Leici DWS-51 Sodium Ion Meter

Overview

The Leici DWS-51 Sodium Ion Meter is a dedicated potentiometric analyzer engineered for precise measurement of sodium ion activity in low-conductivity aqueous samples—particularly critical in high-purity water monitoring for power generation, semiconductor manufacturing, and pharmaceutical water systems. Based on the Nernst equation, the instrument measures the potential difference between a selective sodium ion-selective electrode (ISE) and a reference electrode, converting the resulting millivolt signal into logarithmic pNa units (pNa = –log₁₀[Na⁺]) and linear sodium concentration values in µg/L. Its design prioritizes stability and reproducibility in environments where trace sodium contamination (<10 µg/L) directly impacts boiler tube integrity or ultrapure water (UPW) resistivity. The DWS-51 operates as a benchtop electrochemical analyzer with fixed two-electrode architecture and does not integrate digital communication protocols or automated fluid handling.

Key Features

• Segment-type LCD display optimized for legibility under laboratory lighting conditions, showing both pNa and [Na⁺] simultaneously without screen clutter
• Dual-parameter output: direct readout of pNa (0.00–9.00) and corresponding sodium concentration (2.3×10⁻² to 2.3×10⁷ µg/L), enabling immediate interpretation across regulatory reporting formats
• Manual temperature compensation (0–60 °C range) using integrated thermistor input—calibrated per ISE response slope requirements per ISO 17025-compliant verification procedures
• Two-point calibration capability supporting both static (immersed electrode in standard solution) and dynamic (flow-through) modes; dynamic operation requires optional DWS-51-1 alkalizing unit to suppress hydrogen ion interference via pH elevation (>10.5)
• Instrument class 0.05 compliance per JJG 757–2015 (Chinese national metrological verification regulation for ion meters), ensuring traceable accuracy for routine QC applications
• Compact form factor (290 × 210 × 95 mm; 1.5 kg) with robust ABS housing suitable for controlled lab environments and mobile field deployment in utility substations

Sample Compatibility & Compliance

The DWS-51 is validated for use with deionized water, condensate, feedwater, steam cycle samples, and dilute saline solutions. It requires sample alkalization (via NaOH or diethylamine addition) when measuring below 10 µg/L to mitigate H⁺ interference—a prerequisite specified in ASTM D4582 and EP 2.2.37 for low-level sodium analysis in high-purity water. While not designed for GMP-regulated environments requiring full 21 CFR Part 11 compliance, its manual calibration logs, fixed measurement range, and stable analog circuitry support GLP-aligned documentation practices when paired with external lab notebooks or LIMS-integrated data entry workflows. CE marking is not applicable; the device meets GB/T 12519–2013 general specifications for analytical instruments manufactured in China.

Software & Data Management

The DWS-51 operates as a standalone analog-digital hybrid instrument with no embedded microprocessor-based software, firmware updates, or USB/RS-232 connectivity. All measurements are displayed in real time on the fixed-segment LCD with no internal memory or data logging capability. Users must manually record readings alongside calibration timestamps, electrode lot numbers, and temperature values to satisfy audit trails required by ISO/IEC 17025 Clause 7.7. For laboratories implementing electronic records, integration is achieved externally—e.g., via digital camera capture of displayed values or manual transcription into validated spreadsheets compliant with ALCOA+ principles (Attributable, Legible, Contemporaneous, Original, Accurate, Complete, Consistent, Enduring, Available).

Applications

• Monitoring sodium breakthrough in mixed-bed ion exchange effluents for thermal power plant water-steam cycles
• Verifying sodium carryover in turbine condensate return systems per ASME PTC 19.11 guidelines
• Quality control of purified water (PW) and water for injection (WFI) during pharmaceutical equipment rinsing validation
• Calibration verification of online sodium analyzers using grab-sample correlation protocols
• Educational laboratories teaching fundamental potentiometry, ISE theory, and Nernstian behavior in aqueous electrolytes

FAQ

Does the DWS-51 support automatic temperature compensation?
No—it provides only manual temperature input via front-panel keypad. Users must measure sample temperature separately and enter it prior to reading acquisition.
Can the DWS-51 measure potassium or chloride ions?
No—it is hardware-configured exclusively for sodium-selective electrodes. No electrode port reconfiguration or firmware adaptation is supported.
Is the DWS-51 compliant with USP or ASTM D1129?
It meets the measurement principle and sensitivity thresholds cited in these standards but lacks documented validation reports or certified conformance certificates required for formal regulatory submission.
What electrode types are compatible with the DWS-51?
Standard BNC-input sodium ISEs and double-junction reference electrodes (e.g., Leici 6801 or Orion 94–02) with liquid-filled KCl junctions; gel-filled or sleeve-type references are not recommended due to increased junction potential drift.
How often should calibration be performed?
Per ASTM D4582, calibration is required before each analytical batch and after every 2 hours of continuous use—or immediately following electrode cleaning, storage, or exposure to high-sodium matrices (>1 mg/L).