CHROMATOGRAPHY (ANALISIS CHEMISTRY) Coursework Example | Topics and Well Written Essays - 1000 words

CHROMATOGRAPHY (ANALISIS CHEMISTRY) - Coursework Example In thin layer chromatography, a thin, uniform layer of silica or alumina gel was traditionally coated on a piece of glass. The mixture was dissolved in an appropriate solvent and the glass plate was immersed in the liquid. The movement of the individual components of a mixture takes place at different rates and the distance travelled by each component is measured and the data so obtained is used to calculate the Rf value is calculated by dividing the distance travelled by the component with the distance travelled by the solvent. Rf values are then compared with standard values to identify the suspected component. Fluorescent materials are incorporated into the stationary phase to identify colorless components which are invisible to the naked eye. Such components are visualized using ultra violet light. Separation of components of a mixture depends upon their affinity for the solvent as well as the capability of bonding with the stationary phase which is rich in hydroxyl groups. Van d er Waals forces also operate between the components and their affinity or repulsion from the stationary phase and determine the distance moved. Column chromatography was advancement in the technique where the stationary phase was packed inside a column (glass tube) and the mobile phase with the dissolved investigative mixture poured from the top. The movement occurred under the influence of gravity as well as the attraction of the components in the stationary phase, allowing identification of individual components. HPLC (High Performance Liquid Chromatography/High Pressure Liquid Chromatography) is a modern technique used to separate desirable or investigative chemical compounds from other compounds in a liquid sample. The investigative compounds are dissolved in an appropriate organic or inorganic solvent known as the mobile phase and the mixture is passed under pressure through specific columns which constitute the stationary phase.

Critical Issues in Policing Essay Example | Topics and Well Written Essays - 1250 words

Critical Issues in Policing - Essay Example In addition, there are also state police agencies and federal-non-military agencies. This paper looks at various issues affecting policing in the United States. Dangers of Policing Police officers are at serious risk of losing their lives to criminals that are heavily armed. Police officers have encountered dangerous and senseless shootings from criminals. They have been gunned down while investigating cases in the United States. The criminals who possess guns kill the police officers to prevent evidence from being used in a court of law against them. In addition, terror attacks have posed dangers to the police. In particular, the 9/11 terror attacks killed several police officers (Walker and Katz, 2011). Police officers are also vulnerable to vehicle accidents. Police officers use vehicles every day and are therefore vulnerable to traffic accidents. In addition, many police officers have lost their lives in acts of homicide or in the line of duty. Police officers are also at risk of getting infected with dangerous diseases after getting into contact with body fluids of those injured during incidents. During treatment in the event of serious injuries, the officers face the risk of contracting diseases especially if proper screening of blood is not done by medical practitioners (Walker and Katz, 2011). Stress is another danger to the police officers. ... Stress has also been attributed to the increasing level of divorce cases among police officers and their spouses (Walker and Katz, 2011). Less-Than-Lethal Weapons Use of excessive force by the police officers is not allowed by law. In particular, the police officers are not required to use firearms when carrying out their normal duties in the society. Less-than-lethal weapons have been recommended for use instead. The police officers are trained to effectively use â€Å"less-than-lethal weapons† so as to reduce fatalities as they go about their duties. A verbal command is one example of less-than-lethal weapon that police officers are required to use. Suspects are commanded to do what the police officers have told them. Failure to adhere to the police verbal demands lead to another level in the use of justified force (Dempsey and Forst, 2011). Police officers can use batons and beanbags that are aimed at incapacitating a criminal from a distance. These non-lethal weapons have no penetrating contact energy and thus the criminal cannot be grossly harmed by them. The police officers are advised not to aim at the suspect’s head because the effects can be diverse when the batons or beanbags hit the head. Chemical agents such as pepper spray and mace also form part of non-lethal-weapons. The chemicals are meant to create irritation on the suspect’s skin, eyes, and cause violent coughing. The police officers can then take control of the suspect after disorienting them with these chemicals (Dempsey and Forst, 2011). Technology Used In Policing Police officers have opted to use computing power and high-tech data transmission equipment to ensure that they collect, store, analyze and share data with other