BRAINCAKEModern Analytical Techniques
Revision notes for Modern Analytical Techniques in Edexcel Chemistry (9CH0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- High Resolution Mass SpectrometryAn ordinary (low resolution) mass spectrometer gives m/z values to the nearest whole number.
- Precise Molecular MassThe precise molecular mass of a compound is found from the m/z value of its molecular ion, M+ (the whole molecule that has lost one electron), in a…
- ChromatographyChromatography separates and identifies the components of a mixture.
- Thin-Layer ChromatographyIn thin-layer chromatography (TLC), the stationary phase is a thin layer of silica (SiO2) or alumina (Al2O3) spread on a glass, metal or plastic…
- High Performance Liquid ChromatographyHigh performance liquid chromatography (HPLC) separates the components of a liquid mixture quickly and precisely.
- Gas ChromatographyGas chromatography (GC) separates mixtures of volatile compounds.
- Retention TimesIn gas chromatography (GC) and high performance liquid chromatography (HPLC), the components of a mixture are carried through a column by the mobile…
- Nuclear Magnetic ResonanceNuclear magnetic resonance (NMR) spectroscopy is used to work out the structure of organic molecules.
- Chemical ShiftThe position of an NMR signal is given as its chemical shift, δ, measured in parts per million (ppm) relative to a reference compound.
- 13C NMR Spectroscopy13C NMR detects the 13C isotope, which makes up only about 1.1% of carbon atoms.
- 1H NMR Spectroscopy1H NMR (proton NMR) detects hydrogen nuclei.
- Integration TracesThe area under each peak in a 1H NMR spectrum is proportional to the number of hydrogen atoms in that environment.
- Spin-Spin SplittingIn a high resolution 1H NMR spectrum, many peaks are split into a group of closely spaced lines.
- The n+1 RuleThe n+1 rule: a hydrogen environment with n hydrogen atoms on the adjacent carbon atom(s) is split into n + 1 lines. • n = 0: singlet • n = 1…
- Deducing Structures from Combined DataNo single technique identifies an unknown compound on its own.