(a)
Interpretation:
The concentration in samples that yielded absorbance of 0.143 should be expressed in ppm. The relative standard deviation of the result should be calculated. The calculation should be repeated assuming the absorbance data are means of three measurements.
Concept introduction:
Standard deviation of the results obtained from the calibration curve =
M − number of replicates
N- number of calibration points.
Answer to Problem 14.12QAP
If absorbance data are means of 3 measurements,
Explanation of Solution
If the experiment was replicated three times,
(b)
Interpretation:
The concentration in samples that yielded absorbance of 0.675 should be expressed in ppm. The relative standard deviation of the result should be calculated. The calculation should be repeated assuming the absorbance data are means of three measurements.
Concept introduction:
Standard deviation of the results obtained from the calibration curve =
M − number of replicates
N- number of calibration points.
Answer to Problem 14.12QAP
If absorbance data are means of 3 measurements,
Explanation of Solution
If the experiment was replicated three times,
(c)
Interpretation:
The concentration in samples that yielded absorbance of 0.068 should be expressed in ppm. The relative standard deviation of the result should be calculated. The calculation should be repeated assuming the absorbance data are means of three measurements.
Concept introduction:
Standard deviation of the results obtained from the calibration curve =
M − number of replicates
N- number of calibration points.
Answer to Problem 14.12QAP
If absorbance data are means of 3 measurements,
Explanation of Solution
If the experiment was replicated three times,
(d)
Interpretation:
The concentration in samples that yielded absorbance of 1.009 should be expressed in ppm. The relative standard deviation of the result should be calculated. The calculation should be repeated assuming the absorbance data are means of three measurements.
Concept introduction:
Standard deviation of the results obtained from the calibration curve =
M − number of replicates
N- number of calibration points.
Answer to Problem 14.12QAP
If absorbance data are means of 3 measurements,
Explanation of Solution
If the experiment was replicated three times,
(e)
Interpretation:
The concentration in samples that yielded absorbance of 1.512 should be expressed in ppm. The relative standard deviation of the result should be calculated. The calculation should be repeated assuming the absorbance data are means of three measurements.
Concept introduction:
Standard deviation of the results obtained from the calibration curve =
M − number of replicates
N- number of calibration points.
Answer to Problem 14.12QAP
If absorbance data are means of 3 measurements,
Explanation of Solution
If the experiment was replicated three times,
(f)
Interpretation:
The concentration in samples that yielded absorbance of 0.546 should be expressed in ppm. The relative standard deviation of the result should be calculated. The calculation should be repeated assuming the absorbance data are means of three measurements.
Concept introduction:
Standard deviation of the results obtained from the calibration curve =
M − number of replicates
N- number of calibration points.
Answer to Problem 14.12QAP
If absorbance data are means of 3 measurements,
Explanation of Solution
If the experiment was replicated three times,
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Chapter 14 Solutions
Principles of Instrumental Analysis
- The chromium in an aqueous sample was determined by pipetting 10.0 ml. of the unknown into each of five 50.0-mL volumetric flasks. Various volumes of a standard containing 12.2 ppm Cr were added to the flasks, following which the solutions were diluted to volume. Unknown,mLStandard, mLAbsorbancc 10.00.00.201 10.010.0 0.292 10.020.0 0.378 10.030.0 0.467 10.040.0 0.554 (a) Plot the data using a spreadsheet. (b) Determine an equation for the relationship between absorbance and volume of standard. (c) Calculate the statistics for the least-squares relationship in (b). (d) I)ctcrmine the conccnt ration oÍCr in ppm in the sample. (e) Find the standard deviation of the result in (d).arrow_forwardIn spectrophotometric analysis, the relationship between the absorbance A and the analyte's concentration C is: A = ebC + Ablank What is the molar extinction coefficient I and its absolute uncertainty if A is 0.68 ± 0.06; Ablank is 0.06 ± 0.01; b is 1.00 cm; and C is (0.45 ± 0.03)x10-5 mol/L?arrow_forwardThe 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. 0.25arrow_forward
- You are developing a procedure for determining traces of copper in biological materials using a wet digestion followed by measurements by atomic absorption spectrophotometry. In order to test the validity of the method, you obtain a NIST orchard leaves standard reference material and analyze this material with your procedure five times and obtain a mean of 12.27 ppm with a standard deviation of 0.097 ppm. The NIST sample is listed as 11.7 ppm. Does your method give a statistically valid value at the 95% confidence level?arrow_forwardThe 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.arrow_forward(a) You measure the percent transmittance of a solution containing chromophore X at 400nm in a 1-cm path length cuvette and find it to be 50%. What is the absorbance of this solution? (b) What is the molar absorptivity of chromophore X if the concentration of X in the solution measured in question (a) is 0.5mM? (c) What is the concentration range of chromophore X that can be assayed if, when using a sample cell of path length 1, you are required to keep the aborbance between 0.2 and 0.8?arrow_forward
- You are developing a Ca detection method for a graphite furnace AA instrument. Your analysis of ten blank samples gives a standard deviation of 0.265 ppb. To establish your limit of detection (LOD), what concentration of Ca should be spiked into your blanks?arrow_forwardIn the analysis conducted with flame AAS, standard solutions of the X-type are analyzed individually and the absorbance values obtained are plotted against concentration (ppm). It was seen that the slope of the calibration line obtained was 0.0925. The standard deviation of the absorbance values obtained by reading the blank 10 times under the same conditions was calculated as 0.00183 ppm. According to this; For the X-type calculate the following: a) LOD b) LOQ c) Sensitivityarrow_forwardTo determine the instrument detection limit of Pb2+ ions, a student made 10 blank solutions and measured their signals. The standard deviation of the signals are 0.199. Then the student made a series of Pb2+ standard solutions (concentration range is 2.00 ppm to 15.00 ppm) and measured their signals. The equation of the calibration curve is: y = 3.413 x+ (b). What is the instrument detection limit of Pb2+ in ppm? %3Darrow_forward
- 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.arrow_forward2 (1) When performing chemical measurements, replicate experiments are often needed. This is to mitigate (Systematic or Random) error. (2) A CHEM 215 student performed 5 measurements of the wt% of SO4²- of a solid power sample. The results are 8.75%, 8.85%, 8.89%, 8.71%, 8.64%. The standard deviation is 0.10%. What is the confidence interval for this student's experiment at 95% confidence level. The t values for 95% confidence for degree of freedom from 1 to 5 are 12.71, 4.303, 3.182, 2.776, 2.571, respectively. Show your work!arrow_forwardAn atomic absorption method for the determination of the amount of iron present in used jet engine oil was found from pooling 30 triplicate analyses to have a standard deviation s = 3.6 mg Fe/mL. If s is a good estimate of σ, calculate the 95 and 99% confidence intervals for the result 18.5 mg Fe/mL if it was based on (a) a single analysis, (b) the mean of two analyses, and (c) the mean of four analyses.arrow_forward
- Principles of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage Learning