BS EN 16318:2013+A1:2016 BSI Standards Publication Fertilizers and liming materials — Determination of chromium(VI) by photometry (method A) and by ion chromatography with spectrophotometric detection (method B) BS EN 16318:2013+A1:2016 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 16318:2013+A1:2016 It supersedes BS EN 16318:2013 which is withdrawn The start and finish of text introduced or altered by amendment is indicated in the text by tags Tags indicating changes to CEN text carry the number of the CEN amendment For example, text altered by CEN amendment A1 is indicated by The UK participation in its preparation was entrusted to Technical Committee CII/37, Fertilisers and related chemicals A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © The British Standards Institution 2016 Published by BSI Standards Limited 2016 ISBN 978 580 89467 ICS 65.080 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October 2013 Amendments/corrigenda issued since publication Date Text affected 31 March 2016 Implementation of CEN amendment A1:2016 Standard title amended EN 16318:2013+A1 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM February 2016 ICS 65.080 Supersedes EN 16318:2013 English Version Fertilizers and liming materials - Determination of chromium(VI) by photometry (method A) and by ion chromatography with spectrophotometric detection (method B) Engrais et amendements minéraux basiques - Dosage du chrome (VI) par spectrophotométrie (méthode A) et chromatographie ionique avec détection spectrophotométrique (méthode B) Düngemittel und Kalkdünger - Bestimmung von Chrom (VI) mit Photometrie (Verfahren A) und mit Ionenchromatographie mit spektrometrischer Detektion (Verfahren B) This European Standard was approved by CEN on 15 September 2013 and includes Amendment approved by CEN on 19 December 2015 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 EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2016 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 16318:2013+A1:2016 E BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Contents Page European foreword Scope Normative references Terms and definitions Sampling and sample preparation 5 5.1 5.2 5.3 5.4 5.4.1 5.4.2 5.4.3 5.5 5.5.1 5.5.2 Method A: Determination by water extraction and spectrophotometric detection Principle Reagents Apparatus Procedure Preparation of the test solution Preparation of the blank test solution Spectrophotometric measurement Calculation and expression of the results Calibration Calculation of the element content in the sample 6.1 6.1.1 6.1.2 6.1.3 6.2 6.3 6.4 6.4.1 6.4.2 6.5 6.5.1 6.5.2 6.5.3 6.6 6.6.1 6.6.2 6.6.3 6.6.4 6.6.5 6.6.6 6.6.7 6.7 6.7.1 6.7.2 Method B: Determination by alkaline digestion and ion chromatography with spectrophotometric detection Principle Digestion Determination Interferences and sources of error 10 Reagents 10 Apparatus 12 Alkaline digestion procedure 13 General 13 Preparation of test solutions using a hotplate or heating block 13 Procedure 13 Instrumental set-up 13 Calibration 13 Test solution measurement 14 Quality control 14 General 14 Blank test solution 14 Verification of method 14 Duplicate samples 14 Cr(VI) spiked samples 15 Cr(III) spiked samples 15 Interpretation of Quality Control data 15 Calculation and expression of results 15 Calculation 15 Expression of results 16 !Precision— Inter-laboratory tests" 16 Test report 16 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Annex A (informative) Results of the inter-laboratory test performed by VDLUFA on method A 17 A.1 Inter-laboratory tests 17 A.2 Statistical results for the determination of chromium(VI) by photometry (method A) 17 Annex B (informative) Results of a validation study on spiked water samples 18 Bibliography 19 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) European foreword This document (EN 16318:2013+A1:2016) has been prepared by Technical Committee CEN/TC 260 “Fertilizers and liming materials”, the secretariat of which is held by DIN 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 August 2016, and conflicting national standards shall be withdrawn at the latest by August 2016 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 includes Amendment approved by CEN on 2015-12-19 This document supersedes !EN 16318:2013" The start and finish of text introduced or altered by amendment is indicated in the text by tags !" This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association !deleted text" !WARNING — Avoid any contact with the skin, ingestion or inhalation of Cr(VI) compounds Cr(VI) compounds are genotoxic and potentially carcinogenic to humans." 