A. Comparison of the area under the peak produced by the substance with the areas under the peaks produced by a standard

B. From the R_t value of the substance

C. Measurement of the height of the peak produced by the substance

D. Comparison of the R_f of the substance with that of a standard

Gas Chromatography Concentration Peak Area Standard

In gas chromatography, concentration is determined by comparing peak areas with standards. The correct answer is option A.

Question Breakdown

This MCQ tests quantitative analysis methods in GC, essential for GATE Life Sciences and analytical biochemistry.

Option Analysis

• A. Comparison of the area under the peak produced by the substance with the areas under the peaks produced by a standard: Correct. Peak area is proportional to concentration; calibration curves use area ratios for quantification.

• B. From the Rt value of the substance: Incorrect. Retention time (Rt) identifies compounds qualitatively, not quantifies them.

• C. Measurement of the height of the peak produced by the substance: Partially correct for narrow peaks, but area is standard and more accurate for varying peak shapes.

• D. Comparison of the Rf of the substance with that of a standard: Incorrect. Rf values apply to paper/TLC, not gas chromatography.

Introduction
In gas chromatography, the concentration of a substance can be determined by comparison of the area under the peak with areas from standards via calibration curves. This external/internal standard method powers precise quantification in pharma, environmental, and biochemical analysis.

Quantitative Methods

External Standard: Plot peak area vs known concentrations; interpolate unknowns.

Internal Standard: Use area ratios to correct injection variability—most reliable.

Peak Area vs Height: Area integrates entire signal; preferred for accuracy across peak widths.

GC vs Other Techniques

Applications

Drug purity, VOC analysis, pesticide residues—GC quantifies ppb levels reliably.