Measurement Methods & Reagents

1. Ion-Selective Electrode (ISE) Method (Most common in modern analyzers)

Reagents include:

• Reference (internal standard) solution

• Electrode electrolyte solution

• Conditioning solution

• Cleaning solution

• Calibrators (Low and High Chloride)

Principle:

A chloride-selective membrane develops an electrical potential proportional to chloride concentration.
ISE systems require stable calibration solutions and maintenance reagents.

2. Mercuric Thiocyanate Colorimetric Method

How it works:

1. Chloride reacts with mercuric ions, forming mercuric chloride.

2. Released thiocyanate ions form a red-colored complex with ferric ions.

3. The color intensity is measured photometrically at 480–520 nm.

Reagents contain:

• Mercuric thiocyanate

• Ferric nitrate or ferric ammonium sulfate

• Buffer system

• Surfactants and stabilizers

Advantages:

• Reliable for automated chemistry analyzers

• High precision

3. Colorimetric TPTZ Method (Less common)

Chloride displaces iron from a complex; the released iron reacts with TPTZ dye to form a measurable color.

Packaging Formats

• Single-liquid reagent

• Two-reagent kits (R1 buffer + R2 color reagent)

• ISE-specific reagent packs

• Ready-to-use liquid stable formulations

Typical volumes: 25 ml, 50 ml, 100 ml, 250 ml.