Stuart SM27 Portable Magnetic Stirrer

Overview

The Stuart SM27 Portable Magnetic Stirrer is an engineered solution for reliable, low-power magnetic agitation in resource-constrained or mobile laboratory environments. Designed around a permanent-magnet rotor driven by a brushless DC motor, the SM27 operates on the principle of rotating magnetic field coupling—inducing torque on ferromagnetic or PTFE-coated stir bars without mechanical contact. Its compact form factor and dual-power architecture (rechargeable battery or AC/DC adapter) enable consistent performance across non-traditional settings: incubators with limited access to mains power, field-deployed quality control stations, agricultural sample prep labs, and teaching laboratories where portability and safety are prioritized. Unlike benchtop stirrers reliant on fixed AC supply, the SM27 maintains stable rotational output across its full 0–1300 rpm range regardless of power source, delivering reproducible mixing for aqueous and low-viscosity solutions up to 1.5 L volume.

Key Features

• True dual-power operation: supports both 4 × D-size alkaline batteries (IEC LR20, 1.5 V each) and external 9 V DC input via interchangeable adapters (UK, EU, or automotive cigarette-lighter interface)
• Robust housing constructed from chemical-resistant ABS polymer, rated for incidental exposure to common solvents, dilute acids, and bases
• Precise analog speed control with calibrated dial offering smooth, stepless adjustment from standstill to maximum 1300 rpm
• Optimized thermal management: passive cooling design ensures stable motor performance during extended operation (>600 h nominal battery life at mid-range speeds)
• Low electromagnetic interference (EMI) profile—validated for use inside CO₂ incubators and near sensitive instrumentation such as pH meters and balances
• Integrated safety circuitry prevents motor stall damage and automatically limits current draw during high-load conditions

Sample Compatibility & Compliance

The SM27 is validated for homogeneous mixing of aqueous buffers, saline solutions, cell culture media, and low-viscosity reagents (dynamic viscosity < 50 mPa·s). It accommodates standard cylindrical glass or plastic vessels (minimum diameter 40 mm, max height 120 mm) and is compatible with all commercially available PTFE- or glass-coated stir bars ≤ 30 mm in length. While not certified for hazardous location use (e.g., ATEX or IECEx), the device complies with essential requirements of the EU Low Voltage Directive 2014/35/EU and Electromagnetic Compatibility Directive 2014/30/EU. Its battery-powered mode satisfies ISO/IEC 17025 clause 5.5.2 regarding equipment suitability for field-based testing when traceable calibration records are maintained.

Software & Data Management

The SM27 is a standalone analog instrument with no embedded firmware, network interface, or data logging capability. This design intentionally eliminates software validation burden and aligns with GLP and GMP Annex 11 principles for “simple devices” where operational parameters are directly observable and manually recorded. Users maintain full audit trail integrity by documenting speed setting, duration, vessel type, and ambient conditions in paper or electronic lab notebooks per 21 CFR Part 11-compliant systems. Optional accessories—including calibrated stir bar sets and NIST-traceable tachometer verification tools—are available to support IQ/OQ protocols during installation qualification.

Applications

• Routine preparation of microbiological growth media in biosafety cabinets or transportable field labs
• Homogenization of soil extracts and water samples prior to filtration or spectrophotometric analysis
• Controlled dissolution testing of pharmaceutical excipients under variable temperature conditions (e.g., inside environmental chambers)
• Student-led experiments in undergraduate chemistry and biology curricula requiring fail-safe, low-voltage agitation
• QC sampling workflows in food processing facilities where electrical outlets are inaccessible or explosion-proofing is impractical
• Pre-analytical mixing of clinical specimens (e.g., whole blood anticoagulant blends) in point-of-care diagnostic setups

FAQ

Can the SM27 operate inside a CO₂ incubator at 37 °C and 5% CO₂?
Yes—the ABS housing and sealed motor assembly are rated for continuous operation within standard incubator environments; no condensation ingress or material degradation has been observed after 1000+ hours of validation testing.
Is the included 25 mm stir bar chemically inert for use with 1 M NaOH?
The PTFE coating provides resistance to concentrated alkalis up to 80 °C; however, prolonged exposure above 60 °C may accelerate surface wear—verify compatibility per ASTM D1711 before extended use.
Does the SM27 meet FDA requirements for use in regulated pharmaceutical manufacturing?
As a Class I general-purpose laboratory device, it requires user-defined risk assessment and documented calibration against traceable standards per USP ; no factory-installed software necessitates 21 CFR Part 11 validation.
What is the recommended recalibration interval for speed accuracy?
Annual verification using a handheld optical tachometer is advised; deviation exceeding ±3% of setpoint at any speed warrants adjustment per Stuart Service Bulletin SB-SM27-REV2.
Can the unit be cleaned with 70% ethanol without damaging the control dial?
Yes—wipe only with lint-free cloth dampened with ethanol; avoid pooling liquid near the potentiometer shaft to prevent contact oxidation over time.