FOSFA INTERNATIONAL OFFICIAL METHOD

Transcription

1 FOSFA INTERNATIONAL OFFICIAL METHOD HANDLING OF LABORATORY SAMPLES This procedure shall be used by all laboratories carrying out analysis of samples drawn from commodities traded under FOSFA terms. It is for use in conjunction with the Federation's Standard Contractual Methods of Analysis. 1 Sequence of procedures The laboratory shall have a stipulated sequence for all the procedures listed below (plus any others) in order to ensure that the handling of each sample follows a clearly defined and co-ordinated programme for its administration and analysis. 2 Physical receipt of samples On receipt of a sample for analysis, the following visual checks should be carried out. 2.1 Check the labelling to ensure that the sample is fully identifiable. 2.2 Check that the seals are intact. If tampering is suspected, request a second sample. 2.3 Check sample visually and any sample odour to assess condition and whether it is contaminated. Any unusual condition should be noted at this stage and further action taken accordingly. If any microbiological or insect activity is noted, the sample should be segregated to prevent contamination of other samples. 2.4 Check that sufficient quantity of the sample has been received for analysis taking into account of the possible need to repeat analysis. The quantity should conform to minimum requirements for the analytical methods for all determinations requested as per the FOSFA current method for the packaging of oilseed samples or other commodities. 2.5 Check that the sample received conforms to the description given in the instructions for analysis. 2.6 When a second or duplicate sample is received, check that it satisfactorily conforms to the above visual checks and the original samples. If any of the above criteria are not fulfilled, further samples should be requested from the parties to the contract. Laboratories may find it useful to compose a physical check list based on the above items. 3 Sample labelling All samples must be clearly labelled (including the labelling of both jar and lid if appropriate). 4 Identification during analysis Identification of each individual sample must be ensured throughout each stage of analysis. This identification might consist of simple number referencing of the sample and accompanying worksheets and does not need to carry full details of the sample's origin. 5 Worksheets Specially designed worksheets or notebooks should be used to enable information to be recorded at each stage of any determination, including details of the calculation of results. The design should also facilitate close supervision by senior personnel. The date of each stage of a determination should always be shown on the worksheet, as should the date the sample was received and analysis commenced. 15

2 6 Supervision Analysis should be under the supervision of technically qualified senior personnel at all times. Only such personnel should be responsible for checking results and signing certificates. Additionally in signing certificates, they are responsible for ensuring that the correct methods are used in accordance with the FOSFA Analysis Certificate requirements and that, when analysis is being carried out under the terms of FOSFA contracts, these methods conform to the FOSFA Standard Contractual Methods of Analysis. 7 Handling of samples Laboratory staff should take great care over the handling of samples at all times in order that they remain, as far as possible, in the same condition as they were when they arrived at the laboratory. All samples should be returned to the correct sample store when not in use in accordance with FOSFA Official Method of Storage. The melting and solidification of oil and fat samples should be kept to a minimum. Samples should not be allowed to stand on laboratory benches where they are subjected to direct sunlight or under heat, as this can lead to changes in the sample's properties (e.g. moisture and volatile matter, peroxide value or free fatty acid content of the oil). 8 Oilseed samples When oil content analysis is requested, if no request for admixture separation is also received for the same sample, it is none the less recommended that this should still be done if visual inspection of the sample suggests that admixture exceeds 2 %. If it is more than 2 %, report this to the principal to the contract. The oil content is then calculated on a pure basis, with back calculation to a tale quale basis, taking account of the oil content of the admixture if necessary. This operation must be performed when using infra-red equipment. An approximate sorting test can be used to estimate whether admixture analysis is necessary. 9 Analysis in duplicate Results of duplicate analyses are only acceptable if they are within the acceptable repeatability range quoted in the method, when it is normal to average the results to show the final result. If the duplicates are outside the acceptable repeatability range, then the entire determination should be repeated, preferably using a second analyst, to obtain two further results. 10 Time span of analysis With several determinations (e.g. moisture, peroxide value), differences can arise in the results if there are delays in carrying out analysis. Duplicate determination should be carried out in rapid succession. 11 Dating of certificates Analysis should be completed as near to the date of drawing a sample as practically possible. The certificates should show the date of analysis, any re-test and the date that they were issued. 12 Storage conditions Samples shall be stored prior to examination and during the post-analysis retention period in a location that is dark and cool (less than 20 C), dry and free of pests and rodents. It is recommended that the atmosphere of the store should contain a mild insecticide, when being used for the storage of oilseeds. 13 Retention of samples In order to re-check samples and, in the event of any dispute arising, it is necessary to keep samples three months after the issue of certificates. When an arbitration or appeal is involved and this is notified to the analyst, the sample must be kept until further notice. In other circumstances, the analyst may also be requested to keep samples for longer than three months. 16

