Optical lithium sensors

Advances in Therapeutic Monitoring of Lithium in the Management of Bipolar Disorder

“…Furthermore, in the development of optical lithium ligands, the response time for signal detection should be considered. The response time of small ligands used for lithium detection has been reported to vary from a few seconds to 30 min, with most of the optical sensors displaying detection after 1–10 min, because of the time needed for Li + cation to coordinate with ionophore, and the necessary duration for stabilizing the detection signal [ 50 ]. Therefore, the equilibration time for Li + coordination must be considered which depends on the ligand that is employed in the membrane for preparation of the optical sensor.…”

“…Lithium measurements can be performed based on absorbance change (colorimetry) or fluorescence emission (fluorometry). A lithium ligand unit and a chromophore/luminophore unit are required for formation of lithium coordination complex, which is directly associated with its detection [ 50 ]. Therefore, the optical sensors are designed and fabricated by insertion of a ligand into a detection system such as a membrane or an optical fiber [ 50 ].…”

“…A lithium ligand unit and a chromophore/luminophore unit are required for formation of lithium coordination complex, which is directly associated with its detection [ 50 ]. Therefore, the optical sensors are designed and fabricated by insertion of a ligand into a detection system such as a membrane or an optical fiber [ 50 ]. A number of studies have employed colorimetric reagents such as thoron [ 51 ] and quinizarin [ 52 ] as optical ligands that are able to form a complex with lithium and result in a shift of its spectrum.…”

“…Due to their lipophilicities, these ionophores can be used to extract Li+ from aqueous solution into organic solvents to achieve spectrophotometric analyses of lithium levels. Therefore, selective lithium extraction towards sodium cations can be achieved based on the cavity size of the crown ether used [ 50 ]. Nevertheless, the development of optical sensors utilizing different chemical ligands for selective and efficient lithium monitoring requires achieving high levels of stability and reversibility and short response time.…”

“…However, lithium detection using optical sensors often suffers from limitations regarding reversibility. This is because after Li+ detection, the lithium sensor is classically non-reusable due to the low reversibility or the non-reversibility of Li+ coordination in the ionophore unit [ 50 ]. Therefore, optical properties of inorganic materials or nanocomposites should be more exploited to develop reversible and innovative optical lithium sensors.…”