Amount Of Melamine Research Articles

English

The objectives of this paper were to evaluate the effects of feeding diets containing different levels of melamine on melamine concentrations in milk, plasma, rumen fluid, urine and feces in Holstein dairy cows. Sixteen Chinese Holstein dairy cows fixed with permanent ruminal cannulas were assigned to 1 of 4 treatments within a completely randomized design for 10 days. Cows were fed different amounts of melamine {20 (group 1), 40 (group 2), 60 (group 3) or 80 (group 4) g/day/cow} once daily in the morning mixed with a melamine free basal diet for 7-days adaptation followed by 3-days urine and feces sample collections. Melamine was found in all samples tested and its concentration generally increased as dose increased in the diet. These results indicated that different doses of melamine in the diet could result in different concentrations of melamine in milk, plasma, rumen fluid, urine and feces. Data suggested that melamine primarily cleared by urinary excretion, followed by fecal excretion in lactating dairy cows. Mammary tissue was apparently not a major tissue to dispose melamine, especially when fed a relatively low dose (lower than 40 g/day/cow).   Key words: Melamine, excretion, lactating dairy cow.

High melamine migration in daily-use melamine-made tableware

Melamine is commonly used to manufacture tableware, and this could be one of the important exposure sources in humans. The study aims to measure melamine migrated from different material-made tableware by the most sensitive technique of liquid chromatography–tandem mass spectrometry (LC–MS/MS). The test samples were filled with pre-warmed designated-temperature (from room temperature (∼20 °C), 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, to 90 °C) simulant (either distilled water or 3% acetic acid) up to 20 ml and immersed in a water bath at that designated temperature for 15 or 30 minutes (min). High melamine migration levels, ranging from 6.97 to 19.03 μg/ml, can be measured from all melamine-made samples containing 20 ml 3% acetic acid in water bath of 90 °C for 30 min, whereas melamine cannot be detectable in all other material-made samples in the same condition. In addition, the cheaper the melamine-made tableware samples, the higher the melamine migration levels. The migration of melamine amount is dependent on different temperatures, contact times, simulant, and prices of tableware. Since tableware is used in daily life, it is prudent to cautiously select materials that contain foodstuffs.

Magnetic properties of nanocrystalline Fe/Fe3C composites

Nanocrystalline Fe/Fe3C composites have been fabricated by an efficient solid-state synthesis route. In this reaction process, we choose the organic compound melamine as the carbon source and hydrothermally prepared nanocrystalline Fe/Fe3O4 composite as metal precursor. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and vibrating sample magnetometry have been used to characterize the composites. The experimental results show that changing reaction temperature, reaction time and the amount of melamine allows control over the composition of Fe/Fe3C composites, particle morphology and magnetic properties. The possible formation mechanisms of as-prepared nanostructures with different morphologies are discussed briefly. Magnetization measurements indicate that the composites display ferromagnetic properties at room temperature.

Naked eye sensing of melamine using rationally tailored gold nanoparticles: hydrogen-bonding and charge-transfer recognition

A highly sensitive analytical method based on Au nanoparticles rationally tailored with recognition elements uracil-5-carboxylic acid (UCA) and 2,4,6-trinitrobenzenesulfonic acid (TNBS) for the visual sensing of melamine at the parts-per-billion (ppb) level is described. The tailored Au nanoparticles function as an excellent color indicating reporter and it recognizes the target analytes by triple hydrogen-bonding or charge-transfer interaction in aqueous solution. The interaction of melamine with UCA- or TNBS-tailored reporters induces a rapid visible color change due to the aggregation of reporters. The color change was spectrally monitored to precisely quantify the amount of melamine. The charge-transfer interaction of melamine with TNBS-tailored reporter brings a remarkable change in the spectral signature even at the ppb level. Such an interaction paves the way for the detection of melamine at the 5 ppb level, which is well below the safety limit set by UN food standard commission. This method is highly selective and the common interfering analytes such as cyanuric acid, cytosine, glucose, thymine, uracil, etc., do not interfere in the sensing of melamine. The practical utility of the method is demonstrated by quantifying the amount melamine in real samples.

