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Anions

Most anionic or neutral inorganic substances, which includes oxyanions, are best measured with DGT passive samplers that incorporate an oxide in the binding layer. The exceptions are: As(III), Cr, nitrate, sulphide or Tc. For advice on the specialist DGT passive sampler you need, please click on:

As(III)            Cr           nitrate           sulphide      or       Tc

Al, As((III) and (V)), phosphate, Se(IV), Sb(V), Mo(VI), V(V), W(VI) can be measured simultaneously using standard DGT devices for anions. Three types are available, with binding agents of ferrihydrite, titanium oxide (Metsorb) or zirconium oxide. Their relative merits can be briefly summarised. 

Ferrihydrite: simplest elution procedure, particularly good for freshwaters and soils, simplest for phosphate, less effective for longer-term measurements in seawater.

For deployments in waters you will need ferrihydrite device LSNP-NP

For deployments in soilsA you will need ferrihydrite device LSLP-NP

For deployments in sedimentsB you will need ferrihydrite device LSPP-NP

Titanium oxide: good for measurements in seawater and freshwater, elution procedure more complicated.

For deployments in all types of waters you will need Metsorb device LSNT-NP

For deployment in soilsA you will need Metsorb device LSLT-NP

For deployments in sedimentsB you will need Metsorb device LSPT-NP

Zirconium oxide: good for measurements in seawater and freshwater, elution procedure most complicated.

Phosphate

If phosphate is the sole analyte of interest we strongly recommend using the ferrihydrite device.  It works very well for phosphate and is used routinely for soil testing. Because 100% elution can be achieved using dilute sulfuric acid,  measurement using the standard colorimetric molybdenum blue method is quick and easy. Deployments in seawater of a few days work well using this method, but if longer deployments are required we recommend using Metsorb or ZrO. Note that in these cases, elution is by base and neutralisation is required prior to the colorimetric measurement.

Detailed instructions for the use of most DGT passive samplers are available.

AThese soil devices are designed for deployment in homogenised hydrated soil samples.

BThe sediment probes can be inserted directly into sediment and have a large enough area (exposure window 150 x 18 mm) to be capable of providing spatial information, e.g. vertical profiles or 2-D images. They have also been used to obtain similar information in hydrated soils (e.g. Luo et al., 2013).