Sample preparation for VA: UV digestion

Voltammetry, being highly specific, can deal with high salt loads.

Organic contamination of a sample, however, can interfere with the VA trace analysis of heavy metals. The 909 UV Digester quickly and effectively breaks down organic molecules by UV photolysis, thereby enabling reliable determinations.

909 UV Digester with operator

Key features

  • Suitable for transparent samples with low to medium organic contamination
  • Fully automatic simultaneous processing of up to 12 samples at a time
  • Low risk of sample contamination due to minute amounts of required reagents
  • Method recommended by standards
  • Controlled digestion temperature and time

UV digestion: How it works

After a small amount of H2O2 has been added to the sample as radical initiator, the sample is irradiated with UV light with wavelengths of 200 to 400 nm, producing OH radicals that spontaneously react with the organic molecules.

In the resulting radical chain reaction, all the organic molecules are broken down to low-molecular-weight compounds such as CO2, H2O, N2, or NH3, which do not interfere with VA analysis.

Diagram of UV Digester used to remove organic contamination from samples

Effective sample preparation – recommended by standards

For transparent samples that exhibit low to medium organic contamination, i.e., carbon concentrations up to approximately 100 mg/L, UV digestion is the method of choice. Standards recommending sample preparation by UV photolysis include the following:
  • DIN 38406, Part 16: Determination of zinc, cadmium, lead, copper, thallium, nickel, cobalt by voltammetry
  • DIN 38406, Part 17: Determination of uranium – Method using adsorptive stripping voltammetry in surface water, raw water and drinking water

Fully automatic digestion

The 909 UV Digester handles your sample preparation fully automatically.

Up to 12 samples, arranged concentrically around the UV lamp to achieve uniform irradiation, can be treated at a time.

Sample holder of UV Digester for sample preparation for voltammetric analysis

Photolysis under controlled conditions

After the user has entered the digestion temperature and time, the 909 UV Digester makes sure that these are maintained: a Pt1000 temperature sensor measures the digestion temperature in a reference sample while an integral microprocessor controls the digestion temperature and the digestion time.
Control display of UV Digester for sample prepration by photolysis

No sample evaporation or losses of volatile analytes

PTFE stoppers that are placed on the quartz sample vessels act as condensation fingers, preventing sample evaporation.

This also means that the 909 UV Digester can be used for sample preparation when analyzing samples containing mercury, arsenic, or selenium which are volatile at elevated temperatures or readily form volatile compounds.

Temperature sensor immersed in sample vessel for the removal of organic contamination by UV photolysis

Low-maintenance air cooling

The UV lamp that is at the heart of the 909 UV Digester generates heat; this is dissipated by a fan located in the base of the instrument. This air cooling has the advantage that no cooling water supply is needed.
UV Digester to break down organic contamination by UV photolysis

Easy and safe operation

The 909 UV Digester integrates in one housing the wet section and the control unit.

The latter serves the operation of the instrument and, via a display, provides information on the ongoing digestion. Users operating the instrument are protected from harmful UV radiation by a shield mounted on it.

UV Digester for sample preparation for voltammetric analysis