Portable COD Analyzer

What is the Portable COD Analyzer?

A portable COD analyzer brings sealed-tube digestion and colorimetric reading to the plant or field in a battery-powered case. It provides rapid COD screening away from the laboratory for process checks and surveys.

Overview

The portable system usually comprises a compact two- or four-cell digestion block powered by a car battery or mains adapter and a handheld colorimeter for 16 mm tubes. The chemistry is identical to the laboratory method, so results are directly comparable when the same reagents, digestion time and calibration are used. Ranges typically cover 0 to 150, 0 to 1500 and 0 to 15,000 mg/L, and reading takes seconds after a two-hour digestion and cooling period. Cases hold reagents, tubes, pipettes and the meter, and some colorimeters accept additional parameters such as ammonia, nitrate, phosphate and chlorine, making the kit useful for wider field water testing programmes.

How does it work?

Chemical oxygen demand is determined by oxidising the sample with potassium dichromate in strong sulfuric acid at about 150 °C for two hours, usually in sealed tubes. Silver sulfate catalyses the oxidation of most organic compounds, and mercury sulfate masks chloride, which would otherwise be oxidised and inflate the result. The dichromate consumed is proportional to the oxidisable material and is measured either photometrically, from the colour change of dichromate to chromium(III) at 600 nm or by the decrease in dichromate absorbance at 440 nm, or by titration of the remaining dichromate with ferrous ammonium sulfate. Results are reported as milligrams of oxygen per litre. COD is faster than BOD and includes material that is not biodegradable, which is why it is used for discharge compliance and process control.

What are the key features?

• Battery-powered compact digestion block for 2–4 tubes
• Handheld colorimeter for 16 mm sealed tubes
• Same reagents and chemistry as laboratory systems
• Ranges covering 0–150 to 0–15,000 mg/L
• Rechargeable battery or 12 V vehicle supply
• Portable case with reagents, tubes and accessories

What are the technical specifications?

A typical portable cod analyzer configuration offers digestion temperature of 150 °C, ±2 °C, digestion capacity of 2–4 tubes, ranges of 0–150, 0–1500, 0–15,000 mg/L, wavelengths of 440 nm and 600 nm, reading time of 2–5 s and accuracy of ±3 percent of reading. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Portable COD Analyzer is used in on-site industrial effluent screening, wastewater plant daily process checks, pollution incident investigation and remote site and field laboratory testing. Across the wider COD Analyzers class, laboratories also deploy it for wastewater treatment influent and effluent monitoring, industrial discharge compliance testing and municipal plant process control.

Which standards and certifications apply?

Relevant standards and methods include ISO 6060, ISO 15705, EPA 410.4, Standard Methods 5220 D and ISO/IEC 17025. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

COD chemistry is hazardous: dichromate is a carcinogen and strong oxidant, sulfuric acid is corrosive, and mercury salts are toxic, so digestion must be performed in sealed tubes or closed reflux systems with fume control and separate waste collection for heavy-metal-bearing residues. Chloride interferes seriously and is masked with mercury sulfate, so the expected chloride concentration must be known and the masking ratio respected; high-chloride samples may need dilution or a low-range method. Quality control requires blanks, standards, spiked samples and duplicates in each batch, and the dichromate solution should be standardised. Sealed tubes should be mixed thoroughly before reading, and the reading should be taken after the tubes cool to avoid temperature bias.

How do I select the right Portable COD Analyzer?

Choose a portable system when COD checks are needed away from the laboratory and immediate screening value matters. Confirm that the reagents and digestion time match your laboratory method so that results are comparable, and carry a supply of spares and standards for field quality control.

How does it compare with other COD Analyzers variants?

Choose the measurement format from where the sample is taken and how the result will be used. Sealed-tube colorimetric systems with a digestion reactor are the standard for laboratories, offering ranges from 0 to 15,000 mg/L with small sample and reagent volumes. Portable colorimeters bring the same chemistry to the plant or river bank for rapid screening. Titrimetric analysis is used for high-concentration or coloured and turbid samples, where photometry is unreliable, and remains the classic reference for difficult matrices. Automated analysers with autosamplers reduce reagent handling and improve traceability where sample numbers are high. Online UV analysers provide continuous trend data for treatment control but must be correlated with the dichromate method, since UV absorbance responds to aromatic compounds rather than total oxidisable matter.