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 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Scope !This European Standard specifies two methods for the determination of the content of soluble chromate in fertilizers and liming materials." Method A specifies the determination of chromate after extraction with water by photometry This method can be used to determine Cr(VI)-mass fractions in solids higher than mg/kg Method B specifies the determination of chromate by alkaline digestion and ion chromatography with spectrophotometric detection This method can be used to determine Cr(VI)-mass fractions in solids higher than 0,1 mg/kg !NOTE 1" In case of reducing or oxidizing fertilizer matrix, no valid Cr(VI) content can be reported !NOTE The term fertilizer is used throughout the body of this European Standard and includes liming materials unless otherwise indicated." 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 1482-2, Fertilizers and liming materials — Sampling and sample preparation — Part 2: Sample preparation EN 12944-1:1999, Fertilizers and liming materials and soil improvers — Vocabulary — Part 1: General terms EN 12944-2:1999, Fertilizers and liming materials and soil improvers — Vocabulary — Part 2: Terms relating to fertilizers !EN 12944-3:2001, Fertilizers and liming materials — Vocabulary — Part 3: Terms relating to liming materials" EN 15192:2006, Characterisation of waste and soil — Determination of Chromium(VI) in solid material by alkaline digestion and ion chromatography with spectrophotometric detection EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696) Terms and definitions !For the purposes of this document, the terms and definitions given in EN 12944-1:1999, EN 129442:1999 and EN 12944-3:2001 apply." Sampling and sample preparation Sampling is not part of the methods specified in this European Standard A recommended sampling method is given in EN 1482-1 [2] Sample preparation shall be carried out in accordance with EN 1482-2 Reasonable precautions have to be taken to prevent oxidation of chromate present in the sample Samples shall be taken using appropriate devices and placed in containers that not contain stainless steel (e.g plastic, glass) After digestion, the sample shall be analyzed as soon as possible BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Method A: Determination by water extraction and spectrophotometric detection 5.1 Principle Chromate is extracted from the sample with water at room temperature The chromate concentration in the extract is measured by colorimetry using 1,5-diphenylcarbazide When chromate reduces the 1,5-diphenylcarbazide a magenta coloured complex of 1,5diphenylcarbazone and chromium is formed which can be measured colorimetrically at 540 nm 5.2 Reagents Use only reagents of recognized analytical grade and water conforming to 5.2.1 5.2.1 Water, according to EN ISO 3696, grade (electrical conductivity max 0,1 mS × m-1 equivalent to resistivity greater than 0,01 MΩ⋅m at 25 °C) It is recommended that the water used is obtained from a purification system that delivers ultrapure water having a resistivity greater than 0,18 MΩ⋅m 5.2.2 5.2.3 Hydrochloric acid, c(HCl) = 12 mol/l; 37 % volume fraction, ρ ≈ 1,18 g/ml Hydrochloric acid, diluted, c(HCl) approximately mol/l Mix equal volumes of hydrochloric acid (5.2.2) and water (5.2.1) 5.2.4 Diphenylcarbazide solution Dissolve 1,0 g Diphenylcarbazide [CO(NHNHC6H5)2] in 100 ml acetone and add one drop of acetic acid If this solution is stored in a glass bottle in the dark at °C, it may be used for approximately two weeks This solution shall be clear without colour If the diphenylcarbazide solution has become coloured, it shall be discarded and freshly prepared before use 5.2.5 Chromate standard stock solution, ρ(chromate) = 000 mg/l Dissolve 829 mg potassium dichromate (K2Cr2O7) in 000 ml water (5.2.1) using a volumetric flask This solution may be used for two weeks if stored in the dark at °C 5.2.6 Chromate standard stock solution, ρ(chromate) = 50 mg/l Dilute ml chromate stock solution (5.2.5) to 100 ml with water (5.2.1) using a volumetric flask This solution shall be freshly prepared on the day of use 5.2.7 Standard solutions Prepare the standard solutions by diluting aliquots of the 50 mg/l chromate standard stock solution (5.2.6) with water (5.2.1) in 100 ml volumetric flasks The aliquots