Methods for determining chemical composition, structure, and quantity: separation techniques (chromatography, electrophoresis), quantitative spectroscopy, electro-analytical methods, mass spectrometry. Feeds quantitative input to every…
analytical-chemistry
High-performance liquid chromatography (HPLC)
Separation of dissolved analytes by differential partitioning between a mobile liquid phase (pumped at 100–400 bar) and a stationary phase…
Gas chromatography (GC)
Separation of volatile analytes by partitioning between an inert carrier gas (He, H₂, N₂) and a stationary phase coated inside a long…
Inductively-coupled-plasma mass spectrometry (ICP-MS)
Sample is nebulised into an argon plasma (T ≈ 6 000–10 000 K) that atomises and ionises virtually every element, then the resulting cations…
Capillary electrophoresis
Separation of charged species in a narrow (~50 μm ID) buffer-filled capillary under a strong axial electric field (10–30 kV). Migration…
Limit of detection (LOD)
Lowest analyte concentration distinguishable from blank at a stated confidence level: LOD = 3 σ_blank / slope, with σ_blank the standard…
High-resolution MS (Orbitrap, FT-ICR)
Resolving powers 10⁵-10⁶ enable formula assignment from sub-ppm mass accuracy. Orbitrap image-current detection; FT-ICR cyclotron resonance…
Modern NMR (multidim, DOSY, DNP)
2D-COSY/NOESY/HSQC for structure elucidation. DOSY for mixture analysis by diffusion. DNP enhances polarization 10⁴× for low-abundance…
X-ray fluorescence (XRF)
Inner-shell ionization + characteristic X-ray emission; non-destructive elemental analysis. Handheld units for field use; synchrotron µ-XRF…
Chemometrics (PCA, PLS, MCR)
Multivariate analysis of spectroscopic data. PCA for dimension reduction; PLS regression for quantitative analysis; MCR-ALS for…
LOD/LOQ & validation
LOD = 3σ/slope, LOQ = 10σ/slope at blank noise level. Validation per ICH Q2: linearity, accuracy, precision, specificity, robustness.
Van Deemter equation (chromatography)
H = A + B/u + Cu; plate height vs flow velocity; optimum gives maximum efficiency; UPLC small-particle era.
HPLC modes (RP, NP, HILIC, IEX, SEC)
RP most common (C18); HILIC for polar; IEX for charged; SEC by size; method selection by analyte properties.
GC-MS quantitation (SIM, MRM)
SIM for targeted analysis; MRM with triple-quad highest selectivity; SIL internal standards for ppb quantitation.
LC-MS with Orbitrap
High-resolution accurate mass (>100k R, <1 ppm) enables formula assignment; HCD, ETD fragmentation; metabolomics, proteomics.
Capillary electrophoresis (CE, CIEF, CZE, MEKC)
μ_eff = μ_ep + μ_eof; zones separated by charge/size; MEKC for neutrals with SDS micelles; biomarker analysis.
ICP-MS multielement analysis
Inductively-coupled plasma at 10,000 K ionizes; MS at sub-ppt; isotope ratios for geochronology, tracers.
X-ray fluorescence (XRF)
Core hole filled with characteristic X-rays; element identification down to ppm; handheld and benchtop instruments.
Ion-selective electrodes (ISEs)
Glass pH, F⁻/LaF₃, K⁺/valinomycin membranes; Nikolsky-Eisenman selectivity; clinical blood-gas analyzers.
Measurement uncertainty & traceability
GUM expanded U = k u_c; Type A (statistical) and Type B (systematic); SI traceability via CRM hierarchy; ISO 17025.