1. Jaffe Method (Most Common)

• Based on the reaction between creatinine and picric acid in an alkaline medium.

• Produces an orange-red complex.

• Absorbance is measured photometrically, usually at 505–520 nm.

• Some kits include compensated Jaffe formulations to reduce interference from glucose, ketones, and proteins.

2. Enzymatic Method

• Uses a sequence of enzyme reactions (creatininase, creatinase, sarcosine oxidase, peroxidase).

• Produces a colored dye measurable at 550–570 nm.

• Higher specificity than Jaffe, minimal interference.

Reagent Components

Depending on the method, creatinine reagent kits may include:

For Jaffe Method

• Alkaline buffer

• Picric acid

• Stabilizers

• Surfactants

• Preservatives

For Enzymatic Method

• Enzyme mixture (creatininase, creatinase, sarcosine oxidase)

• Chromogenic dye reagents

• Phosphate or Good’s buffer

• Activators

• Preservatives

Packaging Format

Most creatinine reagent kits are provided as:

• Two-reagent system (R1 buffer + R2 working reagent)

• Ready-to-use liquid formulations

• Optional standards or calibrators

Common sizes: 25 ml, 50 ml, 100 ml, 250 ml, or analyzer-specific cartridges.

Sample Type

• Serum

• Plasma (heparin, EDTA)

• Urine (often diluted before analysis)

Crystal violet (also known as Gentian violet or methyl violet 10B) is a synthetic dye widely used in microbiology, histology, and medicine. It is best known as the primary stain in Gram staining, a key technique for classifying bacteria as Gram-positive or Gram-negative.