Test Method Technical Information


Tests For: Sulfate in natural and treated waters
Tests Range: : 0–200 mg/L
Reagent Chemistry Used: Barium sulfate
Basis of Test Method: Modified Standard Method 4500-SO42- -E, ASTM D516-11
Method Detection Limit*: 2 mg/L
Limit of Quantification**: 6 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 Sulfate

Sulfates occur naturally in many waters. Sulfates are introduced into treated waters by the use of such chemicals as aluminium sulfate, sodium bisulfate (dry acid) and sullfauric acid. The presence of high levels of sulfate can be undesirable for a number of reasons.

In industrial waters containing sulfate localised corrosion of iron, steel and aluminium in plant and pipe work can occur through the action of sulfate-reducing bacteria. These bacteria, which generate sullfaides, cause a characteristic pitting of the metal surface.

High sulfate levels can also cause damage to concrete and cement-based materials through the formation of calcium sullfaoaluminate. This causes expan¬sion and crumbling of the cement. It can affect concrete structures and pipes in water distribution systems carrying sulfate-bearing ground waters; and can attack grouting in tiled swimming pools using sodium bisulfate for pH adjustment.

The Palintest Sulfate test provides a simple method of measuring sulfates over the range 0–200 mg/l SO4. Higher levels may be determined by diluting the sample.

Reagent Chemistry

The Palintest Sulfate test is based on a single tablet reagent containing barium chloride in a slightly acidic formulation. Barium salts react with sulfates to form insoluble barium sulfate. At the sulfate levels encountered in the test, this is observed as turbidity in the test sample. The degree of turbidity is proportional to the sulfate concentration and is measured using a Palintest Photometer.

Best Practice Advice for Testing

  • Palintest Sulfate (Turb) tablets each contain 20 mg Barium Chloride. These tablets are harmful if ingested. Avoid handling tablets whenever possible and wash hands after use.

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”).