The SpeedDigester K-439 revolutionizes IR digestion. It combines the benefits of IR and block digestion in one unit. Fast nitrogen determination by Kjeldahl digestion at controlled temperatures enables an increased sample throughput. Multiply the instrument functionality whenever needs are changing. View more
The revolution in sample digestion

High speed and throughput

  • Fast heat transfer of infrared heaters to samples
  • Large time savings due to fast heating and cooling
  • Increased sample throughput due to short process time
  • Accelerated digestion step with continuous addition of H2O2


  • One instrument for both Kjeldahl and reflux digestion
  • All BUCHI sample tubes to be used (100 mL, 300 mL, 500 mL)
  • Sample tubes compliant with ISO 6060 for COD and other reflux digestion (e.g. aqua regia)
  • Optional dedicated suction module for aqueous samples

Excellent reproducibility

  • Accurate temperature control following the programmed profile
  • Storage of up to 50 different method profiles (time / temperature)
  • Digestion process shown graphically
  • Thermal homogeneity due to the innovative insulation plate  
Expert Advice

Why do block digesters need lower set temperatures during digestion than IR digesters?

Due to the direct heat transfer of the contact of block to sample tube, lower set temperatures are required to achieve the boiling temperature.

What are differences between IR and block digesters?

Differences between IR and block digester

Differences between IR and block digesters.

What is the difference between the standard suction module and the suction module with condensate trap?

The standard suction module is mainly used for unproblematic and dry samples. The suction module with condensate trap is used for aqueous samples, to speed up the digestion process as it avoids backflow of the evaporated water into the sample. Hence the evaporation of water is faster and the boiling point is reached earlier, it also helps avoid cross-contamination of problematic samples.

Can the two rows (heating chambers) of the K-439 be controlled individually?

No, only one temperature setting can be applied at the same time.

Which sample tubes can be used with the SpeedDigester?

All types of BUCHI Kjeldahl sample tubes (100 mL, 300 mL, 500 mL) as well as 3rd party tubes with a capacity of 250 mL and flat bottom tubes for reflux digestion (e.g. COD and aqua regia digestion) can be used in the same instrument.

How can I speed up time-consuming digestion periods?

IR digesters are up to 30 minutes faster than block digesters .

Is it possible to totally replace metal salts by H2O2 and what are the benefits?

By using the SpeedDigester with the dedicated H2O2 suction module the sample is digested in absence of any catalyst but by continuously adding H2O2during operation. This further accelerates the process by 70 min (yellow vs. green graph) but involves the operator’s attendance. A very fast (30 minutes) and environmental sound digestion (as no heavy metal catalyst is used) is achie­ved by continuously adding H2O2via capillary funnels (yellow graph). To add H2O2continuously during digestion a specific suction module with funnels is required

How to safe money by reducing the consumption of chemicals?

Weights of samples which are homogenous and high in nitrogen content can be reduced so that micro-Kjeldahl parameters can be applied (e.g. fertilizer , cosmetics). Generally, optimal conditions can be estimated with the help of BUCHI’s Kjeldahl Calculator app. KjelCalc predicts the use of chemicals for digestion and distillation and determines the right parameters.

Selection of sample tubes

The SpeedDigester can flexibly be adapted to use three different sample tube sizes:
100 mL, 300 mL and 500 mL


Suction module types

Specific suction modules are available for aqueous samples and accelerated digestion. The standard suction module is appropriate for most other applications.


Reflux setup (water cooled)

This setup guarantees efficient reflux without the loss of volatile compounds, the main use is for trace metal determination by aqua regia digestion.


COD setup (air cooled)

COD determination according to DIN 380 409 Part 41 and ISO 6060. Sample tubes are compatible with the autosampler from Mettler Toledo for automated COD analysis.