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A standard solution created from a secondary standard cannot have its concentration accurately known without stoichiometric analysis against a primary standard. An example of a secondary standard is sodium hydroxide, a hydroscopic compound that is highly reactive with its surroundings. The concentration of a standard solution made with sodium ...
Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests; Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit; For chemical substances some pharmacopoeias [10] use the WHO terms [11]
A primary standard in metrology is a standard that is sufficiently accurate such that it is not calibrated by or subordinate to other standards. Primary standards are defined via other quantities like length, mass and time. Primary standards are used to calibrate other standards referred to as working standards. [1] [2] See Hierarchy of Standards.
Secondary standards are calibrated with reference to a primary standard. Working standards, used to calibrate (or check) measuring instruments or other material measures, are calibrated with respect to secondary standards. The hierarchy preserves the quality of the higher standards. [20] An example of a standard would be gauge blocks for
Secondary is a term used in organic chemistry to classify various types of compounds (e. g. alcohols, alkyl halides, amines) or reactive intermediates (e. g. alkyl radicals, carbocations). An atom is considered secondary if it has two 'R' Groups attached to it. [ 1 ]
A drug reference standard or pharmaceutical reference standard is a highly characterized material suitable to test the identity, strength, quality and purity of substances for pharmaceutical use and medicinal products.
Since the early 1960s ferrocene has been gaining acceptance as the standard reference for nonaqueous work for a number of reasons, and in 1984, IUPAC recommended ferrocene (0/1+) as a standard redox couple. [8] The preparation of the QRE electrode is simple, allowing for a fresh reference to be prepared with each set of experiments.
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [1] [2] Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combined without reacting, they may form a chemical mixture. [3]