Combination Of Melamine Research Articles

Modulating effect of urea/melamine on Co2+/Co3+ ratio of Co3O4 microplates for rapid hydrogen generation via NaBH4 hydrolysis

The oxidation state of an active metal is vital in the hydrolysis of NaBH4 for rapid hydrogen generation since the electron-rich and electron-deficient sites facilitate BH4− and H2O adsorption. Herein, we systematically design a tunable oxidation state of Co in Co3O4 by in situ N-doing using the combination of melamine (M) and urea (U) as nitrogen precursors during thermal treatment. The oxidation state of Co was tuned via electronic interaction between N and Co. This interaction was optimized by varying the amount of N doping and calcination temperature. The types of heterocyclic nitrogen, mainly pyridinic- and graphitic-N, and their carbon matrix content are critical in controlling the Co oxidation state. Various Co2+/Co3+ ratios showed a different catalytic performance, and the catalytic activity reached its peak at the highest ratio of 2.74 due to the synergetic effect of the maximum adsorption of BH4− and H2O by Co2+ and Co3+, respectively. Consequently, an excellent hydrogen generation rate (2042 mL g−1 min−1) was achieved with a low activation energy of 46.9 kJ mol−1 of M2.5U10Co3O4-400. Hence, N doping from a dual N source significantly enhanced the hydrogen performance compared to the reported cobalt-based catalyst. Furthermore, M2.5U10Co3O4-400 is highly recyclable, implying its stability and practical application.

The Therapeutic Effect of Catechin on Nephrolithiasis Induced by Co-Exposure to Melamine and Cyanuric Acid in Sprague-Dawley Rats.

This study aimed to assess the therapeutic efficacy of catechin against experimentally induced kidney stones resulting from co-exposure to melamine (MEL) and cyanuric acid (CYA) in male Sprague-Dawley rats. To induce nephrolithiasis, a combination of MEL and CYA (1:1 ratio, each at a dose of 31.5 mg/kg bw/day) was administered to the rats for 28 consecutive days. After nephrolithiasis was successfully induced, the rats were randomly divided into two groups: a treatment group and a sham group. The treatment group was given a daily oral dose of 50 mg/kg of catechin for 28 days, while the sham group received no intervention. Urine and blood samples were collected throughout the treatment period, and kidney samples were taken on day 28. Our findings demonstrated that treatment with catechin significantly reduced crystal deposition and pathological damage in the rats from nephrolithiasis. Additionally, renal injury markers were significantly decreased in the treatment group compared to the sham group. These findings suggest that catechin has potential therapeutic benefits in treating nephrolithiasis induced by co-exposure to MEL and CYA.

Co-exposure of melamine and cyanuric acid as a risk factor for oxidative stress and energy metabolism: Adverse effects on hippocampal neuronal and synaptic function induced by excessive ROS production

Melamine (MEL) and cyanuric acid (CA) alone have relatively low toxicity, but together they may cause serious damage to multiple organs, including the central nervous system, however, the underlying mechanism is unknown. This study aimed to determine and compare the neurotoxic effects of MEL (20 μg/mL), CA (20 μg/mL) and their combination (10 μg/mL MEL and 10 μg/mL CA) on cultured hippocampal neurons. The cell viability, apoptosis, anti-oxidative and energy metabolic indices were detected following 24 h of incubations. The miniature excitatory postsynaptic currents (mEPSCs), miniature inhibitory postsynaptic currents (mIPSCs) and synaptic plasticity in the hippocampal CA1 neurons were recorded. Moreover, ROS scavenger NAC was co-infused to investigate the potential mechanism. We found the complex of MEL and CA but not their alone caused severe cell death and disturbed energy production through activation caspase-3-mediated apoptosis. Meanwhile, the combination significantly reduced the amplitude, decay time and frequency of mEPSCs but not mIPSCs, indicating the pre- and post-synaptic inhibitory actions on neuronal activity. Paired-pulsed ratio (PPR) and long-term potentiation (LTP) at the Schaffer collateral-CA1 synapses were critically depressed. However, the co-application of NAC could effectively mitigate the cellular apoptosis, energy metabolism dysfunction and the impairments in neuronal and synaptic function. Our findings provide the first evidence that the combination of MEL and CA can exert more prominently neurotoxic effects than their alone and certify that one of the potential mechanisms for neuronal and synaptic dysfunction is the ROS-mediated signaling pathway.

