th PT 11 th PT 1 1 Round on Milk 11 Round on Milk Preparation - - PowerPoint PPT Presentation

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CRL-ISS Annual Workshop, 19 October 2007

Laura Ciaralli Laura Ciaralli Community Community Reference Reference Laboratory Laboratory for for Chemical Chemical Elements Elements in Food of in Food of Animal Animal Origin Origin CRL CRL-

• ISS

ISS

11 11th

th PT

PT– – 1° Round on Milk 1° Round on Milk Preparation Preparation of material and

• f material and results

results

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CRL-ISS Annual Workshop, 19 October 2007

Liquid milk

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CRL-ISS Annual Workshop, 19 October 2007

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CRL-ISS Annual Workshop, 19 October 2007

Sample Preparation

• Purchasing of commercial partially skimmed milk
• Partition into two aliquots
• Spiking of As, Cd, Pb at two concentration levels
• Homogenization by a peristaltic pump
• Sampling by a peristaltic pump
• Closing of bottles
• Sterilization process in autoclave
• Labelling
• Shipping

SLIDE 5

CRL-ISS Annual Workshop, 19 October 2007

CHARACTERISTICS of TEST TUBES !"# $%&'()*$"+)$*+)# %+%*$)***,%*+ +-$*+)(%%+) $!*( $# $%&,$)' +).'!+).*,/+*,'$/$ 0*, %$" # $1%)(0*$)%0$)'2$'%*+)0 ")*%0"*,/$ $)'*,($

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CRL-ISS Annual Workshop, 19 October 2007

GLASS TEST TUBES

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CRL-ISS Annual Workshop, 19 October 2007

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CRL-ISS Annual Workshop, 19 October 2007

Sterilisation process

Autoclave 3 minutes, 120 ° C

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CRL-ISS Annual Workshop, 19 October 2007

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CRL-ISS Annual Workshop, 19 October 2007

Arsenic

Statistical Tests

N.S. t2vs t1 N.S. t0vs t2 t0vs t1 N.S. P= 0.742 ANOVA T test 4.0 5.8 4.6

CV%

1.82 2.67 2.07

SD

45.7 45.9 45.1

Media (n=10) 2.5 months (t2) 1 month (t1) Time 0(t0)

Level A g/l

SLIDE 11

CRL-ISS Annual Workshop, 19 October 2007

Arsenic

Statistical Tests

N.S. t2vs t1 N.S. t0vs t2 t0vs t1 N.S. P= 0.443 ANOVA T test 3.3 1.7 4.3

CV%

3.14 1.53 3.96

SD

94.2 92.5 92.8

Media (n=10) 2.5 months (t2) 1 month (t1) Time 0(t0)

Level B g/l

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CRL-ISS Annual Workshop, 19 October 2007

Cadmium Cadmium

Statistical Tests

N.S. t2vs t1 N.S. t0vs t2 t0vs t1 N.S. P= 0.765 ANOVA T test 4.6 4.3 3.3

CV%

0.35 0.33 0.25

SD

7.6 7.6 7.5

Media (n=10) 2.5 months (t2) 1 month (t1) Time 0(t0)

Level A g/l

SLIDE 13

CRL-ISS Annual Workshop, 19 October 2007

Cadmium

Statistical Tests

N.S. t2vs t1 N.S. t0vs t2 t0vs t1 N.S. P= 0.661 ANOVA T test 4.8 4.9 7.0

CV%

0.12 0.12 0.18

SD

2.50 2.47 2.64

Media (n=10) 2.5 months (t2) 1 month (t1) Time 0(t0)

Level B g/l

SLIDE 14

CRL-ISS Annual Workshop, 19 October 2007

Lead

Statistical Tests

N.S. t2vs t1 N.S. t0vs t2 t0vs t1 N.S. P= 0.377 ANOVA T test 5.2 6.0 4.0

CV%

0.59 0.7 0.5

SD

11.5 11.4 11.8

Media (n=10) 2.5 months (t2) 1 month (t1) Time 0(t0)

Level A g/l

SLIDE 15

CRL-ISS Annual Workshop, 19 October 2007

Lead

Statistical Tests

N.S. t2vs t1 N.S. t0vs t2 t0vs t1 N.S. P= 0.002 ANOVA T test 4.7 3.8 2.6

CV%

1.08 0.83 0.61

SD

23.2 22.0 23.6

Media (n=10) 2.5 months (t2) 1 month (t1) Time 0(t0)

