C. Gerhardt KI 11/26 Infrared Digestion Furnace for Kjeldahl Flasks

Overview

The C. Gerhardt KI 11/26 Infrared Digestion Furnace is a purpose-engineered thermal digestion system designed specifically for Kjeldahl flasks used in classical wet-chemical nitrogen determination (ISO 8968, AOAC 984.13, DIN EN ISO 14891). Unlike convection or oil-bath heating methods, this furnace employs focused infrared radiation to deliver rapid, uniform, and highly reproducible heat transfer directly to the flask walls and sample matrix. Its robust stainless-steel construction and precisely calibrated IR emitters ensure stable temperature maintenance across all six independent heating zones — critical for achieving consistent digestion kinetics and minimizing inter-sample variability. As one of C. Gerhardt’s longest-standing product lines, the KI series reflects decades of empirical optimization for routine laboratory environments where reliability, ease of operation, and compliance with standardized digestion protocols are paramount.

Key Features

• Six independently controllable infrared heating positions, each with dedicated on/off switch and analog temperature adjustment (0–650 °C range)
• Optimized IR emitter geometry ensures homogeneous thermal distribution around standard 500 mL and expanded-neck 750 mL Kjeldahl flasks
• Integrated centralized exhaust manifold with low-backpressure design minimizes acid vapor recondensation and reduces risk of overflow during high-boiling digestions
• Compact footprint (900 × 250 × 300 mm) and lightweight chassis (15 kg) facilitate placement under standard fume hoods or in space-constrained prep areas
• Industrial-grade 400 V, 3-phase + neutral power supply enables stable operation under continuous load; total rated power: 3480 W
• No moving parts or consumable heating elements — engineered for long-term durability and minimal preventive maintenance

Sample Compatibility & Compliance

The KI 11/26 is validated for use with sulfuric acid-based digestion mixtures (e.g., H₂SO₄ + catalysts such as CuSO₄/K₂SO₄) applied to biological, agricultural, food, feed, and environmental samples per official Kjeldahl methodology. It accommodates both standard tapered-neck and wide-mouth 500 mL flasks, as well as 750 mL flasks with expanded necks for enhanced reflux control during volatile sample digestion. The furnace meets essential safety and electromagnetic compatibility requirements per EU directives (2014/30/EU EMC Directive, 2014/35/EU Low Voltage Directive) and conforms to DIN EN 61000-6-3 (emission limits) and DIN EN 61000-6-2 (immunity). While not a data-acquisition instrument, its mechanical consistency supports GLP-compliant workflows when paired with documented SOPs and manual temperature verification using traceable calibrated thermocouples.

Software & Data Management

The KI 11/26 operates as a stand-alone hardware unit without embedded microprocessor control or digital interface. Temperature regulation is achieved via analog potentiometers per position, ensuring operational simplicity and immunity to software failure modes. No firmware, drivers, or connectivity protocols are required. Laboratories integrating this furnace into regulated environments (e.g., ISO/IEC 17025-accredited testing labs or FDA-regulated QC facilities) typically log operating parameters manually — including start time, setpoint, flask identification, and observed reflux behavior — within bound lab notebooks or LIMS-integrated electronic batch records. For full 21 CFR Part 11 compliance, external temperature dataloggers with audit-trail capability may be deployed per position, though such validation falls outside the scope of the base instrument.

Applications

This furnace serves as a core digestion module in laboratories performing routine nitrogen analysis across diverse sectors: protein quantification in dairy and meat products (AOAC 981.10); crude protein estimation in cereals and forage (ISO 5983-1); total Kjeldahl nitrogen (TKN) determination in wastewater and soil extracts (EPA 351.2, ISO 11261); and nitrogen content verification in pharmaceutical excipients per USP . Its predictable 2-hour digestion cycle — significantly faster than conventional hot plates or sand baths — improves throughput without compromising completeness of organic matrix decomposition. The absence of liquid heating media eliminates cross-contamination risks and simplifies cleaning between batches.

FAQ

Is the KI 11/26 compatible with automated distillation systems?
Yes — it is fully interoperable with C. Gerhardt’s Kjeltec™ and other third-party Kjeldahl distillation units, provided flasks conform to standard taper (24/40 or 29/32) and height specifications.
Does the furnace support programmable ramp/soak temperature profiles?
No — it features fixed analog temperature control per position; for programmable thermal profiles, consider the Kjeldatherm or Turbotherm series.
What safety certifications does the unit carry?
It bears the CE marking and complies with EN 61010-1 (Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use).
Can I use glass digestion tubes instead of Kjeldahl flasks?
Not recommended — the heater geometry and thermal focus are optimized exclusively for conical-bottom Kjeldahl flasks; tube geometry induces uneven heating and potential breakage.
Is routine calibration required?
While no formal recalibration is mandated, periodic verification of setpoint accuracy using a NIST-traceable surface thermometer or IR pyrometer is advised per internal quality procedures.