Abstract
A newly analytical method has been developed to determine total chromium and speciation of this element in water samples through dispersive liquid-liquid microextraction combined with a high-resolution continuum source flame atomic absorption spectrometry. The most significant variables affecting complexation and extraction were optimized by using response surface methodology and univariate optimization. The best conditions for both the complexation and extraction elements in this study were: complexing agent ammonium pyrrolidine dithiocarbamate (APDC 6.0 mmol L-1); pH at 2.0 (CrVI) and at 7.0 (Cr total); NaCl (5% m/v); 1-undecanol (50 µL) and ethanol 300 (CrIV) and 275 µL (total Cr). Under optimal conditions, this method resulted in a 20-100 µg L-1 linear range for CrVI and total chromium, detection limits of 0.35 (CrVI) and 6.7 µg L-1 (total Cr), as well as enriching factor of 26 (CrVI) and 19 for total Cr. The method accuracy was carried out by using certified water reference material (NIST CRM 1643e), and the results achieved were in agreement with the certified value (t-test at a confidence interval of 95%). The method developed was applied in samples of mineral water, tap water (the recovery values ranged from 88 to 115%) and seawater.
Highlights
Chromium is an element commonly found in rocks, animals, plants, soil, rivers and seawater, dusts and volcanic fumes, as well as in Earth’s crust at a concentration of approximately 100 mg kg-1.1 Chromium in the environment can be of natural origins, such as rock and soil erosion, volcanic eruptions, or of anthropogenic origins, through the use of this chemical element in a range of industrial activities such as metallurgy, refractories and chemical industries.[2]
Sodium diethyldithiocarbamate (DDTC) and ammonium pyrrolidine dithiocarbamate (APDC) are two of the most widely used in dispersive liquid-liquid microextraction (DLLME).[13]
Discrete volumes (50 to 200 μL) of a solution containing Cr 50 μg L-1 obtained from the DLLME procedure were manually added to a pipette tip (20 to 200 μL) connected to the nebulizer aspiration tube.[27]
Summary
Chromium is an element commonly found in rocks, animals, plants, soil, rivers and seawater, dusts and volcanic fumes, as well as in Earth’s crust at a concentration of approximately 100 mg kg-1.1 Chromium in the environment can be of natural origins, such as rock and soil erosion, volcanic eruptions, or of anthropogenic origins, through the use of this chemical element in a range of industrial activities such as metallurgy (steel, aluminum and alloys), refractories (cement, glass and clay) and chemical industries (leather tanning, wood preservation and pigments).[2].
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