Sulfide

Test Method Technical Information

TECHNICAL SPECIFICATION

Tests For: Sulfite in Boiler Water
Tests Range: 0–500 mg/L
Reagent Chemistry Used: Bleaching of indicator
Method Detection Limit*: 3.9 mg/L
Limit of Quantification**: 12.5 mg/L

*The Method Detection Limit (MDL) is defined as the minimum measured concentration of a substance that can be reported with 99% confidence to be different from the method blank results.

**The Limit of Quantification (LOQ) is the smallest quantity that can be detected with reasonable certainty for a given analytical procedure.

Testing for Sulfide

Oxygen is a major cause of corrosion in boilers and steam raising plant. Sodium sulfite and catalysed sulfite formulations are extensively used as oxygen scavengers in boiler water treatment.

The Palintest Sulfite test provides a simple means of measuring sulfite levels for the control of such treatments in boiler plant. The test covers the range 0–500 mg/L Na2SO³.

Reagent Chemistry

The Palintest Sulfite test is based on a colorimetric procedure involving the reduction of an indicator dye. Sulfites react with the indicator dye under buffered conditions to destroy the original purple colouration. With increasing sulfite concentrations, a range of colours from purple to colourless is produced.

An advantage of the sulfite test method is that it does not respond to other reducing species as do traditional iodometric methods.

The degree of colour loss observed in the test is proportional to the sulfite concentration and is measured using a Palintest Photometer.

Interferences

The Palintest Sulfite test is based on a colorimetric procedure involving the reduction of an indicator dye. Sulfites react with the indicator dye under buffered conditions to destroy the original purple colouration. With increasing sulfite concentrations, a range of colours from purple to colourless is produced.
An advantage of the sulfite test method is that it does not respond to other reducing species as do traditional iodometric methods.

The degree of colour loss observed in the test is proportional to the sulfite concentration and is measured using a Palintest Photometer.

Best Practice Advice for Testing

• Equipment should be washed immediately after use, with a detergent if necessary, to prevent staining.
• Sulfite concentrations may be expressed as mg/l SO³. To convert from mg/l Na2SO³ to mg/l SO³ multiply by 0.63.

EPA, Definition and Procedure for the Determination of the Method Detection Limit, Revision 2, Dec 2016.
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”).