Curcumin mediated PEG thiol acid conjugated gold nanoparticles for the determination of melamine

Here we describe the successful preparation of gold nanoparticles (AuNPs) coated with three different poly(ethylene glycol) (mPEG thiol, PEG Thiol acid and mPEG Amine) by reducing Au3+ to Au0 using curcumin. Effect of the stabilizing agents (surfactant), pH and temperature has been studied to understand the size and shape of nanoparticles and their influence on surface plasmon resonance (SPR), fluorescence and resonance Rayleigh scattering (RRS) signals. The mPEG thiol coated AuNPs have been employed as an optical method for the determination of melamine. The combination of melamine with the AuNP decreases both SPR signal and the fluorescence intensity of the AuNPs in the range between 0 and 10 mM. The method is simple, cheap and fast with 33 nM detection limit.

Carbonyl-Grafted g-C3 N4 Porous Nanosheets for Efficient Photocatalytic Hydrogen Evolution.

Carbonyl-grafted g-C3 N4 porous nanosheets (COCNPNS) were fabricated by means of a two-step thermal process using melamine and oxalic acid as starting reagents. The combination of melamine with oxalic acid to form a melamine-oxalic acid supramolecule as a precursor is key to synthesizing carbonyl-grafted g-C3 N4 . The bulk carbonyl-grafted g-C3 N4 (COCN) was further thermally etched onto porous nanosheets by O2 under air. In such a process, the carbonyl groups were partly removed and the obtained sample showed remarkably enhanced visible-light harvesting and promoted the separation and transfer of photogenerated electrons and holes. With its unique porous structure and enhanced light-harvesting capability, under visible-light illumination (λ>420 nm) the prepared COCNPNS exhibited a superior photocatalytic hydrogen evolution rate of 83.6 μmol h-1 , which is 26 times that of the p-CN obtained directly from thermal polycondensation of melamine.

ChemInform Abstract: Melamine—ZnI2 as Heterogeneous Catalysts for Efficient Chemical Fixation of Carbon Dioxide to Cyclic Carbonates.

In this contribution, the combination of melamine with Lewis acid ZnI2 was developed as heterogeneous dual catalysts for the cycloaddition of carbon dioxide with epoxides yielding the corresponding cyclic carbonates. With molar ratio of 1 : 3.3 of ZnI2 to melamine, high yield (96%) and selectivity (99%) of propylene carbonate was obtained at 150 °C and 3.0 MPa for 4.0 h. The binary catalysts were also effectively versatile for CO2 cycloaddition to other epoxides, especially the less active epoxides such as styrene oxide and cyclohexene oxide. Additionally, the catalysts could be separated easily from the products after reaction and then reused efficiently. Furthermore, a possible synergistic catalytic mechanism was proposed, wherein, melamine played the dual roles to activate CO2 and epoxide simultaneously, ZnI2 activated epoxide and subsequently attacked the activated epoxide, the synergetic effects from melamine and ZnI2 promoted the reaction smoothly. The binary catalysts showed the advantages of simple preparation, low cost, abundant availability and high catalytic activity for CO2 chemical fixation into valuable chemicals.

Porous structure design of carbon xerogels for advanced supercapacitor

Abstract A porous carbon electrode incorporating considerations both heteroatom doping and pore structure design with: combination of melamine and PEO–PPO–PEO (polyethylene oxide–polypropylene oxide–polyethylene oxide) micelles for the nitrogen-doping and optimization the micron-duct formation; integration of CO2-etching into the carbonization process for the formation of abundant micropores. The structure of these nitrogen-doped carbon xerogels (NCXs) are indeed comprised of a multi-scaled pores having nano-porous carbon in a network of micron-size percolated hollow-channels. The resulted material has an ultrahigh surface area of 4279 m2 g−1 when used as electrode for supercapacitor, which deliver a high specific capacitance of 271 F g−1 with excellent cycle stability and good rate capability.

