1.Quantification of melamine in drinking water and wastewater by micellar liquid chromatography.
Beltrán-Martinavarro B1, Peris-Vicente J, Rambla-Alegre M, Marco-Peiró S, Esteve-Romero J, Carda-Broch S. J AOAC Int. 2013 Jul-Aug;96(4):870-4.
Because of the large potential health impact caused by deliberate contamination with the synthetic chemical melamine of different products for human and animal consumption, the World Health Organization and the Food and Agriculture Organization of the United Nations provided a range of recommendations in order to facilitate obtaining needed data, among which was the determination of the background levels of melamine in drinking water and wastewater (December 4, 2008). A chromatographic procedure using a C18 column, a micellar mobile phase consisting of sodium dodecyl sulfate (0.1 M), and 1-propanol (7.5%) buffered at pH 3, and detection by absorbance at 210 nm is reported in this paper for the quantification of melamine in drinking water and wastewater. Samples were filtered and directly injected into the chromatographic system, thus avoiding an extraction procedure. The optimal mobile phase composition was obtained by a chemometrics approach that considered the retention factor, efficiency, and peak shape.
2.Coherent fusion of water array and protonated amine in a metal-sulfate-based coordination polymer for proton conduction.
Manna B1, Anothumakkool B2,3, Desai AV1, Samanta P1, Kurungot S2,3, Ghosh SK1. Inorg Chem. 2015 Jun 1;54(11):5366-71. doi: 10.1021/acs.inorgchem.5b00416. Epub 2015 May 18.
A new function of metal-sulfate-based coordination polymer (CP) for proton conduction was investigated through rational integration of a continuous water array and protonated amine in the coordination space of the CP. The H-bonded arrays of water molecules along with nitrogen-rich aromatic cation (protonated melamine) facilitate proton conduction in the compound under humid conditions. Although several reports of metal-oxalate/phosphate-based CPs showing proton conduction are known, this is the first designed synthesis of a metal-sulfate-based CP bearing water arrays functioning as a solid-state proton conductor.
3.Identification of ɛ-caprolactam, melamine and urea in polyvinylpyrrolidone powders by micellar electrokinetic chromatography.
Amini A1. J Pharm Biomed Anal. 2014 Mar;91:12-6. doi: 10.1016/j.jpba.2013.12.010. Epub 2013 Dec 22.
A sodium dodecyl sulfate micellar electrokinetic chromatography (SDS-MEKC) method for the simultaneous separation and identification of ɛ-caprolactam, melamine and urea deliberately added to polyvinylpyrrolidone (povidone) products has been developed. All samples to be analyzed contained paracetamol as an internal marker (IM). The optimized separations were performed in 50mM phosphate buffer (pH 7.0) containing 2% (w/v) sodium dodecyl sulfate (SDS) in fused silica capillaries with UV absorption detection at 200nm. The method was validated with respect to repeatability and intermediate precision, selectivity and robustness with satisfactory results. The relative migration times (RMT) were found to be between 0.03% and 0.13% for intra-day precision and between 0.50% and 0.60% for inter-day precision in four days. The detection limits were determined to be 1.3 (11.5μM), 0.4 (3.5μM) and 41μg/ml (0.4mM) for ɛ-caprolactam, melamine and urea, respectively.
4.Melamine nanosensing with chondroitin sulfate-reduced gold nanoparticles.
Noh HJ1, Kim HS, Cho S, Park Y. J Nanosci Nanotechnol. 2013 Dec;13(12):8229-38.
Gold nanoparticles were green-synthesized using a glycosaminoglycan, chondroitin sulfate, as the reducing agent by mixing Au3+ and chondroitin sulfate under heating. Chondroitin sulfate-reduced gold nanoparticles were characterized by UV-Vis spectrophotometry, high resolution transmission electron microscopy and atomic force microscopy. The yield of Au3+ to Au0 was measured as 80.1% by inductively coupled plasma-atomic emission spectroscopy. A mostly spherical shape, with an average diameter of 44.68 +/- 11.25 nm, was observed from the atomic force microscopy images. Using chondroitin sulfate-reduced gold nanoparticles, we developed a melamine nanosensor that provides a simplified method to detect melamine in infant formula. With an increase in the melamine concentration in the gold nanoparticle solution, the characteristic surface plasmon resonance band of gold nanoparticles at 530 nm decreased, whereas a new peak appeared at 620 nm. There was a linear relationship between the absorbance ratio (A620/A530) and the melamine concentration in the range of 0.