Reference library

Foundations

Explore concepts, laws, equations and methods, with clear explanations of their use and sources. Choose an area of study or find a specific entry.

More filters

Entry type

Reference entries

Showing 241–270 of 1709 reference entries

Physics · Earth & cosmosNuclear binding energy

A bound nucleus has less rest mass than its separated nucleons.

Model Physics · Earth & cosmosExponential radioactive decay

A fixed decay probability per time gives a population timescale.

Model Physics · Earth & cosmosFission, fusion and reaction energy

Nuclear rearrangement can release or require energy.

Model PhysicsScattering cross section

Normalize a scattering rate by incident flux.

Model PhysicsStandard Model matter families

Quarks and leptons form three generations.

Model PhysicsStandard Model interactions

Gauge fields mediate three interactions; the Higgs is a scalar sector.

Model PhysicsInteraction-specific quantum-number balances

A balance rule must name the interaction where it applies.

Model Physics · ChemistryBloch states and electronic bands

A periodic crystal potential organizes energies by wavevector and band.

Model Physics · ChemistrySemiconductor electrons and holes

Band occupancy and doping control mobile carriers.

Model PhysicsBose and Fermi thermal occupations

Indistinguishable particles have different equilibrium state populations.

Model ChemistryElectron screening and effective nuclear attraction

Other electrons modify the attraction experienced by an electron in an atom.

Model ChemistryMultielectron ground-state configurations

Orbital occupations connect atomic electronic structure with valence chemistry.

Model ChemistryLocalized bonds and resonance descriptions

Localized orbital overlap and resonance are complementary chemical descriptions.

Model ChemistryMolecular orbitals and bonding occupation

A molecular orbital description distributes electronic states across a molecule.

Model ChemistryIntermolecular interactions

Dispersion, dipole interactions and hydrogen bonding influence molecular materials.

Model ChemistryBonding classes of solids

Ionic, metallic, molecular and network solids organize common bonding patterns.

Definition ChemistryPolymers and macromolecular architecture

Polymers are substances composed of macromolecules with recurring structural units.

Definition ChemistryCoordination compounds and ligands

Ligand donor atoms surround a central metal in a coordination sphere.

Definition ChemistryActivities and chemical potentials

Activity expresses composition relative to a specified thermodynamic standard state.

Definition ChemistrypH and hydrogen-ion activity

pH is an activity-based quantity realized through measurement conventions.

Definition ChemistryBuffers and finite buffering capacity

An acid–base pair can resist limited changes in solution pH.

Model ChemistrySolubility products and precipitation

An equilibrium product constrains dissolution of a specified solid phase.

Model ChemistryReference electrodes and redox potentials

Electrode potentials are specified relative to a reference half-cell.

Definition ChemistryThe Nernst equilibrium relation

Reversible electrochemical potential depends on activities and temperature.

Model ChemistryElementary steps and reaction mechanisms

A mechanism proposes steps that account for an overall chemical transformation.

Model ChemistryArrhenius temperature dependence

Many rate constants follow an exponential temperature model over a limited range.

Approximation ChemistryHess's law and thermochemical accounting

Reaction enthalpies can be combined because enthalpy is a state function.

Model ChemistryPhase diagrams and coexistence

Phase diagrams describe equilibrium states under stated conditions.

Model ChemistryCalibration, standards and matrix effects

Quantitative analysis needs a validated relation between response and analyte amount.

Method ChemistryChromatographic retention and separation

Differential interactions with mobile and stationary phases separate mixture components.

MethodSource checked

Chromatographic retention and separation

Chemistry

Differential interactions with mobile and stationary phases separate mixture components.

Key knowledge

In chromatography, components travel with a mobile phase while interacting differently with a stationary phase. Differences in retention can produce separated bands, while band broadening limits resolution. Retention is conditional on the system, rather than a unique identity by itself.

Conditions and scope

Specify phases, flow, temperature and the measured separation conditions.
Equilibrium partition models require sufficiently rapid interphase exchange relative to motion; coelution can persist.

Sources · 1

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

12.2: General Theory of Column ChromatographyDavid Harvey, DePauw University — Analytical Chemistry 2.1Textbook chapterchem.libretexts.orgRead source

Evidence and review

Harvey's column separation, retention and exchange-rate assumptions.

2026-10-10 · Checked retention versus identification and the local-equilibrium approximation.

Entry details

Permanent link to this entry ↗

Record identity: chem-chromatographic-separation
Revision: university-reference.1
Structured reference record: University reference