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Table 5 Method calibration

From: Rapid extraction of total lipids and lipophilic POPs from all EU-regulated foods of animal origin: Smedes’ method revisited and enhanced

Parameter

Unit

Chicken eggs

Fat, bovine

Liver, bovine

Fish meat

Meat, bovine

Whole milk

Maximum level [90, 91]

pg TEQ/g

5.0

4.0

0.50

6.5

4.0

5.5

Weight basis

 

fat

fat

ww

ww

fat

fat

Number of samples

 

36

31

44

36

50

44

Range, extracted lipids, TW

% ww

7.4–22.3

67.9–92.6

2.9–6.7

0.40–27.0

1.6–43.5

2.7–5.6

Range, extracted lipids, MSE

% ww

8.7–27.3

78.8–98.0

3.0–7.1

0.64–35.4

2.0–53.6

2.7–5.5

Centre of mass (CoM, lipids TW)

% ww

9.3

86.3

3.8

8.2

17.9

3.9

Centre of mass (CoM, lipids MSE)

% ww

11.0

91.3

4.8

10.0

19.5

3.8

CALUX cell line used

 

H4L7.5c2 rat

H1L6.1c3 mouse

H4L7.5c2 rat

H4L7.5c2 rat

H4L7.5c2 rat

H1L6.1c3 mouse

Range, TEQ concentrations

pg TEQ/g

0.57–9.23

0.91–12.7

0.076–1.19

0.55–8.01

0.30–8.24

0.53–14.0

Range, BEQ concentrations

pg BEQ/g

0.45–9.40

0.69–11.5

0.100–1.27

0.51–8.19

0.49–7.64

0.38–13.8

Centre of mass (CoM, TEQ)

pg TEQ/g

3.53

4.64

0.416

2.64

3.30

6.63

Centre of mass (CoM, BEQ)

pg BEQ/g

3.68

4.79

0.426

2.78

2.99

6.31

Correlation coefficient (r)

 

0.9911

0.9801

0.9830

0.9850

0.9841

0.9744

Critical value for r (df = n-2, p = 0.05, two-sided)

 

0.3291

0.3550

0.2973

0.3291

0.2787

0.2973

Square correlation coefficient (r2)

 

0.9822

0.9606

0.9663

0.9702

0.9685

0.9495

Slope (sensitivity)

 

0.979

0.950

0.925

0.989

0.920

0.912

Standard error of the slope

 

0.023

0.036

0.027

0.030

0.024

0.031

y-Intercept (mean blank signal)

pg BEQ/g

0.224

0.379

0.041

0.16

 − 0.04

0.27

Standard error of the y-intercept

pg BEQ/g

0.098

0.197

0.013

0.101

0.090

0.228

Residual standard deviation (syx)

pg BEQ/g

0.34

0.59

0.047

0.38

0.31

0.69

Relative residual SD (syx,rel) at CoMa

%

9.3

12.3

10.9

13.8

10.2

10.9

Error margin at CoM (α = 0.05)

pg BEQ/g

0.95

1.65

0.128

1.06

0.83

1.87

95% Prediction interval (PI+) at CoM

pg BEQ/g

4.62

6.44

0.554

3.84

3.82

8.18

95% Prediction interval (PI−) at CoM

pg BEQ/g

2.73

3.14

0.299

1.72

2.17

4.45

  1. Regression on results (dioxins and DL-PCBs) from the modified Smedes [46] extraction (MSE, this work) followed by CALUX bioassay analysis, and from Twisselmann [65] extraction (TW) followed by GC/HRMS analysis, of chicken eggs, bovine fat, bovine liver, fish meat, bovine meat and (human) whole milk
  2. aInstead of RSDR, the relative residual standard deviation (syx,rel) at CoM was calculated to assess variability of MSE/bioanalytical results based on the calibrated range.