3 FOSFA INTERNATIONAL OFFICIAL METHOD PACKAGING AND STORAGE OF OILS AND FATS SAMPLES 1 Scope This FOSFA method for the labelling, packaging, transport and storage of samples is applicable to all samples drawn under the terms of FOSFA International contracts for analysis, arbitration or standards purposes. 2 Label design 2.1 Labels must comply with ISO 5555:2001 Section Labels should be completed in legible handwriting, preferably in capital letters, or typed. Labels should be securely attached to the samples they represent. 3 Sample labelling, sealing and distribution The label is to be affixed to the sample bottle and sealed to the bottle (jointly where appropriate) and to clearly indicate the appropriate FOSFA International contract number. Sealing wax, if used, should not contain copper. If a sealing wax does contain copper or the composition is unknown, the sample container shall be placed in a tight-fitting plastic bag and labelled and sealed therein. Samples shall be distributed in accordance with the relevant FOSFA International contract requirements. 4 Packaging of oils and fats samples for analysis The samples shall be packed in accordance with ISO 5555:2001. For contractual analysis a sample of 250 ml is sufficient. Where special analyses are needed, a sample of 500 ml or more will be required. 5 Storage of samples after analysis Samples should be clearly marked and stored with an in-house reference number in cool, dry conditions, away from strong light. The sample area should be insect and rodent free and hygienic. In normal circumstances, it has been the experience that contractual samples should be stored for a minimum of three months and longer if circumstances so dictate. 18

4 FOSFA INTERNATIONAL OFFICIAL METHOD DETERMINATION OF SEA WATER CONTAMINATION IN OILS 1 Scope The method is applicable to all oils, with the exception of those (such as acid oils) which are known to have been treated with hydrochloric acid. 2 Principle The oil is examined for the presence of chloride ions in the aqueous contaminant. If chloride ions are detected and the amount of aqueous phase permits, quantitative determinations of chloride and other ions may be carried out. 3 References 3.1 Official, Standardised and Recommended Methods of Analysis. The Society for Analytical Chemistry, London, Analysis of Raw, Potable and Waste Waters. HMSO, Methods for the examination of Water and Associated Materials. The National Water Council, Department of the Environment. 3.4 Official Methods of Analysis of the Association of Official Analytical Chemists. 13th edition, Washington, Reagents 4.1 Silver nitrate solution, approximately 0.1 M. 4.2 Nitric acid, concentrated, AR. 5 Procedure 5.1 Sample preparation If the nature of the sample permits, separate the aqueous and oil components by centrifugation, or by allowing the sample to stand. Determine the volume of aqueous contaminant in the oil If the amount of the contaminant is small, extract it by shaking the oil with water. Dilution of the oil with petroleum ether may assist the separation of the aqueous layer. If this procedure is unsatisfactory the oil should ashed at a temperature of not more than 450 C and the tests carried out on an aqueous solution of the ash. 5.2 Qualitative test Acidify a portion of the aqueous phase with a few drops of concentrated nitric acid, and add a few drops of silver nitrate solution. A white precipitate which darkens upon exposure to light, especially sunlight, (or turbidity if the sample solution is very dilute) indicates the presence of chloride and suggests that the sample may have been contaminated with sea water. 27

