INSTRUMENTAL ANALYSIS EXAM SCRIPT QUESTIONS AND
SOLUTIONS 2025/2026 ALL GRADED A+
✔✔Purpose of gas chromatography - ✔✔To separate and analyze thermally stable,
mostly non-polar compounds.
✔✔Applications of GC - ✔✔Drug testing, blood alcohol, food flavor analysis,
environmental testing, forensic toxicology.
✔✔Main GC components - ✔✔Carrier gas, inlet, column, detector, and data system.
✔✔Van Deemter equation purpose - ✔✔Describes factors affecting column efficiency
and band broadening.
✔✔Goal of chromatography - ✔✔Achieve narrow, well-resolved peaks.
✔✔Split injection use - ✔✔High-concentration samples; prevents column overload.
✔✔Splitless injection use - ✔✔Trace analysis; full sample enters column.
✔✔On-column injection use - ✔✔Thermally labile compounds.
✔✔Headspace injection use - ✔✔Volatile analytes.
✔✔Purge and trap injection use - ✔✔Volatile compounds in liquids.
✔✔Typical GC column dimensions - ✔✔10-100 m long, 0.1-0.53 mm ID.
✔✔Effect of thick film on GC column - ✔✔Increases retention time and sample capacity.
✔✔Effect of thin film on GC column - ✔✔Speeds up elution and improves resolution but
risks overload.
✔✔Two oven temperature modes - ✔✔Isothermal and temperature programmed.
✔✔Retention Time Locking (RTL) - ✔✔Method that standardizes retention times across
instruments and runs.
✔✔Benefits of RTL - ✔✔Enables shared databases, deconvolution, and identification of
isomers.
✔✔Three main derivatization reactions - ✔✔Alkylation, acylation, and silylation.
SOLUTIONS 2025/2026 ALL GRADED A+
✔✔Purpose of gas chromatography - ✔✔To separate and analyze thermally stable,
mostly non-polar compounds.
✔✔Applications of GC - ✔✔Drug testing, blood alcohol, food flavor analysis,
environmental testing, forensic toxicology.
✔✔Main GC components - ✔✔Carrier gas, inlet, column, detector, and data system.
✔✔Van Deemter equation purpose - ✔✔Describes factors affecting column efficiency
and band broadening.
✔✔Goal of chromatography - ✔✔Achieve narrow, well-resolved peaks.
✔✔Split injection use - ✔✔High-concentration samples; prevents column overload.
✔✔Splitless injection use - ✔✔Trace analysis; full sample enters column.
✔✔On-column injection use - ✔✔Thermally labile compounds.
✔✔Headspace injection use - ✔✔Volatile analytes.
✔✔Purge and trap injection use - ✔✔Volatile compounds in liquids.
✔✔Typical GC column dimensions - ✔✔10-100 m long, 0.1-0.53 mm ID.
✔✔Effect of thick film on GC column - ✔✔Increases retention time and sample capacity.
✔✔Effect of thin film on GC column - ✔✔Speeds up elution and improves resolution but
risks overload.
✔✔Two oven temperature modes - ✔✔Isothermal and temperature programmed.
✔✔Retention Time Locking (RTL) - ✔✔Method that standardizes retention times across
instruments and runs.
✔✔Benefits of RTL - ✔✔Enables shared databases, deconvolution, and identification of
isomers.
✔✔Three main derivatization reactions - ✔✔Alkylation, acylation, and silylation.
