To establish linearity, five concentrations of Na2CaEDTA
standard were used (1, 5, 10, 15 and 20 mg/L). The
homogeneity variance test was applied to each of the seven
peak areas of each level, and no significant differences were
found between the variances of the different levels. The
linearity test was assessed using Infostat Professional
Version 2004d.1. A value of F ¼ 2:21 (mean square
linearity deviation/mean square pure error) was obtained
and P ¼ 0:1317 (n ¼ 35). Therefore, it was concluded that
the selected range behaves in linear form. The average
linear regression equation for EDTA in standard solution
presented a slope of 34.01 with a lower limit (LL) 95% of
33.64 and an upper limit (UL) of 34.38, intercept of 13.57
with an LL of 10.07 and UL of 17.01, and a correlation
coefficient (r2) of 0.9993. Previously, higher Na2CaEDTA
concentrations than 20 mg/L were evaluated, and it was
observed that the correlation between the EDTA peak area
and the corresponding concentration did not follow a
linear response.