MEL and Analogues: Structures and Properties

MEL and Analogues: Structures and Properties CHAPTER 2 LITERATURE REVIEW 2.1 Melamine MEL is an organic compound which had been closely associated with milk adulterant scandal between the year 2007 and 2008. Having a chemical formula of C3H6N6, makes it a nitrogen rich compound, thus giving the false impression of real protein content (Y.-N. Wu, Zhao, Li, 2009). Manufacturing companies who bought raw milk for further production usually carry out protein tests by monitoring the nitrogen levels. MEL can be hydrolysed to ammelide, ammeline and CYA, the derivatives are many produce for the synthesis of formaldehyde resin in the manufacturing of plastics, kitchenware or laminates (Y. Wu Zhang, 2013). CYA commonly used as a bleaching component in swimming pools. MEL and CYA are soluble in water, however when the two combined they will form a MEL and CYA complex which is an insoluble crystal through cross linking hydrogen bonding network (Mukherjee Ren, 2010). 2.1.1 Structures and properties of MEL and analogues The triazine derivative, MEL has three reactive amine groups (-NH2) and one aromatic s-triazine ring or 1,3,5-triazine ring. Replacing the amine groups (-NH2) with hydroxyl group (-OH) through hydrolysis or metabolism by microorganism will form analogues as ammeline, ammelide and CYA (Kim, 2009). Figure 2.1 Structure of MEL, ammeline, ammelide and CYA (Kim, 2009) Physical properties of MEL and its analogues are shown in Table 2.1. MEL has an appearance in form of white powder with a melting point of 354oC. This shows that MEL is thermally stable and explains that it is often used as fire retardant. Furthermore, MEL is sparingly soluble in either acidic pH or polar organic solvent such as acetone or ethanol, due to like-dissolve-like interaction of polar compound MEL. On the contrary, MEL would be insoluble in non-polar solvents such as benzene or hexane (EFSA, 2010). Ammeline on the other hand is a white powder that decomposes prior to melting. It possesses weak acidic properties and is soluble in both mineral acid and alkaline solutions. Ammelide is also a form of white powder that is almost insoluble in water. It decomposes at temperatures range of 170oC to form carbon dioxide and ammonia. The crystal complex of MEL and CYA is very stable at only hydrolyses at either very low or high pH. Basically the complex crystal compound are insoluble at pH below 5.0, which is mostly occurred in the urinary tract (Tolleson, Diachenko, Heller, 2008). Table 2.1 Physical properties of MEL, ammeline, ammelide and CYA (Kim, 2009) 2.2 MEL and analogues toxicity The toxic effects of MEL ingestion are closely linked with high dosage and low dosage of MEL would not be as toxic that will cause any adverse effect to human health. However, having said that, non toxic does not necessarily mean that it is safe for consumption. On December 2008, the US FDA recommends a TDI for MEL was 0.63 mg kg-1 body weight per day for food and other food ingredients excluding infant milk formula (Venkatasami Sowa, 2010). This meant 100 kg person can be subjected to a tolerable amount of 60 mg MEL. Infant formula are given a closer monitoring because it is a primary source of nutrient and calorie for infants, plus kidney functions in infant are still premature. Therefore the FDA has set a limit of 1  µg mL-1 for MEL in infant formula (Venkatasami Sowa, 2010). Different countries apply different limit of the TDI, for instance EFSA recommended a TDI of 0.5 mg kg-1 of body weight per day. Whereas Health Canada revealed the risk assessment of MEL-contaminated milk and milk based product to be 0.35 mg kg-1 body weight per day (WHO, 2008). Over Southeast Asia, the Malaysian Ministry of Health has set the maximum levels of MEL in baby and adult food product to be 1.0 mg kg-1, 2.5 mg kg-1 respectively (Y. Wu Zhang, 2013). This incident cause the FDA, European community and other countries to introduce a standard limit for MEL in infant formula and in other milk products to be at 1 ppm and 2.5 ppm, respectively. WHO established the TDI for MEL at 0.2 mg kg-1 (Sun et al., 2010). 