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
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.
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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

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

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

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
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