Screening melamine contaminant in eggs with portable surface-enhanced Raman Spectroscopy based on gold nanosubstrate

A novel fast ultra-sensitive approach was developed herein to identify melamine contaminant in eggs using portable compact surface-enhanced Raman Spectroscopy (SERS) on gold nanosubstrates. Trace amounts of melamine spiked in albumen and yolk were characterized and quantified by SERS with partial least squares (PLS) analysis, good models were acquired for melamine in albumen at concentration range of 2.5–100 mg/kg with the determination coefficient of actual concentration versus predicted concentration R2 = 0.94, the root mean standard error of cross validation RMSECV = 12.38, the limit of detection (LOD) 1.1 mg/kg, and in yolk 5.0–200 mg/kg with R2 = 0.98, RMSECV = 12.14, LOD = 2.1 mg/kg, respectively. The assay was rapid in less than 30 min, and the detection was sensitive. As a fast screening scheme, the method could be suitably applied to the domain of on-site egg products quality control and market surveillance thereof.

Preparation and characterization of novel melamine modified poly(urea–formaldehyde) self-repairing microcapsules

Microcapsules with adequate performance are required for self-healing materials. Novel self-repairing microcapsules with better heat resistance and water resistance were prepared by introducing melamine to urea–formaldehyde resin as wall material. The as-synthesized microcapsules were studied by various characterizations techniques, including scanning electron microscope (SEM), optical microscope (OM), particle size analyzer (PSA), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and contact angle meter. Spherical poly(urea–formaldehyde) microcapsules (mean size: 96 μm) and melamine modified poly(urea–formaldehyde) microcapsules (mean size: 46 μm, wall thickness: ∼3 μm) were obtained when the amount of melamine was 6–8 wt% and the amount of core materials was 75 wt%. After modified by melamine, the water-resistance of microcapsule is improved and contact angle increases from 43° to 50°. The heat resistance, solvent resistance, acid resistance and alkali resistance are improved because of triazine ring in melamine, which resulting in long storage time for microcapsule at room temperature.

Detection of Melamine in Powdered Milk Using Surface-Enhanced Raman Scattering with No Pretreatment

We detected a trace amount of melamine in powdered milk using surface enhanced Raman scattering (SERS) on gold surfaces at an excitation wavelength of 632.8 nm. A detection limit of ∼100 ppm (μg/g) melamine in milk was attained within a few minutes by the gold nanoparticle substrate from chemical reduction; whereas, better sensitivity, as low as ∼200 ppb (ng/g), was achieved by the roughened gold substrate. Our method has the advantage of fast and sensitive detection of melamine in powdered milk without pre-treating the samples.

Melamine Toxicity

Melamine contamination of infant formula in China and its health effects highlight the safety of the global food supply especially as it relates to formula-fed infants. Melamine is a widely used industrial chemical not considered acutely toxic with a high LD(50) in animals. The data available on acute and chronic human exposure to melamine have been limited and extrapolated from animal data. Pet food contamination in 2004 and 2007 showed stone formation and illness in animals when melamine was co-ingested with cyanuric acid. The recent outbreak in infants showed that melamine ingested in large doses may cause stones and illness without significant ingestion of cyanuric acid or other melamine-related chemicals. This may be due to increased uric acid excretion in infants and formation of melamine-uric acid stones. Diagnosis and treatment of infants exposed to melamine requires further study. Clinical signs and symptoms in infants are nonspecific. The stones may be radiolucent and are not consistently seen on ultrasound. The use of alkalinization of the urine for treatment has been proposed, but is of unproven benefit. The FDA and other regulatory agencies have recommended acceptable levels of melamine in foods for consumption. Melamine ingestion has been implicated in stone formation when co-ingested with cyanuric acid, but will cause urinary stones in infants when large amounts of melamine alone are ingested.

