For some classes of chemical, robust analytical methodology
may not be currently available. The determination of short-chain
polychlorinated alkanes (SCCPs) is an example. SCCPs are technical
mixtures of C10 to C12 chain length alkanes, of varying degree of
chlorination and with up to 8000 congeners. SCCPs have replaced
PCBs in some industrial applications and were subsequently found
to be persistent in the environment with the potential to accumulate
in organisms. The complexity of the SCCP mixtures found in
the environment means that they cannot be chromatographically
separated into discrete components [24]. This creates a problem
in detector calibration and quantification. Consequently, analytical
data are based on a total peak area with relatively high uncertainty.
Developmental toxicity has been observed for SCCPs [25], but can
only be linked to the degree of chlorination rather than to specific
chemical entities, because of the complexity of the mixture.
In the same way as analytical methodology for PCBs has evolved
from the measurement of Aroclor equivalents to congener-specific
determination, future chromatographic developmentsmay resolve
complex mixtures such as SCCPs. For the present, measurement
uncertainty remains a key limitation in exposure assessment for
these compounds.