Samplingand sample processing - CTAA whole fruit, vegetable or natural bunch of them ... Precautions to be taken: ... contact of pesticides on peel with juices. Ambient milling:

SamplingSampling and sample processingand sample processing

FrancescoFrancesco Sbrana

Why sampling and sample processing are important?

Risks associated with incorrect sampling

MRL

False positive

Loss of perishable foodEconomic damage for

farmers and importers/exporters

False negative

Environmentaland consumer

safety are compromised

From: "Sampling and Sample Processing in Pesticide Residue Analysis”, Steven J. Lehotay and Jo Marie Cook, J. Agric. Food Chem., 2015, 63 (18), pp 4395–4404

Commission Regulation (EC) No 401/2006 of 23February 2006 laying down the methods of samplingand analysis for the official control of the levels ofmycotoxins in food

EU Regulations on sampling

Commission Directive 2002/63/EC of 11 July 2002 establishing Community methods of sampling for the official control of pesticide residues in and on products of plant and animal origin and repealing Directive 79/700/EEC

EU Regulations on sampling

Commission Regulation (EU) No 836/2011 of 19 August 2011 amending Regulation (EC) No 333/2007 laying down the methods of sampling and analysis for the official control of the levels of lead, cadmium, the official control of the levels of lead, cadmium, mercury, inorganic tin, 3-MCPD and benzo(a)pyrene in foodstuffs

Who takes the sample?

Person trained in sampling procedures and where required, authorised by authorities.

Enforcement agencies

-Government officials-Local authority personnel-Port of entry officials

Pesticide residues in food:Sampling-definitions

Commission Directive 2002/63

Lot: A quantity of a food material delivered at one time and known, or presumed, by the sampling officer to have uniform characteristics such as: origin, producer, variety, packer, type of packing, markings, consignor, etc

LOT

One which, for any reason, is suspected to is suspected to contain an excessive contain an excessive residueresidue.

One for whichthere is no reason to suspect that it may contain an excessive residue.

Suspect lot Non-suspect lot



a) Fresh fruit and vegetables.

The smallest discrete portion in a lot, which should be withdrawn to form the whole or part of a primary sample.

UNIT

a) Fresh fruit and vegetables.

Each whole fruit, vegetable or natural bunch of them (e.g. grapes) should form a unit, except where these are small.Units of packaged small products may be identified as in (d). Where a sampling device may be used without damaging the material, units may be created by this means. Individual eggs, fresh fruit or vegetables must not be cut or broken to produce units.



b) Large animals or parts or organs of them. A portion, or the whole, of a specified part or organ

UNIT

portion, or the whole, of a specified part or organ should form a unit. Parts or organs may be cut to form units.



c) Small animals or parts or organs of them. Each whole animal or complete animal part or organ present may form

UNIT

animal or complete animal part or organ present may form a unit.Where packaged, units may be identified as in (d), below. Where a sampling device may be used without affecting residues, units may be created by this means.



• d) Packaged materials. The smallest discrete packages should be taken as units. Where the smallest packages are very large, they should be sampled as bulk, as in (e).

UNIT

very large, they should be sampled as bulk, as in (e). Where the smallest packages are very small, a pack of packages may form the unit.



e) Bulk materials and large packages (such as drums, cheeses, etc) which are individually too large to be taken

UNIT

as primary samples. The units are created with a sampling device.



Primary sample /Incremental sample: One or more units taken from one position in a lot

SAMPLE

The position from which a primary sample is taken in the lot should preferably be chosen randomly but, where this is physically impractical, it should be from a random position in the accessible parts of the lot



BULK SAMPLE/AGGREGATE SAMPLE

Products other than meatand poultry:

Meat and poultry:and poultry:

the combined and well-mixed aggregate of the primary samples takenfrom a lot

Equal to primary sample



Laboratory sample: The sample sent to, or received by, thelaboratory. A representative quantity of material removed fromthe bulk sample.

