1
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Instrumental Analysis Questions and
Answers (100% Correct Answers) Already
Graded A+
Instrumental analytical chemist [ Ans: ] -how to evaluate the
accuracy of the method being used
-statements of error/uncertainty along with the results
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-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
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-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
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
, 2
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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
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-comparison of independent methods
-spike recovery tests (a poor measure; better measure of
instrumental response)
Standard deviation [ Ans: ] the measure of dispersion tells us
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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 [ 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)
, 3
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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
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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.
Guru01 - Stuvia
Where detection limits are especially important [ Ans: ] forensic
work
regulatory work
pre employment and workplace monitoring for illicit substances
screening and testing for disease vectors
Instrumental detection limits (IDLs) [ Ans: ] what the instrument
can detect in a simple matrix the instrument when decoupled
from the sample preparation process
Method detection limits (MDLs) [ Ans: ] what can be detected in
a real sample, figuring in a ll steps in the sample introduction
process
Detection limits and precision [ Ans: ] precision will be rather
poor at the detection limit (~25-40% RSD). Information is essentially
qualitative
Binary [ Ans: ] analyte is present or not
Limit of quantitation [ Ans: ] reliable quantitation (~10% RSD) can
be achieved
For Expert help and assignment solutions, +254707240657
Instrumental Analysis Questions and
Answers (100% Correct Answers) Already
Graded A+
Instrumental analytical chemist [ Ans: ] -how to evaluate the
accuracy of the method being used
-statements of error/uncertainty along with the results
© 2025 Assignment Expert
-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
Guru01 - Stuvia
-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
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
, 2
For Expert help and assignment solutions, +254707240657
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
© 2025 Assignment Expert
-comparison of independent methods
-spike recovery tests (a poor measure; better measure of
instrumental response)
Standard deviation [ Ans: ] the measure of dispersion tells us
Guru01 - Stuvia
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 [ 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)
, 3
For Expert help and assignment solutions, +254707240657
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
© 2025 Assignment Expert
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.
Guru01 - Stuvia
Where detection limits are especially important [ Ans: ] forensic
work
regulatory work
pre employment and workplace monitoring for illicit substances
screening and testing for disease vectors
Instrumental detection limits (IDLs) [ Ans: ] what the instrument
can detect in a simple matrix the instrument when decoupled
from the sample preparation process
Method detection limits (MDLs) [ Ans: ] what can be detected in
a real sample, figuring in a ll steps in the sample introduction
process
Detection limits and precision [ Ans: ] precision will be rather
poor at the detection limit (~25-40% RSD). Information is essentially
qualitative
Binary [ Ans: ] analyte is present or not
Limit of quantitation [ Ans: ] reliable quantitation (~10% RSD) can
be achieved
