Optical device for non-invasive monitoring of lithium in bipolar disorder patients

This research aims at developing a device to measure lithium ions level in patients suffered from bipolar disorder. Therapeutically range of lithium is from ∼0.6 to 1.2 mM which is slightly lower than toxic threshold of 1.5 mM. Hence, during the treatment, it is important to carefully monitor the concentration of lithium to avoid toxicity. A portable device which offers very sensitive analysis of lithium in saliva is presented. The device employs spectrofluorimetric method base on its reaction with 1,4- dihydroxyanthraquinone (Quinizarin) for the determination of lithium ions. The fluorescence is measured at an emission wavelength of 620 nm using an excitation wavelength of 590 nm. The device was validated with aqueous lithium containing sample and then saliva sample was tested. The results obtained from saliva samples show that the linear detection range was 0.25 mM ∼6.0 mM of Li⁺ with R ²=0.99. The range of detection covers sufficiently the therapeutic range of lithium drugs.