Anodic Peak

Source: Okamoto, A., et al. Self-standing Electrochemical Set-up to Enrich Anode-respiring Bacteria On-site. J. Vis. Exp. (2018)This video demonstrates the use of an on-site electrochemical system to enrich anode-respiring bacteria (ARB) from natural reservoirs. A redox gradient is established by placing the anode in oxygen-free deep water and the cathode in oxygen-rich surface water. ARB form biofilms and transfer electrons to the anode, which flows to the cathode, where oxygen is reduced,...

The dipole moment of a bond is the product of the partial charge on either atom and the distance between them. Dipole moments influence the efficiency of IR absorption and the peak intensity. When a bond with a dipole moment is placed in an electric field, the direction of the field determines if the bond is compressed or stretched. Electromagnetic radiation consists of an electric field component that rapidly reverses direction. It follows that polar bonds are alternately stretched and...

When infrared radiation is passed through a molecule, absorption occurs if the molecule's vibration leads to a substantial change in its bond dipole moment. Transitions between vibrational energy levels, typically corresponding to infrared frequencies (4000–400 cm−1), allow absorption if the vibration significantly alters the dipole moment, making the molecule infrared active. The molecular bonds have different stretching and bending vibrations, resulting in various peaks with varying...

The vibrational frequency of a bond is directly proportional to its bond strength. As a result, stronger bonds vibrate at higher frequencies, while weaker bonds vibrate at lower frequencies. The stretching vibration of the strong O–H bond in alcohols and phenols (very dilute solution or gas phase) appears as a sharp peak at 3600–3650 cm−1. However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular hydrogen bonding...

Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...