2.2.1 Toxicity in animals and humans The data available on the dangers and chronic human exposure to MEL are limited, therefore the information on MEL toxin are extrapolated from animal data. MEL and CYA are considered as low toxin due to their large median LD50. For MEL in rats, the LD50 ranges from 3.1 g kg ­-1 to 6.4 g kg-1 and from 3.2 g kg-1 up to 7.0 g kg-1 in mice. Whilst for CYA, the estimated LD50 are 7.7 g kg-1 in rats and 3.4 g kg-1 in mice (Skinner et al., 2010). The study on the toxicity of MEL and CYA focuses on the urinary system for both humans and animals. The experimental studies on the effects of MEL on kidney in humans are unavailable. Nonetheless, consistent observation was made during the experiment with animals on the effects of MEL is bladder stones. The same result was reported with a following exposure to CYA, and that is formation of some bladder stones. Inflammatory reaction was observed in the rats and mice urinary bladder after dietary exposure to MEL. This indicates as one of the main effects of the toxic of MEL (Bingham et al., 2001). In general death cause by MEL are relatively low in human but there is a high rate of stones formation. In the height of the MEL food scandal, there are many deaths of pets animals in USA, Canada and South Africa due to kidney failure. Later the Veterinary Information Network (VIN) found that the number of deaths due to MEL and CYA contaminated pet feed was in the range of 2000 to 7000 (Puschner and Reimschuessel, 2011). In 2008 there were high detection of MEL in infant formula and other milk product and surely enough this resulted in severe health effects amongst infant and young children. As much as 294,000 were diagnosed with urinary tract stones and at least 50,000 were hospitalised. Six children were confirmed dead cause of kidney failures (Dorne et al., 2013). After this incident strict rules and regulation was implemented, and lots of method was developed in order to get a rapid and sensitive detection of MEL. 2.3 Analysis of MEL It is important to have rapid, widely available, cost effective methods for detecting MEL in various samples. Few of the advance analytical methods for detection of MEL are High Performance Liquid Chromatography (HPLC), Liquid Chromatography with Mass spectroscopy (LC-MS), LC with tandem (LC-MS2) and Gas Chromatography with MS (GC-MS). Sample preparation required prior to instrumental analysis, this is because the sample in question are high in protein and carbohydrates content which would hinder MEL detection. Therefore effective extraction methods is necessary, by removing other constituents in the matrix would mean lower limit of detection (LODs) can be achieved. Due to the polarity MEL compound it is best to extract it using SPE with a polar cartridge. The most common SPE tubes used for the separation of MEL is Supelco Discovery DSC-SCX 500 mg/6 ml (Sigma-Aldrich, n.d.). Before the SPE methods are applied it is best to precipitate out the protein by adding acetonitrile which acts as a protein precipitant and then centrifuge (Mosch, Kiranoglu, Fromme, Và ¶lkel, 2010). 2.3.1 Gas Chromatography with Mass Spectroscopy (GC-MS) GC-MS is often used to detect MEL and its analogs for quantification and confirmation. It was reported that it is a sensitive, reliable instrumental analytical method for the simultaneous detection and quantification of MEL in animal feed. However, it requires a tedious sample preparation which renders the methodology impractical for analysing large samples (Venkatasami Sowa, 2010). 2.3.2 High Performance Liquid Chromatography (HPLC) HPLC is known as common method for quantitative determination of MEL. It can carry out simultaneous detection of MEL, ammeline, ammelide and CYA with LOD of 5 ppm. By current standards, this method of analysis does not show great sensitivity in detection of MEL. This is because UV of MEL exhibits absorption bands below 250 nm which meant that HPLC method will not be able to confirm the target analyte (Sun et al., 2010). Quantification error can occur if insufficient attention is given to chromatographic conditions or if sample preparation is not optimised. To increase sensitivity investigators used DAD system of detection, this gives improvement in term of better LOD of 0.1 ppm using HPLC-DAD (Sun et al., 2010). It is difficult to retain MEL on a reverse phase column due to it high polarity, so to compensate for this problem hydrophilic interaction chromatography technique is used (Han et al., 2011). Figure 2.3.2 Retention time of melamine standards using HILIC-UV (Zheng, Yu, Li, Dai, 2012) 2.3.3 Liquid Chromatography with Mass Spectroscopy (LC-MS) and tandem Mass spectroscopy (LC-MS2) MS techniques are widely used for the determination of contaminants of MEL, because it shows molecular specificity and high sensitivity of detection. This means a MEL AND CYA having fairly low LOD 30 ppb and LOQ 40 ppb in serum sample. Mostly the method based on LC-MS2 with HILIC and ESI is positive ion mode. Positive ion mode is chosen because of the presence of nitrogen in the compound. The past researcher used two selected reaction monitoring (SRM) transitions of m/z 127 till 85 and 127 till 68 were monitored, figure 2.3.3. By applying these ion transitions for SRM allows quantitative and qualitative analysis of MEL residues at an LOD of 3.2 ppb (Sun et al., 2010). Figure 2.3.3 The positive ion electrospray full scan mass spectrum (bottom) and product ion spectra (top) of melamine, acquired by infusion of 0.5 g mL -1 standard solution (Sancho, Ibà ¡Ãƒ ±ez, Grimalt, Pozo, Hernà ¡ndez, 2005). 