INSTRUMENTAL ANALYSIS EXAM
QUESTIONS AND DETAILED ANSWERS.
EXPERT VERIFIED FOR GUARANTEED
PASS.
Instrumental analytical chemist - ANS -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... - ANS method development, QA, sample preparation
-precision and accuracy usually poorer than in classical analyses
-sensitivity micro grams to fg (sensitivity is better)
Classical analysis - ANS titrations, measuring mass
Instrument - ANS assemblages of components for making a measurement of
concentration/amount or identification/characterization of matter
-exploits some chemical and physical property
-easy to generate bad data
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,Figures of merit: Quantitative - ANS -mathematically definable and transportable between
places
-precision, bias, sensitivity, detection limit, concentration range, selectivity
Figures of merit: Qualitative - ANS -not mathematical or situation dependable
-speed, convenience (ease of use), required skill, cost
Precision - ANS 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 - ANS -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.
Other methods of establishing accuracy - ANS -use a definite analytical method
-comparison of independent methods
-spike recovery tests (a poor measure; better measure of instrumental response)
Standard deviation - ANS 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
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Degrees of freedom - ANS -estimate of flexibility around model
-start with 1 d.f. for each parameter in model
One sample t test - ANS comparing a result to a known group of observations
two sample t test - ANS comparing two groups of objects: are the average different?
the Q test - ANS testing the outliers
Random errors - ANS equally likely to be positive or negative (precision is a measure of
random error)
Systematic errors - ANS one-directional (always high or always low); bias is a measure of
systematic error
Gross errors - ANS screw ups such as switching sample ID's, spilling, etc.
Propagation of uncertainties - ANS base on a simple partial derivative
-for multiplication and division, the relative uncertainties are added
Detection limit - ANS 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 - ANS forensic work
regulatory work
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
QUESTIONS AND DETAILED ANSWERS.
EXPERT VERIFIED FOR GUARANTEED
PASS.
Instrumental analytical chemist - ANS -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... - ANS method development, QA, sample preparation
-precision and accuracy usually poorer than in classical analyses
-sensitivity micro grams to fg (sensitivity is better)
Classical analysis - ANS titrations, measuring mass
Instrument - ANS assemblages of components for making a measurement of
concentration/amount or identification/characterization of matter
-exploits some chemical and physical property
-easy to generate bad data
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,Figures of merit: Quantitative - ANS -mathematically definable and transportable between
places
-precision, bias, sensitivity, detection limit, concentration range, selectivity
Figures of merit: Qualitative - ANS -not mathematical or situation dependable
-speed, convenience (ease of use), required skill, cost
Precision - ANS 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 - ANS -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.
Other methods of establishing accuracy - ANS -use a definite analytical method
-comparison of independent methods
-spike recovery tests (a poor measure; better measure of instrumental response)
Standard deviation - ANS 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
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Degrees of freedom - ANS -estimate of flexibility around model
-start with 1 d.f. for each parameter in model
One sample t test - ANS comparing a result to a known group of observations
two sample t test - ANS comparing two groups of objects: are the average different?
the Q test - ANS testing the outliers
Random errors - ANS equally likely to be positive or negative (precision is a measure of
random error)
Systematic errors - ANS one-directional (always high or always low); bias is a measure of
systematic error
Gross errors - ANS screw ups such as switching sample ID's, spilling, etc.
Propagation of uncertainties - ANS base on a simple partial derivative
-for multiplication and division, the relative uncertainties are added
Detection limit - ANS 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 - ANS forensic work
regulatory work
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
