Es el término usado en cromatografía (placa o papel). Cada "punto de siembra" es un "spot", por eso es común también expresarlo como verbo y te lo ofrezco como variante. Algunas referencias:

[DOC]
THIN LAYER CHROMATOGRAPHY OF VEGETABLES
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Place the TLC plate in the chromatography chamber with the sample spot toward the bottom. Be sure the sample spot is above the level of the solvent. ...
www.upb.pitt.edu/.../Chemistry_Labs/chem014_Thin Layer Chro... - Similar pages - Note this

Paper Chromatography: Loading the Sample on the Paper
To spot the sample, touch the capillary to the line on the chromatogram. ... More than one sample can be loaded onto a single piece of chromatography paper. ...
jchemed.chem.wisc.edu/JCESoft/Programs/VideoCD/CPL/Sample/Modules/paprchrom/paprchromload.htm - 10k - Cached - Similar pages - Note this

Journal of Chromatography A : Influence of sample application mode ...
The chromatographic plate with sample spot on it was prewetted using special .... influencing on final separation quality in liquid chromatography [25]. ...
linkinghub.elsevier.com/retrieve/pii/S0021967307014963 - Similar pages - Note this

Thin Layer Chromatography
Thin‑layer chromatography involves the same principles as column ... The spot of sample must be applied to the plate with care; it should not be large, ...
chemistry.csudh.edu/faculty/noel/CHE317L/Thin%20Layer%20Chromatorgaphy%20Experiment.htm - 37k - Cached - Similar pages - Note this

[DOC]
CHROMATOGRAPHY OF MAGIC MARKERS
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These inks can be separated using paper chromatography. ... Carefully spot the sample where the other tic mark intersects the origin. Spot quickly so the ...
services.juniata.edu/ScienceInMotion/chem/labs/chrom/forensic.doc - Similar pages - Note this