2.4 Optimization of buffer pH MEL is a weak alkaline compound that can hydrolyze in strong acid or alkali solutions. MEL extraction can be carried out in neutral, acidic and alkali conditions, but acidic pH lower than 3 and neutral extraction conditions are most common for food. Neutral extraction can be carried out using acetonitrile-water or methanol-water. Factors of affecting retention of melamine were explored, including buffer concentration, pH, and percentage of organic solvent in the mobile phase. The optimal UV detection wavelength was selected. Satisfactory retention of melamine, good peak shape, and high sensitivity were obtained under the chosen conditions. Tables 2.4 Effects of pH on melamine retention time

Hamlet Speech Draft Essay

In Shakespeare’s famous play â€Å"Hamlet†, Hamlet reveals the duality of human nature as he is the hero of one plot whilst a villain in the other. Hamlet portrays the heroic characteristics through bravery and fearlessness. On the other hand, he is a villain because he is a coward, disrespectful and he would do anything to achieve and benefit for himself. But Hamlet is neither a complete hero nor a complete villain. He is both, and this contributes to Shakespeare’s message concerning the duality of human nature. The following paragraphs will elaborate on Hamlet’s 3 different types of personalities. Hamlet being a hero of a plot is a major theme in the play. This is shown by through his actions of avenging his father’s death by killing the current king Claudius, Hamlets uncle. Hamlet demonstrates the quality of braveness by following the ghost ignoring the fears of his friend for him strong enough to break the restraining hold and follows the horrible illusion not knowing what could happen to him. [Hamlet-Shakespeare Act 1, Scene 4, 88 – 95] â€Å"Hold off your hands†, â€Å"My fate cries out and makes each petty artery in this body as hardy as the Nemean lion’s nerve. Still am I called.- Unhand me, gentleman. By heaven, I’ll make a ghost of him that lets me! I say, away. -Go on. I’ll follow thee. Hamlet does this because he is in desperate urge of wanting to discover how his father died and that he truly loves his father. The final reason for Hamlet being a hero is because he is not afraid of facing a politically superior man. This means that hamlet is not afraid to face the king; a person more powerful than him and tell everyone the truth about what happened to his father. Hamlet demonstrates the quality of fearlessness when is ready to fight the king. This is proven when he says [Hamlet-Shakespeare Act 5, Scene2 198 -200] â€Å"I am constant to my purpose, they follow the King’s pleasure. If his fitness speaks, mine is ready. Now or whensoever, provided I be so able as now† These words show that Hamlet’s fearlessness quality and that he is not afraid of facing a person much more powerful than him. Hamlet shows his bravery, fearlessness and determination through his action and speech and those are the qualities of a hero. Although Hamlet has many great Heroic qualities, he also has numerous villain characteristics shown through his actions and speech. He may be seen as a villain because he caused the death to the whole royal family including Polonius, Ophelia and even himself. One of his villain characteristics is portrayed when Hamlet said some harsh words to his mother making her feel threatened. [Hamlet-Shakespeare, Act 3, Scene 4, 21-23] â€Å"Come, come, and sit you down. You shall not budge. You go not till I set you up a glass Where you may see the inmost part of you†. These words illustrate one of Hamlet’s villain characteristics of being disrespectful. In addition to that, he broke Ophelia’s heart, as well as killing her father which caused her to become insane and lead her to commit suiciding. He also lied to his friends Rosencrantz and Guildenstern changing the letter making them the suspect of execution. Hamlet says [Hamlet-Shakespeare Act 5, Scene 2, 61-66] â€Å"Why, man, they did make love to this employment. They are not near my conscience. Their defeat does by their own insinuation grow. ‘Tis dangerous when the baser nature comes between the pass and fell incensed points of mighty opposites.