(a)
Interpretation:
A working curve from the data should be constructed.
Concept introduction:
Standard addition method is used to analyze complex samples which matrix effect is significant. One common approach is standard addition technique is spiking of sample. In this method, one or more increments of a standard solution is added to the several aliquots of sample containing same volume. Each solution is then diluted to a fixed volume and experiment is proceeded.
(b)
Interpretation:
A linear least-squares equation for the data should be determined.
Concept introduction:
The slope of the line,
The intercept,
(c)
Interpretation:
The standard deviation of the slope and intercept and the standard deviation about regression for the curve should be determined.
Concept introduction:
Standard deviation about regression,
N − number of points used.
The standard deviation of the slope,
The standard deviation of the intercept,
(d)
Interpretation:
The concentration of Zn2+ in the sample should be calculated.
Concept introduction:
Standard addition method is used to analyze complex samples which matrix effect is significant. One common approach is standard addition technique is spiking of sample. In this method, one or more increments of a standard solution is added to the several aliquots of sample containing same volume. Each solution is then diluted to a fixed volume and experiment is proceeded.
(e)
Interpretation:
The standard deviation for the result in part (d) should be calculated.
Concept introduction:
Standard deviation of the results obtained from standard addition method =
M − number of replicates
N- number of calibration points.
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Chapter 15 Solutions
Principles of Instrumental Analysis
- In order to measure riboflavin in a breakfast cereal, a 5.00-gram sample of the cereal was extracted with acetic acid and filtered. The extract was transferred to a 50.0 mL volumetric flask and diluted to the mark. The sample was transferred to a cuvette and the fluorescence was measured. The instrument read 59 units (Fluorescence units –an arbitrary scale). 24.00 mL of the cereal extract was sample was mixed with 1.0 mL of a riboflavin standard that was 0.500 ug/mL. The fluorescence of this mixture was measured and read 94 fluorescence units. Calculate the concentration of riboflavin per gram of cereal (use µg/gram of cereal).arrow_forwardAn absorbance calibration curve for Zn was fitted to equation A = 0.913×`Zn, ppm`. Flask 1: To the first flask, a 1.00 mL aliquot of the unknown Zn solution was diluted to 100.0 mL in a volumetric flask; the absorption intensity from this sample was measured to be A = 0.204. Flask 2: To a second flask, a 1.00 mL aliquot of the unknown Zn sample and a 1.00 mL aliquot of 10.00 ppm Zn solution were added and diluted to 100.0 mL in a volumetric flask; the absorbance of this sample was measured to be A = 0.294. Calculate the % spike recovery for the analysis and report to the nearest whole number. Hint: A=mC of the type y=mx, so C=A/m %Spike=100%((Cspike-Coriginal)/Cadded)) Cadded can be found from C1 V1=Cadded V2.arrow_forwardA new water-soluble anti-diabetic drug with a molecular weight of 210.2 g/mol has an absorption maximum at 278 nm and a molar absorptivity (ε) of 6.15 x 103 M-1cm-1. One tablet of the drug was crushed and quantitatively transferred to a 100 mL volumetric flask and the flask was filled to the mark with deionized water. This solution had an absorbance of 0.770 at 278 nm in 1.00-cm cell. A blank was prepared by treating a tablet with identical composition but without the anti-diabetic drug in an identical manner. The absorbance of this blank solution was 0.052 at 278 nm in a 1.00-cm cell. (Show your work) a. Calculate the concentration of the final solution from Beer’s Law. b. Calculate the mass in mg of the anti-diabetic drug in the tablet.arrow_forward
