NMR spectroscopy
NMR detects nuclei (¹H, ¹³C) in a magnetic field; each environment gives a signal at a chemical shift δ (ppm) relative to TMS (δ = 0). Samples are dissolved in CDCl₃ (no ¹H signal). ¹³C NMR: number of peaks = number of carbon environments; shift identifies type (C=O 160–220; C–O 50–90; aromatic 110–160). ¹H NMR: number of peaks = H environments; integration gives the ratio of H atoms; splitting follows the n + 1 rule (n = H on neighbouring carbons): singlet, doublet, triplet, quartet. O–H/N–H peaks disappear on shaking with D₂O. Combine with IR and mass spectra to identify unknowns.
≈ 55 minChromatography techniques
Chromatography separates mixtures using a stationary phase and a mobile phase. Components that interact more strongly with the stationary phase move more slowly. TLC: silica/alumina on a plate (stationary), solvent (mobile); adsorption; ; colourless spots shown by UV, iodine or ninhydrin (amino acids). Gas chromatography (GC): liquid coating on a column (stationary), inert carrier gas (mobile); separation by partition and boiling point; retention time identifies compounds; peak area gives relative amount. GC–MS feeds each separated component into a mass spectrometer for identification. Column chromatography and HPLC separate larger quantities.
≈ 40 min