In this study, ascorbic acid (Vc) was employed as a matrix modifier to develop a direct method for the determination of trace platinum in tailings using graphite furnace atomic absorption spectrometry (GFAAS). The influence of various matrix modifiers on the analytical performance was investigated. The method exhibits a characteristic mass of 1.3×10â»â´ μg and a detection limit of 1.9×10â»âµ μg/mL. The recovery rates of the samples ranged from 100.7% to 104.0%, indicating high accuracy and reliability.
The atomic absorption technique has been widely applied for platinum analysis across different materials. However, due to its low concentration in most matrices and the complex nature of the sample, pre-treatment steps such as foam adsorption or ion exchange are often necessary. These procedures can complicate the measurement process, especially when using GFAAS, which is known for its long measurement times. To address these challenges, the use of matrix modifiers has gained popularity for reducing interferences and enhancing sensitivity. In this work, we explored the effectiveness of ascorbic acid as a matrix modifier, leading to a simple and efficient method for platinum determination in tailings.
The experimental setup included a Hitachi Zeeman 180-70 polarized atomic absorption spectrometer equipped with a GA-3 graphite furnace and an automatic sample introduction system. Platinum standard solutions were prepared by dissolving high-purity platinum in aqua regia and diluting to the desired concentration. Ascorbic acid was used as the matrix modifier, and all reagents were of analytical grade. The water used was deionized and distilled.
Instrument parameters were optimized, including a slit width of 0.4 nm, a tube wall atomization mode, and a measurement time of 20 µL. Graphite furnace conditions were carefully adjusted to ensure accurate and reproducible results. The method involved adding ascorbic acid to the sample solution before measurement, with absorbance readings taken against a reagent blank.
The influence of acidic media on platinum determination was studied, and it was found that 0.1 mol/L nitric acid provided optimal conditions. Various matrix modifiers, including cerium, palladium, and nickel, were evaluated, with ascorbic acid showing the best performance in reducing the atomization temperature and improving sensitivity. The mechanism behind this effect was analyzed through atomization and ashing curves, revealing that ascorbic acid creates a reducing atmosphere that enhances platinum atomization.
The amount of ascorbic acid used was also optimized, with 4 µg per measurement yielding the best results. Atomization time was set to 7 seconds to achieve maximum precision. The presence of coexisting ions was tested, and no significant interference was observed under the selected conditions.
A calibration curve was constructed over a concentration range of 2–500 ng/mL, with a linear regression equation of A = 0.0108 + 0.0025C and a correlation coefficient of 0.9984. The detection limit was determined to be 1.9×10â»âµ µg/mL.
Sample preparation involved digesting tailings sand with hydrofluoric acid and aqua regia, followed by dilution and analysis. Spike recovery tests confirmed the accuracy of the method, with recoveries within the acceptable range. This approach offers a practical and reliable way to determine trace platinum in complex matrices like tailings.
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