da Silva José Edson, da Silva Fábio André, Pimentel M Fernanda, Honorato Ricardo Saldanha, da Silva Valdinete Lins, Montenegro Maria da Conceição B S M, Araújo Alberto N
Depto de Química Fundamental (UFPE), Recife, Brazil.
Talanta. 2006 Oct 15;70(3):522-6. doi: 10.1016/j.talanta.2005.12.057. Epub 2006 Feb 13.
A flow-batch manifold coupled to a flame atomic absorption spectrometer was evaluated to assess the iron content by the internal standard method in hydrated ethanol used as fuel in automotive industry. For this assessment official methods require calibration procedures with matrix matching, making it difficult to obtain accurate results for samples adulterated by the addition of water. Nickel was selected as the internal standard since it is usually absent in samples and because it requires similar conditions of atomization. After procedure optimization, which requires about 4.25mL of sample and standard per measurement, it was possible to get linear analytical response for iron concentrations between 0.12 and 1.40mgL(-1) and a detection limit of 0.04mgL(-1). Eighteen samples were collected randomly from fuel stations in Pernambuco (Brazil) and iron concentration was determined using the proposed procedure. Comparison of results obtained (0.20-1.50mgL(-1)) showed a mean standard error of 3.9%, with 3.8% and 2.3% calculated for the mean variation coefficients of the proposed method and the reference procedure, respectively. For adulterated samples (0.12-0.64mgL(-1)), the mean standard error was 4.8% when compared with the standard addition method. These results allowed concluding that the proposed procedure is adequate to accomplish the determination of iron in ethanol fuel in a large scale basis with a sampling rate of about 10h(-1).
对与火焰原子吸收光谱仪相连的流动-间歇式歧管进行了评估，以通过内标法测定汽车工业中用作燃料的水合乙醇中的铁含量。对于此评估，官方方法要求进行基体匹配的校准程序，这使得难以获得因加水而掺假的样品的准确结果。选择镍作为内标，因为它通常不存在于样品中，并且因为它需要相似的雾化条件。经过程序优化（每次测量需要约4.25mL样品和标准品），可以得到铁浓度在0.12至1.40mgL(-1)之间的线性分析响应，检测限为0.04mgL(-1)。从巴西伯南布哥州的加油站随机采集了18个样品，并使用所提出的程序测定了铁浓度。所得结果（0.20 - 1.50mgL(-1)）的比较显示平均标准误差为3.9%，所提出方法和参考程序的平均变异系数分别计算为3.8%和2.3%。对于掺假样品（0.12 - 0.64mgL(-1)），与标准加入法相比，平均标准误差为4.8%。这些结果可以得出结论，所提出的程序足以在大约10h(-1)的采样率下大规模完成乙醇燃料中铁的测定。
