Leichi ZDJ-5 Automatic Potentiometric Titrator

Overview

The Leichi ZDJ-5 Automatic Potentiometric Titrator is a modular, benchtop analytical instrument engineered for high-precision volumetric analysis in regulated and research laboratory environments. It operates on the fundamental principle of potentiometric endpoint detection—measuring the potential difference between a reference electrode and an indicator electrode as titrant is incrementally delivered. This enables accurate determination of stoichiometric equivalence points in acid-base, redox, precipitation, and complexometric titrations. In addition to potentiometric mode, the ZDJ-5 supports amperometric (dead-stop) and conductometric titration via interchangeable measurement modules, offering method flexibility without hardware replacement. Its architecture complies with core design conventions for GLP-compliant titration systems, including traceable electrode calibration routines, configurable stirring control, and programmable dosing kinetics—making it suitable for routine QC testing as well as method development in pharmaceutical, petrochemical, metallurgical, and academic laboratories.

Key Features

• Modular three-unit architecture: independent titration unit (burette drive + piston pump), control unit (embedded microprocessor or optional PC-based software interface), and multi-mode measurement unit (potentiometric, amperometric, conductometric)
• Triple-sensor compatibility: simultaneous support for pH/mV/temperature electrodes, polarographic dual-electrode cells, and conductivity cells—enabling cross-validated endpoint confirmation
• Precision burette system with 1/1,500,000 resolution and ±0.03% full-scale volumetric accuracy, calibrated per ISO 8655-3 for piston burettes
• Programmable titration modes including pre-titration, preset-endpoint, blank correction, manual stepwise addition, and user-defined multi-step sequences
• Integrated temperature compensation across all measurement domains (pH, mV, conductivity) using Pt1000-class sensor input with ±0.3 °C accuracy
• Real-time graphical display of titration curves (E vs. V, dE/dV vs. V, or Δ²E/ΔV² vs. V) with automatic inflection-point calculation and derivative peak identification

Sample Compatibility & Compliance

The ZDJ-5 accommodates aqueous and non-aqueous samples within standard laboratory vial formats (50–250 mL capacity), compatible with common titrant solvents including water, ethanol, glacial acetic acid, and mixed organic-aqueous media. Electrode interfaces conform to DIN 19262 and ASTM E2087 standards for reference junction compatibility and liquid junction potential minimization. The instrument meets essential requirements for ISO/IEC 17025-accredited testing laboratories when operated with documented calibration procedures, certified reference materials (e.g., NIST-traceable pH buffers, KCl conductivity standards), and validated electrode maintenance protocols. While not inherently 21 CFR Part 11 compliant in standalone configuration, audit trails and electronic signatures can be implemented via optional PC software with role-based access control and immutable data logging.

Software & Data Management

Local operation is managed through an intuitive LCD interface with menu-driven method setup, real-time curve visualization, and on-device data storage (≥100 titration records). For advanced data handling, optional Windows-compatible software provides comprehensive functionality: method template libraries, customizable report generation (PDF/CSV/XLSX), statistical evaluation of replicate runs (RSD, confidence intervals), and integration with LIMS via ODBC or ASCII export. All raw sensor signals (mV, µS, °C), volume increments, and calculated endpoints are timestamped and stored with metadata—including operator ID, electrode serial number, calibration date, and environmental conditions—to support GLP/GMP documentation requirements.

Applications

• Pharmaceutical QC: assay of active pharmaceutical ingredients (APIs) such as aspirin, chlorhexidine, or sulfonamides via acid-base or redox titration
• Petrochemical analysis: determination of total acid number (TAN) and total base number (TBN) in lubricants and fuels per ASTM D664 and D2896
• Food & beverage testing: titratable acidity in wines, dairy products, and fruit juices; chloride content by Mohr or Volhard methods
• Environmental monitoring: alkalinity and hardness profiling in wastewater and surface water per APHA Standard Methods 2320 and 2340
• Academic research: kinetic studies of slow-reacting systems using controlled-rate titration, or multi-equivalence point resolution in polyprotic acid analysis

FAQ

What electrode types are supported for potentiometric titration?
The ZDJ-5 accepts standard BNC-input pH/mV electrodes with Ag/AgCl or calomel reference systems, as well as combination electrodes with integrated temperature sensors (ATC). Double-junction electrodes are recommended for samples containing sulfides, proteins, or heavy metals.
Can the instrument perform Karl Fischer titration?
No—the ZDJ-5 does not include coulometric or volumetric KF reagent handling, oven integration, or moisture-specific detector circuitry. It is designed for classical electrochemical endpoint detection only.
Is firmware upgradable in the field?
Yes—firmware updates are delivered via USB memory stick and installed through the instrument’s service menu, preserving all user methods and calibration history.
How is calibration traceability maintained?
Calibration certificates for pH, mV, and conductivity modules reference NIST-traceable standards (e.g., SRM 186, SRM 3119); electrode verification follows ISO 17025 clause 5.5.2 for measurement uncertainty estimation.
What safety features prevent over-titration or reagent waste?
The system implements dynamic volume limiting based on preliminary coarse titration, adjustable slope thresholds for endpoint recognition, and automatic stop-on-stability criteria (e.g., <0.1 mV change over 10 s), minimizing excess titrant consumption and electrode exposure time.