Nephrotoxic Potential and Toxicokinetics of Melamine Combined with Cyanuric Acid in Rats

To investigate the nephrotoxic potential of melamine (MEL) and cyanuric acid (CA) in male Sprague-Dawley rats, 7-d repeated-dose studies were performed. The experimental groups of MEL100 and CA100 were orally administered with MEL and CA at 100 mg/kg/d for 7 d, respectively. In groups dosed with MEL–CA mixtures, melamine and cyanuric acid (1:1) were simultaneously administered at 4, 20, or 100 mg/kg/d for 7 d (i.e., MEL-CA4, MEL-CA20, or MEL-CA100, respectively). Body weights were not markedly affected in MEL100, CA100, and MEL-CA4 groups, but significantly reduced in MEL-CA 20 and 100 rats. Most parameters determined in sera and tissues were not markedly altered in MEL100, CA100, and MEL-CA4-treated rodents. However, BUN, creatinine, total protein, and kidney weights were significantly increased in MEL-CA20- and MEL-CA100-treated animals. Renal histopathologic findings also revealed signs of toxicity, including tubular dilatation, crystal deposition, granulomatous tubulo-interstitial inflammation, and tubular necrosis with regeneration. Data suggested that the combination of MEL and CA might be responsible for observed nephrotoxicity that was not seen following individual exposure to either MEL or CA alone. Subsequently, the concentrations of MEL and CA were determined in serum, urine, and kidney tissues by using liquid chromatography–mass spectrometry. Toxicokinetic studies indicated that MEL or CA alone might be eliminated almost completely within 24 h after dosing showing no accumulation in kidney. However, the combined MEL-CA dose produced marked accumulation of chemicals in blood and kidneys. These results suggested that combined MEL and CA might produce renal toxicity due to significant chemical accumulation in kidney accompanied by low excretion.

Pathophysiological changes associated with dietary melamine and cyanuric acid toxicity in red tilapia

This study examined the adverse effects of feed-delivered melamine (MEL) and cyanuric acid (CYA) in red tilapia. Diet 1 (without MEL and CYA), diets 2-4 (with MEL and CYA at 2.5, 5 and 7.5 g kg(-1) diet, respectively) and diets 5 and 6 (with either MEL or CYA at 10 g kg(-1) diet) were examined. MEL alone lowered both growth and FCR (P < 0.05), and CYA alone reduced the FCR of tilapia. Protein efficiency ratio and apparent net utilization of fish on diets 2-6 were poor (P < 0.05). The renal tubules of fish ingested MEL-CYA combination had melamine-cyanurate crystals. On the other hand, diets with only one chemical did not induce such crystals. MEL and CYA in whole body, fillet or viscera reflected their dietary inclusion levels. The levels of Hsp70 were increased in the liver of fish that ingested MEL and CYA, in combination or singly (P < 0.05). However, in the kidney, such an increase was visible only in the fish that received diet 4 (P < 0.05). Combination of MEL and CYA at inclusion levels > 5 g kg(-1) diet induced the activity of catalase in liver and the activity of glutathione peroxidase in liver and kidneys. Therefore, these adulterants should not be included in fish feeds.

The reproductive toxicity of melamine in the absence and presence of cyanuric acid in male mice

Melamine, a chemical compound, was used widely in the manufacture of amino resins and plastics. Cyanuric acid related structurally to melamine was used as a water stabilizer in swimming pools. The combination of melamine and cyanuric acid was thought to be responsible for renal impairment in mammals. In the present work, we investigated the reproductive toxicity of melamine in the absence and presence of cyanuric acid in male mice. Pathological damages in different degrees were observed in the testis of male mice treated with different doses of both melamine alone and combination of melamine and cyanuric acid in a dose-dependent manner. Based on the TUNEL assay, the mice treated with high dose of melamine (50mg/kg/day) had a significant increase in apoptotic index of spermatogenic cells (p<0.05) compared with the control group. Sperm abnormality test indicated that melamine alone resulted in abnormal sperm morphology. The mice from co-administration groups of melamine and cyanuric acid were not eating, and were most likely in renal failure. The combined exposure to melamine and cyanuric acid was revealed to have certain toxic effects on testis of male mice at a relative low dose (each at 1mg/kg/day). Also, in comparison to melamine treated groups, more severe apoptosis was observed in co-administration groups of melamine and cyanuric acid with both middle (each at 5mg/kg/day) and high doses (each at 25mg/kg/day). However, all mice administrated with combination of melamine and cyanuric acid (each at 206, 412, or 824mg/kg/day) died before day 6 from which no data were obtained on sperm abnormality. These results from this study demonstrated that melamine had certain toxic effects on testes of male mice, especially when ingested in high concentration. These results might be useful in evaluating the toxicity of melamine on reproductive system of male animal, and they also would be a supplement to the existing toxic profile of melamine.

