L

La

atomic symbol for lanthanum

laboratory control sample (LCS)

artificial sample prepared at a laboratory by adding a measured amount of a standard solution to an essentially analyte-free matrix, and analyzed for the purpose of assessing the performance of the measurement process

laboratory duplicate

second test portion removed from a test sample and analyzed in the same manner as the original for the purpose of checking the precision of the measurement process (including subsampling)

laboratory information management system (LIMS)

automated information system for tracking and managing laboratory samples, projects, analyses, measuring instruments, and quality control information, and for generating reports to clients

laboratory sample

physical sample sent to or received by a laboratory (cf. test sample and test portion)

law of propagation of uncertainty

uncertainty propagation formula

leach

to dissolve out of a solid material, as for example by the action of water or acid.

Leaching is sometimes used in the laboratory as a technique for partial sample digestion, but since the chemical yield usually cannot be determined, the technique is appropriate only in special circumstances.

leachate

liquid into which some soluble substance has leached

Li

atomic symbol for lithium

(linear) attenuation coefficient

for a parallel beam of pho­tons pass­ing through a material, the frac­tion of the pho­tons removed in a short dis­tance, divided by that dis­tance (see also mass attenuation coefficient)

linearity

degree to which the response curve for a measuring device tends to follow a straight line

The linearity may be expressed as the maximum deviation of the response curve from such a straight line.

liquid scintillation cocktail

mixture of chemicals including a scintillator designed to be mixed with a portion of a liquid sample in a vial before the vial is assayed for radiation using a liquid scintillation counter

liquid scintillation counter

specialized instrument used for liquid-scintillation counting

liquid scintillation counting

scintillation counting in which a portion of the sample is combined with the scintillator in a liquid mixture

liter, litre (L)

special name for the cubic decimeter, dm³, a unit of volume

Note: The liter is accepted for use with the SI, but is not recommended for use when giving the results of high-accuracy measurements of volumes. The unit symbol for the liter is either a lower-case or upper-case L, but the upper-case symbol is preferred in the United States.

live time

real time of an instrumental measurement (e.g., a radiation counting measurement) minus the integrated dead time of the measurement

LN₂ (or LN2)

liquid nitrogen (N₂ denotes a diatomic molecule of nitrogen)

log-normal distribution

A type of probability distribution. A numerical random variable X has a log-normal distribution if ln X has a normal distribution.

lot

in the theory of material sampling, a quantity of material from which a sample is taken for testing

Note: In the laboratory, the “lot” is often a test sample, while the “sample” is actually a subsample.

lower limit of detection (LLD)

1. “the smallest concentration of radioactive material in a sample that will yield a net count, above the measurement process (MP) blank, that will be detected with at least a 95 percent probability with no greater than a 5 percent probability of falsely concluding that a blank observation represents a ‘real’ signal” [NRC 1984].
2. minimum detectable value

Lr

atomic symbol for lawrencium

Note: The symbol Lw was originally proposed.

Lu

atomic symbol for lutetium

Lucas cell

an alpha scintillation cell that meets certain design specifications (of H.F. Lucas)

luminescence

emission of light from material when its atoms are excited by any means other than raising its temperature (see also chemiluminescence and photoluminescence)

Lw

the atomic symbol first proposed for lawrencium (see Lr)