Potential of SERS for rapid detection of melamine and cyanuric acid extracted from milk

Melamine, a nitrogen-rich chemical, was implicated in the pet and human food recalls in 2007 and in the global food safety scares in 2008 involving milk and other milk-derived products. In this study, we investigated the feasibility of using surface-enhanced Raman spectroscopy (SERS) coupled with SERS-active gold substrates for rapid detection of trace amounts of melamine and its analogue (that is, cyanuric acid) in liquid milk. Raman signals of tested samples were significantly enhanced by SERS. The identification limit for SERS using gold substrate can reach 2 ppm of melamine in liquid milk. Partial least squares (PLS) models were established for the quantification of melamine in liquid milk by SERS: R = 0.90, RMSEP = 1.48 × 10−5. Our results demonstrate that rapid detection of melamine in milk can be achieved by SERS; while detection of cyanuric acid in milk remains a challenging task due to rapid enol-keto tautomerism of cyanuric acid. The SERS method is faster and simpler than other traditional methods, and requires minimum sample preparation. These results demonstrate that SERS could be used to detect food contaminants such as melamine in foods and food ingredients quickly and accurately.

Structural and morphological control of aligned nitrogen-doped carbon nanotubes

Nitrogen-doped carbon nanotubes (CNx–NTs) were prepared using a floating catalyst chemical vapor deposition method. Melamine precursor was employed to effectively control nitrogen content within the CNx–NTs and modulate their structure. X-ray photoelectron spectroscopy (XPS) analysis of the nitrogen bonding demonstrates the nitrogen-incorporation profile according to the precursor amount, which indicates the correlation between the nitrogen concentration and morphology of nanotubes. With the increase of melamine amount, the growth rate of nanotubes increases significantly, and the inner structure of CNx–NTs displayed a regular morphology transition from straight and smooth walls (0at.% nitrogen) to cone-stacked shapes or bamboo-like structure (1.5%), then to corrugated structures (3.1% and above). Both XPS and CHN group results indicate that the nitrogen concentration of CNx–NTs remained almost constant even after exposing them to air for 5months, revealing superior nitrogen stability in CNTs. Raman analysis shows that the intensity ratio of D to G bands (ID/IG) of nanotubes increases with the melamine amount and position of G-band undergoes a down-shift due to increasing nitrogen doping. The aligned CNx–NTs with modulated morphology, controlled nitrogen concentration and superior stability may find potential applications in developing various nanodevices such as fuel cells and nanoenergetic functional components.

Thermal degradation study of intumescent flame retardants by TG and FTIR: Melamine phosphate and its mixture with pentaerythritol

Thermal degradation of intumescent flame retardants, such as melamine phosphate (MP) and the mixture of MP and pentaerythritol (PER) was studied by TG, FTIR gas analyser (G-FTIR), and FTIR spectrometry. The results indicate that the degradation behavior of MP or PER itself is different from the one of them in the mixture. The volatile degradation products of MP contain mainly NH 3, and H 2O, as well as small amounts of melamine (MEL), whereas no MEL is found in the degradation of the mixture of MP and PER. Moreover, degradation products of PER are composed of a lot of volatile combustibles such as formaldehydes, alcohols, and C–H compounds except for H 2O. The mixture of MP and PER, however, produces much less volatile combustibles during its degradation leading to the production of more charring materials.

Rapid nondestructive screening for melamine in dried milk by Raman spectroscopy

Melamine is a raw ingredient for the manufacture of plastics, but it is frequently misused by adding it to food to raise the nitrogen content, thereby giving the false impression of a high protein content. Varied amounts of melamine were added to samples of dried milk obtained from five manufacturers in Japan. The samples were illuminated by a small cross section of a laser beam and the scattered light was examined. The presence of melamine in milk could be immediately detected without any chemical or physical alteration of the milk by interpreting its Raman scattering spectra. Among the many Raman bands, an intense band at 676 cm−1 was the most useful for detecting melamine; the detection limit was about 1% (w/w). Because this method does not extract melamine from the dried milk sample, it reduces the risk of error that may occur during extraction or from interaction with chemical reagents. The method provides a very rapid screening test for melamineadulterated dried milk in food chemistry and forensic toxicology.