Level B g/l

SLIDE 16

CRL-ISS Annual Workshop, 19 October 2007

Sample Preparation

• Purchasing of commercial partially skimmed milk
• Partition into two aliquots
• Spiking of As, Cd, Pb at two concentration levels
• Homogenization by a peristaltic pump
• Sampling by a peristaltic pump
• Closing of bottles
• Sterilization process in autoclave
• Samples immersion in chilled water
• Labelling
• Shipping

SLIDE 17

CRL-ISS Annual Workshop, 19 October 2007

Procedure adopted for the evaluation of the material homogeneity

The adopted procedure was that of Thompson and Fearn (1), which is an improvement of the process described in the International Harmonised Protocol (2).

(1) Fearn, T. and Thompson, M, A new test for ‘sufficient homogeneity’, Analyst, 2001, 126, 1414-1417. (2) M. Thompson and R. Wood, The International Harmonised Protocol for the Proficiency Testing of (Chemical) Analytical Laboratories, Pure & Applied Chemistry, 1993, 65 (9),2123-2144.

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CRL-ISS Annual Workshop, 19 October 2007

Selection of the bottles for the test of homogeneity

The selection was performed by a table of records generated by a computer package. The number of the bottles was obtained through this formula ( √n - 1) Two equally sized portions were taken from the same bottle and analysed

SLIDE 19

CRL-ISS Annual Workshop, 19 October 2007

The analytical determinations were performed on aliquots of milk, previously mineralized with an acid digestion through Micro-Wave oven, by Inductively Coupled Plasma with Mass Detector (ICP-MS)

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CRL-ISS Annual Workshop, 19 October 2007

Arsenic

Level A

35.0 45.0 55.0 18 31 43 53 57 62 84 89 100 126 bottle n° C (µg kg-1) Replicate A Replicate B

Level B

80.0 105.0 18 31 43 53 57 62 84 89 100 126 bottle n° C (µg kg-1) Replicate A Replicate B

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CRL-ISS Annual Workshop, 19 October 2007

Cadmium

Level A

6.5 7.0 7.5 8.0 8.5 18 31 43 53 57 62 84 89 100 126 bottle n° C (µg kg-1) Replicate A Replicate B

Level B

2.0 2.5 3.0 3.5 4.0 18 31 43 53 57 62 84 89 100 126 bottle n°

C (µg kg-1) Replicate A Replicate B

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CRL-ISS Annual Workshop, 19 October 2007

Lead

Level B 20.0 22.0 24.0 26.0 28.0 30.0 18 31 43 53 57 62 84 89 100 126 bottle n° C (µg kg-1) Replicate A Replicate B

Level A 10.0 12.5 15.0 17.5 20.0 18 31 43 53 57 62 84 89 100 126 bottle n° C (µg kg-1) Replicate A Replicate B

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CRL-ISS Annual Workshop, 19 October 2007

STATISTICAL EVALUATION OF PERFORMANCE

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CRL-ISS Annual Workshop, 19 October 2007

Summary Level A

Pb Cd As

(mg kg-1) (mg kg-1) (mg kg-1)

0,0044 0,0016 0,0112

σ σ σ σp

0,0047 0,0012 0,0047 Robust SD

0,0144 0,0074 0,0511

Robust Mean

0,0130 0,0077 0,0516

Median 0,0044 0,0012 0,0086 SD

0,0145 0,0074 0,0522

Mean 0,0240 0,0100 0,0740 max 0,0080 0,0050 0,0370 min 23 23 17

• N. of Results

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CRL-ISS Annual Workshop, 19 October 2007

Summary Level B

Pb Cd As

(mg kg-1) (mg kg-1) (mg kg-1)

0,0069 0,0006 0,0228

σ σ σ σp

0,0037 0,0004 0,0137 Robust SD 0,0247 0,0029 0,1037 Robust Mean 0,0250 0,0030 0,1026 Median 0,0057 0,0006 0,0209 SD 0,0254 0,0030 0,1062 Mean 0,0420 0,0050 0,1610 max 0,0150 0,0020 0,0700 min 23 23 17

• N. of Results

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CRL-ISS Annual Workshop, 19 October 2007