Toxicity of melamine and cyanuric acid in broilers and residues in tissues

The purpose of this study was to characterize the toxicity potential of melamine (MEL), cyanuric acid (CYA), and a combination of MEL and CYA in broilers. A total of 720 commercial 1-day-old COBB 500 male broilers were randomly allotted into 6 groups with 6 replicates each and 20 broilers in each replicate. The dietary treatments were as follows: group I was the control group, group II included 10 mg/kg MEL and 3.3 mg/kg CYA, group III included 30 mg/kg MEL and 10 mg/kg CYA, group IV included 100 mg/kg MEL and 33.3 mg/kg CYA, group V included 100 mg/kg MEL, and group VI included 33.3 mg/kg CYA. The trial lasted for 42 days. CYA alone and the combination of MEL and CYA had adverse effects on the performance, but MEL alone had no effects on the performance. On day 21, the uric acid (UA) content of group IV was increased in serum (p < 0.05); on day 42, the serum aspartate aminotransferase (AST) activity and the level of tumor necrosis factor (TNF)-α and interleukin (IL)-8 increased in group IV (p < 0.05); 100 mg/kg MEL alone increased the level of TNF-α and the rate of renal apoptosis (p < 0.05); and 33.3 mg/kg CYA alone increased the level of IL-8 and the rate of renal apoptosis (p < 0.05). The livers contained MEL concentrations of 17-125 μg/kg wet weight and CYA concentrations of 28-73 μg/kg, and the muscle contained MEL concentrations of 14-105 μg/kg wet weight. It was indicated that MEL alone, CYA alone, and a combination of MEL and CYA inhibit the growth and damage the kidney and liver.

Toxicity of cyanuric acid to broilers on hepatic and renal health with and without melamine

The purpose of this study was to evaluate the toxicity potential of cyanuric acid (CYA) and a combination of melamine (MEL) and CYA in broilers. A total of 1200 male COBB 500 broilers were randomly allocated into 1 of 10 treatment groups by a 5 × 2 factorial design in a 42-d experiment. The dietary treatments were as follows: T(1) to T(5): basal diets with 0, 10, 20, 33.3, and 50 mg CYA per kg diet; T(6) to T(10): basal diet with CYA regimens similar to T(1) to T(5) but with 100 mg MEL per kg diet. There were 6 replication pens with 20 chicks per pen. No differences were observed in alanine transaminase (ALT) and aspartate aminotransferase (AST) activities. But on d 22, uric acid (UA) and creatinine (Crea) concentrations were significantly greater when birds were fed CYA at 33.3 mg/kg with MEL 100 mg/kg, and Crea concentration was also higher when birds were fed CYA at 50 mg/kg. No crystals were found in kidneys but dilated renal tubules and small blood vessel expansion were found in kidneys of birds fed CYA at 50 mg/kg and CYA at 33.3 mg/kg with MEL 100 mg/kg. The apoptosis rate (AR) of kidneys of all birds fed CYA and MEL contaminated diets were higher than the control group. These results indicated that the dietary addition of CYA and MEL could induce kidney damage, and the effects were harmful when the ratio of CYA/MEL was 1:3.

Intumescent polylactide: A nonflammable material

AbstractIn this article, we examine intumescent polylactide, which exhibits a nonburning behavior upon heating. The combination of melamine and ammonium polyphosphate incorporated in the polylactide allowed us to obtain an intumescent char and low flammability. The incorporation of an additional ingredient such as organomodified montmorillonite Cloisite 30B or multiwall carbon nanotubes demonstrated varying effects on the material's reaction to fire, i.e., a large synergistic effect was observed when Cloisite 30B was used, whereas it was antagonistic when multiwall carbon nanotubes were used. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Determination and Confirmation of Melamine Residues in Catfish, Trout, Tilapia, Salmon, and Shrimp by Liquid Chromatography with Tandem Mass Spectrometry