† This shows that Hamlet is a coward, not facing execution himself but had to make his innocent friends face execution for him. These evidences proves that Hamlet is a villain because the death of the king Claudius, Gertrude, Ophelia, Laertes, Polonius, Rosencrantz, Guildenstern and himself is caused by him either directly or indirectly. Shakespeare uses the characters in the play Hamlet, especially the protagonist Hamlet to imitate the duality of human nature. Hamlet is a perfect example of a duality because he is both noble and immoral at the same time. An example of this is at the beginning when he is shocked over his father death and his mother’s quick remarriage to his uncle. This is shown in the text when Hamlet says [Hamlet-Shakespeare Act 1, Scene 2, 151-158] â€Å"even she – O, God, a beast, that wants discourse of reason would have mourned longer – married with my uncle, my father’s brother, but no more like my father than I to Hercules. Within a month, ere yet the salt of most unrighteous tears had left the flushing in her galled eyes, She married.† He then changes when he soon discovers about how his father was murdered and desires to seek revenge. Another example of a duality is that Hamlet exposes the noble side of himself. This is when he grieves for his father and despises the situation that his mother has left him in. He says [Hamlet-Shakespeare Act 1, Scene 2, 85-88] â€Å"These indeed seem, for they are actions that a man might play. But I have that within which passes show these but the trappings and the suits of woe.† This makes the reader feel that he dislikes his mother but on the contrary he still loves her even though she has left him in a miserable situation. These examples portray the duality of human nature from the character Hamlet. Hamlet can be both the hero due to the bravery and fearlessness he has shown through his actions. Although he shows heroic qualities, he can still be a villain through his coward, disrespectful and immoral actions. Hamlet is often noticed that he has more than one side to his personality at the same time and this is revealed through the play when he stands for what he believes in and takes avenge for his father’s death but in the contrary not only did he kill Claudius, he was involved in everyone’s death including Ophelia, Polonius, Gertrude, Laertes, Rosencrantz and Guildenstern and that he would do anything to achieve and benefit for himself. Through these actions, Hamlet portrays the qualities of the duality of human nature.

How to Write an Argumentative Essay Samples Reviews & Guide

How to Write an Argumentative Essay Samples Reviews & Guide Key Pieces of How to Write an Argumentative Essay Samples When you are finished with your essay, you must not merely check it for spelling and grammatical errors, but nevertheless, it also has to be checked for logical fallacies. Normally, it doesn't include references and quotes in it. In instances when you get to select the topic for an argumentative essay, you need to be wise and locate a title that will intrigue a reader. You will need to back up your viewpoint with well-researched facts and data also. Spam mail needs to be outlawed. It is vital to opt for a great topic so as to compose a wonderful paper. The fundamental rules behind a common paper are quite straightforward. With our company, your assignment will acquire high marks not based on the argumentative essay topics you select. So be sure you select a subject, which has values in it. Recent argumentative essay topics that are related to society is going to do. To locate argumentative essay topics easy on various platforms, you will need to comprehend about the argumentative essay. An argumentative essay requires you to choose a topic and have a position on it. It is a particular type of academic writing. How to Get Started with How to Write an Argumentative Essay Samples? Argumentative essay is about arguing and debating on a subject, which is debatable. Instead of just immediately writing about your argumentative essay topic, you should first think about what you're likely to put back on your paper through a procedure of brainstorming and pre-writing. Understanding how to compose a strong argumentative paper can help you advance your very own argumentative thinking. The purpose of such essays isn't to demonstrate your knowledge, yet to exhibit the crucial thinking and analytical skills. Argumentative essay topics are so important since they are debatableand it's vital to at all times be critically considering the world around us. There are many kinds of essays, and every one of them is challenging in a different way. In this kind of situation, it's more convenient to discover ready-made essays and use them as an example. Facts, finally, will always win out against how folks are feeling at a specific