Portable DPD Chlorine Colorimeter

What is the Portable DPD Chlorine Colorimeter?

A portable DPD chlorine colorimeter measures free, combined and total chlorine in the field using tablet or powder reagents and a photometer. It brings reliable disinfection checks to treatment works, pools and distribution sampling points.

Overview

The instrument holds a 10 mL sample in a capped vial, and a DPD tablet or powder pillow is added and dissolved by shaking. Free chlorine develops as a magenta colour within one minute, and the photometer reads absorbance at about 515 nm against a blank. Adding a second reagent containing potassium iodide releases combined chlorine for a total chlorine reading, and the difference gives combined chlorine. Ranges typically span 0 to 6 mg/L with resolution of 0.01 mg/L, and optional high-range methods extend to 0 to 200 mg/L for shock dosing. Instrument cases include vials, reagents, a cleaning cloth and calibration standards, and readings are logged with time and location for reporting.

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?

• Free, combined and total chlorine in one workflow
• DPD tablet or powder reagent compatibility
• Range 0–6 mg/L with 0.01 mg/L resolution
• High-range method option to 200 mg/L
• Water-resistant housing for field use
• Reading log with time and location

What are the technical specifications?

A typical portable dpd chlorine colorimeter configuration offers parameters of Free, combined and total chlorine, ranges of 0–6 mg/L and 0–200 mg/L (high range), resolution of 0.01 mg/L at low range, wavelengths of 515 nm and 555 nm for high range, accuracy of ±3 percent of reading and sample volume of 10 mL. 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 DPD Chlorine Colorimeter is used in drinking water distribution sampling, swimming pool and spa monitoring, wastewater effluent chlorination checks and emergency and field water disinfection testing. 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 Portable DPD Chlorine Colorimeter?

Choose a portable colorimeter when chlorine must be checked at multiple sites and results are needed immediately. Confirm the range needed for your water, especially if pool shock dosing is monitored, and check reagent availability and shelf life before field campaigns.

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.