🔬 1. IFCC Kinetic ALP Method (Standard)

Principle

ALP + p-Nitrophenyl phosphate (pNPP)
→ p-Nitrophenol (yellow) + Phosphate

• Absorbance increases as p-nitrophenol is formed.

• The rate of increase (ΔA/min) at 405 nm is proportional to ALP activity.

Measurement

• Wavelength: 405 nm

• Mode: Kinetic (multiple interval readings)

• Temperature: 37°C (IFCC standard)

🧪 2. Reagent Composition (Typical)

Most ALP kits use single-reagent or two-reagent formats.

R1 (Main Buffer Reagent)

• Diethanolamine (DEA) buffer (high pH ~10.3)

• Magnesium ions (Mg²⁺) — ALP cofactor

• Zinc ions (Zn²⁺) — enzyme stabilizer

• Surfactants

• Preservatives

R2 (Substrate Reagent)

• p-Nitrophenyl phosphate (pNPP)

• Stabilizers

• Preservatives