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brief description of Pyxis method names and their corresponding Hach® program
number. Hach® reagents for 10 ml sample can be used for the test.
4.3 Single Timing Step Method
Most of colorimetric methods have only one timing step. As an example, in the DPD
total chlorine method, it takes three minutes for the DPD powder reagent to completely
react with chlorine in the water sample. The DPD total chlorine method has a single
three-minute timing step. Figure 8 shows the main page of a method with a single
timing step.
Figure 9 Single Timer Method
4.4 Single-Vial Procedure
1. Place the sample vial filled with the water sample in the Pyxis SP-900 sample vial
compartment and press the ZERO button. Pyxis SP-900 will display the page
shown in Figure 8.
2. Take the sample vial out and add the reagent to the sample vial.
3. Place sample vial back into the sample vial compartment and press the timer
button TMR1. Pyxis SP-900 will start to monitor the reaction between the reagent
and the species you want to measure in the water sample. The concentration is
shown in the chart as a function of time (Figure 9).
4. When the timer reaches the preset time and the reaction is complete, the value of
concentration will be shown on the top right corner of the page.
5. The rate of the reaction is often faster than the standard pre-set time, which will
become apparent from the concentration-time plot. You can press the STOP
button to stop the timer and terminate the timing step. The last read concentration
value will be displayed on the top right corner of the page after you terminate the
timing step.
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