Abstract
This communication introduces the first-time application of high-resolution continuum-source molecular absorption spectrometry (HR CS MAS) for the quantification of a peptide. The graphite furnace technique was employed and the tripeptide glutathione (GSH) served as a model compound. Based on measuring sulfur in terms of carbon monosulfide (CS), a method was elaborated to analyze aqueous solutions of GSH. The most prominent wavelength of the CS molecule occurred at 258.0560 nm and was adduced for monitoring. The methodological development covered the optimization of the pyrolysis and vaporization temperatures. These were found optimally to be 250 °C and 2250 °C, respectively. Moreover, the effect of modifiers (zirconium, calcium, magnesium, palladium) on the absorption signals was investigated. The best results were obtained after permanent coating of the graphite tube with zirconium (total amount of 400 μg) and adding a combination of palladium (10 µL, 10 g L−1) and calcium (2 µL, 1 g L−1) as a chemical modifier to the probes (10 µL). Aqueous standard samples of GSH were used for the calibration. It showed a linear range of 2.5–100 µg mL−1 sulfur contained in GSH with a correlation coefficient R2 > 0.997. The developed method exhibited a limit of detection (LOD) and quantification (LOQ) of 2.1 µg mL−1 and 4.3 µg mL−1 sulfur, respectively. The characteristic mass accounted for 5.9 ng sulfur. The method confirmed the general suitability of MAS for the analysis of an oligopeptide. Thus, this study serves as groundwork for further development in order to extend the application of classical atomic absorption spectrometry (AAS).
Highlights
Introduction published maps and institutional affilPeptides generally play essential roles in life sciences, for instance in the discovery of drugs such as synthetic peptide vaccines [1]
atomic absorption spectrometry (AAS) standard solution were purchased from Carl Roth (Karlsruhe, Germany); palladium acetate was from Sigma-Aldrich (Steinheim, Germany); calcium nitrate, magnesium nitrate
The diatomic molecule represents the most commost commonly adduced molecule for the determination of sulfur based on Molecular absorption spectrometry (MAS)
Summary
Peptides generally play essential roles in life sciences, for instance in the discovery of drugs such as synthetic peptide vaccines [1]. The increasing interest in peptides is accompanied by the demand for analytical techniques to investigate the biological behavior of pharmacologically active peptides. The revival of old analytical techniques may open novel possibilities for the analysis of peptide therapeutics or peptides participating in the metabolism of new drugs. GSH is a tripeptide comprising the amino acids L-cysteine (Cys), L-glutaminic acid (Glu) and glycin (Gly). It is the gamma carboxyl group of Glu that is linked to Cys, while the carboxyl group of Cys forms a conventional peptide bond with Gly (γ-Glu-Cys-Gly). Reduced GSH is abundant in mammalian cells at concentrations in the low micromolar range (between 0.1 and 15 mmol L−1 ) [3] and is critical for the maintenance of the intracellular iations
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