5 6 Further examination If a more detailed examination of the aqueous contaminant is required, quantitative determination of chloride and sodium should first be carried out. Determinations of other major constituents of sea water, such as sulphate, magnesium, potassium and calcium may then be carried out as further confirmatory tests. The principal inorganic constituents of typical sea water are: % m/m Chloride 1.90 Sodium (as Na) 1.06 Sulphate 0.26 Magnesium (as Mg) 0.13 Calcium (as Ca) 0.04 Potassium (as K) 0.01 Bicarbonate 0.01 Bromide The methods of analysis will depend on the quantity of the aqueous contaminant available. Some sources of suitable analytical methods are given in Section 3 (References). 7 Test report The Analyst's report shall indicate the method(s) of analysis employed. 28

6 FOSFA INTERNATIONAL OFFICIAL METHOD DETERMINATION OF SOAP IN ACID OILS 1 Scope A non-aqueous titration method is described for the determination of soap in all types of acid oils. 2 Definition The soap content is expressed as sodium oleate as a percentage by mass calculated from the total alkalinity of the oil. 3 Principle The total alkalinity is determined by titration in neutral solvent solution of the oil using standard ethanolic hydrochloric acid and bromophenol blue indicator solution. For dark coloured and/or very low expected soap contents (less than 0.01 % by mass) the end-point is measured electrometrically. 4 Reagents Use only reagents of recognised analytical quality. 4.1 Ethanolic hydrochloric acid solution 0.01N and/or 0.1N accurately standardised. 4.2 Bromophenol blue indicator. Solution of 49 g per litre of 95 % (m/m) ethanol. 4.3 Solvent mixture. 1 volume ethanol/2 volumes acetone neutralised by adding a few drops of indicator solution (4.2) and titrating with hydrochloric acid solution (4.1) or with ethanolic potassium hydroxide solution until just yellow. 5 Apparatus Use laboratory apparatus and in particular the following. 5.1 Burette 10 ml graduated in 0.02 ml. 5.2 ph meter fitted with automatic temperature compensation and equipped with a suitable electrode system. The electrode assembly should be washed with neutral solvent (4.3) before use. NOTE It is essential that the ph equipment be very carefully checked for both repeatability and reproducibility at the required operational temperatures. Some equipment has been found to give variations in excess of 0.6 ph units in day-to-say measurements on the same solvent mixture and to require several minutes to give a constant reading after agitation has ceased. 5.3 ph electrode suitable for work in non-aqueous solvent mixture is recommended. 5.4 Suitable means of heating the solvent mixture and oil solution such as a water bath thermostatically controlled at about 46 C. 5.5 Conical Erlenmeyer flasks (250 ml) having no alkaline reaction. 6 Preparation of sample Melt the oil sample and mix thoroughly. 29

7 7 Procedure 7.1 Oils which yield a clear colourless solution in the solvent mixture (4.3) Test solution Accurately weigh a suitable mass of sample (6) directly into a 250 ml conical (Erlenmeyer) flask then add 100 ml of solvent mixture (4.3) and dissolve at 40 C to 45 C Titration Add a few drops of indicator solution (4.2). The formation of a green colour indicates the presence of soap. Titrate the test solution (7.1.1) with ethanolic hydrochloric acid (4.1) until the solution is just yellow at its initial temperature (40 C to 45 C). Allow adequate time (5 min) for reaction of calcium soaps etc. 7.2 Oils which yield a dark solution in the solvent mixture (4.3) and/or are expected to have a very low (less than 0.01 % by mass) soap content ph of solvent mixture Warm 100 ml solvent mixture (4.3) to 40 C to 45 C, Measure the temperature accurately and adjust the ph meter (5.2) for operation at this temperature and measure the ph. Determine end-point by reference to a calibration curve. NOTE Choose the vessel to contain the solvent mixture which will subsequently permit the insertion of the ph electrodes (5), such as a beaker or wide-necked conical flask. 8 Expression of results 8.1 Method of calculation Calculate the soap content, expressed as a percentage (mass/mass) of sodium oleate in the original sample (6) from the formula. % Soap content = V x N x 30.4 (as sodium oleate) W Where: V is volume in ml of ethanolic hydrochloric acid used (7.1.2 or 7.2.2) to reach equivalence N is normality of ethanolic hydrochloric acid (4.1) W is mass of sample used to prepare test solution (7.1.1 or 7.2.2) 30

