Hanna-instruments HI 4012 Manual de usuario descargar pdf (Pagina 6)

VIIVII

VII.

General GuidelinesGeneral Guidelines

General Guidelines

• Use of a hood and protective clothings is advised

when handling lead solutions.

• Concentrated samples (>0.10 M) should be diluted

before measurement. Multiply the final result by the

corresponding dilution factor.

• Calibration standards and sample solutions should

have the same ionic strength. ISA and Methanol/

Formalin should be added to both samples and stan-

dards in the same ratio. 2 parts ISA to 50 parts stan-

dard (or sample)/50 parts Methanol/Formalin is the

normal dosing. Note: no correction for dilution factor is

required for this because standards and samples are

treated in the same way.

• For high ionic strength samples, use standard addi-

tion or titration methods.

• Calibration standards and sample solutions should

be at same temperature.

• 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 lead sensor in a dilute standard will opti-

mize response. Use concentrations approximately

-3

M or less with Methanol/Formalim and ISA added.

• A scratched, pitted, or oxidized pellet surface can cause

drift, a loss of low level response, or poor repeatability.

Optimum response can be restored by removing the

damaged surface with the microabrasive strip HI 4000-

70. Use gloves to protect skin.

• Avoid large changes in temperature (thermal shock)

as it may damage the sensor.

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Hanna-instruments HI 4012 Manual de usuario Pagina 6