Set new standards in terms of digestion speed, flexible use and result reproducibility with the IR SpeedDigester. Achieve an increased sample throughput for nitrogen determination by Kjeldahl digestion and multiply instrument functionality whenever needs are changing. View more
The entry level IR digester

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 shortened 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 or other reflux digestion (e.g. aqua regia)
  • Dedicated suction module for aqueous samples


  • Sealed suction module for effective transfer of harmful fumes
  • Effective neutralization of fumes by the Scrubber K-415
  • Safe operation and extended lifetime of fume hood
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.

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.

Can the set heating levels be correlated to a specific temperature?

Yes, as the SpeedDigester K-425 / K-436 are equipped with thermostats. The table below lists the correlated temperature (typical average values) for the set heating level position of the thermostat.

Why is level 9 and 10 highlighted red?

Level 9 and 10 are highlighted in red,as at these high temperatures the condensation zone can be displaced inside the safety zone, close to the suction module. This can cause ineffective digestion and corrosion of sealings and glassware!

Can the two heating chambers in the K-436 be controlled individually?

Yes, as heating chambers are equipped with individual thermostats it is possible to set heating levels independently.

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