8 DETERMINATION OF SOAP IN ACID OILS Figure 1: Curve of change in scale reading per unit volume of acid added against volume of acid added and from this measure the equivalence volume corresponding to the curve maximum Volume of HCL (ml) 31

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10 FOSFA INTERNATIONAL OFFICIAL METHOD OILSEEDS SAMPLING 1 Scope This FOSFA Method specifies methods of sampling oilseeds for the assessment of their quality and condition. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 664, Oilseeds Reduction of laboratory sample to test sample. 3 Terms and definitions For the purposes of this FOSFA Method, the following definitions apply. 3.1 consignment The quantity of oilseeds dispatched or received at one time and covered by a particular contract or shipping document. It may be composed of one or more lots or parts of a lot. 3.2 lot A stated quantity of the consignment, which in itself is presumed to be of uniform characteristics, and which will allow the quality to be assessed. 3.3 increment A small quantity of oilseeds taken at one time from a single position from a stationary lot, or taken throughout the moving lot. A series of increments is taken from different parts of the stationary lot, or throughout the moving lot, so that when they are bulked, they are representative of the lot. 3.4 bulk sample The quantity of oilseeds obtained by combining and blending the increments taken from a stationary lot or throughout a moving lot. 3.5 laboratory sample Representative quantity of oilseeds obtained by division of the bulk sample and intended for analysis or other examination. 4 General 4.1 Samples shall be representative of the lots from which they are taken. For this purpose, each consignment shall be divided, actually or notionally, into lots as given in Table 1. Increments from each lot shall be mixed to give a bulk sample of an appropriate quantity. Laboratory samples are obtained by the successive division and reduction of the bulk sample. A laboratory sample shall be produced for each lot. 34

11 4.2 Manual sampling equipment and mechanical samplers shall be clean, dry, free from foreign odours and made from material which will not contaminate the oilseeds. Manual sampling shall be carried out and mechanical samplers shall operate in such manner as to protect samples. Sample containers shall be protected to prevent contamination of the samples. 4.3 All sampling operations shall be carried out over a sufficiently short period of time so as to avoid any alteration in the composition of the samples. If one of the sampling stages will require too long a period of time, the samples or intermediate samples shall be preserved in airtight containers. Table 1 Size of lots and number and size of samples for oilseeds consignments Nominal consignment size t 0-5,000 >5,000-10,000 >10,000-25,000 > 25,000 Lot size t ,000 2,500 5,000 No of increments per lot # Min 20 Min 30 Min 40 Min 50 Wt of increments kg Min 0.4 Min 0.4 Min 0.4 Min 0.4 Wt of laboratory sample (depending kg on seed size) 2 No of laboratory samples produced per consignment # ~15 1 When the consignment size is lower than 500 t the lot size should be agreed between the parties. 2 The size of the laboratory sample varies according to seed sizes. Table 2 is given as an example of different laboratory sample sizes. NOTE Where pre-set mechanical samplers are in use, the size of increment in the primary sampler will usually be as large as that recommended and the rate of cut greater than that recommended. In the secondary system, where known, the quantity of the delivered sample relative to the rate of flow should be stated in order that the final sample may be aggregated to meet the quantity recommended. 5 Apparatus The apparatus required for sampling and division falls under the following headings. 5.1 Apparatus for sampling from bags, sack-type spears or triers, cylindrical samplers, conical samplers and hand-scoops. 5.2 Apparatus for sampling from stationary lots in bulk and for manual sampling from moving lots, shovels, hand-scoops (e.g. Ellis cup), cylindrical samplers, conical samplers and other apparatus for taking small periodical increments from a flow of seeds (e.g. Pelican sampler). 5.3 Mechanical equipment for sampling moving lots, comprising primary samplers and secondary systems. NOTE There are many types of systems such as rotary hammer samplers, slotted vessel samplers, diverter samplers and bucket elevator samplers. These are ideally based on principles such that the sample is taken from across the whole of the flow of the product with the exception of the bucket elevator sampler which for practical reasons and in the interests of safety takes samples in the direction of the flow. 5.4 Apparatus for mixing and dividing, shovels and quartering irons, dividing instruments for dividing and reducing individual samples manually drawn or delivered from secondary systems of mechanical samplers. 35

