiation by simply mixing the commonly adopted MALDI matrixes with melamine cyanurate in urine residue.…”

“…To shorten the preparation time, several improvements have been developed. MALDI-MS has been applied to the direct analysis of melamine cyanurate and MEL in urine (Tang et al, 2009). A low temperature plasma ambient ionization source, coupled to a portable mass spectrometer (Mini 10.5), has been used to determine MEL contamination in whole milk and related materials, such as synthetic urine and fish meat (Huang et al, 2010).…”

“…A low temperature plasma ambient ionization source, coupled to a portable mass spectrometer (Mini 10.5), has been used to determine MEL contamination in whole milk and related materials, such as synthetic urine and fish meat (Huang et al, 2010). However, the urine matrix results in interfering ion peaks and suppresses the ion intensity of MEL, while a clean up process consisting of simply washing with water eliminates such interference and enhances the ion intensity (Tang et al, 2009). …”