Spectroscopy is the study of light. A spectrophotometer is a machine used to determine the absorbance of light at any given wavelength. It does this by using a source of white light through a prism, which gives multiple wavelengths that can be individually focused (Ayyagari and Nigam, 2007). Substances are put into cuvettes that are glass or quartz containers that light can easily travel through. The light that is being focused travels through the substance gets absorbed by the
10 microliters of the sample is then added and the assay absorption is measured at 340nm. If absorbance was above 1.5, samples were diluted.
To begin, we formulated a method in which each unknown substance and compound were compared to find their molar relationships. In the experiment we calculated the molar mass of every compound by determining the amount of moles per gram in each element using the periodic table and then added them together. We then
A spectrophotometer’s purpose is to use colors of the light spectrum to determine the concentration of light absorbing molecules in a solution. (p.59) In this particular lab, our mission was to determine the protein concentration and the standard curve of the unknown sample of BSA. This, by preparing five dilutions of the unknown solution of BSA together with other known concentrations, and then experimenting by observing how the concentrations were passed through the spectrophotometer. The outcome resolved in the absorption levels being decreased, and this
The absorbance is measured using a Plate reader and a Standard curve is generated. Also, the different types of pipetting techniques are assessed in this Assay.
Scientists use an instrument called a spectrometer to quantitatively determine the amount of light absorbed by a solution. The primary inner parts of a typical spectrometer are described below. The spectrometer has a light source that emits white light containing a vast mixture of different wavelengths of electromagnetic radiation. The wavelength of interest is then selected using a monochromator (“mono” meaning one and “chromate” meaning color) and an additional exit slit. The separation of white light into different colors (wavelengths) is known as diffraction. The selected light then reaches the sample and depending on how the light interacts with the chemical compound of interest, some of the light is absorbed and some passes straight through. By comparing the amount of light entering the sample (P0) with the amount of light reaching the detector (P), the spectrometer is able to tell how much light is absorbed by the sample.
Using elemental analysis to determine the percent mass composition of each element in a compound is the first step in creating an empirical formula. There are many different types of elemental analysis, but in this experiment gravitational analysis and Beer’s Law are used. Elemental analysis is first used to find the moles of each element, then converted to mass, and then the percent mass of the element in the product is found (2).
The main point of lecture was to continue discussing about the light spectra and atoms. Specifically, we used the equations and calculated a photon of light’s energy at a certain wavelength. Also, we discussed the light spectrum and how particular wavelengths of light are absorbed by matter.
Evers, D. J., B. Hendricks, G. Lucassen, and T. Ruers. "Optical Spectroscopy: Current Advances and Future Applications in Cancer Diagnostics and Therapy." NCBI. National Center for Biotechnology Information, 8 Mar. 2012. Web. 13 Sept. 2015.
AAS has contributed to the understanding of elements having different absorption emission spectra due to their difference in energy levels. In the absorption spectrum, the absorbed light are shown as black gaps. As the number of electrons increase, the number of spectral lines also increase. Hence, by measuring the absorption of light, the concentration of the element within a sample can be determined. By knowing the concentrations of an element, scientists are now aware that even the smallest amount can make a significant impact towards the biological system. Therefore, scientists have brainstormed ways to monitor the use of chemicals in the
Fifield, F. W. and Kealey, D. 1995. Principles and Practice of Analytical chemistry. (4th ed) Glasgow, Blackie Academic and professional.
Absorbance and concentration provide a starting point for an analysis of many substances. The absorbencies of solutions of known concentrations are plotted on a Beer 's law plot. Then, using absorbencies calculated and dilution factors, one can calculate the concentration of a substance in a solution. In this lab, I was able to successfully use spectrophotometry to calculate the average concentration of iron in an unknown solution.
Incorporation of assay controls included setting up a spectrophotomer and running the chart recorder with a full-scale deflection before the start of the assay. The set recorder had a corresponding value of 1 for the change in the absorbance. Therefore, prior testing was done to observe whether a change occurred in the readings. This helped to indicate that the results were valid, as they could have been affected by a fault during the setting up of the spectrophotometer. On the other hand this was considered as one of the controls for the experiment. Nevertheless, a new cuvette had to be used for each assay.
In nuclear medicine diagnosing techniques, a very small amount of radioactive material is introduced into the body. Because medical isotopes are attracted to specific organs, bones or tissues, the emissions they produce can provide crucial information about a particular type of cancer or disease. Information gathered during a nuclear medicine technique is more comprehensive than other imaging procedures because it describes organ function, not just structure. The result is that many diseases and cancers can be diagnosed much earlier.
Spectrophotometry is a routine laboratory test that has the added advantage of being able to