SIST EN 16277:2012

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.VSHNWURPHWULMRFuttermittel - Bestimmung von Quecksilber mit Kaltdampf-Atomabsorptionsspektrometrie (KD-AAS) nach Mikrowellen-Druckaufschluss (Extraktion mit 65 % Salpetersäure und 30 % Wasserstoffperoxid)Aliments des animaux - Dosage du mercure par spectrométrie d'absorption atomique à vapeur froide (SAVVF) après digestion sous pression par micro-ondes (extraction avec de l'acide nitrique à 65 % et du peroxyde d'hydrogène à 30 %)Animal feeding stuffs - Determination of mercury by cold-vapour atomic absorption spectrometry (CVAAS) after microwave pressure digestion (extraction with 65 % nitric acid and 30 % hydrogen peroxide)65.120KrmilaAnimal feeding stuffsICS:Ta slovenski standard je istoveten z:EN 16277:2012SIST EN 16277:2012en,fr,de01-september-2012SIST EN 16277:2012SLOVENSKI
STANDARD



SIST EN 16277:2012



EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 16277
July 2012 ICS 65.120 English Version
Animal feeding stuffs - Determination of mercury by cold-vapour atomic absorption spectrometry (CVAAS) after microwave pressure digestion (extraction with 65 % nitric acid and 30 % hydrogen peroxide)
Aliments des animaux - Dosage du mercure par spectrométrie d'absorption atomique à vapeur froide (SAVVF) après digestion sous pression par micro-ondes (extraction avec de l'acide nitrique à 65 % et du peroxyde d'hydrogène à 30 %)
Futtermittel - Bestimmung von Quecksilber mit Kaltdampf-Atomabsorptionsspektrometrie (KD-AAS) nach Mikrowellen-Druckaufschluss (Extraktion mit 65 % Salpetersäure und 30 % Wasserstoffperoxid) This European Standard was approved by CEN on 17 May 2012.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
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EN 16277:2012 (E) 2 Contents Page Foreword .31Scope .42Normative references .43Principle .44Reagents .46Procedure .77Calculation .98Precision .99Test report . 10Annex A (informative)
Results of the interlaboratory tests . 11Annex B (informative)
Flowchart – Determination of mercury by CVAAS after microwave digestion . 12Annex C (informative)
Alternative digestion procedure with the same extraction efficiency:
Acid digestion with a mixture of 65 % nitric acid and 70 % perchloric acid (7:3 v/v) at atmospheric pressure . 13Annex D (informative)
Alternative digestion procedure with the same extraction efficiency:
Acid digestion with a mixture of 65 % nitric acid, 37 % hydrochloric acid and 30 % hydrogen peroxide under reflux . 15Bibliography . 16 SIST EN 16277:2012



EN 16277:2012 (E) 3 Foreword This document (EN 16277:2012) has been prepared by Technical Committee CEN/TC 327 “Animal feeding stuffs – Methods of sampling and analysis”, the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by January 2013, and conflicting national standards shall be withdrawn at the latest by January 2013. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 16277:2012



EN 16277:2012 (E) 4 1 Scope This European Standard specifies a method for the determination of mercury in animal feeding stuffs by Cold-Vapour Atomic Absorption Spectrometry (CVAAS) after microwave pressure digestion. The limit of quantification in the test solution should be 0,25 µg/l or lower. Using a test portion of 0,5 g and a volume of the test solution of 25 ml a limit of quantification of 0,0125 mg/kg or lower should be obtained. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696) EN ISO 6497, Animal feeding stuffs — Sampling (ISO 6497) EN ISO 6498, Animal feeding stuffs — Guidelines for sample preparation (ISO/FDIS 6498) 3 Principle Mercury is determined in the test solution by cold-vapour atomic absorption spectrometry (CVAAS) after microwave pressure digestion. The homogenised feeding stuff test sample is digested with nitric acid and hydrogen peroxide under pressure and high temperatures in a microwave-heated pressure digestion system.
The test solution is transferred to the reaction vessel of the mercury analysis unit. The mercury is reduced with sodium borohydride or tin(II) chloride to elemental volatile mercury and flushed into the cell of the AAS instrument using a carrier gas stream. As an option with an additional amalgamation step, sensitivity could be increased and matrix effects could be decreased. The absorption at 253,7 nm (mercury line) is used as a measure of the mercury concentration in the cell. Other digestion procedures with the same extraction efficiency (see Annex D and Annex E) or other measurement systems like Fl-CVAAS (flow injection cold-vapour atomic absorption spectroscopy) or CV-ICP-AES (cold-vapour inductively coupled plasma atomic emission spectroscopy) are possible. WARNING — The use of this standard can involve hazardous materials, operations and equipment. This standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 4 Reagents
The concentration of the trace elements in the reagents and water used shall be low enough not to affect the results of the determination. A blank should be measured simultaneously with the test samples on each day of analysis to control contamination and carry over with mercury in the reagents and apparatus used. Use water conforming to grade 2 of EN ISO 3696. 4.1 Nitric acid (HNO3), not less than 65 % (mass fraction), of approximately (HNO3) = 1,4 g/ml. NOTE Use nitric acid available with high purity or perform a sub-boiling distillation. 4.2 Hydrogen peroxide (H2O2), not less than 30 % (mass fraction). SIST EN 16277:2012



