Measurement Methods & Corresponding Reagents

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

Reagents include:

• Internal standard (reference solution)

• Electrolyte solution for K⁺ electrode balance

• Conditioning solution

• Electrode cleaning solution

• Calibrators (Low & High K⁺)

Principle:

Potassium-selective membranes generate an electrical potential when exposed to K⁺ ions.
The potential difference is proportional to potassium concentration.
ISE is fast, accurate, and ideal for automated analyzers.

2. Turbidimetric/Colorimetric Tetraphenylboron Method

How it works:

1. Potassium reacts with sodium tetraphenylboron.

2. Forms a turbid or cloudy precipitate.

3. The degree of turbidity is measured photometrically at 510–550 nm.

4. Intensity correlates with potassium concentration.

Reagents contain:

• Sodium tetraphenylboron

• Buffer solution

• Surfactants

• Stabilizers

• Preservatives

Used in: Semi-auto analyzers and manual systems.

Packaging Formats

• Single-liquid reagent bottles

• Multi-solution electrolyte packs (for ISE analyzers)

• Ready-to-use liquid stable reagents

• Analyzer-specific cartridges

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

Sample Types

• Serum

• Plasma

• Urine (may require dilution)

• Whole blood (in ISE/blood gas analyzers)