moment. You ought to make people change their mind, and that's a very challenging job! Consider picking a topic that has been discussed by a great deal of individuals. Some individuals may think that the very good content could be written on any topic and the paper success is dependent just on the mastery of the writer. If you are in possession of a valid issue and you may offer sufficient arguments on it, then go with this. When you are requested to decide on a great topic for your argument, start with something you're familiarized with. You'll wind up lost without having the capability to make an argument and develop it correctly. It's possible for you to restate your argument, which is quite a common practice amongst essayists. It's essential not just to supply the evidence to back up your position but also to refute that of your opponents. Finally you've got to reach a conclusion together with convincing the reader your conclusion is the best one. A conclusion is, undoubtedly, the most crucial portion of the argumentative essay as possible either support the superior impression or destroy it entirely. If you must compose your whole essay in 1 day, do your very best to give yourself breaks so you don't burn out. If you decide to be an independent essay writer, you can expect the exact same. You will be assigned a topic, or your professor will enable you to select your own. You don't need to lose grades as a result of incorrect essay format.

Lord Of The Flies Character Analysis - 947 Words

Austin Curtis Ms. Tantlinger Honors English 10 2 January 2018 Title In William Golding’s novel, Lord of the Flies, a group of children are deserted on an uncharted island due to the conflict of a world war. As the boys live on the island, they begin to have conflicts among themselves, and Jack, an older boy on the island, begins to become power-hungry. Jack falls far from the rules of society as he is overcome by the power of the mask, Jack also conceals his humanity by using his war mask; Golding uses this to portray one of the main themes being the duality of man. The mask compels Jack from his emotions and causes him to lose his sense of innocence. Golding writes, â€Å"He paused and looked round. He was safe from shame for self†¦show more content†¦Golding writes, â€Å"Beside the pool his sinewy body held up the mask that drew eyes and appealed them. He began to dance and his laughter became a bloodthirsty snarling.†(64) All of Jacks tribe are now known as savages instead of the nice boys they once were. Jack is different when he has the mask on, he is more dangerous. The boys even knew that the paint that jack uses to conceal his identity is a sign for his change of actions. The boys thoughts are, â€Å"They understood only too well the liberation into savagery that the concealing paint brought.†. Golding says â€Å"For hunting. Like In the war. You know- - dazzle paint. Like things trying to look like something else† (65). Meaning Jack is like another person when he wears the mask. Goldings novel Lord of the Flies, can be related to the text of the Case of Dr.Jekyll and. Mr.Hyde. The main themes to both of these novels, is the duality of man. In Golding’s piece he uses this theme to describe the good and evil that is personified on the island, and is shown in the two groups of boys on the island by Jack’s savages, and the few boys on Ralph’s side that are somewhat innocent. Golding shows the good by the character of simon who is the only pure one on the island. The evil is portrayed as the â€Å"lord of the flies† which is a pigs head on a stick. The pig head is symbolism for the demon beelzebub which translate to â€Å"prince of the demons† or in thisShow MoreRelatedLord Of The Flies Character Analysis1584 Words   |  7 Pages Lord of the Flies, by William Golding, is a story about a troop of boys who are on a plane out of war-torn England. However, their plane crashes and strands them on an island without any adults. The b oys, who are anywhere from age six to age twelve, must learn to survive not only the elements, but each other as well. By the end of the story, at least three of the boys have died, two of which were killed knowingly by other boys on the island. When the boys first arrive, they appoint Ralph as chiefRead MoreLord Of The Flies Character Analysis807 Words   |  4 Pagesstranded the more they think they will never find civilization, making them turn inhuman and careless. As their behavior gets worse they end up killing their only source of survival but eventually get rescued. In the novel ,†Lord Of The Flies†, written by William Golding, the character Piggy represents human intelligence, Ralph illustrates leadership, while Jack