never came across it before, but found this definition:
aliquot (in analytical chemistry)
A known amount of a homogeneous material, assumed to be taken with negligible sampling error. The term is usually applied to fluids. The term ‘aliquot’ is usually used when the fractional part is an exact divisor of the whole; the term ‘aliquant’ has been used when the fractional part is not an exact divisor of the whole (e.g. a 15 mL portion is an aliquant of 100 mL). When a laboratory sample or test sample is ‘aliquoted’ or otherwise subdivided, the portions have been called split samples.
source: IUPAC Compendium of Chemical Terminology