Total chlorine is often measured using colorimetric analysis, specifically the N, N-diethyl-p-phenylenediamine (DPD) method. This method has been a gold standard for chlorine measurement.
Understanding the DPD Method
The DPD method relies on a chemical reaction that produces a color change proportional to the chlorine concentration in a water sample. The intensity of the color is then measured using a colorimeter or spectrophotometer, which provides an accurate determination of total chlorine.
Steps involved:
- Sample Collection: A representative water sample is collected.
- DPD Reagent Addition: The DPD reagent is added to the water sample.
- Color Development: Chlorine in the sample reacts with DPD, causing a pink or red color to develop.
- Color Measurement: A colorimeter or spectrophotometer measures the intensity of the color.
- Concentration Determination: The instrument correlates the color intensity with the chlorine concentration, displaying the result.
Why is DPD the Gold Standard?
- Accuracy: Provides reliable and accurate chlorine measurements.
- Simplicity: Relatively easy to perform with readily available reagents and equipment.
- Versatility: Applicable in various water matrices, including drinking water, wastewater, and pool water.
Here's a simple table summarizing the method:
| Method | Description |
|---|---|
| DPD Method | Colorimetric analysis where DPD reagent reacts with chlorine, creating color. |
| Instrumentation | Colorimeter or spectrophotometer. |
| Application | Measuring free and total chlorine in water samples. |
