Determination of Trace Lithium in Human Urine by Electrothermal Atomic Absorption Spectrometry Using Nitric Acid as a Chemical Modifier to Eliminate the Interference of Chloride

Abstract

Electrothermal atomic absorption spectrometry (ETAAS) is considered the most common and advanced technique to determine trace lithium in biological fluids. However, chloride existing in samples has been reported to create serious interferences. Nitric acid was verified as a chemical modifier to eliminate the interference of chloride in determining trace lithium in urine samples and the possible mechanism was also elucidated. The influence of chloride was completely eliminated by using 0.5% (v/v) HNO3 as a chemical modifier. Confidence interval analysis on the difference for the slopes of linear regression curves indicated no significant difference between the slopes of aqueous and of urine-matched standard curves with and without 30 mmol/L NaCl in the presence of 0.5% (v/v) HNO3 (P = 0.146). Thus the direct standardization with an aqueous calibration curve could be used instead of the standard-addition method. We conclude that the developed method is accurate and easily applicable for both routine use and research investigations.

Rapid and simple pretreatment of human body fluids using electromembrane extraction across supported liquid membrane for capillary electrophoretic determination of lithium

“…Precise determination of lithium in body fluids is therefore essential in a concentration range of about four orders of magnitude. Several analytical methods can be used including flame emission spectroscopy and flame atomic absorption spectroscopy (AAS) [26], ion selective electrodes (ISE) [27], inductively coupled plasma-mass spectrometry (ICP-MS) [23,24,28,29] and -atomic emission spectrometry (ICP-AES) [30,31], electrothermal AAS [23,32,33], and CE [10,11,34]. Note, however, that these methods require complex sample pretreatment, some are not sensitive enough to determine lithium at endogenous concentrations (flame spectroscopic methods, ion selective electrodes, CE), are extremely costly (ICP-MS/AES), suffer from spectral and nonspectral interferences (spectroscopic methods, ICP-MS/ AES) and none is fully amenable to injection of whole blood.…”

The discrimination of acute tubular necrosis and prerenal azotemia using two biomarkers simultaneously

“…Second, it must not be reabsorbed in the proximal tubule (8). Therefore, lithium may be a more specific indicator for proximal tubule, due to the parallel reabsorption of sodium and water in the proximal tubule, but reabsorption is limited after the other proximal tubule (9).…”

“…Lithium may be a more superior and specific parameter than sodium. However, it is parallel to the reabsorption of sodium and water, in the proximal tubule but its reabsorption is limited after passing the proximal tubules (9).…”

Blood pressure and arterial stiffness in patients with high sodium intake in relation to sodium handling and left ventricular diastolic dysfunction status

“…19,20 Urinary lithium levels were detected using the flame injection AAS and the graphite furnace AAS for urine measurements in the case of lithium concentrations below the 10 μg l − 1 . Serum lithium concentrations were detected with graphite furnace AAS.…”