12 6 Time and place of sampling and limitation of the size of lots 6.1 General Whether the consignment is in bulk or in bags, sampling is normally carried out during, and at the place of, loading into or discharge from the ship, barge, wagon or lorry or at the time of entry into or exit from the silo or warehouse, as agreed between the parties concerned. For sampling purposes, consignments of oilseeds are separated into the following descriptions Stationary consignments in bags or in bulk in stockpiles, ships or barge holds, vehicles Consignments in motion sampled by manual means Consignments in motion sampled by mechanical means. 6.2 Bulk transfer It is generally advisable to use the following procedures in the case of the bulk transfer of oilseeds Transfer from ship, barge or stockpile to lorries and wagons The increments should be taken either from the flow of product (preferred method) during loading or discharge (particularly for tanker-wagons where internal sampling is not possible), or in the lorry or wagon, as soon as possible after loading, by sampling at least five different positions according to the size of the lorry or wagon (see ), for the purpose of providing one bulk sample representing each lot Transfer from stockpile or ship to barges The increments should be selected during loading, by sampling from each hold throughout the duration of loading, for the purpose of providing one bulk sample representing each lot Transfer to and from stockpiles and/or ships When samples are taken manually, these should be taken across the falling stream taking account of the size of the increment and rate of flow of product When primary samples are taken by mechanical samplers, these would normally be taken directly from the conveyor belt or across the falling stream taking account of the size of the primary sample and rate of flow of product With knowledge of the detail and function of the primary sampler, that is, the volume of sample and frequency of cuts relative to the flow of the main product and thence with the density of the product, it is possible to determine the amount of primary sample drawn from a known mass of product moved. Similarly with knowledge of the secondary system, it is possible to determine the mass of product moved represented by each delivered sample. Apart from the manual sampling quoted in above, where samples are taken by mechanical samplers it may be assumed that the product of the increment taken by the primary sampler and the frequency of the cut and the subsequent mixing and reduction in the secondary system provides the number of delivered samples which make a bulk sample representing the nominal lot size for the particular consignment. In addition to the general comments above, attention is drawn to the NOTE below Table 1. 36

