MKN 85-1 Stainless Steel Magnetic Stirrer

Overview

The MKN 85-1 Stainless Steel Magnetic Stirrer is a precision-engineered benchtop mixing instrument designed for consistent, contamination-free agitation of liquid samples in analytical, quality control, and research laboratories. It operates on the principle of magnetic coupling: a rotating permanent magnet assembly beneath the work surface induces synchronous rotation of a magnetic stir bar immersed in the sample vessel. This contactless drive mechanism eliminates mechanical shaft seals and bearings—significantly reducing wear, maintenance, and risk of cross-contamination. The unit features a fully passivated 304 stainless steel housing and baseplate, offering superior corrosion resistance against solvents, acids, bases, and cleaning agents—making it suitable for demanding environments including GLP-compliant labs, pharmaceutical process development, and routine QC testing where material compatibility and cleanability are critical.

Key Features

• Fully stainless steel construction (housing, baseplate, and control panel bezel) for long-term durability and ease of decontamination
• Brushless DC motor delivering quiet operation (<45 dB[A] at 1 m), high torque stability across the full speed range, and extended service life with no carbon brush replacement required
• Continuously variable speed control (0–2400 rpm) with analog rotary dial and LED digital speed display for precise repeatability
• Thermally stable platform with integrated overheat protection; automatic shutdown triggered if internal temperature exceeds safe operating limits
• Low-profile design optimized for use under fume hoods or inside environmental chambers; base dimensions: 140 × 140 mm
• Stir bar detection not implemented — operation assumes proper placement and sizing of PTFE- or glass-coated stir bars compatible with vessel geometry and viscosity

Sample Compatibility & Compliance

The MKN 85-1 supports vessels ranging from small 20 mL test tubes to standard 3 L beakers or Erlenmeyer flasks. Its magnetic drive system delivers sufficient torque for low-to-medium viscosity liquids (up to ~500 mPa·s at 1000 rpm with appropriate stir bar selection). Compatibility with aggressive reagents—including 37% HCl, 70% HNO₃, and 50% NaOH—is ensured by the inert stainless steel surface and fluoropolymer-coated stir bar interface. The device conforms to IEC 61010-1:2010 (Edition 3) for safety requirements of electrical equipment for measurement, control, and laboratory use. It carries CE marking indicating compliance with EU electromagnetic compatibility (2014/30/EU) and low-voltage (2014/35/EU) directives. While not intrinsically rated for hazardous locations, its sealed electronics and non-sparking motor make it suitable for general-purpose use in ISO Class 7/8 cleanrooms when paired with appropriate labware.

Software & Data Management

The MKN 85-1 is a standalone analog/digital hybrid instrument with no embedded microprocessor, network interface, or data logging capability. Speed setting and operational status are indicated via front-panel LED display only. As such, it does not support FDA 21 CFR Part 11 electronic record or signature functionality, nor does it generate audit trails. For regulated environments requiring traceable agitation parameters, external validation protocols—such as periodic speed calibration using a certified tachometer and documented SOPs for stir bar selection and vessel positioning—are recommended. Integration with LIMS or ELN systems requires third-party hardware-based signal capture (e.g., pulse-output tachometer + USB DAQ module).

Applications

• Homogenization of buffer solutions, culture media, and reagent dilutions prior to pH measurement or spectrophotometric analysis
• Supporting dissolution testing in pharmaceutical QA/QC per USP , particularly for sink condition maintenance in USP Apparatus 2 (paddle) auxiliary setups
• Facilitating chemical reactions requiring gentle, uniform mixing without introducing air bubbles or shear degradation (e.g., polymerization initiators, enzyme assays)
• Preparation of calibration standards and reference materials where metallic leaching must be avoided—stainless steel construction prevents iron or nickel ion contamination
• Routine use in academic teaching labs due to robustness, intuitive operation, and compatibility with standard borosilicate glassware

FAQ

Is the MKN 85-1 suitable for use with corrosive solvents such as concentrated sulfuric acid?
The stainless steel housing resists splashes and ambient vapor exposure, but direct prolonged contact with >80% H₂SO₄ may cause pitting over time. Always consult chemical compatibility charts for specific concentration/temperature combinations and use secondary containment.
What stir bar size is recommended for optimal performance at 3000 mL volume?
A 40–50 mm elliptical or cross-shaped PTFE-coated stir bar with embedded neodymium magnets is recommended; verify vortex formation and bottom-layer mixing empirically for your vessel geometry and fluid rheology.
Does the unit include overload or stall protection?
Yes—the motor driver circuit incorporates thermal cutoff and current limiting to prevent damage during temporary stall conditions (e.g., viscous sample startup or oversized stir bar).