Atomic Spectrometry in Clinical Chemistry

Abstract

Atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES) are two closely related instrumental techniques that have many applications in many different fields. In clinical chemistry, these techniques are well established for the quantitative measurement of essential and nonessential elements found in body tissues and fluids. For most practical purposes, the elements that are routinely measured with modern commercial instrumentation include almost all of the metallic elements of the s, d and p blocks of the periodic table. The exceptions in the p block include the halogens, the noble gases and the elements C, H, N, O and S. Above atomic number 83 (Bi), only U is measured in absorption. With the emergence of commercial instrumentation for atomic mass spectrometry, e.g. inductively coupled plasma mass spectrometry (ICPMS) clinical chemists have another powerful tool with which to measure multielement composition of biological specimens at ultratrace concentrations, i.e. <10 µg L −1 . With ICPMS, the halogens become detectable, along with B, C, N and Th. The coupling of ICPMS with separation technologies has opened new possibilities in clinical laboratory medicine in the field of speciation. In some areas of clinical chemistry, older atomic spectroscopy techniques are still considered the reference method for selected clinical applications, e.g. the determination of serum K and serum Na by flame atomic emission spectrometry (FAES). In other areas, flame atomic absorption spectrometry (FAAS) remains the method of choice for serum Mg and serum Cu because of its sensitivity, rapid throughput and the relatively low cost of instrumentation. Electrothermal atomic absorption spectrometry (ETAAS), while more complex than flame atomization methods, is the method of choice for applications such as blood Pb, serum Al and serum Se, where physiological concentrations are too low to be measured in the flame without laborious preconcentration efforts. Robust procedures for quality assurance (QA) and quality control (QC) are now well established within the clinical laboratory and cover the entire spectrum of clinical laboratory activities. These include preanalytical issues, personnel training and education, and also the appropriate use of certified reference materials (CRMs) for method validation purposes. Participation in proficiency testing (PT) programs and external quality assessment schemes (EQAS) for trace elements in biological fluids have also contributed to improved clinical laboratory performance. Despite the advent of ever more sensitive techniques and robust procedures, the quality of results is still only as good as the specimen collected. Contamination can occur at the preanalytical stage of the analysis and also during the analysis. Selection of the appropriate specimen is critical to obtaining meaningful clinical information about nutritional trace element status or exposure to toxic elements.

Re-examining ferritin-bound iron: current and developing clinical tools

“…Instead, the majority of extant measurements come from a two-step process, first requiring purification and measurement of ferritin concentration, followed by liberation of the iron core which can be assessed by a variety of methods, with the most common being atomic absorption spectroscopy (AAS) [100-102, 104, 105]. The need for a twostep measurement protocol introduces an opportunity for loss of the Fe atoms, as well as contamination from other sources, such as iron from haem [106]. Additionally, AAS has a detection limit above much of the physiological range, with one study reporting the requirement of an initial sample with a ferritin concentration of >200 μg/L to adequately measure its corresponding iron content [101].…”

X-ray optics: an enabling technology for science, medicine, and industry

“…World and US levels for Arsenic have been set at 10 ppb 20,21,22 with indications that even lower levels may be mandated for some regions in the United States. Currently, measurements at these levels require slow and costly laboratory measurements 23 . The need for high resolution is the close overlap of the As Kα x-ray energy at 10.54 keV and Pb Lα at 10.55 keV.…”

Evaluation of a Prototype Point-of-care Instrument Based on Monochromatic X-Ray Fluorescence Spectrometry: Potential for Monitoring Trace Element Status of Subjects with Neurodegenerative Disease

“…Certified clinical trace element laboratories are limited in number and regional in distribution, and utilize high-complexity instrumentation such as inductively coupled plasma mass spectrometry (ICP-MS) for these measurements. In clinical trace element analysis, ICP-MS is often considered the "gold" standard (Parsons 2000). Available technologies for determination of metals in body fluids in a clinical setting are limited.…”