MKN 85-1 Magnetic Stirrer

Overview

The MKN 85-1 Magnetic Stirrer is a precision-engineered benchtop mixing instrument designed for consistent, low-shear agitation of liquid samples in analytical, quality control, and research laboratories. It operates on the principle of magnetic coupling: a rotating permanent magnet beneath the work surface generates a time-varying magnetic field that induces synchronous rotation of a magnetically responsive stir bar immersed in the sample vessel. This contactless drive mechanism eliminates mechanical shaft penetration, ensuring leak-tight operation, minimal contamination risk, and compatibility with sealed or sterile containers. Engineered for reliability in routine laboratory workflows, the unit integrates a brushless DC motor—delivering quiet operation (<45 dB(A) at 1 m), extended service life, and stable rotational output across its full speed range without torque drop-off.

Key Features

• Brushless DC motor architecture ensures zero carbon brush wear, reduced electromagnetic interference, and maintenance-free long-term performance.
• Continuously variable speed control (0–2400 rpm) via calibrated rotary encoder, enabling precise replication of mixing intensity for method standardization.
• High-strength neodymium magnet assembly optimized for torque transmission—capable of driving PTFE- or glass-coated stir bars in vessels up to 3 L volume, even under moderate viscosity conditions (up to ~500 mPa·s).
• Chemically resistant ceramic-coated top plate withstands incidental spills of common solvents, acids, and bases; surface hardness exceeds 800 HV for abrasion resistance.
• Integrated thermal cut-off circuitry automatically deactivates the unit if internal temperature exceeds safe operational limits, complying with IEC 61010-1 safety requirements for laboratory equipment.
• Compact footprint (160 × 140 × 95 mm) and lightweight design (1.8 kg) facilitate placement within fume hoods, laminar flow cabinets, or crowded benchtop environments.

Sample Compatibility & Compliance

The MKN 85-1 supports standard laboratory glassware including beakers (50–2000 mL), Erlenmeyer flasks, and cylindrical reaction vessels. Stir bar selection must match vessel geometry and fluid rheology—recommended configurations include cross-shaped bars for high-viscosity media and oval bars for low-volume micro-reactions. The device conforms to GB/T 25107–2010 (Chinese national standard for magnetic stirrers) and meets essential safety requirements of IEC 61010-1:2010 (Edition 3) for electrical equipment used in laboratory settings. While not certified for GMP or GLP environments out-of-the-box, its stable speed control and absence of moving parts beyond the stir bar make it suitable for use in SOP-defined mixing steps where auditability of parameters (e.g., speed, duration) is maintained externally.

Software & Data Management

The MKN 85-1 is a standalone analog-controlled instrument with no embedded firmware, digital interface, or data logging capability. All operational parameters—including set speed—are adjusted manually and not recorded internally. For laboratories requiring traceable mixing protocols, integration with external timers or programmable lab automation systems is recommended. When deployed in regulated environments (e.g., pharmaceutical QC per USP Analytical Instrument Qualification), users must establish documented procedures for periodic verification of speed accuracy using a calibrated tachometer (e.g., ASTM E1577–22), as well as visual inspection of stir bar integrity and top-plate surface condition prior to each use.

Applications

• Homogenization of aqueous and organic solutions during titration, pH adjustment, or reagent dissolution.
• Supporting crystallization studies by maintaining supersaturation uniformity during controlled cooling.
• Facilitating solid-liquid extractions in environmental testing (e.g., EPA Method 3510C).
• Pre-mixing of calibration standards and reference materials in clinical chemistry and food testing labs.
• Enabling gentle suspension of cell cultures or particulate suspensions in microbiological and material science applications—provided shear-sensitive components are verified compatible at selected rpm.

FAQ

Is the MKN 85-1 suitable for use with corrosive solvents such as concentrated HCl or NaOH?

Yes—the ceramic-coated plate and PTFE-encapsulated stir bars resist degradation from common inorganic acids and alkalis at ambient temperatures; however, prolonged exposure to hot fuming nitric acid or molten alkali hydroxides is not recommended.
Can this stirrer maintain constant speed when viscosity increases during a reaction?

It maintains set speed under load up to ~500 mPa·s; beyond that, observable speed droop may occur depending on stir bar geometry and vessel fill level—users should validate performance empirically for high-viscosity applications.
Does the unit include a temperature control function?

No—temperature regulation requires an external hotplate or water bath; the MKN 85-1 is strictly a stirring-only device.
What is the expected service life of the brushless motor under continuous operation?

Rated for >20,000 hours of operation at nominal load, assuming ambient temperature ≤35 °C and adequate ventilation around the rear vent grille.
Are replacement stir bars available in standardized dimensions?

Yes—MKN supplies ISO-compliant stir bars in lengths from 10 mm to 60 mm, with diameter options of 4 mm and 6 mm, all featuring sintered NdFeB cores and dual-layer PTFE/glass encapsulation.