Analytical curve or standard addition method: how to elect and design—a strategy applied to copper determination in sugarcane spirits using AAS

Abstract

In most instrumental analysis, the analyte concentration is usually obtained the by Analytical Curve Method (ACM) or Standard Addition Method (SAM). Thus, it is important for the analyst to select the most appropriate method, to seek the best conditions of analysis, and to provide parameters of analytical performance. A strategy to do so is proposed in this paper in conjunction with MATLAB software to implement it. The proposed strategy was applied to copper determination by atomic absorption spectrometry in Brazilian sugarcane spirits termed 'Cachaça' and SAM was chosen as the most appropriate method. To select the best experimental design for SAM, the influence of some factors, such as the number of standard additions and concentration levels, the location of the levels and the average concentration of the standard additions were demonstrated. The design with six standard additions, four concentration levels located near the inferior and superior levels and the average concentration of the standard additions closer to zero yielded SAM with an adequate compromise between precision, cost and time of analysis. The uniform distribution of concentration levels, usually used in routine analysis, is not a good design regarding precision. On the other hand, it is adequate when the linear range is unknown. Generally, the proposed strategy can be applied to different instrumental techniques and samples, which aim to improve their analytical performance.

Determinação dos teores de cobre e grau alcoólico em aguardentes de cana produzidas no estado de Minas Gerais

“…A "Association of Official Analytical Chemists (AOAC)" recomenda, para determinação do cobre em bebidas destiladas, a espectrometria de absorção atômi-ca em chama, com os padrões preparados em solução 50% v/v de etanol e água 18 . Este método apresenta a vantagem de possuir menor limite de detecção, ser mais rápido e aceito 19 internacionalmente.…”

Application of a macromolecular micellar system formed by the P123 triblock copolymer for determination of copper concentrations

“…Previously published methods to determine copper concentrations, include the use of several analytical techniques, such as flame and graphite furnace atomic absorption spectrometry (FAAS and GFAAS) [2][3][4], inductively coupled plasma (ICP) with various detectors [5,6], voltametry [7,8], spectrophotometry [9], and potentiometry [10]. AAS and ICP, are the most selective and sensitive techniques for copper concentration determination.…”

An automatic flow-batch standard-addition method for sodium determination in alcohol fuel by flame photometry

“…3 Since the composition or matrix effect of actual alcohol fuel samples varies significantly, this methodology can produce inexact results. 3,4 To overcome this problem, the standard-addition method (SAM) 5 should be used to accurately analyse each sample.…”

“…These results are also shown in Table 1, as well as the results using ABNT methodology. The differences observed between the SAM and ABNT results can be justified by using the t-Student test to compare the inclinations of SAM curves, as described by Honorato et al 4 For example, the inclinations of SAM curves of synthetic sample 1 and alcohol fuel 6 in Table 1 are statistically different. Therefore, ACMMS yields different results if applied to estimate the analyte concentration in both samples.…”

“…3 Since the composition or matrix effect of actual alcohol fuel samples varies significantly, this methodology can produce inexact results. 3,4 To overcome this problem, the standard-addition method (SAM) 5 should be used to accurately analyse each sample.One of the ways to implement SAM 5 is to add increasing amounts of analyte to identical aliquots of the sample; these mixtures are then diluted to the same total volume. This ensures that sample matrix effects are the same throughout 6 and a SAM curve is constructed with exact matrix-matching between samples and standards.…”