INSTRUMENTAL ANALYSIS FINAL PAPER QUESTIONS AND
SOLUTIONS 2025/2026 ALL GRADED A+
✔✔Method detection limits (MDLs) - ✔✔what can be detected in a real sample, figuring
in a ll steps in the sample introduction process
✔✔Detection limits and precision - ✔✔precision will be rather poor at the detection limit
(~25-40% RSD). Information is essentially qualitative
✔✔Binary - ✔✔analyte is present or not
✔✔Limit of quantitation - ✔✔reliable quantitation (~10% RSD) can be achieved
✔✔Analyte loss - ✔✔-incomplete dissolution or extraction
-volatilization (low bp and high pressure causing fast evaporation of the substance)
-precipitation after dissolution
-mechanical losses (splashes, spills)
-decomposition during dissolution, storage
-absorption onto container walls
-incomplete separation or collection during a pre concentration process
✔✔Goals when preparing samples - ✔✔-the sample is converted into a form more
suitable for chemical analysis
-preserve "representativeness" of the sample
-minimize losses of analyze
-minimize contamination
-remove matrix components as needed
-get concentration into an appropriate range
✔✔Yield tracers - ✔✔add a radioactive form of the analyze and measure recovery by
counting
✔✔Surrogates - ✔✔add a non-native substance which emulates the chemical behavior
of one or more analytes
✔✔Soxhlet extractor - ✔✔-sample is places in a thimble and the solvent is placed in the
bottom flask
-solvent is boiled, condensed, and the condensed solvent is percolated through the
sample
-the dissolved components collect in the flask at the bottom of the apparatus
✔✔Supercritical fluid extraction - ✔✔-common gases are elevated above their critical
points and used to extract organic contaminants from the environmental samples.
Supercritical fluids have properties of both liquid and gases which facilitates rapid and
highly selective extractions (40 min).
, ✔✔Preparation for elemental constituents - ✔✔-leaching with acids: HCl, HNO3
-complete dissolution of silicates with HF-containing mixes
-destroy/oxidize organic matter with oxidizing agents such as HClO4, H2O2
-complete dissolution of silicates by molten salt fusion
✔✔Acid dissolution in beakers - ✔✔-the sample is mixed with appropriate reagents, and
is heated in a glass or plastic container
-simple, but slow and prone to contamination
✔✔Microwave- assisted digestion - ✔✔-sample and reagents are mixed and heated in a
loser, pressurized container
-higher temperatures due to "pressure cooker" effect
-faster digestion
-dangerous, expensive
✔✔Sources of contamination: reagents - ✔✔levels of impurities vary greatly, should be
screened before critical uses
✔✔Sources of contamination:containers - ✔✔may intrinsically contain analyze, or may
contain residues form previous uses- cleaning protocols important
✔✔Sources of contamination: atmosphere - ✔✔deposition of atmospheric particles
should be controlled/ avoided
✔✔Reagent purification - ✔✔distillation in Teflon or fluropolymer vessels is often used
to produce high- grade acids for elemental analysis
✔✔"clean: sample preparation: portable clean air hood - ✔✔-to minimize introduction of
contaminants during the smile prep process, the prep is conducted under HEPA- filtered
air
✔✔Calibration of instrumental methods: standard-less - ✔✔Coulometry (Faraday's Law)
✔✔Calibration of instrumental methods:comparison with standards - ✔✔-isometric
methods
-titration
✔✔Calibration of instrumental methods: external calibration (used in most instrumental
techniques) - ✔✔-signal=f(concentration)
-establish a calibration curve for known concentration
-compare unknown response to calibration curve
-multivariate calibration
SOLUTIONS 2025/2026 ALL GRADED A+
✔✔Method detection limits (MDLs) - ✔✔what can be detected in a real sample, figuring
in a ll steps in the sample introduction process
✔✔Detection limits and precision - ✔✔precision will be rather poor at the detection limit
(~25-40% RSD). Information is essentially qualitative
✔✔Binary - ✔✔analyte is present or not
✔✔Limit of quantitation - ✔✔reliable quantitation (~10% RSD) can be achieved
✔✔Analyte loss - ✔✔-incomplete dissolution or extraction
-volatilization (low bp and high pressure causing fast evaporation of the substance)
-precipitation after dissolution
-mechanical losses (splashes, spills)
-decomposition during dissolution, storage
-absorption onto container walls
-incomplete separation or collection during a pre concentration process
✔✔Goals when preparing samples - ✔✔-the sample is converted into a form more
suitable for chemical analysis
-preserve "representativeness" of the sample
-minimize losses of analyze
-minimize contamination
-remove matrix components as needed
-get concentration into an appropriate range
✔✔Yield tracers - ✔✔add a radioactive form of the analyze and measure recovery by
counting
✔✔Surrogates - ✔✔add a non-native substance which emulates the chemical behavior
of one or more analytes
✔✔Soxhlet extractor - ✔✔-sample is places in a thimble and the solvent is placed in the
bottom flask
-solvent is boiled, condensed, and the condensed solvent is percolated through the
sample
-the dissolved components collect in the flask at the bottom of the apparatus
✔✔Supercritical fluid extraction - ✔✔-common gases are elevated above their critical
points and used to extract organic contaminants from the environmental samples.
Supercritical fluids have properties of both liquid and gases which facilitates rapid and
highly selective extractions (40 min).
, ✔✔Preparation for elemental constituents - ✔✔-leaching with acids: HCl, HNO3
-complete dissolution of silicates with HF-containing mixes
-destroy/oxidize organic matter with oxidizing agents such as HClO4, H2O2
-complete dissolution of silicates by molten salt fusion
✔✔Acid dissolution in beakers - ✔✔-the sample is mixed with appropriate reagents, and
is heated in a glass or plastic container
-simple, but slow and prone to contamination
✔✔Microwave- assisted digestion - ✔✔-sample and reagents are mixed and heated in a
loser, pressurized container
-higher temperatures due to "pressure cooker" effect
-faster digestion
-dangerous, expensive
✔✔Sources of contamination: reagents - ✔✔levels of impurities vary greatly, should be
screened before critical uses
✔✔Sources of contamination:containers - ✔✔may intrinsically contain analyze, or may
contain residues form previous uses- cleaning protocols important
✔✔Sources of contamination: atmosphere - ✔✔deposition of atmospheric particles
should be controlled/ avoided
✔✔Reagent purification - ✔✔distillation in Teflon or fluropolymer vessels is often used
to produce high- grade acids for elemental analysis
✔✔"clean: sample preparation: portable clean air hood - ✔✔-to minimize introduction of
contaminants during the smile prep process, the prep is conducted under HEPA- filtered
air
✔✔Calibration of instrumental methods: standard-less - ✔✔Coulometry (Faraday's Law)
✔✔Calibration of instrumental methods:comparison with standards - ✔✔-isometric
methods
-titration
✔✔Calibration of instrumental methods: external calibration (used in most instrumental
techniques) - ✔✔-signal=f(concentration)
-establish a calibration curve for known concentration
-compare unknown response to calibration curve
-multivariate calibration
