Hanna Instruments HI 4014 - Manual (Page 8)

14 15
XIII. XIII. XIII. XIII. XIII. pH pH pH pH pH
HI 4014/ HI 4114 potassium electrodes operate over a wide
pH range. The pH range 1.5 - 12 is acceptable for
measurements. Samples and standards can be adjusted to
be within the working pH range.
XIV. XIV. XIV. XIV. XIV. Storage and Care of the HI 4014 sensor and Storage and Care of the HI 4014 sensor and Storage and Care of the HI 4014 sensor and Storage and Care of the HI 4014 sensor and Storage and Care of the HI 4014 sensor and
HI 4114 electrode HI 4114 electrode HI 4114 electrode HI 4114 electrode HI 4114 electrode
HI 4014 sensor can be stored in dilute standards near the
sample concentration for short periods of time and should
be disassembled and stored dry in the shipping vial when
not in use for long periods of time. Do not expose module to
elevated temperatures. Refrigeration of module will extend
life time.
HI 4114 combination electrode can be left in dilute stan-
dards near the sample concentration for short periods of
time. If the electrode will be used frequently and needs to
be ready for use, take measures to prevent evaporation of
fill solution. Top off fill solution, replace o-ring, fill hole
cover on the fill hole opening, and place in dilute potas-
sium solution. Store electrode upright. Before using, flush
junction once and top off fill solution.
For long-term storage, disassemble electrode and wash all
salts from assembly with deionized water. Wrap ceramic
junction on inner stem in Parafilm
® or other sealing film.
Unscrew module from the inner stem and blot dry. Store
module in shipping vial. Store electrode assembly disas-
sembled. Do not expose module to elevated temperatures.
Refrigeration of module will extend its life.
XV XV XV XV XV. . . . . Conversion T Conversion T Conversion T Conversion T Conversion Tables ables ables ables ables
Multiply by Multiply by Multiply by Multiply by Multiply by
Moles/L (M) K + to ppm K + (mg/L) 39100
ppm K + (mg/L) to M K + (Moles/L) 2.56 X 10 -5 -5 -5 -5 -5
C
sample
=
(V
T
)10 ∆E/S - (V
S’
)
C
standard
V
standard
V
sample
V
S’
(V
sample
+V
standard
+V
ISA
)= V
T
(V
sample
+V
ISA
)= V
S’
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 Known addition Known addition Known addition Known addition
An unknown concentration can be determined by adding a
known amount (volume and concentration) of K
+ standard
to the sample. mV values are noted before and after the
addition of standard (
∆
E). An ideal sensor slope can be
used in the equation but actual determined slopes at the
temperature of measurement should be used if known (S).
This method is preprogrammed in the Hanna HI 4222 pH/
ISE/mV meter, which greatly simplifies the method .
Example:
Potassium ion determination with known addition.
1. A 50 mL sample of unknown (V
SAMPLE
) is placed in an
clean plastic beaker with a thoroughly cleaned elec-
trode (s). Add 1 mL of ISA to sample. Mix. The mV
1
is
recorded.
2. 5 mL (V
STD
) of 10 -1 M (C
STD
) standard is added to the
beaker and the mV value increases. (Note: for other
concentration samples, add a known volume and
concentration of standard to produce approximately
30 mV change).
3. The unknown potassium concentration in the original
sample (C
SAMPLE
) can then be determined by using the
equation that follows.
The procedure can be repeated with a second standard
addition to verify slope and operation of the method.