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Lime mortar has been used throughout history despite current substitution by hydraulic mortars (cements). The chemical composition of the lime used in its manufacture, however, is determined by local geology. In addition, the type of slaking, which depends on the amount of water used, gives rise to different types of lime. The result is that the behavior of lime mortar can vary depending on the composition and type of lime used. A three-way ANOVA analysis was carried out to determine the composition, type, and temporal evolution and the interactions of these three variables for evaluation of the characteristics of air lime mortars for their use in cultural heritage conservation projects.

The proposal of a new analytical method implies two important steps: the optimization of the experimental variables and the validation of the proposed method. The first one involves the selection of the values of the factors which have an influence on the analytical signal and produce the best results in the analytical process. To develop the optimization of analytical methods, two different strategies can be used. In the traditional "oneat-a-time" operation, all the values of the different factors except one are constant, and this one is the object of the survey. The alternative to this strategy is the Experimental Design; in this case the whole set of the factors comprising the system is simultaneously modified, making it possible to identify the factors which modify the analytical response. The latter strategy allows us to understand circumstances which are not explained by the traditional mode, such as those in which the analytical response is a multimodal function of the independent variables or when the effects of the variables are not additive and there is interaction among them. The validation of an analytical method verifies that the characteristics of the method fit the requirements of the application domain, that is, the whole set of specifications: concentration interval of the analyte, level of uncertainty accepted, selectivity, application conditions, etc. 2 Consequently, the validation methodology involves the definition of the quantitative characteristics that determine whether the different stages of the procedure are suitable for a particular analysis.The use of chemometric techniques in the two steps makes it possible to ensure quality control in the laboratory; furthermore, less time is necessary for development of the method and improved characteristics are obtained. Thus, using experimental designs a greater quantity and higher quality of information is obtained, in relation to the variables of the analytical system and its characteristics.Solid-phase spectrophotometry (SPS) 3,4 is a methodology that includes the preconcentration of the analyte on a solid, with a previous or simultaneous reaction step to produce a chromogenic compound, and the subsequent measurement of the absorbance in the solid phase. This provides an increase in selectivity and sensitivity to SPS methods in relation to solution methods. This paper describes the use of experimental design and chemometric techniques to develop and validate a SPS method for the determination of zinc in environmental samples. The optimization of variables was studied both in the traditional mode ("one-at-a-time") and using Doehlert's design 5 in order to perform a comparative study. Robust regression 6,7 was applied to detect the outliers and for the determination of the upper limit of the calibration graph for the 100 cm 3 sample system. Saturated fractional factorial designs at two levels were used to evaluate the robustness of the proposed method. In the study of the performance characteristics, special attention was paid to the pres- Gr...

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Paper 5/028OO K