Determination of serum lithium: comparison between atomic emission and absorption spectrometry methods

Abstract

Introduction: The therapeutic monitoring of lithium, through concentration measurements, is important for individual dose adjustment, as a marker of treatment adherence and to prevent poisoning and side effects. Objectives: Validate and compare two methods-atomic emission and atomic absorption-for the determination of lithium in serum samples. Methodology: Parameters such as specificity, precision, accuracy, limit of detection (LOD) and linearity were considered. The atomic absorption spectrometer was used, operating in either emission or absorption mode. For the quantitative comparison of 30 serum samples from patients with mood disorder treated with lithium, the results were submitted to Student's t-test, F-test and Pearson's correlation. Results: The limit of quantification (LOQ) was established as 0.05 mEq/l of lithium, and calibration curves were constructed in the range of 0.05-2 mEq/l of lithium, using aqueous standards. Sample preparation time was reduced, what is important in medical laboratory. Conclusion: Both methods were considered satisfactory, precise and accurate and can be adopted for lithium quantification. In the comparison of quantitative results in lithium-treated patients through statistical tests, no significant differences were observed. Therefore the methods for lithium quantification by flame atomic absorption spectrometry (FAAS) and flame atomic emission spectrometry (FAES) may be considered similar.

Validation of a flame photometric method for serum lithium estimation

“…Therefore, the matrix effect observed was minimal. Santo et al have reported of the absence of a matrix effect between serum and aqueous media, which is similar to our findings [7]. The absence of a significant matrix effect is also evident as the two slopes of the lithium concentration verses response plots are similar in aqueous solution (Figure 1) and serum solution (Figure 2).…”

“…Many methods are employed to determine the serum lithium concentrations. As reported in literature, photometric methods such as flame photometry, flame atomic absorption spectrophotometry and colorimetry are widely used, while ion-selective electrodes are also used to determine lithium concentrations [4][5][6][7]. Among these methods flame photometry is regarded as a simple, rapid and cost-effective method.…”

Individualization of lithium therapy based on the monitoring of its level in saliva

“…No differences were observed between the concentrations of lithium ions in men and women, unlike another study which found a higher correlation between the concentrations of lithium in saliva and serum in women [ 29 ]. In general, the concentration of lithium in saliva is about 2-3 times higher than in serum [ 40 , 41 ]. This can be explained by the slower removal of lithium ions from saliva than from serum.…”