Chemistry Reference
In-Depth Information
Mobile phase:
Carries the analyte through the stationary phase. It is usually
an inert gas such as helium, nitrogen or hydrogen.
Molecule:
The smallest part of a substance that is composed of two or more
atoms of the same or different type that are held together by chemi-
cal forces.
Peak area:
A measure of the area under the curve or peak within a
chromatogram.
Polarity:
Polarity of a bond refers to the distribution of the electrical charge
over the atoms that are joined together by the bond. In a polar com-
pound, the charge is distributed asymmetrically due to the differences
in electronegativity between the atoms that make up the compound.
Precision:
The closeness of agreement between a series of measurements
obtained from multiple sampling of the same sample. It can be
considered at three levels: repeatability, intermediate precision and
reproducibility.
Qualitative:
An analysis in which identification of the analyte of interest is
determined. This is usually achieved using a particular characteristic
of the compound of interest, such as retention time, detector response
(e.g., flame ionisation detector) and reference standard comparison.
Quality assurance:
The process of establishing whether a process or product
meets customer expectations and is suitable for its intended purpose.
Quality control:
The systems that are put in place in order to ensure that the
product is fit for its intended purpose.
Quantitative:
An analysis in which the amount of the analyte of interest is
determined using a reference standard material of the same chemi-
cal structure.
Quantum theory:
The study of the interactions of matter and radiation at
the atomic and subatomic levels.
Range:
The interval between the upper and lower concentration for which
it has been demonstrated that there is a suitable level of accuracy,
precision and linearity.
Repeatability:
A measure of the precision of the method over a short period
of time using the same sample solution.
Resistance to mass transfer:
The time taken for the analyte to transfer from
the mobile to the stationary phase.
Resolution:
A measure of the separation between two adjacent compounds
within a chromatographic separation. Under ideal conditions, reso-
lution should be ≥1 and ≤10.
Retention factor:
A measure of the amount of time an analyte spends in the
stationary phase relative to the mobile phase.
Retention time:
Time taken for an analyte to travel from the point of injec-
tion to the point of detection within a GC system.
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