Wine Chemistry and Biochemistry

692 P.J. Mart ́ın-Alvarez ́

0123456

Concentration

0.00

0.05

0.10

0.15

0.20

Relative area

Relative Area = .00589 + .030635*Concentration

r = .980

Limit of

detection = 0.9

Fig. 13.3Plot of the observed relative area versus the concentration of analyte in the standard
solution, the estimated calibration line with its 95% confidence interval, and a possible way of
calculating the limit of detection

table with thelack of fit testobtained with the STATGRAPHICS program (Statis-

tical Graphics Corp., http://www.statgraphics.com/)) using theCalibration Models

procedure in theSpecial Advanced Regressionmodule (the model appears to be

adequate for the observed data, becauseP>0.10). Figure 13.3 displays plots of the

observed relative area to the internal standard versus the concentration of analyte

in the standard solution, the estimated calibration line with its 95% confidence

interval, and a possible way of calculating thedetection limit(the upper value of

the 95% confidence interval for the estimatedXconcentration corresponding to the

upper value of the 95% confidence interval for the true mean value ofYatX= 0

(Sharaf et al. 1986). The calibration range for the analyte and the results of recovery

experiments to evaluate the occurrence of proportional systematic errors are often

included in the calibration results.

13.3 Multivariate Statistical Techniques

13.3.1 Introduction

Multivariate analysis can be defined as the set ofstatistical and mathematical meth-

odsto analyse, describe and interpretmultidimensional observations. Application