Speed­Digester K-425 / K-436 / K-439

The entry level IR digester

Set new standards for digestion speed, flexible use and result reproducibility with the IR SpeedDigester. Achieve higher sample throughput for nitrogen determination by Kjeldahl digestion and multiply functionality with this entry level IR digester.

  • Max. Temperature:580°C
  • Sample Positions:5 - 12
  • Sample Parameters:Total Kjeldahl Nitrogen (TKN), Chemical Oxygen Demand (COD), heavy metals, phosphate
SpeedDigester K-425 / K-436 / K-439

High speed and throughput

Save time thanks to faster heat transfer from infrared heaters to samples and a quicker cool-down process. Increase your sample throughput by reducing the processing times. Accelerate your digestion step with continuous addition of H2O2.

High speed and throughput


The SpeedDigester K-425 / K-436 combines both Kjeldahl and reflux digestion in one instrument. Flexibly use any BUCHI sample tubes (100 mL, 300 mL, 500 mL), which are compliant with ISO 6060 for COD or other reflux digestion (e.g. aqua regia). The SpeedDigester is also suitable for aqueous samples thanks to a dedicated suction module.



Improve your safety with sealed suction modules that make efficent transfer of harmful fumes possible. Combine with Scrubber K-415 to achieve effective neutralization of fumes, operate the unit safely and extend the lifetime of your fumehood.



  • Reduce digestion time up to two hours by fast heating, cooling and the continuous addition of H2O2 through the capillary funnels. 

    Short digestion process
  • Use the SpeedDigester for multiple applications like Kjeldahl, micro-Kjeldahl, COD, hydroxyproline or aqua regia digestion and choose the appropriate glass assembly. 

    Application multiplicity
  • Drip tray for convenient and safe storage of the suction modules. Save bench space and store the rack in the cooling position. 

  • Individual operation of each heating chamber. Manual temperature setting are infinitely variable from level 1 to 10.  

    Select the suction module that suits your need best.

    • Standard: suitable for most applications
    • With condensate trap: perfect for aqueous samples
    • Suction module with capillary funnels: to accelerate the digestions 
    Perfect fit
  • Operation is safe and lifetime of the fume hood is extended. A sealed suction system captures harmful fumes and the Scrubber K-415 neutralizes them. 


Compare the SpeedDigester K-425 / K-436 / K-439

  • SpeedDigester K-425

    • Maximum number of samples:6
    • Display:No
    • Temperature programs:No
    • Scrubber Control:No
    • Temperature range:70 – 580 °C
    • Possibility to have an IQ/OQ:No
  • SpeedDigester K-436

    • Maximum number of samples:12
    • Display:No
    • Temperature programs:No
    • Scrubber Control:No
    • Temperature range:70 – 580 °C
    • Possibility to have an IQ/OQ:No
  • SpeedDigester K-439

    • Maximum number of samples:12
    • Display:Yes
    • Temperature programs:Yes
    • Scrubber Control:Yes
    • Temperature range:50 – 580 °C
    • Possibility to have an IQ/OQ:Yes
Since the system is automated, other jobs in the laboratory can be done while digestion is taking place. The distillation unit has also shown to give good recoveries and precision.P. Shah, Analytical chemist - Butterworth Laboratories, United Kingdom


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From milling to analysis

For more than 50 years BUCHI has been developing outstanding solutions for the determination of Kjeldahl nitrogen and steam-volatile analytes. It is our utmost ambition to understand and meet your personal demands. Our solutions include innovative products for the entire process workflow, bespoke application support, sophisticated data management and professional maintenance. Thousands of satisfied customers all over the world in quality control and R&D laboratories enjoy our comprehensive approach.
  • Environmental Analysis

    Total Kjeldahl Nitrogen (TKN), phosphate, Chemical Oxygen Demand (COD), heavy metals

    Environmental Analysis
  • Food

    Protein, Non-Protein Nitrogen (NPN), casein (NCN), hydroxyproline