SAMPLE

Analytical sample: The material prepared for analysis from Analytical sample: The material prepared for analysis from the laboratory sample, by separation of the portion of the product to be analysed and then by mixing, grinding, fine chopping, etc., for the removal of analytical portions with minimal sampling error.

Analytical portion: A representative quantity of material removed from the analytical sample, of proper size for measurement of the residue concentration.

Schematic representation of sampling procedures

Precautions to be taken: Contamination and deterioration of samples must be prevented at all stages, because they may affect the analyticalresults. Each lot to be checked for compliance must be sampled separately

Collection of primary samples: Each primary sample should be taken

Pesticide residues in food:Sampling procedures


Collection of primary samples: Each primary sample should be taken from a randomly chosen position in the lot, as far as practicable. The primary samples must consist of sufficient material to provide the laboratory sample(s) required from the lot.

Preparation of the bulk sample: the primary samples should be combined and mixed well, if practicable, to form the bulk sample.



Preparation of the laboratory sample: where the bulk sample is larger than is required for a laboratory sample, it should be divided to provide a representative portion. The minimum sizes required for laboratory samples are given in Tables 3, 4 and 5.

Small sized fresh products(UNIT < 25 g)

Primary sample: Laboratory sample



Primary sample:

Whole units or packages or unitstaken using a sampling device

Laboratory sample

1 KG

Medium sized fresh products(25 g < UNIT < 250 g)

Primarysample:



sample:

Whole units

Laboratorysample

A minimum of 1 kg or 10 individual units (whichever is the greater).

Large sized fresh products(UNIT > 250 g)

Primarysample:

Whole units



Whole units

Laboratorysample

A minimum of 2 kg or 5 individual units (whichever is greater)

Sampling record: The sampling officer must record the nature and origin of the lot; the owner, supplier or carrier of it; the date and place of sampling; and any other relevant information. Any departure from the recommended method of



Sampling record

information. Any departure from the recommended method of sampling must be recorded.

Sampling record: A signed copy of the record must accompany each replicate laboratory sample and a copy should be retained by the sampling officer.A copy of the sampling record should be given to the owner of



Sampling record

A copy of the sampling record should be given to the owner of the lot, or a representative of the owner, whether or not they are to be provided with a laboratory sample.If sampling records are produced in computerised form, these should be distributed to the same recipients and a similar verifiable audit trail maintained.


Sampling record

• Article 11(7) of Regulation (EC) No 882/2004 requires that samples must be handled and labelled requires that samples must be handled and labelled in such a way as to guarantee their legal and analytical validity

SANTE 11945/2015

Packaging and transmissionof the laboratory sample

Samples must be transported in clean containers and robustpackaging. Polythene bags are acceptable for most samplesbut low permeability bags (e.g. nylon film) must be used forsamples to be analysed for residues of fumigants.samples to be analysed for residues of fumigants.

Samples of commodities pre-packed for retail sale should notbe removed from their packaging before transport.

SANTE 11945/2015


Very fragile or perishable products (e.g. ripe raspberries)may have to be frozen to avoid spoilage and thentransported in “dry ice” or similar, to avoid thawing in transit.

Samples that are frozen at the time of collection must betransported without thawing.

Samples that may be damaged by chilling (e.g. bananas) must be protected from both high and lowtemperatures.

Rapid transportation to the laboratory, preferably within one

SANTE 11945/2015


Rapid transportation to the laboratory, preferably within oneday, is essential for samples of most fresh products. Thecondition of samples delivered to the laboratory shouldapproximate to that acceptable to a discerning purchaser.

Samples must be identified clearly and indelibly, in a waythat prevents inadvertent loss or confusion of labelling. Theuse of marker pens containing organic solvents should beavoided for labelling bags containing samples to be

SANTE 11945/2015


avoided for labelling bags containing samples to beanalysed for fumigant residues, especially if an electroncapture detector is to be used.

The laboratory sample must be placed in a clean, inert container which provides secure protection from contamination, damage and leakage


Packaging and transmission of the laboratory sample

The container should be sealed, securely labelled and the sampling record must be attached.


