Specifications

Complete specifications for COD digestion tubes. Items marked Customizable available upon request.

Capacity (ml)	Outer Diameter (mm)	Height (mm)	Typical Use
20	25	80	Micro samples, low COD
30	30	95	Routine COD (recommended)
50	38	120	Routine COD
100	48	150	Large volume, high COD
200	60	180	Large volume, industrial wastewater

Custom sizes available upon request.

📌 Customization Options:
• Material Upgrade: PFA (translucent, visible contents, lower metal leaching)
• Custom Sizes: Non-standard capacities and diameters available
• Cap Configuration: PTFE screw caps or sealing plugs available
• Custom specifications available upon request — consult our technical team

Product Description

I. Overview

The COD digestion tube is precision-machined from high-purity PTFE resin, specifically designed for Chemical Oxygen Demand (COD) determination. Offering exceptional chemical resistance, non-stick properties, and wide temperature tolerance for water, wastewater, and surface water sample digestion.

Compared to traditional glass COD tubes, PTFE offers significant advantages in chemical resistance — compatible with concentrated sulfuric acid, potassium dichromate, silver sulfate, and other strong oxidizing digestion reagents — without surface degradation or sample contamination. PTFE's non-stick properties ensure easy sample transfer and effortless cleaning.

Available in 20ml, 30ml, 50ml, 100ml, and 200ml sizes — compatible with all standard COD digesters and reflux systems. Widely used in environmental monitoring, wastewater treatment, and water quality analysis.

II. Core Performance Parameters

Purity: High-purity PTFE with ultra-low metal leaching (Pb, U < 0.01ppb)
Operating Temperature: -196℃ ~ 260℃, short-term up to 300℃
Surface Energy: 18.5 mN/m (lowest among solid materials)
Chemical Resistance: Resistant to conc. H₂SO₄, K₂Cr₂O₇, Ag₂SO₄, strong alkalis, organic solvents
Surface: Non-stick, minimal sample residue, easy to clean
Sterilization: Autoclavable (121℃, 2bar) or dry heat sterilization

III. Material & Workmanship

Manufactured from imported high-purity PTFE resin using precision machining in cleanroom environments — ensuring a dense, smooth, dimensionally accurate product. Both inner and outer surfaces are smooth with no bubbles or burrs for minimal sample residue.

Each product undergoes rigorous visual and dimensional inspection to ensure precision and surface quality.

Applications

Typical Applications

Chemical Oxygen Demand

COD determination in water, wastewater, surface water, groundwater

Water Quality Monitoring

WWTP influent/effluent, industrial wastewater, domestic sewage

Environmental Monitoring

Organic pollution assessment in rivers, lakes, oceans

Process Control

COD monitoring and control in wastewater treatment

Research

Water treatment technology research, pollutant degradation studies

Method Validation

New COD method development and validation

Industries

Environmental Monitoring Water quality analysis, pollution source monitoring
Wastewater Treatment Process control, discharge monitoring
Pharmaceutical Wastewater treatment, water quality monitoring
Food Industry Wastewater treatment, environmental compliance
Research Water treatment research, environmental science

Chemical	PTFE Compatibility	Recommended Temperature	Notes
Conc. H₂SO₄ (98%)	✅ Fully Compatible	≤ 250℃	Handle with care when digesting
Potassium Dichromate	✅ Fully Compatible	≤ 200℃	Strong oxidizer — use PPE
Silver Sulfate	✅ Fully Compatible	≤ 200℃	Catalyst — routine use
Mercury Sulfate	✅ Fully Compatible	≤ 200℃	Masking agent — handle with care
NaOH (50%)	✅ Fully Compatible	≤ 200℃	Safe handling required for concentrated alkalis
Organic Solvents	✅ Fully Compatible	≤ Solvent BP	Ensure ventilation and fire safety

Selection Guide

I. By Sample Volume

Sample Volume	Recommended Capacity	Typical Use
< 10ml	20ml	Micro samples, low COD
10ml ~ 25ml	30ml	Routine COD (recommended)
25ml ~ 40ml	50ml	Routine COD
40ml ~ 80ml	100ml	Large volume, high COD
80ml ~ 150ml	200ml	Large volume, industrial wastewater

II. By Digestion Method

Reflux Digestion: 30ml or 50ml — compatible with standard reflux systems
Closed Vessel Digestion: 20ml or 30ml — compatible with COD digesters
Rapid Digestion: 20ml — compatible with rapid COD digesters

💡 Selection Tip: 30ml is the most common lab size — suitable for most standard COD methods. Choose this as your default.
Tube capacity should be slightly larger than the combined sample and reagent volume to allow boiling space.
For high salinity or high concentration samples, choose a larger capacity tube to prevent spillover during digestion.
For low-temperature storage or long-term preservation of digested samples, choose tubes with PTFE screw caps.

