Reagents contaminations increase the background
concentration of the analytes present
in a sample. The amount contributed is a function
of the total quantity of reagent used.
For example, 50 mL of a reagent that contain a
contaminant at the 100 ppb level will contribute
5 μg of that species as contamination.
Currently, many laboratories purchase expensive
high purity acids for trace elemental analysis
(in the US, the price of five liters of high purity
HNO3 is about $ 1,500.00).
There is, however, an alternative. Milestone has
developed the DuoPUR, a sub-boiling distillation
system which allows laboratories to make
their own high purity acids. Producing high
purity acid on demand reduces the cost of 5
liters of high-purity acid to about $ 90.00 (US).
The SubPUR and DuoPUR from Milestone are
high performance sub-boiling distillation units
made of high purity quartz and PFA.
The DuoPUR can produce 1 liter (500 mL per
quartz unit) of high purity acid from reagent
grade acid in 6 hours. The savings on reagents
alone, dramatically reduces the total cost per
sample. The DuoPUR also gives you the ability
to re-purify acids that have become contaminated,
further adding to your cost savings.
The principle of subboiling
Subboiling distillation is recognized as the best
method to obtain high purity reagents and the
lowest blank values for ultratrace analysis.
Subboiling distillation is based upon vaporizing
a liquid by radiative heating of its surface
to prevent boiling. This technique prevents the
formation of spray or droplets. In conventional
distillation, violent boiling action generates
aerosolized particles, resulting in contamination
of the original liquid with the distillate.
Surface evaporation during subboiling distillation
prevents this, thus yielding a higher purity
distillate.
SubPUR/DupPUR how it works
The DuoPUR consists of two high-purity
quartz distillation units. Each unit contains two
heating elements, (which supply a maximum
power of 1250 W), a water cooled condenser,
reagent addition and collection bottles, and a
drain.
The distillation process is microprocessor controlled,
allowing the user to set the distillation
time and power level. Infrared heating gently
vaporizes the surface liquid, accelerating evaporation,
and preventing aerosolized particles.
Vaporized liquid is collected on an inclined
cold finger where it condenses and drips into
the high purity PFA collection container.
