Hach AutoCAT 9000, Instruction Manual

Page: 121 / 176

Total Oxidants
50081_TotalOxidants.fm
Page 119
Total Oxidants
*
• Soak all glassware in a strong chlorine dioxide (ClO
2
) solution (300–500 mg/L) for at least 1 hour.
Rinse thoroughly with deionized water. Use the glassware for this method only.
• Chlorine dioxide and its by-products are volatile and can be easily lost from aqueous solution. Minimize air contact by attaching a
flexible hose to a tap and placing the end at the bottom of a 1-L amber glass bottle. Turn on the tap and allow several volumes to
overflow, then slowly remove the sample line and cap the container with minimum headspace.
• Minimize agitation when measuring sample volumes. Remove sample portions with a volumetric pipet. Always place the tip at the
bottom of the sample container. If using 200-mL sample increments, use a 100-mL pipet to withdraw two portions of sample.
• Always use organic-free water for sample dilution (Cat. No. 26415-49).
• Rinse the electrode, temperature probe, and anti-diffusion tip with deionized water before every titration.
.
• Download the “Certificate of Analysis” (COA) to obtain the exact concentration of any unopened bottle of Hach titrant or standard
solution. See
Obtaining the Certificate of Analysis for Hach Reagents
on page
41
.
• Hach buffer reagents for chlorine titrations are highly recommended for this analysis.
• Never substitute buffers designed for calibrating pH meters. They may contain dyes that interfere with amperometric titration.
• Never use buffers contaminated with mold or bacteria.
• Adjust the contrast of the display by accessing the Methods menu and pressing
7
to lighten or
0
to darken.
• A distinction is drawn between running a new Test and a new Sample. Each Test is a replicate run of the current or previous
sample analysis. The AutoCAT 9000 automatically tracks the results of a series of tests, and automatically calculates the mean
and standard deviation for all the results. Each Test is given a different number, all of which are listed under the same Sample ID.
When starting a new Sample, a new ID is assigned.
• The AutoCAT 9000 can accommodate any sample size.
Standard Methods
recommends a default volume of 200 mL. The
volume can be adjusted to expand the test range.
• The AutoCAT 9000 calculates concentration based on the sample volume. Make sure that the sample volume is correct.
• Press
STOP
at any time to interrupt instrument operation; the user can resume, restart, or quit completely.
• Press the
CHECK MARK
key at any time during data acquisition to halt data collection.
• Press
DEL
during any timer period (except Start Timer) to immediately exit the timer and proceed to the next step.
• Press
ESC
during any titration/calibration data collection period or timer to access Edition mode. See
Edition Mode
on page
30
.
• Flush the burette each day before the first sample test or calibration is performed. See
Daily Start-up
on page
26
.
• Flush the burette when changing titrants. See
Changing Titrants
on page
25
.
* Adapted from Gates, “The Chlorine Dioxide Handbook”, AWWA, 1998. Not suitable for compliance testing.
Ch Chlorine Dioxide
“Quick” Two Step Amperometric Titration
Titration Workstation
0.1–5.0 mg/L as Cl0
2
+ ClO
2
–
Scope and Application:
For drinking water
Sample Tips and Techniques
Reagent Tips and Techniques
Instrument Tips and Techniques