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

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.

FOOD SAFETY Food & Drug Administration sets melamine safety level in food

In the midst of a widening scandal involving melamine-contaminated milk products originating from China, FDA declared on Oct. 3 that food products with levels of the industrial chemical below 2.5 ppm pose little risk. The agency says it arrived at this threshold through a mix of hard data and scientific assumptions. But it says that no amount of melamine is acceptable in infant formula because there is too much uncertainty to “rule out any public health concern.” Setting a safety standard for melamine angered some members of Congress, who would rather see an outright ban on the toxic chemical in food. “By not insisting on a zero-tolerance policy with melamine, FDA is failing to protect consumers,” Rep. Rosa L. DeLauro (D-Conn.), chair of the House subcommittee that oversees FDA’s budget, said in a written statement. Melamine first turned up last year in U.S. pet food, causing thousands of cats and dogs to die of kidney ...

A new approach to measure melamine, cyanuric acid, and melamine cyanurate using surface enhanced Raman spectroscopy coupled with gold nanosubstrates

Vibrational spectroscopic characteristics of melamine, cyanuric acid, and melamine cyanurate were measured using surface-enhanced Raman spectroscopy (SERS) coupled with gold nanosubstrates. Trace amounts of melamine and its analogues (cyanuric acid and melamine cyanurate) were characterized and quantified quickly and accurately by SERS in combination with partial least squares (PLS) analysis. Based on the relationship between the Raman intensity of the most prominent peak at around 676 cm−1 and log values of melamine concentrations, the limit of detection (LOD) of SERS for melamine was estimated to be 2.6 × 10−7 mol L−1 (∼33 ppb). An approximately 3 × 104 fold of enhancement factor for SERS signals of melamine on gold nanosubstrates was obtained. This result was based upon the comparison of the peak at around 676 cm−1 in the SERS spectra with that of normal Raman spectra of melamine in aqueous solutions. SERS spectra of cyanuric acid acquired from its solid form differ significantly from this compound in an aqueous solution, indicating a possible keto-enol isomerization reaction of cyanuric acid in water. When equal amounts of melamine and cyanuric acid were added together, spoke-like crystals of melamine cyanurate formed instantly, which could be measured and characterized by SERS. This study demonstrates that SERS could provide a fast and ultra-sensitive tool for detection and characterization of melamine and its derivative compounds in aqueous solutions.

Effect of molecular chain structure of the cured epoxy resin containing hyperbranched (3‐hydroxyphenyl) phosphate on expansion and flame retardance

AbstractMelamine is widely used as a blowing agent in intumescent flame‐retardant systems. However, when it was blended into the epoxy resin cured with hyperbranched (3‐hydroxyphenyl) phosphate (HHPP), neither greater expansion nor improved limiting oxygen index (LOI) was obtained during combustion compared with that without melamine addition. When a portion of HHPP was replaced by polyethylene glycol (PEG), both the expansion degree and the LOI increased, along with the content of PEG, even if the same amount of melamine was blended. This phenomenon shows that the molecular chain structure of the cured epoxy resin based on HHPP has a substantial effect on the flame retardance. Only when the degraded products are sufficiently viscous, at the decomposition temperature of the blowing agent, can the material be bubbled to form an expanding charred crust. The morphologic structure of the crust of the epoxy resin cured with HHPP shows that there were many holes on the surface because the degraded products were too rigid to be bubbled, from which the gases formed by melamine evolved. With increasing PEG content, the degraded products became increasingly viscous and bulged more easily with the gases. No holes appeared on the charred crust of the sample cured with the mixture of HHPP and PEG at a ratio of 3:1. In this case, most of the gases were entrapped and caused the material to expand, resulting in the increases of expansion degree and LOI. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2065–2070, 2004