0,0

• 0,5
• 0,6

0,2 0,1

• 0,1

0,3

0,0 1,3 0,0 0,0 0,1 0,2

• 0,4

1,2

• 0,2
• 0,8

0,0 0,0

• 0,4
• 0,5
• 1,4

0,4

• 1,5
• 1,3

0,0

• 0,3

0,1 0,4 0,1 0,2 0,3

• 0,8

0,1

• 1,5

1,0 0,2 0,0

• 0,8

0,1 0,4 0,4 0,3 0,0

• 0,5

0,1

• 0,2

1,6 1,6

• 0,1
• 0,3

0,1 0,4

• 0,1

0,1 1,5 0,6 1,7 1,0 0,0 0,0 1,5 2,2 1,1

• 0,2
• 0,2
• 0,1

0,0

• 0,2
• 0,2

0,2

• 0,2
• 0,1
• 0,6
• 1,4

0,1 0,2

• 0,4
• 0,3
• 0,7
• 0,5
• 2,5

1,8 3,2 1,6

• 0,8

1,3 0,1

• 0,2
• 0,2
• 0,1
• 1,4
• 1,2
• 0,9
• 1,1
• 0,0
• 0,3

0,1 1,0 0,0 0,3

• 0,5
• 1,5

0,1

• 0,2
• 0,9
• 0,7

0,1

• 0,3

0,7 0,3

• 0,4

1,1

• 1,4
• 0,8

2,5 2,0

• 0,5
• 0,8
• 1,3
• 0,8
• 0,0

0,6 0,1 0,4

• 0,2
• 0,5

Level B Level A Level B Level A Level B Level A

Pb Cd As

z-scores

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CRL-ISS Annual Workshop, 19 October 2007

Arsenic Arsenic

Percentage Percentage of

• f z

z-

• scores

scores

Level B

88% 6% 6% lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

Level A

88% 12% lzl ≤ 1 1< lzl ≤ 2

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CRL-ISS Annual Workshop, 19 October 2007

Cadmium Cadmium

Percentage Percentage of

• f z

z-

• scores

scores

Level A

96% 4% lzl ≤ 1 1< lzl ≤ 2

Level B

83% 13% 4% lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

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CRL-ISS Annual Workshop, 19 October 2007

Lead Lead

Percentage Percentage of

• f z

z-

• scores

scores

Level A 14.4 µg/kg

71% 25% 4%

lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

Level B 24.7 µg/kg

83% 13% 4%

lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

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CRL-ISS Annual Workshop, 19 October 2007

Pb Pb z z-

• scores

scores 10th PT 10th PT vs vs 11thPT 11thPT

Level A 14.4 µg/kg

71% 25% 4%

lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

Level B 24.7 µg/kg

83% 13% 4%

lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

76% 14% 10% 0< lzl ≤ 1 1< lzl ≤ 2 lzl > 3

Level A 17.3 µg/kg

85% 5% 10% 0< lzl ≤ 1 1< lzl ≤ 2 2< lzl ≤ 3

Level B 39.7 µg/kg

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CRL-ISS Annual Workshop, 19 October 2007

Distribution of Analytical Techniques

Arsenic

60% 40% HG-AAS MS

Cadmium and Lead

70% 30% ETA-AAS MS

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CRL-ISS Annual Workshop, 19 October 2007

Samples Treatment

Arsenic

50% 43% 7% Dry Ash. MW Wet Dig.

Cadmium/Lead

35% 60% 5% Dry Ash. MW Wet Dig.

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CRL-ISS Annual Workshop, 19 October 2007

Treatment/Techniques

As Milk 11 PT

1 2 3 4 5 6 7

• Ash. HG-AAS

MW MS MW HG-AAS Wet dig. MS Ash./AAS

Participants

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CRL-ISS Annual Workshop, 19 October 2007

Treatment/Techniques

Cd- Pb Milk 11 PT

1 2 3 4 5 6 7 8 Ashing AAS MW MS MW AAS Wet dig. AAS

Participants

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CRL-ISS Annual Workshop, 19 October 2007

This last round on milk gave us interesting

• information. As in the previous PT, once

again, results confirmed that Lead was the most difficult element to analyse among the elements considered, even if a good performance was shown by most laboratories.

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CRL-ISS Annual Workshop, 19 October 2007

THANK YOU FOR YOUR ATTENTION!!!!!!!!!!!!!!!!!!

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CRL-ISS Annual Workshop, 19 October 2007

Spiked samples concentration

24.70±0.61 13.68±0.5 Pb 2.94±0.08 7.7±0.17 Cd 97.79±1.17 48.16±0.9 As Level B Level A