Pet and food animal (hogs, chicken, and fish) feeds were recently found to be contaminated with melamine (MEL). A quantitative and confirmatory method is presented to determine MEL residues in edible tissues from fish fed this contaminant. Edible tissues were extracted with acidic acetonitrile, defatted with dichloromethane, and cleaned up using mixed-mode cation exchange solid-phase extraction cartridges. Extracts were analyzed by liquid chromatography with tandem mass spectrometry with hydrophilic interaction chromatography and electrospray ionization in positive ion mode. Fish and shrimp tissues were fortified with 10-500 microg/kg (ppb) of MEL with an average recovery of 63.8% (21.5% relative standard deviation, n = 121). Incurred fish tissues were generated by feeding fish up to 400 mg/kg of MEL or a combination of MEL and the related triazine cyanuric acid (CYA). MEL and CYA are known to form an insoluble complex in the kidneys, which may lead to renal failure. Fifty-five treated catfish, trout, tilapia, and salmon were analyzed after withdrawal times of 1-14 days. MEL residues were found in edible tissues from all of the fish with concentrations ranging from 0.011 to 210 mg/kg (ppm). Incurred shrimp and a survey of market seafood products were also analyzed as part of this study.

Assessment of Melamine and Cyanuric Acid Toxicity in Cats

The major pet food recall associated with acute renal failure in dogs and cats focused initially on melamine as the suspect toxicant. In the course of the investigation, cyanuric acid was identified in addition to melamine in the offending food. The purpose of this study was to characterize the toxicity potential of melamine, cyanuric acid, and a combination of melamine and cyanuric acid in cats. In this pilot study, melamine was added to the diet of 2 cats at 0.5% and 1%, respectively. Cyanuric acid was added to the diet of 1 cat at increasing doses of 0.2%, 0.5%, and 1% over the course of 10 days. Melamine and cyanuric acid were administered together at 0%, 0.2%, 0.5%, and 1% to 1 cat per dose group. No effect on renal function was observed in cats fed with melamine or cyanuric acid alone. Cats dosed with a combination were euthanized at 48 hours after dosing because of acute renal failure. Urine and touch impressions of kidneys from all cats dosed with the combination revealed the presence of fan-shaped, birefringent crystals. Histopathologic findings were limited to the kidneys and included crystals primarily within tubules of the distal nephron, severe renal interstitial edema, and hemorrhage at the corticomedullary junction. The kidneys contained estimated melamine concentrations of 496 to 734 mg/kg wet weight and estimated cyanuric acid concentrations of 487 to 690 mg/kg wet weight. The results demonstrate that the combination of melamine and cyanuric acid is responsible for acute renal failure in cats.

The Mechanism and Performance of Combustion Modified Flexible Foams in Small Scale Fire Tests

The subject of the behaviour of flexible polyurethane foams in a "fire situation" has always been a controversial issue. The introduction in March 1989 of legislation in the United Kingdom requiring all furniture and bedding sold to contain filling materials meeting BS 5852 has led to a complete new grade range of flexible foams. Currently these Combustion Modified High Resilience (CMHR) Foams are, in the main, based on "polymer polyols" or "grafted polyols" and contain Melamine as the major fire retardant additive. Some conventional fire retardant of the phosphorus-halogen type is also in cluded in the formulation. Samples of CMHR foams typical of those available on the European market have been evaluated in small scale fire tests, and their performance used to ob tain "targets" or "yardsticks" for further work. A Limiting Oxygen Index of 25% vol. O2 appears to be typical for these CMHR foams of density 25 kg/m3. We have shown that the combination of melamine and a phosphorus-halogen fire retardant is superior to that of either additive used singly and that the choice of the base polymer polyol also appears to have an influence on the per formance of the final foam. Both the PHD and PIPA polyols require less fire retardant additive than the SAN polyol, Polyurax U.1408, to achieve the same performance in the particular tests used. However these advantages are less obvious at higher fire retardant loadings. Of the potential alternatives to melamine screened in this evaluation urea appears to be the most obvious candidate. Foams containing urea were superior to those based on melamine in all the fire tests used. As an example an increase of about 2% vol. O 2 requirement in the LOI test was obtained. Additives such as alumina trihydrate, magnesium hydroxide, ammonium polyphosphate and ammonium borates were not as effective as melamine in im proving the fire properties of the CMHR-foams. They did not interact benefi cially with the polymer, nor did they volatilise/decompose over the required temperature range.