Chemistry Labs

Analytical chemistry

Gas chromatography (GC), high-performance liquid chromatography (HPLC)

Chromatography separates components because they partition differently between mobile and stationary phases.

1 Lower secondary2 Upper secondary3 Undergraduate4 Advanced5 Research

IntuitionIntuition: the measurement idea

Chromatography lets a moving phase carry a mixture over a stationary phase. Components that interact differently travel at different speeds and emerge as separated peaks.

Explore the Gas chromatography (GC), high-performance liquid chromatography (HPLC) measurement concept in this interactive signal.

SchoolSchool level: signal and result

Chromatographic theory uses retention factor, column efficiency and resolution. Peak separation improves with selectivity, efficiency and adequate retention.

Definition:

Chromatography separates components because they partition differently between mobile and stationary phases.

First identify the measurand, choose a signal that responds to it, and compare the sample with a calibrated standard or a validated model.

k=tR−tMtM,Rs=2(tR,2−tR,1)w1+w2k=\dfrac{t_R-t_M}{t_M},\qquad R_s=\dfrac{2(t_{R,2}-t_{R,1})}{w_1+w_2}

Example: Worked analytical example

Calculate the analyte result from the stated measurement and method relation.

Solution

If tM=1.0 min and tR=5.0 min, retention factor k=4.0. A baseline width of 0.40 min for adjacent peaks separated by 0.60 min gives Rs=1.5.

Method checkpoints
StagePurpose
PrepareControl matrix and contamination
MeasureAcquire a calibrated response
ValidateCheck recovery and uncertainty

UndergraduateUniversity: quantitative method

Chromatography is described by plate theory and kinetic band-broadening. Resolution combines efficiency, selectivity and retention; method development optimizes temperature program, solvent strength and stationary-phase chemistry.

Calibration, selectivity, sample preparation and uncertainty belong to the method itself, not to afterthoughts. Report units, conditions and the calibration range.

k=tR−tMtM,Rs=2(tR,2−tR,1)w1+w2k=\dfrac{t_R-t_M}{t_M},\qquad R_s=\dfrac{2(t_{R,2}-t_{R,1})}{w_1+w_2}

References