Determination of natural levels of lithium and strontium in human blood serum by discrete injection and atomic emission spectrometry with a nitrous oxide—acetylene flame

Dried Blood Spots and Miniaturized Ultrasonic Nebulization Microplasma Optical Emission Spectrometry for Point-of-Care Testing of Blood Lithium

Despite the significant importance of blood lithium (Li) detection in the treatment of bipolar disorder (BD), its point-of-care testing (POCT) remains a great challenge due to tedious sample preparation and the use of large-footprint atomic spectrometers. Herein, a system coupling dried blood spots (DBS) with a point discharge optical emission spectrometer equipped with a miniaturized ultrasonic nebulizer (MUN-μPD-OES) was developed for POCT of blood Li. Three microliters of whole blood were used to prepare a dried blood spot on a piece of filter paper to which 10 μL of eluent (1% (v/v) formic acid and 0.05% (v/v) Triton-X) was added. Subsequently, the paper was placed onto the vibrating steel membrane of the ultrasonic nebulizer and powered on to generate aerosol. The aerosol was directly introduced to the μPD-OES for quantification of Li by monitoring its atomic emission line at 670.8 nm. The proposed method minimized matrix interference caused by high levels of salts and protein. It is worth noting that the MUN suitably matches the needs of DBS sampling and can provide aerosolized introduction of Li into the assembled μPD-OES, thus eliminating all tedious sample preparation and the need for a commercial atomic spectrometer. Calibration response is linear in the therapeutic range and a limit of detection (LOD) of 1.3 μg L-1 is well below the Li minimum therapeutic concentration (2800 μg L-1). Li in mouse blood was successfully detected in real-time using MUN-μPD-OES after intraperitoneal injection of lithium carbonate, confirming that the system holds great potential for POCT of blood Li for patients with BD.

Determination of nickel, calcium and magnesium in xylem sap by flame atomic absorption spectrometry using a microsampling technique

INTRODUCTION

Knowledge of xylem sap chemical composition is important to the understanding of translocation, detoxification and tolerance mechanisms. However, the small amount of sample available often hampers its characterisation. Hence, low volume consumption techniques are needed for xylem sap analysis.

OBJECTIVE

To develop a microsampling technique for the determination of elements in xylem sap from different plants by flame atomic absorption spectrometry (FAAS).

METHODOLOGY

The microsampling device was optimised in terms of sample volume and integration time. The analytical characteristics of the microsampling technique (micro-FAAS) were established and compared with those of FAAS with traditional continuous nebulisation. The method was validated by means of an independent technique.

RESULTS

Ca, Mg and Ni were determined in a 50 microL aliquot of xylem sap solution/element that was introduced directly into the flame via the microsampling accessory. Good precision was obtained with relative standard deviations of 1.1, 0.6 and 2.3% for Ca, Mg and Ni, respectively. Matrix effects resulting from the physical characteristics of the samples and possible chemical interferences caused by phosphate and/or sulphate were ruled out.

CONCLUSION

A simple, rapid and reproducible microsampling technique coupled to FAAS was developed and successfully applied in the determination of Ca, Mg and Ni in xylem sap.

Study of lithium absorption by users of spas treated with lithium ion

This study examines the possible dermal absorption of lithium ion into the blood serum of spa/hot tub bathers. Fifty-three participants (28 males and 25 females) spent 20 minutes per day, 4 days per week for 2 consecutive weeks in one of two assigned spas. The participants were randomly assigned to one of the two spas after matching based on sex, age, and use of oral contraceptives. The test spa contained 40 +/- 5 ppm lithium ion, while the control spa contained no additional lithium ion above the background levels of approximately 0.02 ppm. The exposure in the spa treated with lithium ion (from lithium chloride) simulated the maximum exposure that would be expected in a spa sanitized with lithium hypochlorite. The two spas were maintained at 101 +/- 2 degrees F. Serum lithium ion levels before and after spa use were determined using graphite-furnace atomic absorption spectroscopy with a minimum detectable level of lithium ion in serum of 2 micrograms l-1 (ppb). There was no statistically significant difference in serum lithium levels between the control and treatment group at any stage. We conclude that dermal exposure to lithium ion (as would be present after treatment of a spa with lithium hypochlorite) did not result in a detectable increase in the serum lithium ion level.