Table 1 Obtained statistical values for the simultaneous analysis of ET and TC multivariate calibration methods (PLS, PCR, and ILS)

Parameters

 Concentration range (μg/mL)

 Spectral region (nm)

Cross-validation results

PLS

PCR

ILS

PLS

PCR

ILS

 Optimum number of factors

4

5

–

4

6

–

 Slope

1.0043

0.9925

1.025

0.9974

0.9880

0.9960

 Intercept

− 0.0237

0.0003

0.097

0.2963

0.5764

0.0007

 R²

0.9998

0.9997

0.9991

0.9999

0.9994

0.9998

 RMSE-CV (μg/mL)

0.3686

0.4113

–

2.7289

3.6878

–

 RMSEC

0.2447

0.2620

0.7372

2.3330

2.9049

2.6381

 RMSEP

0.6092

0.3050

–

5.2988

2.8973

–

 SEC

–

–

0.6036

–

–

2.5262

 Slope

0.9956

1.0076

1.010

1.0019

1.0009

1.013

 Intercept

0.0640

− 0.0187

0.018

0.0027

0.1834

0.854

 R²

0.9993

0.9992

0.9995

0.9991

0.9993

0.9997

 RMSEC

0.2047

0.2445

0.6036

1.692

1.295

2.5262