Instrumental Analysis Exam 2026
Questions And Answers
Instrumental analytical chemist - Correct answer--how to evaluate the accuracy of
the method being used
-statements of error/uncertainty along with the results
-select techniques, design the entire measurement process so that accuracy
objectives are always met
Instrumental Analysis: The work is in... - Correct answer-method development,
QA, sample preparation
-precision and accuracy usually poorer than in classical analyses
-sensitivity micro grams to fg (sensitivity is better)
Classical analysis - Correct answer-titrations, measuring mass
Instrument - Correct answer-assemblages of components for making a
measurement of concentration/amount or identification/characterization of matter
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,-exploits some chemical and physical property
-easy to generate bad data
Figures of merit: Quantitative - Correct answer--mathematically definable and
transportable between places
-precision, bias, sensitivity, detection limit, concentration range, selectivity
Figures of merit: Qualitative - Correct answer--not mathematical or situation
dependable
-speed, convenience (ease of use), required skill, cost
Precision - Correct answer-reproducibility without regard for closeness to true
value, measure via standard deviation, relative standard deviation (RSD),
coefficient of variation, variance, 95% confidence interval of the mean, standard
error of the mean
-essentially a measure of dispersion or spread of the results
Accuracy - Correct answer--correctness/trueness of the measurement
-bias a way to quantify accuracy. how much does it deviate from the true mean?
-accuracy involves comparing the experimental results to "known" and "true"
value.
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,Other methods of establishing accuracy - Correct answer--use a definite analytical
method
-comparison of independent methods
-spike recovery tests (a poor measure; better measure of instrumental response)
Standard deviation - Correct answer-the measure of dispersion tells us about the
width of the distribution but not about its shape or appearance
-a distribution of our results may follow a specific type such as a "normal"
distribution
-normal distribution means a bell curve
-closer to the x axis means large standard deviation
-farther from the x axis means smaller standard deviation
Degrees of freedom - Correct answer--estimate of flexibility around model
-start with 1 d.f. for each parameter in model
One sample t test - Correct answer-comparing a result to a known group of
observations
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, two sample t test - Correct answer-comparing two groups of objects: are the
average different?
the Q test - Correct answer-testing the outliers
Random errors - Correct answer-equally likely to be positive or negative (precision
is a measure of random error)
Systematic errors - Correct answer-one-directional (always high or always low);
bias is a measure of systematic error
Gross errors - Correct answer-screw ups such as switching sample ID's, spilling,
etc.
Propagation of uncertainties - Correct answer-base on a simple partial derivative
-for multiplication and division, the relative uncertainties are added
Detection limit - Correct answer-the lowest concentration of analyte that the
analytical process can reliably detect
-needed, when measuring low concentrations of analyte, when signals are close to
the distribution of blank results, an objective rather than a subjective basis is
needed for deciding whether the analyte is present or not.
Where detection limits are especially important - Correct answer-forensic work
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Questions And Answers
Instrumental analytical chemist - Correct answer--how to evaluate the accuracy of
the method being used
-statements of error/uncertainty along with the results
-select techniques, design the entire measurement process so that accuracy
objectives are always met
Instrumental Analysis: The work is in... - Correct answer-method development,
QA, sample preparation
-precision and accuracy usually poorer than in classical analyses
-sensitivity micro grams to fg (sensitivity is better)
Classical analysis - Correct answer-titrations, measuring mass
Instrument - Correct answer-assemblages of components for making a
measurement of concentration/amount or identification/characterization of matter
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,-exploits some chemical and physical property
-easy to generate bad data
Figures of merit: Quantitative - Correct answer--mathematically definable and
transportable between places
-precision, bias, sensitivity, detection limit, concentration range, selectivity
Figures of merit: Qualitative - Correct answer--not mathematical or situation
dependable
-speed, convenience (ease of use), required skill, cost
Precision - Correct answer-reproducibility without regard for closeness to true
value, measure via standard deviation, relative standard deviation (RSD),
coefficient of variation, variance, 95% confidence interval of the mean, standard
error of the mean
-essentially a measure of dispersion or spread of the results
Accuracy - Correct answer--correctness/trueness of the measurement
-bias a way to quantify accuracy. how much does it deviate from the true mean?
-accuracy involves comparing the experimental results to "known" and "true"
value.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,Other methods of establishing accuracy - Correct answer--use a definite analytical
method
-comparison of independent methods
-spike recovery tests (a poor measure; better measure of instrumental response)
Standard deviation - Correct answer-the measure of dispersion tells us about the
width of the distribution but not about its shape or appearance
-a distribution of our results may follow a specific type such as a "normal"
distribution
-normal distribution means a bell curve
-closer to the x axis means large standard deviation
-farther from the x axis means smaller standard deviation
Degrees of freedom - Correct answer--estimate of flexibility around model
-start with 1 d.f. for each parameter in model
One sample t test - Correct answer-comparing a result to a known group of
observations
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, two sample t test - Correct answer-comparing two groups of objects: are the
average different?
the Q test - Correct answer-testing the outliers
Random errors - Correct answer-equally likely to be positive or negative (precision
is a measure of random error)
Systematic errors - Correct answer-one-directional (always high or always low);
bias is a measure of systematic error
Gross errors - Correct answer-screw ups such as switching sample ID's, spilling,
etc.
Propagation of uncertainties - Correct answer-base on a simple partial derivative
-for multiplication and division, the relative uncertainties are added
Detection limit - Correct answer-the lowest concentration of analyte that the
analytical process can reliably detect
-needed, when measuring low concentrations of analyte, when signals are close to
the distribution of blank results, an objective rather than a subjective basis is
needed for deciding whether the analyte is present or not.
Where detection limits are especially important - Correct answer-forensic work
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
