Measurements of nitrate and nitrite anions in biological samples.
The measurements of nitrate and nitrite anions in biological samples have gained more interest due to their association with the nitric oxide (NO) pathway. Since nitrate and nitrite are oxidation products of NO, their presence can be used as an indicator of NO production activities and there are many methods available for both direct and indirect measurement of nitrite.
This is not the case for nitrate due to its different chemical reactivity. Therefore, most of the analytical procedures involving nitrate include its conversion to nitrite using either enzymatic reduction or cadmium-based reductors. Unfortunately, these conversion procedures are tedious, time consuming, expensive, require multiple sample transfer, and suffer from diminished activity.
Conventional bi-metallic composition-based reductors are based on copper-plated cadmium beads. The presence of copper metal alters the potential energy of the cadmium electrons enhancing their transfer rate to nitrate. Even though this design has been used successfully for many years, it has two main drawbacks. The first is loss of catalytic activity after use on a number of samples requires that the reductor be reactivated. The second problem deals with the difficulty in handling and utilizing the beads with very small sample volume containers to avoid dilution. (Unfortunately, these beads are normally packed in a column.)
Our nitrate reducing wire is based on a unique multi-metal alloy structure. This multi-metallic structure preserves the activity of the reductor and enhances the rate of electron transfer in the following chemical reactions:
M " M+2 + 2e-
NO3- + 2e- + H2O " NO2- + 2OH-
This alloy structure completely eliminates the need to reactivate the nitrate reductor. The design of the reductor is in the form of a wire, enabling it to be used on very small samples, removing the restriction of having to move your precious sample to a specialized container.