EN 16277:2012 (E) 5 4.3 Hydrochloric acid (HCl), not less than or equal to 30 % (mass fraction), of approximately (HCl) ≥ 1,15 g/ml. 4.4 Diluted hydrochloric acid, e.g. about 3 % (mass fraction), as carrier solution for the use in the flow-injection-system and for dilution of the mercury stock solution to the standard solution and furthermore to the calibration solutions. EXAMPLE Dilute approximately 90 ml of hydrochloric acid (4.3) to 1 l with water. 4.5 Reducing agents. Tin(II) chloride or sodium borohydride may be used as the reducing agent, but it is not advisable to use the two reagents alternately. The concentration by mass of the reducing agent solutions may be varied to suit the system and the relevant information provided by the manufacturer of the apparatus shall be observed.
4.5.1 Tin(II) chloride solution, c(SnCl2ú2H2O) = 100 g/l. Dissolve 50 g of tin(II) chloride in approximately 100 ml of hydrochloric acid (4.3) in a 500 ml volumetric flask (5.2) and dilute to the mark with water. Prepare a fresh solution daily. 4.5.2 Sodium borohydride solution, e.g. c(NaBH4) = 2 g/l. Dissolve 2 g of sodium hydroxide pellets in water using a 1 000 ml flask (5.2), add 2 g of sodium borohydride and dilute to the mark with water. Prepare a fresh solution daily and, when necessary, filter before use. When the analysis procedure requires a longer time it is recommended to cool the sodium borohydride solution, i.e. with ice around the flask, during its use in the CVAAS measurement. NOTE Sodium borohydride, stable aq. solution, 4,4 mol/l in 14 mol/l NaOH, is also commercially available. WARNING – It is essential to observe the safety instructions for working with sodium borohydride. Sodium borohydride forms hydrogen with acids and this can result in an explosive air/hydrogen mixture. A permanent extraction system shall be provided at the point where measurements are carried out. 4.6 Mercury stock solution, c(Hg) = 1 000 mg/l. The stock solution is commercially available. It is advisable to use certified stock solutions. Otherwise, dissolve 1,080 g of mercury(II) oxide in 10 ml of potassium dichromate solution and dilute to 1 l with water. Use a potassium dichromate solution with a concentration of 5 g/l. Dissolve 5 g of potassium dichromate with 500 ml nitric acid (4.1) and dilute to 1l with water. 4.7 Mercury standard solution, c(Hg) = 1 mg/l. Dilute 100 µl the stock solution (4.6) with diluted hydrochloric acid (4.4) in a 100 ml flask (5.2) to a concentration of 1 mg/l.
The standard solution is stable for at least three months. 4.8 Mercury calibration solutions. Dilute the standard solution (4.7) to the concentrations needed for calibration with diluted hydrochloric acid (4.4). The following calibration solutions are recommended (see Table 1). Take aliquots of 0 µl, 25 µl, 50 µl, 250 µl, 500 µl of the mercury standard solution (4.7) into flasks of 50 ml (5.2) and fill up with diluted hydrochloric acid (4.4) to concentrations of 0 µg/l, 0,5 µg/l, 1 µg/l, 5 µg/l and 10 µg/l. SIST EN 16277:2012