Packaging and transmission of the laboratory sample

The laboratory sample should be given a unique identifier which, together with the date of receipt and the sample size, should be added to the sample record.The part of the commodity to be analysed, i.e. the analytical


Directive No 2002/63

The part of the commodity to be analysed, i.e. the analytical sample, should be separated as soon as practicable.Where the residue level must be calculated to include parts which are not analysed,the weights of the separated parts must be recorded.

The analytical sample should be comminuted, if appropriate, and mixed well, to enable representative analytical portions to be withdrawn.


Directive No 2002/63

Preparation and storage of the analytical portion

be withdrawn. The size of the analytical portion should be determined by the analytical method and the efficiency of mixing.The methods for comminution and mixing should be recorded and should not affect the residues present in the analytical sample

Sample pathway

Sample preparation, sample processing and sub-sampling to obtain portions shouldtake place before any visible deterioration occurs

Sample preparation and processing

The parts of the commodity that should be analysed are stipulated in Regulation (EC) No 396/2005 Annex 1

Sample Preparation

Procedure used , if required , to convert thelaboratory sample into an analytical sample by removal of parts (soil, stones, bones etc.)

(Hill & Reynolds, Analyst 124, 1999)

by removal of parts (soil, stones, bones etc.) not to be analysed

Sample Processing

Procedure (e.g. cutting grinding, mixing)used to make the analytical sampleacceptably homogeneous with respect toanalyte, distribution prior to removal of theanalyte, distribution prior to removal of theanalytical portion

(Hill & Reynolds, Analyst 124, 1999)

Sample Processing - Main Aims

Produce representative analytical samples- issue with fruit/vegetable unit to unit variability

Minimise apparent losses of pesticide- issue with stability of pesticides

Special cases

Fumigants (cereals)

-storage in nylon bags

Dithiocarbamates (fruit and vegetables)

- segmentation to minimise tissue disruption

Ambient Ambient millingmilling

Losses during Sample Preparation

No single mechanism involved

Volatility (e.g. fumigants, biphenyl, dichlorvos)Chemical reactions (e.g. hydrolysis, oxidation)

Many Factors play a role:pHpHPresence of reactive matrix-componentsPresence of retentive matrix-components (water, lipids)Presence of active enzymesPresence of oxygenTemperatureExposition time

ImplicationsTrue concentration underestimated

MRL-exceedances /misuse may not be detected

Sample Processing Losses at Ambient Temperature

Investigations have indicated losses of a number of pesticides during sample processingat ambient temperatures:

bitertanol dichlofluanid isofenphoscaptan dicofol tebuconazolecaptafol etridiazole tolylfluanidchlorothalonil folpet

CryogenicCryogenic millingmilling

Wait time needed for coarsely cut

Critical Steps prior to Critical Steps prior to extractionextraction

Ambient Processing Cryogenic Processing

Wait time between homogenizationand extraction

Wait time needed for coarsely cutsample to freeze. During this time

contact of pesticides on peel with juices

Ambient milling: Distributional Distributional inhomogeneityinhomogeneity

Flesh

Large Peel

Pieces

Juice

Cryogenic milling: Distributional homogeneityDistributional homogeneity

Particle size comparison

Cryogenic millingCryogenic millingDownsidesDownsides

Composite samples need to be frozen in chunks before comminution with dry ice, or else an eruption of CO2 gas will occur when the dry ice is exposed to the sample at room temperature.

Much freezer space depending on sample throughput needs.

It often takes an extra day to cut and freeze the composite samples for cryogenic processing.

IAEA Sample Processing Study

Aims

To assess the homogeneity of sub-samples

To assess the relative stability of pesticides duringcryogenic and ambient sample processing

Project Scale

4 year project

18 laboratories, 14 countries

5 commodities

Regulation 625/2017

Samples shall be taken, handled and labelled in such a way as to ensure their legal, scientific and technical validity.

Thank you for yourattentionattention

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Samplingand sample processing - CTAA whole fruit, vegetable or natural bunch of them ... Precautions to be taken: ... contact of pesticides on peel with juices. Ambient milling: