Neogen offers an expanding line of colorimetric (chromogenic) substrates and reagents to meet our customers’ immunoassay needs. The substrates are available for use with horseradish peroxidase (HRP) and alkaline phosphatase (AP) based microwell and membrane assays.

Neogen’s colorimetric (chromogenic) substrates offer excellent sensitivity, stability and lot-to-lot consistency. These features make them ideal for inclusion in commercial immunoassay test kits or individual in-house assay projects. We also offer immunoassay reagents including a stop solution and buffers.

Horseradish Peroxidase (HRP) applications

Neogen recognises that one TMB microwell substrate formulation will not meet the specifications of all horseradish peroxidase (HRP)-based immunoassays. Therefore, Neogen offers multiple unique one-bottle TMB microwell colorimetric substrate formulations to meet specific requirements for different assay systems.

Neogen substrates have common characteristics of low background, long-term stability and excellent lot-to-lot consistency.

Alkaline Phosphatase (AP) applications

K-Gold® substrate is a one-bottle stabilised chromogenic substrate for use with alkaline phosphatase (AP)-based immunoassays. K-Gold substrate utilizes the substrate p-nitrophenyl-phosphate (PNPP), which reacts with alkaline phosphatase to produce the chromophore p-nitrophenol. Neogen’s ready-to-use K-Gold is a single-bottle formula and does not require mixing of additional ingredients or stabilizing agents. K-Gold features excellent signal-to-noise and has extremely low background over the 30-month shelf life, making this an ideal formula for assay manufacturers.

Available Products

Colorimetric Horseradish Peroxidase (HRP) microwell

ProductShelf LifeProduct FeaturesAvailable SizesProduct Numbers
K-Blue Advanced 24 months when stored at 2–8°C
  • Superior activity
  • Increased sensitivity at higher HRP concentrations
  • Low background
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 319175
  • 319176
  • 319177
  • 319257
Enhanced K-Blue 48 months when stored at 2–8°C
  • Longest shelf-life of Neogen TMB substrates
  • Low background
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 308175
  • 308176
  • 308177
  • 308257
Custom TMB 36 months when stored at 2–8°C
  • Ideal for assays requiring a less active substrate
  • Low background
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 309175
  • 309176
  • 309177
  • 309257
K-Blue Aqueous 36 months when stored at 2–8°C
  • 100% solvent-free
  • Ideal when working under strict regulatory requirements
  • Low background
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 331175
  • 331176
  • 331177
  • 33125
Alert K-Blue Aqueous 36 months when stored at 2–8°C
  • 100% solvent-free
  • Clearly indicates when substrate and acid stop have been added to the wells (turns pink)
  • Ideal for sandwich based assays
  • Low background
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 334175
  • 334176
  • 334177
  • 334257
ABTS 36 months when stored at 4°C
  • Produces a soluble blue-green reaction
  • Results are read at 405/410 nm
  • 100 ml
  • 1 l
  • 310247
  • 310177

Colorimetric Alkaline Phosphatase (AP) Microwell

ProductShelf LifeProduct FeaturesAvailable SizesProduct Numbers
K-Gold 30 months when stored at 4°C
  • High activity
  • RTU (ready-to-use)
  • Low background
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 303175
  • 303176
  • 303177
  • 303257
K-Gold Plus 24 months when stored at 2-8°C
  • Improved sensitivity and activity
  • Easy-to-use, one-bottle formula
  • Excellent signal-to-background ratio
  • 200 ml
  • 500 ml
  • 1 l
  • 20 l (1 x 20 l)
  • 339175
  • 339176
  • 339177
  • 339257

Colorimetric Horseradish Peroxidase (HRP) Membrane

ProductShelf LifeProduct FeaturesAvailable SizesProduct Numbers
TMB Membrane
  • 48 months when stored at 2–8°
  • 24 months when stored at 15–25°
  • Produces an insoluble, permanent dark blue reaction
  • 100 ml
  • 1 l
  • 311247
  • 311177
TMB Membrane Plus
  • 48 months when stored at 2–8°
  • 24 months when stored at 15–25°
  • Produces an insoluble, permanent dark blue reaction
  • 100 ml
  • 1 l
  • 337247
  • 337177