Analyses of Nanoparticles in the Environment - Nanotechnology and the Environment - page 114

. saMPling and analYsis oF wateRs

and soils FoR nanoPaRtiCles

The. second. subset. of. the. challenge. to. develop. instruments. to. assess. exposure. to.
engineered.nanomaterials.is.“to.develop.instruments.that.can.track.the.release,.con-
centration. and. transformation. of. engineered. nanoparticles. in. water. systems”. [41]..
Measurements.of.natural.nanoparticles.in.environmental.waters.have.been.reported.
by. a. variety. of. techniques,. but. there. are. few. reports. at. this. time. of. ield. studies.
designed.to.detect.engineered.nanoparticles.
A. separation. technique. called. ield-low. fractionation. (FFF). separates.
nanoparticles. from. larger. particles,. permitting. their. direct. analysis. or. collection.
for.detailed.characterization.
As.shown.in.Figure.5.4,.ield-low.fractionation.is.similar.to.the.chromatographic.
separations.typical.of.environmental.analyses.for.organic.contaminants..The.water.
sample.passes.through.a.thin.low.channel.designed.so.that.the.low.will.be.laminar,.
that.is,.not. turbulent. and. faster.in.the. center.of.the. column.than.at.the. walls..The.
bottom.side.of.the.channel.is.a.membrane.that.will.allow.water.through.but.not.the.
particles.of.interest..A.second.force.is.applied.perpendicular.to.the.channel.low.to.
generate.a.cross-low..All.particles.in.the.sample.will.be.pushed.downward.toward.
the.membranes,.but.smaller.particles.will.diffuse.upward.toward.the.center.of.the.
channel. to. a. greater. degree. and. will. be. in. the. faster. stream. lines. of. the. channel.
low..The.smaller.particles.in.the.sample.will.exit.from.the.channel.before.the.larger.
particles.
Once. separated,. natural. particles. in. the. nanometer. size. range. can. be. directly.
introduced.into.an.inductively.coupled.mass.spectrometer.[46].for.elemental.analy-
sis,.collected.for.ESEM.analysis.[47],.and.coupled.to.a.light.scattering.instrument.
for. particle. size. measurements. [48].. Field-low. fractionation. was. applied. for. size.
distribution. analysis. of. trace. concentrations. of. iron. oxi/hydroxide. colloids. being.
considered.as.potential.carriers.for.the.radionuclide.migration.from.a.nuclear.waste.
repository.[49].

FiguRe . Flow.ield.fractionation..(From.Postnova.Analytics,.Inc..With.permission.)