The 909 UV Digester supplied by Metrohm can quickly and effectively decompose organic molecules through UV photolysis, and thus, facilitate consistent analyses. Organic contamination of samples can hamper the voltammetry (VA) trace analysis of heavy metals, but VA can deal with high salt loads as it is highly specific.
After adding a small amount of H2O2 to the sample as a radical initiator, UV light with wavelengths ranging from 200 to 400nm is used to irradiate the sample to create OH radicals, which instantly react with the organic molecules.
This results in a radical chain reaction in which all the organic molecules are decomposed into low-molecular-weight compounds like H2O, CO2, N2, or NH3, which do not impede VA analysis.
UV digestion presents a suitable option for transparent samples with low to medium organic contamination, that is, carbon concentrations up to 100mg/L. The following standards propose sample preparation by UV photolysis:
- DIN 38406, Part 16 - determination of cadmium, zinc, copper, lead, cobalt, nickel, and thallium by voltammetry
- DIN 38406, Part 17 - determination of uranium – method using adsorptive stripping voltammetry in raw water, drinking water, and surface water
Sample preparation in the 909 UV Digester is fully automated. Roughly 12 samples that are concentrically arranged around the UV lamp for irradiation can be treated at a single time.
Once the user has fed the digestion time and temperature, the 909 UV Digester ensures that these are sustained through an integral microprocessor that controls the digestion time and the digestion temperature, and a Pt1000 temperature sensor that determines the digestion temperature in a reference sample.
PTFE stoppers positioned on the quartz sample vessels serve as condensation fingers and prevent evaporation of the sample. This means that the 909 UV Digester can also be utilized for sample preparation when studying samples containing volatile elements such as mercury, selenium or arsenic at increased temperatures or samples that instantly form volatile compounds.
The UV lamp, the core of the 909 UV Digester, produces heat, which is dispersed by a fan placed at the bottom of the instrument. This air cooling eliminates the need for a cooling water supply.
The 909 UV Digester integrates the control unit and the wet section in a single housing. The former controls the working of the instrument, and through a display, gives information about the continuing digestion. A shield is placed on the instrument that protects users from harmful UV radiation.
The 909 UV Digester comes with a wide range of accessories such as a Pt1000 temperature sensor (Class B), thermometer stopper, sample holder, UV protective shield, PTFE stopper, storage vessel holder, UV warning plate, 3-mm hex key for IC sample processors, UV mercury vapor lamp, and a spacer for the Pt1000 temperature sensor.
The main features of the 909 ultraviolet digester are as follows:
- Fully automatic sample preparation
- Fully automatic and concurrent processing of up to 12 samples at a time
- Low risk of sample contamination, thanks to trace amounts of required reagents
- Controlled digestion time and temperature
- Photolysis under controlled conditions
- No sample evaporation or losses of volatile analytes
- Ideal for transparent samples with low to medium organic contamination
- Easy and safe operation
- Low-maintenance air cooling
- Method recommended by standards
Specifications of the 909 ultraviolet digestion instrument are as follows:
- Digestion time: 1 - 999 min
- Digestion temperature: 80 - 100°C (±3°C)
- Cooling: air cooling
- Lamp output (regulated): 300 - 600W
- Measuring range: –20 - +150°C
- Sensor: Pt1000 temperature sensor
- Accuracy: ±0.2 °C (under reference conditions)
- Medium pressure mercury vapor lamp
- Service life: 500 to 1,000h
- Power consumption: 630W
- Frequency: 50 - 60Hz
- Voltage: 220 - 240V