Benchtop Chlorine Colorimeter

What is the Benchtop Chlorine Colorimeter?

A benchtop chlorine colorimeter measures free, combined and total chlorine with stable optics and controlled wavelength selection. It provides the repeatability needed to verify portable field meters and to support routine laboratory reporting.

Overview

The instrument uses a fixed optical bench with interference filters or a monochromator, a sealed sample chamber and a photodetector, giving lower stray light and better wavelength accuracy than handheld devices. Methods are stored for free chlorine, monochloramine, dichloramine and total chlorine, and the instrument can follow the DPD, syringaldazine or amperometric reference procedures depending on the model. Calibration curves are entered from certified standards or generated with standard solutions, and results are printed with method, wavelength and operator data. Benchtop units also handle other parameters such as pH, turbidity and other disinfectants, which makes them useful for pool and drinking water laboratories, and they serve as the reference for checking portable colorimeters used in the field.

How does it work?

Chlorine measurement uses either a colorimetric or an electrochemical principle. In the DPD method, N,N-diethyl-p-phenylenediamine reacts with free chlorine to form a magenta colour whose intensity is proportional to concentration and is measured at about 515 nm; adding potassium iodide then reveals combined chlorine so total chlorine can be determined. Because the colour develops quickly and fades, timing and temperature must be controlled. Amperometric analyzers use a membrane-covered electrode where chlorine diffuses to a cathode and produces a current proportional to concentration, giving continuous measurement without reagents. Optical analyzers use a colorimetric reaction in a flow cell with automatic reagent addition. Results are reported in milligrams per litre as free chlorine, combined chlorine, total chlorine or, in pools, as total chlorine with cyanuric acid present.

What are the key features?

• Fixed optical bench with interference filters or monochromator
• Stored methods for free, combined and total chlorine
• Lower stray light and better wavelength accuracy than handhelds
• Calibration from certified standards or standard solutions
• Additional parameters such as pH and turbidity
• Printed and exported results with method details

What are the technical specifications?

A typical benchtop chlorine colorimeter configuration offers parameters of Free, monochloramine, dichloramine, total chlorine, ranges of 0–5 mg/L low, up to 0–200 mg/L high, resolution of 0.01 mg/L, wavelength accuracy of ±1 nm, optical system of Interference filters or monochromator and sample cell of 10 mm or 20 mm cuvette. 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 Benchtop Chlorine Colorimeter is used in drinking water compliance laboratory testing, verification of portable field colorimeters, swimming pool and spa compliance testing and food and beverage plant water control. Across the wider Chlorine Meters class, laboratories also deploy it for drinking water disinfection monitoring, swimming pool and spa water testing and wastewater effluent chlorination control.

Which standards and certifications apply?

Relevant standards and methods include ISO 7393-1, ISO 7393-2, ISO 7393-3, EPA 330.5, Standard Methods 4500-Cl G 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.

DPD reagents and powder pillows have a limited shelf life and are sensitive to heat and moisture, so they must be stored correctly and replaced before expiry. Colour development depends on time and temperature, so sample temperature should be near 20 to 25 °C and readings taken within the specified period. High chlorine concentrations bleach the colour and need dilution, and samples with manganese, ozone or high turbidity can interfere. Membrane electrodes need electrolyte replacement, membrane care and regular calibration against a reference method, and the sample flow, pH and temperature must be within the specified limits. For pools, cyanuric acid affects the ratio of free to combined chlorine and should be known. Keep records of calibration, reagents and reference comparisons.

How do I select the right Benchtop Chlorine Colorimeter?

Choose a benchtop colorimeter when laboratory-grade repeatability is needed, for example to verify field meters or to support compliance reporting. Confirm that the stored methods match the standard you follow and that the calibration standards and cuvettes are available locally.

How does it compare with other Chlorine Meters variants?

Choose the measurement format from where and how often chlorine is measured. Pocket testers and portable colorimeters suit field checks, pool testing and distribution system sampling, where speed and portability matter. Benchtop colorimeters give better optics and repeatability for laboratories and for verifying portable meters. Online amperometric analyzers are needed wherever chlorine dosing must be continuous, as at treatment works, since they respond in seconds and can drive pumps and alarms directly. Consider the expected range, since disinfection residuals are usually 0.2 to 2 mg/L but pool and shock dosing levels are far higher, and confirm whether free, combined or total chlorine is the reported parameter. Check reagent or membrane availability and the calibration standards you will need.