symbolizes social chaos. Being the civilized one in the group, Piggy tries to calm everyone down, but also being the most vulnerable one becauseRead MoreLord Of The Flies Character Analysis940 Words   |  4 PagesAll people have evil inside them, sometimes deep enough for it to not come out. William Golding’s novel Lord of The Flies theme is that all people have evil inside them, and only rules and order can keep them from acting upon it. Ralph’s character disputes this theory because of his knowledge and wisdom, him seeking civilization and his leadership skills. Ralph seeking for civilization helps prove that he is not leaning towards the evil inside him. For example, the signal fire which is used toRead MoreLord Of The Flies Character Analysis1161 Words   |  5 Pages The novel â€Å"Lord of the Flies†, written by William Golding, follows a group of british schoolboys on their fight for survival. After their plane crashed on an island, the boys must work quickly and alert someone of their whereabouts. The main character, Ralph, opens the story as â€Å"a fair boy† meaning the favourite or the most promising of a group. Leading the boys was a job Ralph took on proudly and all was sain in the world. The boys aren’t on the island long before the idea of order starts to fadeRead MoreLord Of The Flies Character Analysis1322 Words   |  6 PagesIn the novel ‘Lord of the Flies’ by William Golding, a group of schoolboys are marooned on a tropical island after their plane crash-lands on it. At first, the boys se e it as a fun adventure but it doesn t take long for them to descend from boys to savages. The novel ends with the boys being rescued, but not before the death of several of them. In the novel, the character of Jack personifies the the evil that lies within man. This is shown through Jack’s tendency towards violence, him becoming aRead MoreLord Of The Flies Character Analysis1009 Words   |  5 PagesFor centuries people have accepted living side by side with good and evil, as they will for years to come. This philosophy is demonstrated in the allegorical novel, Lord of the Flies written by William Golding. Set in an unknown time period, during an atomic war, in which, the attempt to take a group of schoolboys to safety fails and they crash into a deserted island in the Pacific Ocean instead. As the boys realize there is no adult survivors, they celebrate their newfound freedom and try to establishRead MoreLord Of The Flies Character Analysis778 Words   |  4 PagesTo what extent do people feel dependent on those who provide good to society? William Golding, the author of Lord of the Flies, brings out the realities of society. Through multiple characters and relationships, the boys on the island learn of these harsh truths. The death of Simon leads to the deterioration of the boys on the island, proving that once good is removed a society will collapse. Ralph expresses prominent changes at the loss of Simon. Chief of the island, Ralph must keep law and orderRead MoreLord Of The Flies Character Analysis1368 Words   |  6 PagesPicture life today without a structured government: no morals, no laws, and no persecution. People would be able to act however they wanted, without thinking about the consequences. In his novel Lord of the Flies, William Golding uses characters and symbols to provide a complex perspective on the lack of society and its effect on people’s behavior. Golding himself served in the military for five years, and he fuels the plot with his own experiences with corruption. In the text, a pack of BritishRead MoreLord Of The Flies Character Analysis932 Words   |  4 Pagesdesires, power and committed some immoral acts in their life but at what point do these assets effect the amount of corruption present in a person. Lord of The Flies is a 1954 novel written by Nobel Prize winner William Golding. With the stand out themes of savagery and corruption it can be clearly seen why this book has such a large audience. Lord of The Flies is an allegory based around the events of war and destruction going on in the world at this time. The Following is a 2013-2015 crime drama Tv showRead MoreLord Of The Flies Character Analysis848 Words   |  4 PagesIn William Golding’s Lord Of The Flies while the time of a World War, a plane crashed on an uncharted island leaving young boys stranded with no authority. The boys get so caught up in striving for survival that their savage side overtakes them. William Golding proves that men are essentially evil through the inability of the boys to maintain an authority figure that would have prevented the creeping in of savagery because of the loss of societal rules. Simon follows Ralph and the boys but eventually