INSTRUMENTAL ANALYSIS EXAM EVALUATION
QUESTIONS AND SOLUTIONS 2025/2026 ALL GRADED A+
✔✔Internal standard - ✔✔A known amount of a compound, different from analyte, that
is added to the unknown. A signal from the analyte is compared with the signal from the
internal standard to find out how much analyte is present
- method of choice when the instrument response or amount of sample analyzed varies
from run to run
✔✔Three common types of calibration - ✔✔External standard, internal standard, and
standard addition
✔✔Range - ✔✔Concentration interval over which linearity, accuracy and precision meet
specifications
✔✔Dynamic range - ✔✔Concentration interval over which there is a measurable
response to a change in analyte concentration
✔✔Linear range - ✔✔Concentration interval over which the change in detector
response is proportional to analyte quantity
✔✔Mean percent recovery - ✔✔Mean % recovery = average/true value
✔✔Detection limit - ✔✔Limit of detection=3 x's the standard deviation
✔✔Signal detection limit - ✔✔Signal detection limit = mean value of the blank + 3s
✔✔Minimum detectable concentration - ✔✔= 3s/m
✔✔Lower limit of quantification - ✔✔= 10s/m
✔✔Precision - ✔✔= standard deviation/mean x 100
✔✔Accuracy - ✔✔= mean - known value / known value x 100
✔✔Standard addition - ✔✔-known quantities of the analyte are added to the unknown
-method of choice when the matrix of the sample may affect the signal
-from the increase in signal, we deduce that the analyte was in the original unknown
✔✔External standards - ✔✔Consists of a series of standard analyte solutions separate
from the unknown
- used to measure the instrument response as a function of a known analyte
concentration under a set of conditions
, ✔✔Response factor - ✔✔area of analyte signal/concentration of analyte = F (area of
standard signal/concentration of standard)
✔✔Advantages of a furnace over a flame in atomic absorption - ✔✔A smaller sample
amount is required
Higher sensitivity because the atomized sample is in the optical path longer
✔✔Three main methods of atomization in atomic spectroscopy - ✔✔Combustion flames
Graphite furnace
Inductively coupled plasma
✔✔Energy difference between ground and excited states - ✔✔Delta E= hc/lambda
✔✔Fraction of atoms in the excited state - ✔✔N*/N = g*/g x e^(delta E/kT)
✔✔Importance of temp stability of the flame or plasma for emission spectroscopy - ✔✔A
small change in temp has a much greater impact on a few atoms in the excited state
than it does on atoms in the ground state so this affects emission more than absorption
✔✔Purpose of matrix modifier in graphite furnace AA analysis - ✔✔Makes matrix more
volatile and analyte less volatile so they can be better separated before atomization
✔✔Flame AA
Purpose of flame - ✔✔Atomizes the sample
✔✔Flame AA
Hollow-cathode lamp - ✔✔Composed of same element that is being analyzed in the
sample
Emits narrow atomic lines
✔✔Advantages of AA - ✔✔Detection limits in low ppm to high ppb range
Narrow bandwidths = little overlap in spectra, allowing for detection of many elements at
once
✔✔Limitations of AA - ✔✔Need one lamp per element; lamps are expensive
Need separate optimization for each element
✔✔Zeeman effect - ✔✔Splitting of atomic lines in the presence of a parallel magnetic
field
✔✔Pressure broadening - ✔✔An increase in the atomic line width due to collisions
between atoms
QUESTIONS AND SOLUTIONS 2025/2026 ALL GRADED A+
✔✔Internal standard - ✔✔A known amount of a compound, different from analyte, that
is added to the unknown. A signal from the analyte is compared with the signal from the
internal standard to find out how much analyte is present
- method of choice when the instrument response or amount of sample analyzed varies
from run to run
✔✔Three common types of calibration - ✔✔External standard, internal standard, and
standard addition
✔✔Range - ✔✔Concentration interval over which linearity, accuracy and precision meet
specifications
✔✔Dynamic range - ✔✔Concentration interval over which there is a measurable
response to a change in analyte concentration
✔✔Linear range - ✔✔Concentration interval over which the change in detector
response is proportional to analyte quantity
✔✔Mean percent recovery - ✔✔Mean % recovery = average/true value
✔✔Detection limit - ✔✔Limit of detection=3 x's the standard deviation
✔✔Signal detection limit - ✔✔Signal detection limit = mean value of the blank + 3s
✔✔Minimum detectable concentration - ✔✔= 3s/m
✔✔Lower limit of quantification - ✔✔= 10s/m
✔✔Precision - ✔✔= standard deviation/mean x 100
✔✔Accuracy - ✔✔= mean - known value / known value x 100
✔✔Standard addition - ✔✔-known quantities of the analyte are added to the unknown
-method of choice when the matrix of the sample may affect the signal
-from the increase in signal, we deduce that the analyte was in the original unknown
✔✔External standards - ✔✔Consists of a series of standard analyte solutions separate
from the unknown
- used to measure the instrument response as a function of a known analyte
concentration under a set of conditions
, ✔✔Response factor - ✔✔area of analyte signal/concentration of analyte = F (area of
standard signal/concentration of standard)
✔✔Advantages of a furnace over a flame in atomic absorption - ✔✔A smaller sample
amount is required
Higher sensitivity because the atomized sample is in the optical path longer
✔✔Three main methods of atomization in atomic spectroscopy - ✔✔Combustion flames
Graphite furnace
Inductively coupled plasma
✔✔Energy difference between ground and excited states - ✔✔Delta E= hc/lambda
✔✔Fraction of atoms in the excited state - ✔✔N*/N = g*/g x e^(delta E/kT)
✔✔Importance of temp stability of the flame or plasma for emission spectroscopy - ✔✔A
small change in temp has a much greater impact on a few atoms in the excited state
than it does on atoms in the ground state so this affects emission more than absorption
✔✔Purpose of matrix modifier in graphite furnace AA analysis - ✔✔Makes matrix more
volatile and analyte less volatile so they can be better separated before atomization
✔✔Flame AA
Purpose of flame - ✔✔Atomizes the sample
✔✔Flame AA
Hollow-cathode lamp - ✔✔Composed of same element that is being analyzed in the
sample
Emits narrow atomic lines
✔✔Advantages of AA - ✔✔Detection limits in low ppm to high ppb range
Narrow bandwidths = little overlap in spectra, allowing for detection of many elements at
once
✔✔Limitations of AA - ✔✔Need one lamp per element; lamps are expensive
Need separate optimization for each element
✔✔Zeeman effect - ✔✔Splitting of atomic lines in the presence of a parallel magnetic
field
✔✔Pressure broadening - ✔✔An increase in the atomic line width due to collisions
between atoms