EN 16277:2012 (E) 6 Table 1 — Recommended calibration solutions (4.8) for the determination of mercury Mercury (Hg) Concentration of calibration solution (4.8) µg/l Aliquots of standard solution (4.7), transferred in 50 ml flasks µl Calibration standard 1 0 0 Calibration standard 2 0,5 25 Calibration standard 3 1 50 Calibration standard 4 5 250 Calibration standard 5 10 500
Choose the concentrations of the calibration solutions so as not to exceed the linear range of the calibration curve. It is recommended to use a minimum of five calibration solutions with different concentrations. In general, the calibration curve should be linear. Using a non-linear calibration curve is possible if it is well-described. 5 Apparatus and equipment To minimise the contamination, all apparatus which come into direct contact with the sample and the solutions should be carefully pre-treated.
NOTE Recommendations are given in EN 13804. 5.1 Microwave-heated pressure digestion apparatus with inert reaction vessels, made of materials such as Polytetrafluorethen (PTFE), Polyfluoralkan (PFA), Perfluorethylenpropylen (FEP) or quartz and shich are suitable for digestion temperatures exceeding 200 °C. The microwave oven should be generally resistant to corrosion. In particular, the whole electronic area of the microwave oven should be protected against corrosion to ensure safe operation. The ventilation should transfer the acid vapours to an extractor hood. The reaction vessels should have a safety valve designed for a pressure of 10 000 kPa. 5.2 Pipettes, Flasks, of the following capacities: 25 ml, 50 ml, 100 ml, 500 ml and 1 000 ml. 5.3 Flow injection cold-vapour system with sample loop, i.e. 500 µl. 5.4 Atomic absorption spectrometer (AAS), with a heated quartz cell and optionally with an amalgamation system. 5.5 Element-specific lamp for mercury. NOTE
An electrodeless discharge lamp would provide a higher sensitivity compared to a hollow-cathode lamp. 5.6 Ultrasonic bath or water bath. 5.7 Analytical balance, accurate to 0,1 mg. SIST EN 16277:2012



EN 16277:2012 (E) 7 6 Procedure 6.1 General Sampling and preparation of a test sample are not parts of the method. A recommended sampling method and method for sample preparation are given in EN ISO 6497 and EN ISO 6498. To ensure homogeneity, the use of a stationary or, especially for mineral feeds, a rotary riffler for mass reduction and the use of a sieve size of 0,5 mm or lower for particle size reduction are recommended because of the low weights of ≤ 0,5 g of the test portions. 6.2 Preparation of the test solution NOTE 1 The following extraction procedure leads in most cases to results for mercury and for other minerals and trace elements which correspond to the total contents of these elements. For some specific problems, it might be necessary to check whether modifications of the digestion program or other acid mixtures are needed. The mass of a test sample depends on the organic percentage of the sample material and on the size of the reaction vessels of the microwave digestion system. Using reaction vessels of 20 ml to 100 ml sizes respectively, a test portion of 0,2 g to 0,5 g of the homogenised and ground (to a particle size of < 0,5 mm) test sample is weighed to an accuracy of 1 mg for digestion. Add for example 5 ml nitric acid (4.1) and 2,5 ml hydrogen peroxide (4.2) using reaction vessels of 100 ml size. Ensure that the reaction vessels are locked and fixed in the microwave digestion system (5.1). For the pre-reaction, let the reaction vessels bleed before the pressure digestion is started.
WARNING 1 — For some samples, heavy reactions may result after the addition of nitric acid and hydrogen peroxide. Therefore let the reactions fade off at room temperature for a sufficient period of time, i.e. overnight. To avoid contamination and/or carry over, steam stripping of the reaction vessels with nitric acid before use is recommended. To check for potential contamination and/or carry over, digest a control blank in parallel with the test samples. The digestion with the microwave system is performed with a temperature program adapted to the matrices, taking into consideration the operating manual of the manufacturer.
WARNING 2 — For samples of an unknown composition, firstly carry out a digestion procedure with a small test portion. In particular cases, heavy reactions with nitric acid and/or hydrogen peroxide could appear. Formation of highly explosive compounds is also possible when organic matrices are digested. Too high test sample masses could result in uncontrollable reactions.
In principle, the pressure digestion is started with low power which is then
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