Abstract
Analytical procedures for electrothermal atomic absorption spectrometric (ETAAS) determination of arsenic in essential oils from lavender ( Lavendula angustifolia) and rose ( Rosa damascena) are described. For direct ETAAS analysis, oil samples are diluted with ethanol or i-propanol for lavender and rose oil, respectively. Leveling off responses of four different arsenic species (arsenite, arsenate, monomethylarsonate and dimethylarsinate) is achieved by using a composite chemical modifier: l-cysteine (0.05 g l −1) in combination with palladium (2.5 μg) and citric acid (100 μg). Transverse-heated graphite atomizer (THGA) with longitudinal Zeeman-effect background correction and ‘end-capped’ graphite tubes with integrated pyrolytic graphite platforms, pre-treated with Zr–Ir for permanent modification are employed as most appropriate atomizer. Calibration with solvent-matched standard solutions of As(III) is used for four- and five-fold diluted samples of lavender and rose oil, respectively. Lower dilution factors required standard addition calibration by using aqueous (for lavender oil) or i-propanol (for rose oil) solutions of As(III). The limits of detection (LOD) for the whole analytical procedure are 4.4 and 4.7 ng g −1 As in levender and rose oil, respectively. The relative standard deviation (R.S.D.) for As at 6–30 ng g −1 levels is between 8 and 17% for both oils. As an alternative, procedure based on low temperature plasma ashing in oxygen with ETAAS, providing LODs of 2.5 and 2.7 ng g −1 As in levender and rose oil, respectively, and R.S.D. within 8–12% for both oils has been elaborated. Results obtained by both procedures are in good agreement.
Published Version
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