B. The copper concentration in a contaminated salt sample was determined by flame atomic absorption spectrometry. In the analysis, a 10.00-g sample containing an analyte is transferred to a 250-mL volumetric flask and diluted to volume. A series of 10.0 mL of the diluted sample solution was pipetted into each of five 50.0-mL volumetric flasks. Various volumes of a standard containing 12.2 ppm Cu were added to the flasks, and the solutions were then diluted to volume. The corresponding absorbances of each of the solutions are given below: Unknown, mL 10.0 10.0 10.0 10.0 10.0 Standard, mL 0.0 10.0 20.0 30.0 40.0 Absorbance 0.201 0.292 0.378 0.467 0.554 What type of standardization (calibration) technique is used in this problem? What do you think is the main reason why this standardization technique is used?

B. The copper concentration in a contaminated salt sample was determined by flame atomic absorption spectrometry. In the analysis, a 10.00-g sample containing an analyte is transferred to a 250-mL volumetric flask and diluted to volume. A series of 10.0 mL of the diluted sample solution was pipetted into each of five 50.0-mL volumetric flasks. Various volumes of a standard containing 12.2 ppm Cu were added to the flasks, and the solutions were then diluted to volume. The corresponding absorbances of each of the solutions are given below: Unknown, mL 10.0 10.0 10.0 10.0 10.0 Standard, mL 0.0 10.0 20.0 30.0 40.0 Absorbance 0.201 0.292 0.378 0.467 0.554 What type of standardization (calibration) technique is used in this problem? What do you think is the main reason why this standardization technique is used?

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter12: Spectrochemical Methods

