Glossary

A joint program of the California Department of Health Services and Department of Industrial Relations, that reviews and evaluates the scientific literature and provides up-to-date, practical answers to questions such as, which workplace chemicals are harmful to health, do any of these chemicals cause cancer, and can these chemicals affect reproduction.

An atom, other than carbon, in the ring of heterocyclic compound (a ring of atoms of more than one kind)

One of two categories in which microorganisms are classified on the basis of their carbon source. Heterotrophs use organic compounds such as carbohydrates, lipids, and hydrocarbons as a carbon and energy source.

The presence of different alleles at one or more loci on homologous chromosomes.

Height Equivalent to Theoretical Plate (testing)

HETP arises from the “Plate Theory” and is numerically equal to the column length divided by the number of theoretical plates in the column (and in practice is measured in this way). As the HETP is a function of both the properties of the column and the solute, it will vary from one column to another and, more importantly, between different solutes eluted from the same column in the same chromatogram.The HETP is the theoretical link between the “Plate Theory” and the “Rate Theory” as the HETP is numerically equal to the variance per unit length of the column as determined from the Rate Theory. The more efficient the column the more theoretical plates in the column the better the resolution and the smaller the HETP. The rate theory provides an equation for the HETP in terms of the physical properties of the solute and phase system, the operating temperature and the mobile phase velocity.

A graph relating the variance per unit length of a column to the linear velocity of the mobile phase. The variance per unit length of a column, for a specific solute, can be calculated as the ratio of the column length to the column efficiency. For an LC column the mobile phase velocity can be taken as the ratio of the column length to the retention time of an unretained solute of sufficient size so that it can not enter any pores of the support or stationary phase (e.g. a dispersion of silica smoke). The linear velocity in a GC column can be determined by dividing the column exit flow rate by the column cross-sectional area. However, in GC, the linear velocity calculated in this way must also be corrected for the compressibility of the gas. The relationship between the variance per unit length of the column and the linear mobile phase velocity is given by the HETP equation which takes the form of a hyperbolic function. This hyperbolic function may contain three or four individual expressions depending on whether it is for a packed column or for a capillary column. The HETP curve shows a minimum at a particular velocity, which is called the “optimum velocity”. It follows, that at the optimum mobile phase velocity, the column will provide a maximum number of theoretical plates.

nvolving or serving as an aid to learning, discovery, or problem-solving by experiment and specially trial-and-error methods.

Any of various problem-solving techniques that involve the use of subjective knowledge, hunches, trial-and-error, rule-of-thumb, and other such informal but generally accurate methods.

Health, Education, and Welfare

The base 16 number system. Digits are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, & F. This is a convenient form in which to examine binary data because it collects 4 binary digits per hexadecimal digit; e.g., decimal 15 is 1111 in binary and F in hexadecimal.

Hydrofluoroalkane (inhaler technology base)

Hydrofluorocarbon

Hexafluoropropylene

Hard Gelatin Capsule

Human Growth Hormone

An early biopharmaceutical. Formerly derived from cadaveric pituitary glands, this protein is now produced by recombinant expression.

Hypoxanthine-Guanine-Phophoribosyl Transferase (enzyme)

Health and Human Services

Hydraulic Institute

Health Industry Bar Code

Hydrophobic Interaction Chromatography

A type of liquid chromatography that makes use of the relative solubility of proteins and matrix materials. Hydrophobic interactions are strongest at high ionic strengths, so salt is usually included to increase those levels.

High Intensity Discharge