The Physics Of Atomic Absorption Spectrometry

With these absorbance numbers a concentration curve was constructed and the unknown solution was determined by finding the point of absorbance on the curve.

3ml of sample was taken first flask at 4 minutes and added to the appropriate tube of sodium hydroxide, from the second flask at 4.5 minute and so on, each flask was sampled at 30 second intervals. The sampling was then repeated starting at 8,12,16 minutes. The final sample from the last flask was taken at 18.5 minutes. Once the sampling was completed, measurements of absorbance were obtained for solution in each tube at 405 nm.

After this, the solution was poured into a volumetric flask just about to the 1dm3 line and then it was left there to cool to the same temperature as the room before filling precisely to the 1dm3 line with distilled water. The molar mass of CuSO4.5H20 was 249.5 so that means 249.5g of copper sulphate was needed to dissolve, in order to make a standard solution, into 1dm3of distilled water. Following this, a linear dilution of the CuSO4.5H2O was made in order to be used to make a calibration curve after using the colorimeter to write down the absorbance of each sample. A linear dilution is diluted with distilled water in order for it to make the concentration weaker and weaker. For this investigation, the dilutions made ranged from 0.01 to 0.1 M/l . It was essential to only make up 10cm3

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.

The ending result of this experiment confirms that as five test tubes are lined up with the varying level of absorbance, different results in the level of absorbance will appear as well, this is visible in above table. Thus, this is due to the varying amount of water in the solution. The blank sample had a 0.30 in its level of absorbance.

The isosbestic point of the acid (pH6) and basic forms (pH10) of para Nitrophenol (PNP) was expected at 350nm. As you can see in figure 2, the graph shows the intersection of 2 curves at ~350nm, which is matched with the literature value. Also, the pKa of PNP was expected 7.15 at room temperature. Refer to figure 3, the pKa is estimated to be 7.15-7.2, which very close to the literature value. In addition, the lab was succeeded in illustrating the use of a spectrophotometry to analyze concentrations of chemical substance. The absorbances of 2 unknowns were felt on the standard curve as the expectation (refer to table 4). The minimum absorbance of the known standards was 0.193 and the maximum is 1.830. The absorbance of the unknown

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.

The Beers Law calibration experiment used many concentrations of crystal violet solutions. Each of these solutions were test and analyzed in order to determine the absorbance of each concentration The results were than graphed and produced a slope of 1.00E05 with an intercept of -2.21E-02.

The dark, navy blue colored graph represented the absorbance curve for the S1 sample. The red colored graph represented the absorbance curve for the S2 sample. The green colored graph represented the absorbance curve for the P1 sample. The purple colored graph represented the absorbance curve for the P2 sample. The gaps between the P2 curve was due to the oversaturation that led to the inconclusive spectrophotometer readings. The blue colored graph represented the absorbance curve for the P1 low salt sample. The orange colored graph represented the absorbance curve for the P2 low salt sample. The light blue colored graph represented the absorbance curve for the P1 medium salt sample. The light pink colored graph represented the absorbance curve for the P2 medium salt sample. The light green colored graph represented the absorbance curve for the P1 high salt sample. The light purple colored graph represented the absorbance curve for the P2 high salt

5. The degree of precision was to 3 significant figures obtained with the spectrophotometer. The major source of error in our experiment was not calibrating the spectrophotometer with distilled water.

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

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.

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.

The purpose of this experiment was to determine a series of external standards using Atomic Absorption (AA) and Flame Atomic Emission (FEA) spectroscopy. The principles of Atomic Absorption spectroscopy relies on the ability to distinguish one atom from another with great sensitivity as explained in Quantitative Chemical Analysis by Daniel Harris1. Specifically, this high precise determination can be achieved when specific wavelength of light is generated by a hollow-cathode lamp. The light emitted by the lamp travels through the flame until it reaches the mixture of neutral atoms. The electrons of the desired neutral atom gets excited to a certain energy level. As they return to the ground state, the energy emitted in the form of photons is analyzed by the detector. The photomultimeter tube (PMT) inside the detector amplifies the incoming photons into a cascade of electrons, which then is read by the computer and converted it into a function of absorbance.

concentration, record the absorbance readings at a fixed wavelength, and plot the absorbance vs. concentration data. The wavelength of 520 nm was selected for experiment Part