- To determine the content of Pb in a canned sausage, 5.00 g were weighed and after adequate treatment they were gauged to a volume of 100 mL, from there an aliquot of 2 mL was taken and brought to a volume of 250 mL. The readings of a series and of the sample were taken in an Atomic Absorption spectrophotometer, recording the following data: mg Pb/mL 0 1 2 3 4 Sample Absorbance 0.00 0.15 0.29 0.44 0.58 0.38 What is the% Pb in canned sausage?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_forwardMercury(II) forms a 1:1 complex with triphenyltetrazolium chloride that exhibits an absorption maximum at 255 nm. The mercury(II) in a soil sample was extracted into an organic solvent containing an excess of TTC , and the resulting solution was diluted to 100.0 mL in a volumetric flask. Five-milliliter aliquots of the analyte solution were then transferred to six 25-mL volumetric flasks. A standard solution was then prepared that was 5*10^-6 M in . Volumes of the standard solution shown in the table were then pipetted into the volumetric flasks, and each solution was then diluted to 25.00 mL. The absorbance of each solution was measured at 255 nm in 1.00-cm quartz cells. Please solve and explain these questions: A.) Enter the given data pictured above into a spreadsheet and show the correct standard additions plot B.) Determine the slope and the intercept of the line C.)Determine the standard deviation of the slope and the intercept. D.) Calculate the concentration of Hg(II) in the…arrow_forward
- 0.1040 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 20. The final solution was analyzed by atomic absorption spectrophotometry and the concentration was found be 3.109 ppm, What is the weight percentage of copper in the original solid sample? Keep four significant figures in your final answer. Do not try to include the "%" in your answer. e.g. if your final answer is 10.01%, only write 10.01 in the box.arrow_forwardThe intensity of light passing through a 1.00-cm sample of a solution of polystyrene in methyl ethyl ketone was observed to decrease by O.9%. The concentration of the solution was 10.6 kgm-3. Given A =546.1 nm, no= 1.377, and dn/dC" = 2.20x 10-4 %3D m3/ kg. calculate the molar mass of the polystyrene in kg/mol. The relative displacement (r/ro) of bovine serum albumin was observed as a function of time: t (s) 700 3580 4540 5020 r/r. 1.0129 1.0679 1.0871 1.0965 6 260 /s, find the sedimentation coefficient. Assuming Given w = v = 7.34x 10 3 m3 kg and p = 9.93 x 102 kg/m3, diffusivity = 6.97 x 1011 m2/s at 25 °C, determine the molar %3D mass of the sample in kg/mol.arrow_forwardPrepare a calibration curve to determine the Pb content in a well water sample using atomic absorption spectrophotometry; the following data were recorded: % T 100 75.2 56.6 42.5 31.9 24.6 13.8 ppm Pb 0 0.2 0.4 0.6 0.8 1.0 1.4 A 50 mL aliquot of well water is taken and diluted twice, the% T reading is taken and a value of 40.6% is recorded. Calculate the ppm of Pb in the well water.arrow_forward
- Co(II) was used as an internal standard to analyze a sample of Ti(IV) with atomic absorption spectroscopy (AAS). A standard mixture containing 1.22 ug Co/mL and 2.20 ug Ti/mL measured by AAS produced a signal-to-signal ratio of 2.35 Ti : 1.00 Co. A mixture was prepared by combining 6.00 mL of a Ti(IV) solution of unknown concentration with 4.00 mL.of a 12.4 ug/mL solution of Co(II). The absorbance of the mixture at the Ti(IV) wavelength was 0.104 and the absorbance at the Co(II) wavelength was 0.189. Determine the concentration, in moles per liter, of Ti(IV) in the original unknown solution. concentration: M Ti(IV)arrow_forwardA student prepared several solutions of Molecule Bright, each at a different concentration. The absorbance of each solution was measured at 405 nm with a path length of 0.730 cm. The student then plotted the absorbance of each sample vs. its concentration (in mM), and found a best-fit line of y = 3.726x + 0.828. Calculate the molar absorptivity of the Molecule Bright (in M-1 cm-1).arrow_forwardAbsorbance at 453 nm 8393939 7 fl. oz./20 ml Beer-Lambert's Law (Spectrophotometry) #1 Fe (aq) + KSCN(s) FESCN "(aq) + K" (aq) 3+ To determine the moles of Fe (aq) in a 100. mL sample of an unknown solution, excess KSCN(s) is added to convert all the Fe (aq) into the dark red species FeSCN"(aq), as represented by the equation above. The absorbance of FESCN"(aq) at different concentrations is shown in the graph below. 2+ 0.50 目0.40 0.30 0.20 01 0. 0. 5 x 10-5 10 x 10-5 Concentration of FESCN2+ (M) If the absorbance of the mixture is 0.20 at 453 nm, haw many moles of Fe (aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN(s) Iis negligible.) 3+, 4x10-4 mol 3 x 104 mol (B) 4x 10-6 mol 3x 10-6 molarrow_forward
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