HIRANUMA APPLICATION DATA

Data No.

Automatic Titrator

Apr. 5,
2019

G1

Quantitative determination of zinc ion

Metals
1. Abstract

Zinc ion can be readily determined by chelatometric titration. The titration with EDTA can be performed at
the wide pH region (pH 4.5 ~ 10). The stability constant of Zn-EDTA complex is relatively large,1 there are a
lot of highly sensitive indicator reagents for this titration. The report introduces an example that the sample
adjusted to pH around 5.3 is photometrically titrated with EDTA titrant using XO indicator (red purple →yellow).

Zn2+＋Na2EDTA→

Zn-EDTA＋2Na+

2. Configuration of instruments and reagents(1) Configuration
Main unit ：Hiranuma Automatic Titrator COM series (w/ Photometric titrator unit type M)
with 530 nm optical filter(2) Reagents
Titrant：0.1 mol/L EDTA standard solution

Buffer solution：Acetic acid-sodium acetate buffer solution (pH 5 ~ 5.3)

Indicator：1 mL of XO indicator (0.05 % solution)

3. Measurement procedure(1) Dispense 5 mL of sample into a 100 mL beaker with a volumetric pipette.
(2) Add about 60 mL of DI water.
(3) Add 5 mL of acetic acid- sodium acetate buffer solution.
(4) Add 1 mL of XO indicator.
(5) Immerse photometric probe into sample solution and titrate with 0.1 mol/L EDTA standard solution.

4. Measurement conditions and results
Examples of titration conditions
Cnd. No.
Method ﾞBuret No.
Amp No.
D.UnitS- Timer
C.P. mL
T.Timer
D.P. mLEnd Sens
Over mLMax Vol.

1
B cross
12T%
5400500120sec
mLsec
mL
mLmL

Constant No.
SizeBlank
Morality
FactorKLUnitFormula

15 mL0 mL
0.1 mol/L
1.005
65.390g/L(D-B)*K*F*M/S
Decimal Places
3Auto input parameter

None

Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt Speed
Pulse

2000033240

sec
mV
secmV

Measurement results
Number ofSize

Titrant

Zinc ion

Measurement(mL)

Volume (mL)Concentration (g/L)

1

55.3487.030

255.3497.029

355.3487.030

Statistic
calculation

Avg.

7.03 g/L

SD

0.0006 g/L

RSD

0.008 %

Example of titration curve

5. Note(1) Measurement condition
The color of indicator reagent suddenly changes at the endpoint, therefore the minimum increment (0.05 mL inthis report) titration without “Del K” control allows to get good results. The function “CP mL” can reduce themeasurement time by continuously adding 0.5 ~ 1 mL smaller titrant volume than the volume consumed until
the endpoint. The “Method” on condition parameter is set to “B Cross” because the endpoint is defined as thepoint where the color change of the indicator is completed.
(2) Other titration methods for zinc ion determination
There are some other chelatometric titration methods for zinc ion determination depending on indicator
reagents and suitable pH regions.
i) Indicator reagents
BT indicator (red → blue) is often used at alkaline pH besides XO indicator (can be used at acidiccondition) used in this report. It is usable at the pH region from 7 to 10. However, please note that the color
change is interfered by Cu2+, Co2+, and Ni2+ ions when they are contained in the sample.
ii) Interfering ions
There is no interference on the measurement even if alkali metal is contained in the sample. Ni2+, Fe3+, andAl3+ ions could interfere the color change of indicator reagent. The small amount of Al3+ ion does notinterfere the measurement because the reaction rate is slow under the low concentration condition. Cu2+ ion
interfere the measurement but the addition of thiourea or sodium thiosulfate can mask the Cu2+ ion.
Keywords：Zinc ion, Photometric titration, Chelatometric titration
References(1) K. Ueno, “Chelatometry”, 1987, Nankodo, Tokyo.
*Some measurement would not be possible depending on optional configuration of system.