13 7 Method of taking samples 7.1 General Sampling shall be carried out by or in the attendance of sampling superintendents appointed by the parties concerned. As the composition of a lot is seldom, if ever, homogeneous, even in the case of undamaged lots, it is necessary to take a sufficient number of increments either manually or by mechanical sampling to provide a representative bulk sample. Parts of lots which are damaged by sea water or otherwise damaged in transit or out of condition, as well as loose 1 material and sweepings which have been recovered shall be sampled separately from the sound material. Each type of damaged material shall be assessed by mass, sampled and separated from the sound material. 7.2 Taking increments According to circumstances, the increments shall be taken from products in bulk or in bags by means of the sampling apparatus mentioned in 5.1 and 5.2, used in accordance with and Products in bags Unless otherwise specified in the contract or unless the practice at a port requires otherwise, increments shall be taken from 2 % of the bags forming the lot, with a minimum of five bags. If the bags are open, the increments may be taken using cylindrical samplers, conical samplers or other appropriate instruments, preferably after the bags have been emptied. If the bags (for example jute or polypropylene bags) are closed, the increments may be taken using sack-type spears or triers Products in bulk When sampling takes place while the product is in motion, which is the preferred method, where sampling is manual or in mechanical samplers from a falling stream, increments shall taken across the whole section of the flow, perpendicular to the direction of flow and at time intervals depending on the rate of flow. In all cases where manual samplers or slotted primary samplers in mechanical equipment are used, these should have a slot opening at least three times the size of the largest seed but this is generally larger. Where primary samples are taken directly from the conveyor belt, for example by hammer type samplers, account is taken of the size of the primary sample and the rate of flow of product. The distance between plates of hammer type samplers should be at least three times the size of the largest seed but almost invariably this is much larger. NOTE 1 For practical purposes and in the interests of safety it may only be possible to take increments from the stream in the direction of the flow. This would be effected manually by using the Ellis Cup sampler and mechanically by the bucket elevator sampler. NOTE 2 Copra is considered an oilseed within this method but in view of the size, shape and irregularity of copra pieces and the importance of the size and shape of the primary cutters in mechanical samplers and particularly the effect of the entry edges, it is recommended that advice be obtained from the operator of the mechanical sampler that it is capable of handling and producing representative samples of copra. 1 This term is used to designate material which has leaked from its original container, but is not unduly contaminated. 37

14 When bulk material is sampled in holds during discharge, the increments shall be taken from as many places as possible, excluding the run, and at intervals determined by the rate of discharge When sampling takes place from laden wagons or lorries, the increments shall be taken at three levels at least (owing to the fact that layering may occur, particularly in vehicles in motion) with a cylindrical sampler or conical sampler, depending on the product, and at the following points. Wagons up to 15 t Wagons 15 t 30 t Wagons 30 t 50 t Figure 1 Diagram of sampling points in wagons If the type of wagon or lorry does not allow samples to be taken in this manner, the method of sampling shall be as described for products in motion, which, generally, shall be preferred Where samples are taken from product in motion, the procedures indicated in above shall apply. 7.3 Bulk samples The bulk sample for each lot shall be formed by combining the increments taken as described in Laboratory samples The bulk sample for each lot shall be mixed and divided using the apparatus described in 5.4 to obtain the laboratory sample. It is usual that several equivalent laboratory samples are required from each lot for the purposes of analysis, retention or arbitration. This number of sets of laboratory samples is generally specified in the relevant trading contract or otherwise agreed between buyer and seller. For some seeds (e.g. groundnuts in shell) it is advisable to sieve the bulk sample before dividing it and then to add the fines to the laboratory samples in the correct proportion. This is to ensure that the samples contain the same percentage of fines. 8 Sizes of samples related to seed sizes As indicated in Table 1, only sizes of laboratory samples per lot are quoted overall 1 5 kg without reference to seed size. In Table 2, bulk sample quantities are repeated alongside laboratory sample sizes related to seed size. The sizes of samples given in Table 2 are usually suitable. Larger or smaller samples may be required in some cases, according to the tests to be carried out. 38

