During this lab our group successfully learned how to use and analyze samples using the Spec 20. These instruments are intuitive to use , but there are also some common errors. this can easily be overlooked. Once the Spec 20 has had time to warm up, simply select the desired measurement (absorbance or transmittance percentage) as well as the wavelength you will be measuring at 3. Once the appropriate settings are selected, a blank should be placed in the sample. chamber to properly reset the machine using the auto zero function 3. It is imperative to use an appropriate solution as a blank depending on the samples that will be measured. For example, when measuring food colors and aqueous solutions, water should be used as the blank. Once the machine is properly zeroed, individual samples can be measured for their absorbance and transmittance. Although the operation is quite simple, it is important to avoid simple mistakes. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original test First, if the transmission is outside a range of 15% to 85%, a different wavelength should be used. Data measured outside of this range may not accurately display sample properties. Other common problems involve toilet bowls. If a cuvette is not placed in the correct orientation, the readings could be incorrect. To avoid this, always make sure the triangle on the bowl faces the light source. The cuvettes should also be cleaned with chemical wipes to ensure there are no contaminants such as fingerprints or oils on the clear plastic, this will ensure accurate readings. Using data collected from various samples analyzed with the Spec 20, we were able to determine the relationships between wavelength, transmittance, and absorbance. Transmission refers to the percentage of light that passes through a sample from the source and is received by the detector compared to a blank, which has 100% transmission. Absorbance refers to the amount of light absorbed by a sample compared to a blank, which has an absorbance of 0. After taking measurements of red and green food coloring samples at different wavelengths, we have was able to plot both transmission and absorbance on a sample. chart. These graphs showed that absorbance was maximum when transmission was minimum and vice versa, giving them an inverse relationship. The red and green samples also had inverse relationships with each other. This relationship can be explained by looking at the color wheel. The color we see is the wavelength of color that a sample transmits best. The complementary color, which is on the opposite side of the color wheel, is better absorbed by the sample. For example, red and green are opposites on the color wheel. Red has the greatest absorbance when analyzed at a green wavelength (~500 nm) and has the greatest transmittance at red wavelengths (~625 nm). Green has the opposite data values. The observed color of KMnO4 is violet, the complement of which is yellow. As expected, we see that KMnO4 has its greatest absorbance in the yellow wavelength (~550 nm). Another important attribute of absorbance is that it determines the analytical wavelength of a sample. This occurs when the absorbance is maximum, which occurs when a.