Operation & Maintenance

User Guide

Standard operating guidelines for COD digestion tubes. Proper use and maintenance ensure digestion efficiency and product longevity.

I. Pre-use Preparation

Inspect the tube for cracks, deformation, and smooth inner surface
Clean with ultrapure water or 10% nitric acid to remove manufacturing residues
For trace analysis applications, soak in 10% nitric acid for 24 hours, rinse thoroughly with ultrapure water, and dry
Confirm tube compatibility with the digester or reflux system

II. Digestion Operation

Add the accurately measured water sample to the digestion tube
Sequentially add potassium dichromate solution and silver sulfate-sulfuric acid reagent
Place the tube in the COD digester or reflux system
Set digestion temperature and time according to the standard method (typically 165℃, 15-20min)
After digestion, remove the tube and cool to room temperature

III. Post-digestion Treatment

Transfer the digestion solution to a volumetric flask or colorimetric tube
Rinse the tube inner wall with ultrapure water multiple times for complete transfer
PTFE's non-stick surface makes rinsing easy — 2-3 rinses are sufficient

IV. Cleaning & Maintenance

Rinse with ultrapure water after use — PTFE's non-stick surface makes cleaning easy
Stubborn residues may be soaked in dilute nitric acid
Never use hard brushes or abrasives — they may scratch the inner surface
Sterilization: Autoclave (121℃, 15-20min) or dry heat sterilization

V. Important Notes

PTFE is relatively soft — avoid dropping or impact with hard objects
Do not use for high-temperature ashing (> 400℃)
Digestion temperature should not exceed 260℃
Avoid contact with molten alkali metals (Na, K) and elemental fluorine

💡 From a Seasoned Lab Technician: "Correct addition sequence — cool before titration" — Reagent addition sequence should strictly follow the standard method (e.g., HJ 828): water sample → potassium dichromate → slowly add silver sulfate-sulfuric acid — prevents localized overheating and splashing.
Do not open the digester or reflux system frequently during digestion — this may affect temperature stability and results.
After digestion, always cool to room temperature before titration or photometric determination — high temperature affects measurement accuracy.
PTFE's non-stick properties make digestion solution transfer and tube cleaning easy — but mix thoroughly before titration.

Care & Notes

Show care & notes

⚠️ Safety & Compliance Checklist

Chemical Safety

All digestion operations must be performed in a fume hood — concentrated sulfuric acid and potassium dichromate are highly corrosive and oxidizing

Thermal Safety

Digestion tubes are hot during operation — use heat-resistant gloves

PPE

Safety goggles, lab coat, acid/alkali resistant gloves required

Compliance

COD determination should follow HJ 828, ISO 6060, or other standard methods

COD Digestion Tube

Specifications

Product Description

I. Overview

II. Core Performance Parameters

III. Material & Workmanship

Applications

Chemical Oxygen Demand

Water Quality Monitoring

Environmental Monitoring

Process Control

Research

Method Validation

Selection Guide

I. By Sample Volume

II. By Digestion Method

User Guide

I. Pre-use Preparation

II. Digestion Operation

III. Post-digestion Treatment

IV. Cleaning & Maintenance

V. Important Notes

Care & Notes

Chemical Safety

Thermal Safety

PPE

Compliance

Need COD Digestion Tubes?

COD Digestion Tube

Specifications

Product Description

I. Overview

II. Core Performance Parameters

III. Material & Workmanship

Applications

Chemical Oxygen Demand

Water Quality Monitoring

Environmental Monitoring

Process Control

Research

Method Validation

Selection Guide

I. By Sample Volume

II. By Digestion Method

User Guide

I. Pre-use Preparation

II. Digestion Operation

III. Post-digestion Treatment

IV. Cleaning & Maintenance

V. Important Notes

Care & Notes

Chemical Safety

Thermal Safety

PPE

Compliance

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