Quantitative determination of lead ion | Autotitrator COM-A19

HIRANUMA APPLICATION DATA

Automatic Titrator

Data No.

Apr. 5,2019

Metals

Quantitative determination of lead ion

1. Abstract

The chelatometric titration is generally used for the determination of lead ion (Pb2+). The pH region the lead ion can be directly titrated is pH 3.5 ~ 10 (stability constant = 17.88).1 However, it generates Pb(OH)2 precipitation at alkaline region. When performing titration under alkaline condition, the auxiliary complexing agent such as ethanolamine, tartaric acid, or citric acid should be added in advance to generate weak chelatometric complex and avoid the generation of lead hydroxide precipitation.

It is titrated at pH around 4 ~ 5 when performing under acidic condition. This report introduces an example that the lead ion in sample solution adjusted to pH 5 by hexamine solution is determined with using XO indicator (red purple →yellow).

Pb²+　+ Na₂EDTA　　→　　Pb-EDTA　+　2Na+

2. Configuration of instruments and Reagents

(1)	Configuration
	Main unit	:	Hiranuma Automatic Titrator COM series (Photometric titrator unit type M) with 530 nm optical filter
	Electrode	:	Glass – Reference electrode GR-501BZ (for pH confirmation)
(2)	Reagents
	Titrant	:	0.01 mol/L EDTA standard solution
	Buffer solution	:	5 ~ 10 mL of 20 % hexamine solution
	Indicator	:	0.2 mL of XO indicator (0.1 % solution)

3. Measurement procedure

(1)	Dispense 1 mL of sample into a 100 mL beaker with volumetric pipette.
(2)	Add about 60 mL of DI water.
(3)	Add hexamine solution to adjust the pH to 5.
(4)	Add 0.2 mL of XO indicator.
(5)	Immerse photometric probe into sample solution and titrate with 0.01 mol/L EDTA standard solution.