Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful analytical technique to measure trace elements in biological fluids, increasingly used by clinical scientists. Especially in the last decade, there has been a slow shift towards ICP-MS over atomic absorption and emission techniques. Many trace elements play an essential role in a variety of biological functions. Some of these elements such as Lithium (Li) can play a vital role in regulating numerous signalling pathways. In clinical practice, Li is prescribed as the first line of treatment for bipolar disorders.
This work describes an ICP-MS method for rapid, robust, and sensitive quantitative analysis of Li in various types of biological samples collected from pregnant, lactating, and neonatal rats. Quantitative analyses of Li were done in plasma, cerebrospinal fluid, and brain collected from fetal and postnatal pups and dams that were given a long-term exposure to lithium chloride (LiCl). LiCl was injected twice daily over several days (2, 4, 7, 12, or 16/17 days). The samples were digested with different concentrations of nitric acid, a dilution was made where required, and the homogeneous solution was introduced to the ICP-MS via autosampler and peristaltic pump. ICP-MS analysis yielded a method detection limit for Li of less than 0.013μg/l and a limit of quantitation (LOQ) around 0.083μg/l. For different biological sample types, our method shows a relative standard deviation of less than 20%. The data obtained from ICP-MS was compared with data acquired in another lab using Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) which enables elemental analysis of solid samples. The results obtained by ICP-MS and LA-ICP-MS were in close agreement for plasma and CSF but not for the brain samples. This work describes one of the analytical methods used, however it does not discuss the biological mechanisms of Li accumulation in these rats.