15 Table 2 Size of samples of oilseeds (kg) Minimum bulk sample size per lot Laboratory sample size Lot size 500 1,000 2,500 5,000 for all lot sizes Copra Medium/large Small Packing and labelling of samples 9.1 Packing of samples Laboratory samples shall be packed in rigid airtight and moisture-tight containers fitted with airtight and moisture-tight closures. The containers shall be completely filled and the closures shall be sealed to avoid any change in the original moisture content of the sample. 9.2 Labelling of samples If paper labels are used, their quality and size shall be suitable for the purpose. The eyelet hole in the label shall be reinforced Each label shall bear at least the following information. 1. ship or road vehicle; 2. from; 3. to; 4. date arrived; 5. quantity; 6. bulk/bags; 7. goods; 8. identification mark or lot number; 9. number and date of bill of lading or contract; 10. date of sampling; 11. place and point of sampling; 12. sampled by; 13. name of organisation responsible for terms of contract. The information recorded on the label shall be permanent Labels for samples of damaged material shall also indicate the nature of the damage and the proportion or tonnage so affected. 10 Dispatch of samples Laboratory samples shall be dispatched as soon as possible, and only in exceptional circumstances more than 48 h after sampling has been completed, non-business days excluded. 11 Sampling report The sampling report shall make reference to this FOSFA Method and shall indicate, in addition to the information necessary for the identification of the sample, the condition of the oilseeds sampled, including signs of insect, mite or rodent infestation visible either in the silo or warehouse or during the operations carried out in the ship or other carrier. NOTE Such infestation is not always readily apparent in the sample, except on close inspection or sieving. The report shall also refer to any modifications to the technique described in this FOSFA Method, and all the circumstances that may have influenced sampling. 39

16 FOSFA INTERNATIONAL OFFICIAL METHOD PACKAGING AND STORAGE OF OILSEEDS SAMPLES 1 Scope This FOSFA method for the labelling, packaging, transport and storage of oilseeds samples is applicable to all samples drawn under the terms of FOSFA International contracts for analysis, arbitration or standards purposes. 2 Label design 2.1 Labels must comply with the FOSFA International Official Method Section Labels should be completed in legible handwriting, preferably in capital letters, or typed. Labels should be securely attached to the samples they represent. NOTE 1 It is important that principals' instructions to superintendents make it quite clear whether the samples are being drawn for analysis and arbitration purposes. 3 Packaging 3.1 Samples of all oilseeds (other than palm kernels and other lauric seeds) sent to laboratories for analysis should be packed in water-tight plastic jars with screw caps of the same materials or in glass jars with plastic screw caps, of not less than 500 ml, which shall be filled to the top and sealed. 3.2 Palm kernels, illipe nuts, sheanuts, groundnuts to be packed in a woven polypropylene bag closed and/or sealed then packed in a strong cotton or linen bag, which is then sealed bags of plastic sheet must not be used. 4 Storage 4.1 Oilseed samples shall be stored at not more than 20 C. Palm kernel, illipe, sheanuts, copra (and other lauric seeds) should be cold stored at minus 15 C. 4.2 Where the sample is not packed and stored in accordance with this recommendation, the oil content at re-test should be adjusted in relation to the variation in moisture between the original test and the re-test. 40 FOSFA International Copyright 2014 April 2014

17 FOSFA INTERNATIONAL OFFICIAL METHOD SAMPLING OF EDIBLE GROUNDNUTS FOR AFLATOXIN TESTING (Not applicable for groundnuts imported into the European Union) 1 Definitions Please note this method is provisional. 1.1 lot An identifiable quantity of a food commodity delivered at one time and determined by an official to have common characteristics, such as origin, variety, type of packaging, packer, consignor or marking. 1.2 sublot Designated part of a large lot in order to apply the sampling method on that designated part. Each sublot must be physically separate and identifiable. 1.3 incremental sample A quantity of material taken from a single place in the lot or sublot. 1.4 aggregate sample The combined total of all incremental samples taken from a lot or sublot. 1.5 laboratory sample Sample intended for the laboratory (= subsample). 2 General provision 2.1 Material to be sampled Each lot which is to be examined must be sampled separately. In accordance with the provisions in point 4, large lots should be subdivided into sublots and sampled separately. 2.2 Precautions to be taken In the course of sampling and preparation of the laboratory samples precautions must be taken to avoid changes which adversely affect the aflatoxin content and the analytical determination or make the aggregate samples unrepresentative. 2.3 Incremental samples As far as possible incremental samples should be taken at various places distributed throughout the lot or sublot, see Table 1. Departure from this procedure must be recorded in the record referred to in point Preparation of the aggregate sample and laboratory samples The aggregate sample is made up by combining and sufficiently mixing the incremental samples. 2.5 Replicate samples Replicate samples for enforcement, trade (defence) and referee purposes are to be taken from the homogenised laboratory samples. 41 FOSFA International Copyright 2014 April 2014

