6
capped plastic bottle. Using volumetric pipettes and glass-
ware make dilutions to bracket the concentration of the
samples. Store standards in plastic bottles. Standards with
concentrations < 10
-3
M should be prepared daily. One mL
of Hanna ISA and pH adjuster (HI 4001-00) should be
added to each 100 mL of sample or standard.
VII
VII
VII
VII
VII. General Guidelines
General Guidelines
General Guidelines
General Guidelines
General Guidelines
•
Use of a hood and protective clothings is strongly
advised. Use ISA to adjust pH above 11.
•
Calibration standards and sample solutions should
have the same ionic strength. ISA should be added to
both samples and standards in the same ratio. 1 part
ISA to 100 parts standard is the normal dosing.
•
Concentrated samples (>.005 M) should be diluted
before measurement. Multiply the final result by the
corresponding dilution factor.
•
For high ionic strength samples, use standard addi-
tion or titration methods.
•
Calibration standards and sample solutions should
be at same temperature and at elevated pH.
•
The magnetic stirrer may generate heat. Thermally
insulate beaker containing standard or sample from
magnetic stirrer by placing cork or other insulative
sheet between beaker and stirrer plate.
•
Calibration standards and sample solutions should
be stirred at the same rate using identical sized TFE
coated stir bars.
•
Rinse electrode pair with distilled or deionized water
between samples and gently dab dry with soft dis-
posable absorbent toweling. Do not rub electrodes.
•
Presoaking cyanide sensor in a dilute standard will
optimize response. Use concentrations approximately
10
-3
M or less with ISA added.
•
A scratched, pitted, or tarnished pellet surface can
cause drift, a loss of low level response, or poor repeat-
ability. Optimum response can be restored by remov-
ing the damaged surface with the microabrasive strip