Pyxis SP-800 - Multiple Timing Steps Method; Advanced Methods

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3.6 Multiple Timing Steps Method
Some colorimetric methods have two or three timing steps. The SP-800 shows a count-down timer for the
timing steps before the last timing step (Figure 9). During these timing steps, one or more reagents are
added to the sample, or operations such as swirling the vial to mix the reagent and the sample are being
performed. These methods usually use one vial for the prepared blank and the other for the prepared
sample.
Figure 8. Multiple Timer Method
In order to show the concentration-time curve as shown in Figure 8 during the last timing step, The SP-800
must be zeroed using the prepared blank before the last timing step. Thus, the last timer button will not be
selectable until the SP-800 has been zeroed using the prepared blank. Multi-timing step Hach® methods
require zeroing the colorimeter using the prepared blank after the last timing step is completed. The SP-
800 can optionally be re-zeroed using the prepared blank after the last timing step. The blank value
measured will be subtracted from the concentration value measured at the end of the last timing step.
Optionally, the READ button could be pressed to read the prepare sample again.
The following procedure is typical for methods having two-timing steps:
1. Press the TMR1 button to start the first timer. Complete the necessary operations to prepare
the blank and the sample.
2. Place the prepared blank into the SP-800 sample vial compartment and press the ZERO
button.
3. Place the prepared sample into the SP-800 sample vial compartment and press the TMR2
button to start the second timer. The SP-800 will display the measured concentration as a
function of time as shown in Figure 8.
4. When the timing step is completed, the measured concentration will be displayed on the top
right of the screen. The timing step could be terminated earlier by pressing STOP button.
5. Optionally, The SP-800can be re-zeroed using the prepared blank after the timing step is
completed or terminated. The blank reading will be subtracted from the measured
concentration value, and the displayed concentration value on the top-right corner will be
updated. This step is optional. It is only necessary if the prepared blank changes its color
during the timing period.
3.7 Advanced Methods
The SP-800 provides 7 LED wavelengths and can measure absorbance values at multiple LED
wavelengths. Consequently, the SP-800 can provide many predefined advanced methods that traditionally
require complex and often expensive lab testing procedures.