807 Dosing Unit

Importance of the Topic

Precise and reproducible liquid handling is fundamental to analytical chemistry workflows, including titration, sample transfer, dosing of reagents and QA/QC routines. A robust dosing system reduces operator error, lowers reagent consumption, and improves overall data quality in laboratories ranging from research institutions to industrial analytics.

Objectives and Overview

This document presents the Metrohm 807 Dosing Unit, a versatile piston-type buret designed for integration with Dosino dosing drives (700/800 series). It describes the model variants, mechanical construction, operating principles, safety and maintenance guidelines, and performance specifications.

Methodology and Instrumentation

The 807 Dosing Unit consists of:

• Transparent PETG or PVDF housing with data chip and coding magnets for automatic volume recognition
• Piston assembly: ETFE-coated piston in borosilicate or ETFE cylinder (volumes 2, 5, 10, 20, 50 mL)
• Cylinder base with integrated ceramic valve disc and distributor disc for four flexible ports (dosing, fill, waste, vent)
• Centering tube to rotate and actuate the internal stopcock via Dosino drive

Installation involves greasing sliding surfaces, mounting the adsorber tube for moisture or CO₂ control, attaching aspiration and dosing tubing, and configuring buret tips (open or antidiffusion) according to application requirements. The unit interfaces with Metrohm titration and dosing systems via Dosino drives, enabling PREP (filling) and EMPTY (draining) automation.

Main Results and Discussion

Performance tests show:

• Typical systematic deviations: ±0.3–0.5% or 6–50 µL depending on cylinder size
• Compliance with ISO 8655-3 limits (systematic error ≤0.2% for 10–50 mL)
• Efficient bubble trapping prevents air pockets from affecting precision

Key operational insights include the importance of correct housing locking, leak-proof M6 connections tightened with the special wrench, and regular PREP/EMPTY cycles to maintain chemical resistance and accuracy.

Benefits and Practical Applications

The 807 Dosing Unit delivers:

• High precision and reproducibility in titrations and micro-dosing tasks
• Visible piston movement and stopcock position through transparent housing
• Integrated data storage of reagent identity, concentration and tubing parameters
• Flexible port configuration for multi-channel workflows and waste collection

Applications span Karl Fischer titration, potentiometric titrations, sample dilutions, reagent addition in automated analyzers, and repetitive pipetting in process control.

Future Trends and Applications

Emerging directions include integration of smart sensors for real-time monitoring of reagent purity and volume, IoT connectivity for remote management, advanced materials to broaden chemical compatibility, and miniaturization for microfluidic platforms. Machine-learning-driven error detection and adaptive dosing protocols will further enhance reliability.

Conclusion

The Metrohm 807 Dosing Unit represents a highly accurate, modular solution for automated liquid handling in analytical labs. Its transparent design, integrated data management and compliance with international standards make it a reliable component in titration and dosing systems. Proper installation, routine maintenance and adherence to safety instructions ensure long-term performance and reproducibility.

Reference

No external references were provided in the source document.