INSTRUMENTAL ANALYSIS ACS
CERTIFICATION EVALUATION 2026 FULL
SOLUTION VIEW AHEAD QUESTIONS
◉ what are the relative advantages and disadvantages of packed and
open tubular columns in GC
Answer: packed columns have a high sample capacity. Open tubular
columns have a better separation efficiency (smaller plate height),
shorter analysis time and increased sensitivity
◉ why do open tubular columns provide greater resolution than
packed columns in GC
Answer: there is no band broadening due to the multiple path (A)
term in the van Deemeter equation
◉ When would you use ___ injection in GC?
a) split
b) splitless
c) on-column
Answer: a) is good for high concentration samples, scans where you
want high resolution, or if you have a dirty sample
b) good for trace analysis
, c) good for quantitative analysis or thermally sensitive samples
◉ determining resolution from t and W
Answer: resolution = 2(Tr1-Tr2)/(WA +WB)
◉ list the sources of error associated with pH measurements with a
glass electrode
Answer: uncertainty of buffer solutions used, junction potential
errors, junction potential drifts, alkaline or acid errors at extreme
pH values, equilibration time, hydration of glass, temperature
difference of calibration solution and analyte solutions, dirty
electrode
◉ explain the principle operation of an ion-selective electrode
Answer: analyte ions equilabrate between the outer solution and the
membrane ligand, creating a slight charge imbalance. Changes in the
analyte ion concentration can change the potential difference across
the solution-membrane interface, causing a junction potential
◉ Which of the following would decrease retention in ion
chromatography:
a) increasing the column length
b) increasing flow rate of mobile phase
c) decrease the sample size
CERTIFICATION EVALUATION 2026 FULL
SOLUTION VIEW AHEAD QUESTIONS
◉ what are the relative advantages and disadvantages of packed and
open tubular columns in GC
Answer: packed columns have a high sample capacity. Open tubular
columns have a better separation efficiency (smaller plate height),
shorter analysis time and increased sensitivity
◉ why do open tubular columns provide greater resolution than
packed columns in GC
Answer: there is no band broadening due to the multiple path (A)
term in the van Deemeter equation
◉ When would you use ___ injection in GC?
a) split
b) splitless
c) on-column
Answer: a) is good for high concentration samples, scans where you
want high resolution, or if you have a dirty sample
b) good for trace analysis
, c) good for quantitative analysis or thermally sensitive samples
◉ determining resolution from t and W
Answer: resolution = 2(Tr1-Tr2)/(WA +WB)
◉ list the sources of error associated with pH measurements with a
glass electrode
Answer: uncertainty of buffer solutions used, junction potential
errors, junction potential drifts, alkaline or acid errors at extreme
pH values, equilibration time, hydration of glass, temperature
difference of calibration solution and analyte solutions, dirty
electrode
◉ explain the principle operation of an ion-selective electrode
Answer: analyte ions equilabrate between the outer solution and the
membrane ligand, creating a slight charge imbalance. Changes in the
analyte ion concentration can change the potential difference across
the solution-membrane interface, causing a junction potential
◉ Which of the following would decrease retention in ion
chromatography:
a) increasing the column length
b) increasing flow rate of mobile phase
c) decrease the sample size
