1
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Instrumental Analysis Questions and
Answers (100% Correct Answers) Already
Graded A+
Purpose of sample preparation [ Ans: ] To clean up,
concentrate, and make analytes compatible with the analytical
instrument.
Common sample preparation techniques [ Ans: ] Dilute and
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shoot, liquid-liquid extraction (LLE), and solid-phase extraction
(SPE).
Purpose of an internal standard (ISTD) [ Ans: ] To ensure
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quantitative accuracy and compensate for extraction or injection
variability.
Ideal ISTD for non-specific detectors [ Ans: ] Structurally similar to
analyte, not naturally in sample, and chromatographically distinct.
Ideal ISTD for MS detectors [ Ans: ] Isotopically labeled (D, 13C,
or 15N), labeled on fragments, separated by ≥3 mass units.
Minimum recovery for valid internal standard [ Ans: ] At least
50%.
Purpose of a calibration curve [ Ans: ] To relate instrument
response to analyte concentration.
Equation for a linear calibration curve [ Ans: ] y = mx + b.
Analytical Measured Range (AMR) [ Ans: ] The range over which
the instrument can accurately quantify analytes.
LLOQ and ULOQ [ Ans: ] Lower and upper limits of quantitation.
Standard Addition Method use [ Ans: ] Used when external
calibration isn't possible; corrects for matrix interferences.
When pH = pKa [ Ans: ] The compound is 50% ionized and 50%
unionized.
, 2
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Best extraction condition for acidic compounds [ Ans: ] Low pH
(when unionized).
Best extraction condition for basic compounds [ Ans: ] High pH
(when unionized).
What pH measures [ Ans: ] The acidity or basicity of a solution (0-
14 scale).
What pKa measures [ Ans: ] A molecule's ability to donate a
proton (acid strength).
Acidic compound behavior at pH < pKa [ Ans: ] Unionized
(protonated).
Basic compound behavior at pH < pKa [ Ans: ] Ionized
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(protonated).
Importance of pH control in extraction [ Ans: ] Ensures analyte is
in its unionized form for better extraction.
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Four main sample prep methods [ Ans: ] Dilute and shoot,
protein precipitation, LLE, and SPE.
Purpose of derivatization in GC analysis [ Ans: ] To make
compounds volatile, stable, and non-polar for GC analysis.
Functional groups that require derivatization [ Ans: ] -OH, -
COOH, -NH, -SH.
Trimethylsilylation reagent [ Ans: ] BSTFA.
Mass added by trimethylsilylation per site [ Ans: ] +72 amu.
Acylation reagent [ Ans: ] Acetic anhydride.
Mass added by acylation per site [ Ans: ] +42 amu.
Purpose of gas chromatography [ Ans: ] To separate and
analyze thermally stable, mostly non-polar compounds.
Applications of GC [ Ans: ] Drug testing, blood alcohol, food
flavor analysis, environmental testing, forensic toxicology.
Main GC components [ Ans: ] Carrier gas, inlet, column,
detector, and data system.
For Expert help and assignment solutions, +254707240657
Instrumental Analysis Questions and
Answers (100% Correct Answers) Already
Graded A+
Purpose of sample preparation [ Ans: ] To clean up,
concentrate, and make analytes compatible with the analytical
instrument.
Common sample preparation techniques [ Ans: ] Dilute and
© 2025 Assignment Expert
shoot, liquid-liquid extraction (LLE), and solid-phase extraction
(SPE).
Purpose of an internal standard (ISTD) [ Ans: ] To ensure
Guru01 - Stuvia
quantitative accuracy and compensate for extraction or injection
variability.
Ideal ISTD for non-specific detectors [ Ans: ] Structurally similar to
analyte, not naturally in sample, and chromatographically distinct.
Ideal ISTD for MS detectors [ Ans: ] Isotopically labeled (D, 13C,
or 15N), labeled on fragments, separated by ≥3 mass units.
Minimum recovery for valid internal standard [ Ans: ] At least
50%.
Purpose of a calibration curve [ Ans: ] To relate instrument
response to analyte concentration.
Equation for a linear calibration curve [ Ans: ] y = mx + b.
Analytical Measured Range (AMR) [ Ans: ] The range over which
the instrument can accurately quantify analytes.
LLOQ and ULOQ [ Ans: ] Lower and upper limits of quantitation.
Standard Addition Method use [ Ans: ] Used when external
calibration isn't possible; corrects for matrix interferences.
When pH = pKa [ Ans: ] The compound is 50% ionized and 50%
unionized.
, 2
For Expert help and assignment solutions, +254707240657
Best extraction condition for acidic compounds [ Ans: ] Low pH
(when unionized).
Best extraction condition for basic compounds [ Ans: ] High pH
(when unionized).
What pH measures [ Ans: ] The acidity or basicity of a solution (0-
14 scale).
What pKa measures [ Ans: ] A molecule's ability to donate a
proton (acid strength).
Acidic compound behavior at pH < pKa [ Ans: ] Unionized
(protonated).
Basic compound behavior at pH < pKa [ Ans: ] Ionized
© 2025 Assignment Expert
(protonated).
Importance of pH control in extraction [ Ans: ] Ensures analyte is
in its unionized form for better extraction.
Guru01 - Stuvia
Four main sample prep methods [ Ans: ] Dilute and shoot,
protein precipitation, LLE, and SPE.
Purpose of derivatization in GC analysis [ Ans: ] To make
compounds volatile, stable, and non-polar for GC analysis.
Functional groups that require derivatization [ Ans: ] -OH, -
COOH, -NH, -SH.
Trimethylsilylation reagent [ Ans: ] BSTFA.
Mass added by trimethylsilylation per site [ Ans: ] +72 amu.
Acylation reagent [ Ans: ] Acetic anhydride.
Mass added by acylation per site [ Ans: ] +42 amu.
Purpose of gas chromatography [ Ans: ] To separate and
analyze thermally stable, mostly non-polar compounds.
Applications of GC [ Ans: ] Drug testing, blood alcohol, food
flavor analysis, environmental testing, forensic toxicology.
Main GC components [ Ans: ] Carrier gas, inlet, column,
detector, and data system.
