Which type of analyzer is a handheld unit used in water quality testing?

In water quality testing, a handheld analyzer offers convenience and portability, making it easier for field testing and quick assessments. The DPD (N,N-diethyl-p-phenylenediamine) method specifically refers to a colorimetric technique often used to determine chlorine levels in water. Handheld DPD test kits allow users to measure chlorine concentration quickly by mixing water samples with DPD reagents and then visually comparing the resulting color against standard values, making it practical for various testing scenarios. This method's ease of use and immediate results are particularly advantageous for on-site water quality monitoring.

The other options, while relevant to water quality testing, do not primarily describe handheld units. A colorimeter is typically a standalone instrument used for various colorimetric analyses and often requires a laboratory setting. Amperometric titration generally involves laboratory setups for more detailed quantitative analysis. A pH probe, while sometimes handheld, is primarily designed for measuring pH levels directly rather than being a complete system for comprehensive water quality testing like the DPD method. Thus, choosing DPD reflects an understanding of the practicalities of field testing in water quality analysis.