Commission Regulation (EC) No 333/2007Show full title

PART C SAMPLE PREPARATION AND ANALYSIS

C.1. LABORATORY QUALITY STANDARDS

Laboratories shall comply with the provisions of Article 12 of Regulation (EC) No 882/2004(1).

Laboratories shall participate in appropriate proficiency testing schemes which comply with the ‘International Harmonised Protocol for the Proficiency Testing of (Chemical) Analytical Laboratories’(2) developed under the auspices of IUPAC/ISO/AOAC.

Laboratories shall be able to demonstrate that they have internal quality control procedures in place. Examples of these are the ‘ISO/AOAC/IUPAC Guidelines on Internal Quality Control in Analytical Chemistry Laboratories’(3).

Wherever possible the trueness of analysis shall be estimated by including suitable certified reference materials in the analysis.

C.2. SAMPLE PREPARATION

C.2.1. Precautions and general considerations

The basic requirement is to obtain a representative and homogeneous laboratory sample without introducing secondary contamination.

All of the sample material received by the laboratory shall be used for the preparation of the laboratory sample.

Compliance with maximum levels laid down in Regulation (EC) No 1881/2006 shall be established on the basis of the levels determined in the laboratory samples.

C.2.2. Specific sample preparation procedures

C.2.2.1. Specific procedures for lead, cadmium, mercury and inorganic tin

The analyst shall ensure that samples do not become contaminated during sample preparation. Wherever possible, apparatus and equipment coming into contact with the sample shall not contain those metals to be determined and be made of inert materials e.g. plastics such as polypropylene, polytetrafluoroethylene (PTFE) etc. These should be acid cleaned to minimise the risk of contamination. High quality stainless steel may be used for cutting edges.

There are many satisfactory specific sample preparation procedures which may be used for the products under consideration. Those described in the CEN Standard ‘Foodstuffs — Determination of trace elements — Performance criteria, general considerations and sample preparation’(4) have been found to be satisfactory but others may be equally valid.

In the case of inorganic tin, care shall be taken to ensure that all the material is taken into solution as losses are known to occur readily, particularly because of hydrolysis to insoluble hydrated Sn(IV) oxide species.

C.2.2.2. Specific procedures for benzo(a)pyrene

The analyst shall ensure that samples do not become contaminated during sample preparation. Containers shall be rinsed with high purity acetone or hexane before use to minimise the risk of contamination. Wherever possible, apparatus and equipment coming into contact with the sample shall be made of inert materials such as aluminium, glass or polished stainless steel. Plastics such as polypropylene or PTFE shall be avoided because the analyte can adsorb onto these materials.

C.2.3. Treatment of the sample as received in the laboratory

The complete aggregate sample shall be finely ground (where relevant) and thoroughly mixed using a process that has been demonstrated to achieve complete homogenisation.

C.2.4. Samples for enforcement, defence and referee purposes

The samples for enforcement, defence and referee purposes shall be taken from the homogenised material unless this conflicts with the rules of the Member States on sampling as regards the rights of the food business operator.

C.3. METHODS OF ANALYSIS

C.3.1. Definitions

The following definitions shall apply:

‘r’

=

Repeatability the value below which the absolute difference between single test results obtained under repeatability conditions (i.e., same sample, same operator, same apparatus, same laboratory, and short interval of time) may be expected to lie within a specific probability (typically 95 %) and hence r = 2,8 × s_r.

‘s_r’

=

Standard deviation calculated from results generated under repeatability conditions.

‘RSD_r’

=

Relative standard deviation calculated from results generated under repeatability conditions [(s_r/) × 100].

‘R’

=

Reproducibility the value below which the absolute difference between single test results obtained under reproducibility conditions (i.e., on identical material obtained by operators in different laboratories, using the standardised test method), may be expected to lie within a certain probability (typically 95 %); R = 2,8 × s_R.

‘s_R’

=

Standard deviation, calculated from results under reproducibility conditions.

‘RSD_R’

=

Relative standard deviation calculated from results generated under reproducibility conditions [(s_R/) × 100].

‘LOD’

=

Limit of detection, smallest measured content, from which it is possible to deduce the presence of the analyte with reasonable statistical certainty. The limit of detection is numerically equal to three times the standard deviation of the mean of blank determinations (n > 20).

‘LOQ’

=

Limit of quantification, lowest content of the analyte which can be measured with reasonable statistical certainty. If both accuracy and precision are constant over a concentration range around the limit of detection, then the limit of quantification is numerically equal to six or 10 times the standard deviation of the mean of blank determinations (n > 20).

‘HORRAT_r’

=

The observed RSD_r divided by the RSD_r value estimated from the Horwitz equation(5) using the assumption r = 0,66R.

