HJ MT-303 Microbial Limit Tester

Overview

The HJ MT-303 Microbial Limit Tester is a compact, semi-automatic membrane filtration system engineered for compliance with pharmacopoeial standards—including USP <61>, EP 2.6.12, and ChP Appendix XI J—governing microbial enumeration and limit testing of non-sterile pharmaceuticals, water for injection (WFI), purified water, medical devices, food matrices, and environmental samples. It operates on the principle of vacuum-assisted membrane filtration: liquid samples are drawn through sterile, low-protein-binding cellulose ester or mixed cellulose ester membranes (typically 0.45 µm or 0.22 µm pore size), retaining viable microorganisms on the filter surface. Following filtration, the membrane is transferred onto appropriate solid culture media (e.g., Soybean–Casein Digest Agar or Sabouraud Dextrose Agar) and incubated under controlled conditions for colony formation and enumeration. Unlike benchtop vacuum pumps requiring external filtration manifolds and collection flasks, the MT-303 integrates a sealed, oil-free diaphragm pump and triple-head stainless steel manifold into a single footprint—eliminating risk of cross-contamination, reducing setup time, and enabling operation directly inside laminar flow hoods without spatial compromise.

Key Features

• Triple independent filtration channels with individual on/off valves—enabling parallel processing of up to three samples while maintaining full operational flexibility and preventing cross-channel pressure interference.
• Integrated oil-free diaphragm pump delivering ≥300 mL/min flow rate and stable 60 kPa vacuum—ensuring rapid, consistent filtration across variable sample viscosities and particulate loads without lubricant contamination or maintenance downtime.
• AISI 304 stainless steel construction with electropolished mirror-finish surfaces—meeting ISO 14644-1 Class 5 cleanroom compatibility requirements and supporting routine disinfection with 70% ethanol, hydrogen peroxide vapor, or sodium hypochlorite solutions.
• Modular filter cup design accommodating standard 100 mL reusable stainless steel or autoclavable polycarbonate cups—compatible with commercially available sterile filter membranes and regulatory-compliant microbiological test kits (e.g., Millipore Steritop®, Sartorius Minisart® NML).
• Compact form factor (28 × 18 × 14 cm) optimized for placement within ISO Class 5 laminar airflow workstations—reducing footprint by >40% compared to conventional three-pump manifold systems.
• Dual-use functionality: serves both as a dedicated microbial limit tester and as a standalone high-efficiency vacuum source for other laboratory filtration applications (e.g., solvent recovery, buffer degassing, or sample concentration).

Sample Compatibility & Compliance

The MT-303 supports filtration of aqueous and low-viscosity aqueous-organic mixtures—including purified water, WFI, saline solutions, buffered preparations, and clarified biological extracts—within defined flow and particulate load limits. It is validated for use in GLP- and GMP-regulated environments where traceability and audit readiness are critical. While the instrument itself does not generate electronic records, its mechanical operation aligns with FDA 21 CFR Part 11 principles when paired with paper-based or LIMS-integrated logbooks documenting sample ID, operator, date/time, membrane lot, incubation parameters, and colony counts. The stainless steel manifold complies with ASTM A276 and EN 10088-1 for corrosion resistance in repeated exposure to disinfectants and culture media residues.

Software & Data Management

The MT-303 is a hardware-only platform with no embedded firmware or proprietary software. All operational parameters—including filtration duration, vacuum onset timing, and sample identification—are manually recorded per internal SOPs or integrated into existing laboratory information management systems (LIMS) via standardized CSV or PDF report templates. This architecture ensures full data ownership, eliminates vendor lock-in, and simplifies 21 CFR Part 11 validation pathways for regulated users. Optional accessories include calibrated digital timers, vacuum gauges with analog output (4–20 mA), and barcode-scannable filter cup labels compatible with enterprise-grade LIMS workflows.

Applications

• Pharmaceutical QC laboratories performing routine microbial enumeration of purified water and WFI per USP <1231> and Ph. Eur. 2.2.32.
• Biologics and sterile product manufacturers conducting pre-filtration bioburden assessment prior to terminal sterilization or aseptic processing.
• Medical device manufacturers validating cleaning efficacy and verifying endotoxin-free rinse water per ISO 11737-1 and AAMI ST72.
• Food safety labs assessing total aerobic microbial count (TAMC) and total combined yeasts/molds count (TYMC) in beverages and liquid supplements per ISO 4833-1 and AOAC 977.27.
• Environmental monitoring programs in cleanrooms and isolators, where rapid turnaround of settle plate rinsates or air sampler eluates is required.

FAQ

Is the MT-303 compliant with pharmacopoeial methods for microbial limit testing?

Yes—the system implements the membrane filtration method described in USP <61>, EP 2.6.12, and ChP Appendix XI J, provided operators follow validated filter selection, rinsing, and incubation protocols.
Can the stainless steel filter cups be autoclaved?

Yes—AISI 304 cups withstand repeated autoclaving at 121 °C for 20 minutes; however, gaskets and membrane support grids must be verified for thermal stability per supplier specifications.
What vacuum level is required for effective filtration of viscous samples?

For samples with viscosity ≤10 cP (e.g., saline, buffer solutions), 60 kPa is sufficient; higher-viscosity or particulate-laden samples may require pre-dilution or centrifugal clarification to maintain reproducible filtration kinetics.
Does the instrument include built-in data logging or electronic audit trail capabilities?

No—the MT-303 is a mechanical filtration platform. Audit trails must be maintained externally using paper logs or LIMS-integrated workflows per organizational validation protocols.
What maintenance is required for the diaphragm pump?

The oil-free pump requires only periodic inspection of inlet filters and replacement of diaphragms every 12–18 months under typical usage (≤4 hrs/day); no lubrication or calibration is needed.