Development Fingerprints With Ninhydrin (Petroleum Ether Base)

Ninhydrin is used to develop latent prints on porous surfaces. Ninhydrin reacts with the amino acids present in perspiration.

Equipment
Scales, beakers, graduated cylinder, brush, glass tray, magnetic stirrer and stirring bar,
humidity chamber, iron, sprayer, dark storage bottles

Materials and Chemicals
• Ninhydrin
• Methanol
• Isopropanol
• Petroleum ether

Mixing Procedure
0.5 g of ninhydrin crystals are first dissolved in 3 mL of methanol on a stirring device. Then 4 mL of isopropanol is added, followed by 93 mL of the petroleum ether.

Fig. 1. Ninhydrin solution in a spray bottle

Processing Procedure
The ninhydrin solution (Fig. 1) can be applied to a specimen by spraying, dipping, or painting. Once the solution has been applied, it must be dried before any attempt is made to accelerate the development process using a humidified environment (e.g., a humidified chamber or a steam iron). If a humidified chamber is available, set humidity between 60 % and 70 % for best results.

Storage: Dark bottles

Shelf Life: Up to 1 year

Disposal:
Observe all federal, state, and local environmental disposal regulations.