‘HORRAT_R’

=

The observed RSD_R value divided by the RSD_R value calculated from the Horwitz equation.

‘u’

=

Standard measurement uncertainty.

‘U’

=

The expanded measurement uncertainty, using a coverage factor of 2 which gives a level of confidence of approximately 95 % (U = 2u).

‘Uf’

=

Maximum standard measurement uncertainty.

C.3.2. General requirements

Methods of analysis used for food control purposes shall comply with the provisions of points 1 and 2 of Annex III to Regulation (EC) No 882/2004.

Methods of analysis for total tin are appropriate for official control on inorganic tin levels.

For the analysis of lead in wine, Commission Regulation (EEC) No 2676/90(6) lays down the method to be used in chapter 35 of its Annex.

C.3.3. Specific requirements

C.3.3.1. Performance criteria

Where no specific methods for the determination of contaminants in foodstuffs are prescribed at Community level, laboratories may select any validated method of analysis (where possible, the validation shall include a certified reference material) provided the selected method meets the specific performance criteria set out in Tables 5 to 7.

Table 5

Performance criteria for methods of analysis for lead, cadmium, mercury and inorganic tin

Parameter	Value/Comment
Applicability	Foods specified in Regulation (EC) No 1881/2006
LOD	For inorganic tin less than 5 mg/kg. For other elements less than one tenth of the maximum level in Regulation (EC) No 1881/2006, except if the maximum level for lead is less than 100 μg/kg. For the latter, less than one fifth of the maximum level
LOQ	For inorganic tin less than 10 mg/kg. For other elements less than one fifth of the maximum level in Regulation (EC) No 1881/2006, except if the maximum level for lead is less than 100 μg/kg. For the latter, less than two fifth of the maximum level
Precision	HORRATr or HORRATR values of less than 2
Recovery	The provisions of point D.1.2. apply
Specificity	Free from matrix or spectral interferences

Table 6

Performance criteria for methods of analysis for 3-MCPD

Criterion	Recommended Value	Concentration
Field blanks	Less than the LOD	—
Recovery	75 to 110 %	all
LOD	5 μg/kg (or less) on a dry matter basis
LOQ	10 μg/kg (or less) on a dry matter basis	—
Precision	< 4 μg/kg	20 μg/kg
	< 6 μg/kg	30 μg/kg
	< 7 μg/kg	40 μg/kg
	< 8 μg/kg	50 μg/kg
	< 15 μg/kg	100 μg/kg

Table 7

Performance criteria for methods of analysis for benzo(a)pyrene

Parameter	Value/Comment
Applicability	Foods specified in Regulation (EC) No 1881/2006
LOD	Less than 0,3 μg/kg
LOQ	Less than 0,9 μg/kg
Precision	HORRATr or HORRATR values of less than 2
Recovery	50 to 120 %
Specificity	Free from matrix or spectral interferences, verification of positive detection

C.3.3.2. ‘Fitness-for-purpose’ approach

Where a limited number of fully validated methods of analysis exist, alternatively, a ‘fitness-for-purpose’ approach may be used to assess the suitability of the method of analysis. Methods suitable for official control must produce results with standard measurement uncertainties less than the maximum standard measurement uncertainty calculated using the formula below:

where:

• Uf is the maximum standard measurement uncertainty (μg/kg);

• LOD is the limit of detection of the method (μg/kg);

• C is the concentration of interest (μg/kg);

• α is a numeric factor to be used depending on the value of C. The values to be used are given in Table 8.

Table 8

Numeric values to be used for α as constant in formula set out in this point, depending on the concentration of interest

C (μg/kg)	α
≤ 50	0,2
51 to 500	0,18
501 to 1 000	0,15
1 001 to 10 000	0,12
> 10 000	0,1

(1)

As amended by Article 18 of Commission Regulation (EC) No 2076/2005 (OJ L 338, 22.12.2005, p. 83).

(2)

‘The international harmonized protocol for the proficiency testing of analytical chemistry laboratories’ by M. Thompson, S.L.R. Ellison and R. Wood, Pure Appl. Chem., 2006, 78, 145-96.

(3)

Edited by M. Thompson and R. Wood, Pure Appl. Chem., 1995, 67, 649-666.

(4)

Standard EN 13804:2002, ‘Foodstuffs — Determination of trace elements — Performance criteria, general considerations and sample preparation’, CEN, Rue de Stassart 36, B-1050 Brussels.

(5)

M. Thompson, Analyst, 2000, 125, 385-386.

(6)

OJ L 272, 3.10.1990, p. 1. Regulation as last amended by Regulation (EC) No 1293/2005 (OJ L 205, 6.8.2005, p. 12).