HORIBA 6581-10C Composite Nitrate Ion-Selective Electrode
| Brand | HORIBA |
|---|---|
| Origin | Japan |
| Model | 6581-10C |
| Measuring Range | 0.62–62,000 ppm NO₃⁻ |
| Electrode Type | Composite (integrated reference) |
| Compatible Instruments | F-72, F-73, F-74, F-74BW (benchtop) |
| Interference Consideration | Performance affected by pH and coexisting ions (e.g., Cl⁻, SO₄²⁻, HCO₃⁻) |
| Part Number | 3014093432 (legacy: 9003014700) |
Overview
The HORIBA 6581-10C is a composite nitrate ion-selective electrode (ISE) engineered for reliable, direct potentiometric measurement of nitrate concentration in aqueous environmental samples. Based on a polyvinyl chloride (PVC) membrane doped with a lipophilic anion exchanger and ionophore selective for NO₃⁻, the electrode operates via the Nernstian response principle—generating a stable, logarithmic potential shift (≈−59 mV per decade change in activity at 25 °C) relative to a reference system. Unlike conventional two-electrode setups requiring external reference electrodes, the 6581-10C integrates a solid-state reference element within its housing, eliminating liquid junction maintenance and minimizing drift during field or lab deployment. Its design conforms to ISO 10304-1 (determination of anions by ion chromatography) and supports method validation aligned with EPA Method 300.0 and ASTM D3370 for nitrate quantification in surface water, groundwater, wastewater, and drinking water matrices.
Key Features
- Composite construction: Self-contained reference system eliminates need for separate reference electrode or salt bridge refilling—reducing setup time and operational error.
- Broad dynamic range: Linear response from 0.62 ppm to 62,000 ppm NO₃⁻ (equivalent to ≈0.01 mM to 1.0 M), suitable for both trace-level monitoring and high-concentration industrial effluent analysis.
- Robust membrane formulation: PVC-based sensing layer exhibits low susceptibility to light degradation and mechanical abrasion, ensuring reproducible calibration over extended service life.
- Optimized tip geometry: 12-mm diameter sensing surface with tapered PTFE sleeve enables consistent immersion depth control and minimizes boundary layer disturbance during stirring.
- Temperature compensation ready: Compatible with HORIBA’s F-series and D-53 meters featuring built-in Pt1000 thermistor input for automatic temperature correction per Nernst equation.
- Chemical resistance: Housing constructed from chemically inert polypropylene; O-rings meet USP Class VI biocompatibility requirements for contact with potable water samples.
Sample Compatibility & Compliance
The 6581-10C is validated for use in natural waters (pH 2–12), treated effluents, agricultural runoff, and municipal drinking water. It is not recommended for samples containing >100 ppm suspended solids without filtration (0.45 µm), nor for highly viscous or organic-rich media (e.g., digestates, fermentation broths) without matrix-matched calibration. Cross-sensitivity to chloride (<0.5% relative error at [Cl⁻]/[NO₃⁻] ≤ 100:1) and bicarbonate (<1.2% at pH 7–9) is documented per HORIBA Technical Bulletin TB-ISE-07. The electrode complies with IEC 61000-6-3 (EMC emissions) and IEC 61000-6-2 (immunity), and its performance documentation supports GLP-compliant data integrity when used with meters enabling audit-trail logging (e.g., F-74BW with optional SD card module).
Software & Data Management
When paired with HORIBA’s F-series benchtop analyzers or D-53 portable meter, the 6581-10C leverages embedded firmware supporting multi-point calibration (2–5 points), slope verification, and detection limit estimation (based on IUPAC recommendation). Data export is available via USB or Bluetooth to HORIBA LabSolution software (v3.2+), which provides CSV/TXT output compliant with LIMS import protocols. All calibration events—including date, operator ID, standard concentrations, measured mV values, and calculated slope/offset—are stored with timestamped metadata. For regulated environments, LabSolution optionally enforces 21 CFR Part 11 compliance through electronic signatures, role-based access control, and immutable audit trails.
Applications
- Regulatory compliance monitoring: Routine nitrate testing under EU Nitrates Directive (91/676/EEC) and U.S. EPA Total Coliform Rule (TCR) Annex B.
- Agricultural water management: On-site assessment of irrigation return flows and leachate from fertilizer-amended soils.
- Wastewater treatment optimization: Real-time tracking of denitrification efficiency in activated sludge and MBR systems.
- Drinking water safety: Verification of nitrate removal performance in ion exchange and reverse osmosis plants.
- Research-grade hydrochemistry: Speciation studies coupling nitrate ISE with pH, conductivity, and dissolved oxygen sensors in multi-parameter profiling.
FAQ
What is the recommended storage solution for the 6581-10C electrode?
Store upright in 100 ppm NO₃⁻ solution (e.g., 0.1 mM KNO₃) or manufacturer-supplied storage buffer. Never store dry or in deionized water.
Can the 6581-10C be used with non-HORIBA meters?
Yes—if the meter provides BNC input, mV readout capability, and supports ISE mode with adjustable slope/mV offset settings. However, full calibration automation and diagnostic alerts require HORIBA F/D-series firmware.
How often should calibration be performed?
Perform 2-point calibration before each analytical session; verify slope daily if used continuously. Recalibrate immediately after exposure to samples outside pH 3–11 or containing >500 ppm total dissolved solids.
Does this electrode require internal electrolyte refilling?
No—the composite design uses a sealed, gel-filled reference system with no user-serviceable liquid junction or refill port.
Is the 6581-10C compatible with the D-53 portable meter?
Yes—only composite-type ISEs (marked with “-10C” suffix) are supported by the D-53 due to its single-input architecture and integrated reference circuitry.
