An extraction method that separates analytes using a solid phase and a liquid phase. It is used for preparative sample cleanup before analysis by CHROMATOGRAPHY and other analytical methods.
A broad class of substances encompassing all those that do not include carbon and its derivatives as their principal elements. However, carbides, carbonates, cyanides, cyanates, and carbon disulfide are included in this class.
A plant family of the order Sapindales, subclass Rosidae, class Magnoliopsida. They are resinous trees and shrubs with alternate leaves composed of many leaflets.
Determination, by measurement or comparison with a standard, of the correct value of each scale reading on a meter or other measuring instrument; or determination of the settings of a control device that correspond to particular values of voltage, current, frequency or other output.
A mass spectrometry technique using two (MS/MS) or more mass analyzers. With two in tandem, the precursor ions are mass-selected by a first mass analyzer, and focused into a collision region where they are then fragmented into product ions which are then characterized by a second mass analyzer. A variety of techniques are used to separate the compounds, ionize them, and introduce them to the first mass analyzer. For example, for in GC-MS/MS, GAS CHROMATOGRAPHY-MASS SPECTROMETRY is involved in separating relatively small compounds by GAS CHROMATOGRAPHY prior to injecting them into an ionization chamber for the mass selection.
Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.
Chromatographic techniques in which the mobile phase is a liquid.
A plant genus of the family ARALIACEAE. Ciwujia extract, which is prepared from plants of this genus, contains ciwujianosides and is used to enhance PHYSICAL ENDURANCE.
Concentration or quantity that is derived from the smallest measure that can be detected with reasonable certainty for a given analytical procedure.
The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.
Spectrophotometric techniques by which the absorption or emmision spectra of radiation from atoms are produced and analyzed.
A basis of value established for the measure of quantity, weight, extent or quality, e.g. weight standards, standard solutions, methods, techniques, and procedures used in diagnosis and therapy.
A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.
An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers.
A mass spectrometry technique used for analysis of nonvolatile compounds such as proteins and macromolecules. The technique involves preparing electrically charged droplets from analyte molecules dissolved in solvent. The electrically charged droplets enter a vacuum chamber where the solvent is evaporated. Evaporation of solvent reduces the droplet size, thereby increasing the coulombic repulsion within the droplet. As the charged droplets get smaller, the excess charge within them causes them to disintegrate and release analyte molecules. The volatilized analyte molecules are then analyzed by mass spectrometry.
Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)
Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.
Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)
Benzene derivatives that include one or more hydroxyl groups attached to the ring structure.
The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.
A solventless sample preparation method, invented in 1989, that uses a fused silica fiber which is coated with a stationary phase. It is used for sample cleanup before using other analytical methods.
Techniques used to synthesize chemicals using molecular substrates that are bound to a solid surface. Typically a series of reactions are conducted on the bound substrate that results in either the covalent attachment of specific moieties or the modification of existing function groups. These techniques offer an advantage to those involving solution reactions in that the substrate compound does not have to be isolated and purified between the reaction steps.
Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The surgical removal of a tooth. (Dorland, 28th ed)
Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)
A space in which the pressure is far below atmospheric pressure so that the remaining gases do not affect processes being carried on in the space.
The branch of chemistry dealing with detection (qualitative) and determination (quantitative) of substances. (Grant & Hackh's Chemical Dictionary, 5th ed)
Methodologies used for the isolation, identification, detection, and quantitation of chemical substances.
Examination of the mouth and teeth toward the identification and diagnosis of intraoral disease or manifestation of non-oral conditions.
Detection of drugs that have been abused, overused, or misused, including legal and illegal drugs. Urine screening is the usual method of detection.
Exclusive legal rights or privileges applied to inventions, plants, etc.
A form of SILICON DIOXIDE composed of skeletons of prehistoric aquatic plants which is used for its ABSORPTION quality, taking up 1.5-4 times its weight in water. The microscopic sharp edges are useful for insect control but can also be an inhalation hazard. It has been used in baked goods and animal feed. Kieselguhr is German for flint + earthy sediment.
A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer.
A novel composition, device, or process, independently conceived de novo or derived from a pre-existing model.
Property, such as patents, trademarks, and copyright, that results from creative effort. The Patent and Copyright Clause (Art. 1, Sec. 8, cl. 8) of the United States Constitution provides for promoting the progress of science and useful arts by securing for limited times to authors and inventors, the exclusive right to their respective writings and discoveries. (From Black's Law Dictionary, 5th ed, p1014)
Tools used in dentistry that operate at high rotation speeds.
Organic compounds that have a relatively high VAPOR PRESSURE at room temperature.
A chemical process for separating the components of a liquid mixture by boiling and collecting condensed vapors.
The sumac plant family in the order Sapindales, subclass Rosidae, class Magnoliopsida. They are tropical and subtropical trees, shrubs, and woody vines that have resin ducts in the bark. The sap of many of the species is irritating to the skin.
Compounds with a core of 10 carbons generally formed via the mevalonate pathway from the combination of 3,3-dimethylallyl pyrophosphate and isopentenyl pyrophosphate. They are cyclized and oxidized in a variety of ways. Due to the low molecular weight many of them exist in the form of essential oils (OILS, VOLATILE).
A phase transition from liquid state to gas state, which is affected by Raoult's law. It can be accomplished by fractional distillation.
The study of the chemical and physical phenomena of radioactive substances.
Detection and counting of scintillations produced in a fluorescent material by ionizing radiation.
A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Devices or pieces of equipment placed in or around the mouth or attached to instruments to protect the external or internal tissues of the mouth and the teeth.