Distribution of melamine in polyester–melamine surface coatings cured under nonisothermal conditions

AbstractThe influence of experimental cure parameters on the diffusion of reactive species in polyester–melamine thermoset coatings during curing has been investigated with X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared. The diffusion of melamine plays a vital role in the curing process and, therefore, in the ultimate properties of coatings. At a low (<20%) hexamethoxymethylmelamine (HMMM) crosslinker concentration, the matrix composition is uniform, but at high HMMM concentrations, excess HMMM rapidly segregates to the air–coating interface. The rate of migration is governed by the difference in the surface free energies of polyester and HMMM and the concentration gradient of HMMM between the bulk and the surface. An increased rate of energy absorption also increases the rate of migration of HMMM to the surface. A physical model has been proposed to explain this surface segregation phenomenon in terms of cocondensation and self‐condensation reactions. It suggests that an appropriate amount of melamine can be segregated on the surface and allowed to self‐condense to form a desired thickness of a melamine topcoat through the control of the binder composition and cure conditions. This technique can be implemented to apply a melamine topcoat during cure. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 83–91, 2004

Low addition of melamine salts for improved melamine‐urea‐formaldehyde adhesive water resistance

AbstractThe addition of melamine acetate salts to an adhesive glue mix can allow the use of melamine–urea–formaldehyde (MUF) resins of lower melamine contents (rather than just urea–formaldehyde resins) and lower total amounts of melamine. Performances can be obtained that are characteristic of the top‐of‐the‐line, generally higher melamine content MUF adhesive resins for the preparation of wood particleboard panels. Improvements in the panel internal‐bond strength of greater than 30% can be obtained by the addition of melamine acetate salts to top‐of‐the‐line MUF resins. The approach to the concept of increased melamine solubility with a melamine salt is compatible with the approach of increasing melamine solubility with solvents such as acetals (e.g., methylal). However, the synergy advantage of using the two approaches jointly is not very marked. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 287–292, 2003

Supramolecular polymer interactions using melamine

AbstractTriple‐hydrogen bonding between the imide containing polymers 1a‐c and melamine 2 is used to obtain supramolecular interactions between macromolecules. Melamine, known as a compound barely soluble in any organic solvent, is molecularly dissolved in the copolymers 1a‐c by meltprocessing. Maximum concentrations of 1 equivalent amount of melamine per 2.5 equivalent amounts of copolymer are obtained, indicating a 3:1 mol:mol superstructure with physical crosslinking by hydrogen bonding. Crystalline melamine is detected by powder diffraction X‐ray analysis at melamine concentrations exceeding the 3:1 imide‐melamine mole ratio.

Thermodynamics of the Hydroxymethylation of Melamine and Urea with Formaldehyde

Abstract The hydroxymethylation of melamine and urea with formaldehyde in an aqueous solution was studied thermodynamically. The entropy, enthalpy, and free energy of activation for the early stages of the reaction, i. e., the formation of mono-methylol derivatives, and also the changes in the entropy, enthalpy, and molecular heat, etc., were determined in connection with the functionalities. It was confirmed that no marked differences exist between the rate constant of melamine and that of urea, but that the ΔS\eweq and ΔH\eweq values of urea are considerably smaller than the respective values of melamine. Prominent differences do exist between ΔS and ΔH\eweq, the ΔS\eweq and ΔH\eweq terms of melamine amount roughly to 105 times and 105 times those of urea respectively, regardless of the functionalities. These results imply a conspicuous difference between their reaction mechanisms, a difference which is explicable in terms of the characteristics of their amino-group nitrogen. Besides, the solvent effect of dimethylsulfoxide in the hydroxymethylation of melamine was investigated; it will be discussed in connection with the solvation.