Hanna Instruments HI 4012 - Manual (Page 12)

12
Procedure
1) Follow sections VIII and IX to prepare sensors for
measurement.
2) Follow section VI to prepare standards / solution.
Standards should bracket and fall within the range of
interest.
Two mL HI 4012-00 ISA is added to 50 mL of both
samples and standards. Fifty milliliters of the metha-
nol/formalin mixture is also added to each sample or
standard. Add stir bar and mix before taking mea-
surements.
3) Follow section VII; General Guidelines to optimize test
set-up.
4) During calibration it is best to start with lower concen-
tration samples first. Wait for a stable measurement
before recording values. Slightly longer equilibra-
tions are required at lower concentrations .
5) To prevent carry over and contamination of samples,
rinse sensors with deionized and dab dry with
absorbant laboratory tissue between samples.
XII. XII. XII. XII. XII. Other Measurement T Other Measurement T Other Measurement T Other Measurement T Other Measurement Techniques echniques echniques echniques echniques
Known Addition (for Pb 2+ )
An unknown concentration can be determined by adding a
known amount (volume and concentration) of measured
ion to a known volume of the sample. A mV value is taken
before and after the addition of standard, and using the
equation provided, the unknown concentration is found.
Typical Linearity for HI 4012 and HI 4112 Lead Electrodes
-250
-225
-200
-175
-150
-125
-100
-75
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
- Log of the Conc
m
V