How to use beer lamberts lae ro determin iron concentration in waste water experiment
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After setting the spectrophotometer to 0 absorbance (100% transmittance) at 580 nm with a cuvette containing water (blank), measure the absorption of the samples in sample tubes #1-#5 at 580 nm. 1. Set the Spec-20 (spectrophotometer) to a wavelength of 580 nanometers. 2. Zero (Blank) the Spec-20 using water as the blank. 3. Read the absorbance of your solutions from the lowest concentration to the highest concentration. Pour the solution from tube #5 into a clean, dry cuvette. Wipe any fingerprints from the outside of the cuvette with a Kimwipe. Place the cuvette into the Spec-20, making sure the clear side of the cuvette faces you. 4. Dispose of the solution. 5. Rinse the cuvette with the next standard and dispose of the rinse. 6. Repeat steps 3-5 for the remaining four diluted standard solutions. Determine the absorbance of test tube #4, then #3, then #2, and lastly #1. 7. Obtain two solutions of BPB of unknown concentration from your instructor. Procedure Part B: Graphing the Calibration/Standard Curve Plot the absorbance (y-axis) versus concentration of the BPB (x-axis). Draw a best-fit line using your data points. Do this by hand and with a computer. Determine the slope of the lines for each graph. You now have a working relationship between the absorbance and the concentration of BPB. Data Table 2: Absorbance and Concentration of Unknown Solutions Unknown # Absorbance Concentration (ppm) 1 0.220 2 0.632 1. Calculate the ppm of each sample using: a) The slope of your hand-drawn graph b) The slope of your computer-drawn graph c) The Beer-Lambert Law using the molar absorptivity coefficient determined in part A 2. Does the calibration curve obey the Beer-Lambert Law? Why? 3. What is the percent error for the hand-drawn slope compared to the computer-generated slope (actual)? 4. If you rinsed each solution with water between each reading and neglected to dry it completely, how would that affect your results.
Dominador T.
1. Preparation of Standard Solutions: Use this table to indicate the concentration of each standard solution, based on the volumes of stock solution and the concentration of the stock solution. (see bottom part of p. 7-6 in the lab manual.) Concentration of Fe2+ stock solution (from bottle in lab): 24.6 Volume of Stock Solution (mL) 1.00 2.00 5.00 8.00 10.00 UNK Concentration (ppm) Absorbance 0.091 0.169 0.418 0.706 0.854 0.281 Show one sample calculation for determining the concentration of a standard solution:
Madhur L.
Total Iron in water samples can be determined by Visible Spectrophotometry. In this method, Fe2+ ions are reacted with ortho-phenanthroline forming an orange-red complex (Figure 1). Figure 1. Fe2+-phenanthroline Complex In order to determine the total iron and not just the Fe2+ ions, the Fe3+ ions are first reduced to Fe2+ following the reaction: 4 Fe3+ + 2 NH2OH•HCl → 4 Fe2+ + N2O + 4 H+ + H2O In the pillow method, all the reagents are contained in a sachet. Sample Cell #2495402 is filled with the water sample to the mark (10 mL). The reagent mixture contained in the sachet (or pillow) is added into the sample, and the solution is mixed. The instrument timer is started and the absorbance is determined after 3.00 minutes of reaction. The absorbance is corrected against a blank solution. The stored program calculates the concentration as mg Fe per liter water sample. 1. Given the data below, calculate the parameters of the fundamental linear calibration (R2, sy, coefficients a and b and their corresponding standard errors). You can use either R or the Data Analysis in Excel, and make sure that you include these in your submission. Concentration Fe (mg/L): 0.100, 0.125, 0.250, 0.500, 0.750, 0.100 Absorbance (AU): 0.100, 0.120, 0.230, 0.480, 0.730, 0.100 2. Estimate the decision limit (cc̑), detection capability (LOD cc̒) and LOQ of the method using the following measured absorbances of a standard solution of Fe with concentration of 0.02 mg/L: 0.003, 0.004, 0.007, 0.003, 0.007, 0.004, 0.003, 0.003, 0.004, and 0.003.
Adi S.
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