Section: Chapter Questions

Problem 12P

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B. The copper concentration in a contaminated salt sample was determined by flame atomic absorption spectrometry. In the analysis, a 10.00-g sample containing an analyte is transferred to a 250-mL volumetric flask and diluted to volume. A series of 10.0 mL of the diluted sample solution was pipetted into each of five 50.0-mL volumetric flasks. Various volumes of a standard containing 12.2 ppm Cu were added to the flasks, and the solutions were then diluted to volume. The corresponding absorbances of each of the solutions are given below: Unknown, mL 10.0 10.0 10.0 10.0 10.0 Standard, mL 0.0 10.0 20.0 30.0 40.0 Absorbance 0.201 0.292 0.378 0.467 0.554 Calculate the copper concentration (a) in the diluted sample solution expressed in ppm Cu, and (b) in the salt sample as percent copper (%Cu).
A 10.00-g sample containing an analyte was transferred to a 250-mL volumetric flask and diluted to volume. When a 10.00-mL aliquot of the resulting solution was diluted to 25.00 mL it was found to give a signal of o.235 (arbitrary units). A second 10.00-mL aliquot was spiked with 10.00 mL of a 1.00- ppm standard solution of the analyte and diluted to 25.0o mL. The signal for the spiked sample was found to be o.502. Calculate the weight percent of analyte in the original sample.
3. The lead in a swab sample, lead standards, together with a blank were made up in 5.00 mL volumetric flasks using 0.2 % HNO3. 20 μL aliquots of these solutions were injected into the spectrophotometer and the absorbance measured at 217 nm. The following results were obtained. lead / ppb Absorbance 0 0.0591 10.00 0.0858 50.00 0.1926 100.0 0.3260 150.0 0.4594 200.0 0.5929 Swab sample 0.3700 (a) Determine the amount of lead in the swab sample in μg.
Quantitative Analysis by External Standard Method Calcium in a juice sample is determined by atomic absorption spectrophotometry. A stock solution of calcium is prepared by dissolving 1.834 g of CaCl, 2H20 in water and diluting to 1000.0 mL. A substock calcium solution was prepared by transferring 10.00 mL of the stock to a 100.00 mL volumetric flask and diluting to the mark. Three standard solutions of calcium were prepared by transferring 2.500 mL. 5.00 mL and 10.00 mL of substock to 50.00 mL volumetric flasks and diluting to the mark. The sample is prepared by transferring 1.000 mL of fruit juice from the original bottle to a 25.00 mL flask and diluting to the mark. Strontium chloride is added to all solutions before dilution to avoid phosphate interference. Instrumental response of the standards is measured against the blank, and the following readings are recorded: 9.10, 18.6 and 37.0. The sampie reading is 28.1. Using the multipoint method, find the concentration of calcium in…
A 10.00 g sample containing an analyte was transferred to a 250 mL volumetric flask and diluted to volume. When a 10.00 mL aliquot of the resulting solution was diluted to 25.00 mL it was found to give a signal of 0.235 (arbitrary units). A second 10.00 mL aliquot was spiked with 10.00 mL of a 1.00 ppm standard solution of the analyte and diluted to 25.00 mL. The signal for the spiked sample was found to be 0.502. Calculate the weight percent of analyte in the original sample.
The Na* concentration in a blood serum sample was determined using the method of standard addition and atomic spectroscopy. 25.00 mL aliquots of serum were pipetted into five 50.00 mL volumetric flasks into which 2.640 M NaCl standard was added as shown in the table below. After dilution to volume, the emission of each solution was measured and used to plot a calibration graph. Flask 1 23 4 5 Vol. of standard (mL) 0 1.00 2.00 3.00 4.00 Emission signal 3.13 5.40 7.89 10.30 12.48 Analytical signal (emission) 14 42 10 12 4 2 0 0 0.05 y = 44.697x + 3.12 R² = 0.9995 0.1 0.15 Concentration of added analyte (M) 0.2 a) Using the plotted calibration graph, calculate the Na* concentration in the blood serum sample. b) Provide a possible reason why the serum sample might have been analysed using this analytical procedure. 0.25
The determination of iron in wines was carried out by atomic absorption spectrophotometry, using the standard addition method. To do this, 10 mL of wine were placed in five 50 mL volumetric flasks; then 0, 5, 10, 15 and 20 mL of a 10 ppm iron standard solution were added to each of them. Next, they were gauged with distilled water and the absorbance was measured, obtaining the values of 0.040, 0.062, 0.081, 0.102 and 0.125 respectively. Calculate the regression parameters and obtain the iron concentration in the wine, in µg / mL.
0.1120 g of a solid sample containing copper was dissolved by acid and transferred to a 250.00 mL volumetric flask and volume was made up with distilled water. The solution was then diluted by a factor of 25. The final solution was analyzed by atomic absorption spectrophotometry and the concentration was found be 2.982 ppm, What is the weight percentage of copper in the original solid sample? Keep four significant figures in your final answer.
Exactly 5.00 mL aliquots of a solution containing analyte X were transferred into 50.00-mL volumetric flasks and the pH of the solution is adjusted to 9.0. The following volumes of a standard solution containing 2.00 µg/mL of X were then added into each flask and the mixture was diluted to volume: 0.000, 0.500, 1.00, 1.50 and 2.00 mL. The fluorescence of each of these solutions was measured with a fluorometer, and the following values were obtained: 3.26, 4.80, 6.42, 8.02 and 9.56, respectively. ii. Using relevant functions in Excel, derive a least-squares equation for the data, and use the parameters of this equation to find the concentration of the phenobarbital in the unknown solution.
In the process of performing a spectrophotometric determination of Fe, an analyst prepares a calibration curve using a single-beam spectrometer, such as a Spec-20. After preparing the calibration curve, the analyst drops the cuvette used for the method blank and the standards. The analyst acquires a new cuvette, measures the absorbance of the sample, and determines the %w/w Fe in the sample. Will the change in cuvette lead to a determinate error in the analysis? Explain.
Internal standard. Mn was used as an internal standard for measuring Fe by atomic absorption. A standard mixture containing 2.00 g Mn/mL and 2.50 g Fe/mL gave a quotient (Fe signal/Mn signal) 1.05. A mixture with a volume of 6.00 mL was prepared by mixing 5.00 mL of unknown Fe solution with 1.00 mL containing 13.5 g Mn/mL. The absorbance of this mixture at the Mn wavelength was 0.128, and the absorbance at the Fe wavelength was 0.185. Find the molarity of the unknown Fe solution.
To quantify the Cadmium content in a water sample, 5 aliquots of 10 mL were taken, adding to each one of them a volume of a standard solution of Cd (2 mg / mL); after the addition the final volume for all solutions was 50 mL. The absorbance reading was taken in an Atomic Absorption spectrophotometer, the data recorded were: Aliquot 1 2 3 4 5 Cd solution (mL) 0 1 2 3 4 Absorbance 0.163 0.240 0.319 0.402 0.478 Calculate the ppm of Cd.