18 Packaging and transmission of laboratory samples Each laboratory sample must be placed in a clean inert container offering adequate protection from contamination and against damage in transit. All necessary precautions must be taken to avoid any change in composition of the laboratory sample which might arise during transportation or storage. 2.6 Sealing and labelling of laboratory sample Each sample taken from official use shall be sealed at the place of sampling and identified. A record must be kept of each sampling, so that each lot can be identified unambiguously, with the date and place of sampling together with any additional information likely to assist the analyst. 3 Explanatory provisions 3.1 Sampling frequency Without prejudice to the specific provisions as laid down in point 4, the following formula can be used as a guide for the sampling of lots traded in individual packings (sacks, bags, retail packings, etc). Sampling frequency (SF) = Weight of the lot x weight of the incremental sample Weight of the aggregate sample x weight of individual packing Weight: in kg Sampling frequency (SF): every nth sack or bag from which an incremental sample must be taken (decimal figures should be rounded to the nearest whole number). 3.2 Weight of the incremental sample The weight of the increment sample should be about 300 grams, unless otherwise defined in Table 1. For retail packings, the weight of the incremental sample depends on the weight of the retail packing. 4 Specific provisions 4.1 Lots should be subdivided into sublots not exceeding 25 tonnes in weight. The minimum number of incremental samples and aggregate sample size to be taken from each sublot are given in Table 1. a. each sublot must be sampled separately; b. samples shall be taken as randomly as possible from throughout the consignment; c. each sample taken shall be ground finely and mixed thoroughly using a process that has been demonstrated to achieve complete homogenisation; d. samples of nuts that are "in shell" may include the shell in the final homogenate; e. the formal samples for enforcement, trade (defence) and referee purposes shall be taken from the homogenised material. In the case of the formal enforcement samples a minimum of three independent subsamples (each a minimum weight of 50 g) shall be removed from the mixed slurry sample for analysis and the size of the sample shall be sufficient to allow for this. The result shall be taken to be the mean of the analytical results of the three independent subsamples. 4.2 Acceptance of a sublot a. accept if the mean of the independent subsamples conforms with the maximum limit; b. reject if the mean of the independent subsamples exceeds the maximum limit. Table 1 Sample sizes Nuts and nut products Minimum no. of incremental samples Approximate incremental sample size (g) Minimum aggregate sample size (kg) Groundnuts shelled raw/roasted Groundnuts in shell * Peanut butter * weight of nuts in shell 42 FOSFA International Copyright 2014 April 2014

19 FOSFA INTERNATIONAL OFFICIAL METHOD DETERMINATION OF COUNT IN GROUNDNUT KERNELS 1 Scope The method described is applicable to all groundnuts but is usually used for Hand Picked & Selected groundnuts. 2 Principle The groundnut kernels are categorised into whole kernels, half kernels (brissures) and broken and damaged kernels and expressed as groundnut kernels to one ounce avoirdupois. 3 Procedure 3.1 Draw a portion of 500 g of the sample and record the weight to the nearest gram. 3.2 Separate into whole kernels, half kernels and broken and damaged kernels and damaged half kernels. 3.3 Record the weight of each portion to nearest gram. 3.4 Count the whole kernels and record the result. 3.5 Count the half kernels and record the result. 3.6 Perform in duplicate test. 4 Calculation and expression of results Groundnuts kernels, to one ounce avoirdupois = (N + n/2) x W + w Also count to 100 g = (N + n/2) x 100 W + w Where: N is the number of whole kernels; n is the number of half kernels; W is the mass, in grams, of the whole kernels; w is the mass, in grams, of the half kernels. Calculate the mean of the duplicates and quote the count to the nearest whole number. 46 FOSFA International Copyright 2014 April 2014