and final concentrations of chromate are given in Table Other volumes and concentrations may be used for the preparation of standard solutions if appropriate See 5.4.3 for further instructions on how to prepare the standard solutions BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Table — Aliquots and final concentrations for the preparation of chromate standards from a 50 mg/l chromate standard stock solution in 100 ml volumetric flasks Aliquot Final concentration of chromate ml mg/l 0 (calibration blank) 0,20 0,10 0,05 0,50 1,00 1,50 0,025 0,25 0,50 0,75 A blank solution shall be prepared in a separate volumetric flask by adding water (5.2.1) only The standard solutions shall be prepared freshly on the day of use 5.3 Apparatus 5.3.1 Common laboratory glassware 5.3.2 Analytical balance, capable of weighing to an accuracy of mg 5.3.3 Membrane filters and vacuum filtration apparatus The filters should be made of cellulose nitrate, pore size µm and fit into the vacuum filtration apparatus 5.3.4 Mechanical shaker 5.3.5 Pipettes and/or dilutor, pipettes with fixed or variable volume and volumetric glassware to perform dilutions Alternatively, a dilutor may be used, which is an instrument used for automated volumetric dilutions The precision and accuracy of this equipment for volumetric dilutions shall be proved, controlled, and documented regularly 5.3.6 5.3.7 Spectrophotometer, capable to measure transmitted light at 540 nm 100 ml bottles, made from PE or PP, equipped with watertight caps 5.4 Procedure 5.4.1 Preparation of the test solution Weigh approximately 10 g, to the nearest 0,01 g, of the prepared sample and transfer to a suitable extraction vessel (5.3.7) Add 40 ml of water (5.2.1) If the sample material (e.g organic material) absorbs a high amount of water, add additionally water (5.2.1) to obtain a fluid suspension Record the amount of additional water added It may be necessary to use larger extraction vessels in such cases Close the cap tightly and BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) shake vigorously for 15 on a mechanical shaker (5.3.4) Filter the suspension immediately through membrane filters with µm pore size using the vacuum filtration apparatus (5.3.3) Pipette 20 ml of the test solution to a 100 ml volumetric flask and continue immediately with the colorimetric measurement If the test solution shows a yellow colour, the aliquot should be reduced to minimize interferences by the colour of organic substances The test solution may not be stored The chromate content shall be analyzed on the day of preparation 5.4.2 Preparation of the blank test solution Carry out a blank test at the same time as the extraction, with only the reagents and follow the same procedure as for the samples 5.4.3 Spectrophotometric measurement Add approximately 40 ml of water (5.2.1) to all volumetric flasks containing the standard solutions (5.2.7), the blank test solution (5.4.2) and the sample test solutions (5.4.1) Then add ml diluted hydrochloric acid (5.2.3) The pH-value of the resulting solution should be between pH and pH Add more diluted hydrochloric acid (5.2.3) if the pH-value is higher until a pH-value between pH and pH is reached Add ml diphenylcarbazide solution (5.2.4) to each volumetric flask and fill up to the mark with water (5.2.1) Wait 15 and measure the extinction of the solutions on a spectrophotometer at 540 nm 5.5 Calculation and expression of the results 5.5.1 Calibration In the case of a linear calibration curve, the calibration function can be described according to Formula (1) S = c×b + a where S c b a (1) is the net signal for Cr(VI) in a solution; is the concentration of Cr(VI) in this solution, in milligrams per litre or in micrograms per litre; is the slope of the linear calibration function; is the intersection of the linear calibration function Calculate the analyte concentration, cf, in the filtrate of the test portion using the slope b and the intersection a according to Formula (2): cf = where Sf Sf − a b (2) is the net signal of the test solution 5.5.2 Calculation of the element content in the sample Calculate the analyte concentration in the sample or the mass fraction of the analyte, wE, expressed in milligrams of analyte per kilogram of fertilizer according to Formula (3) BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) = wE where cf ( cf − cbl ) × V × 000 m t (3) is the concentration, in milligrams per litre, of the filtrate of the test portion, as determined according to Formula (2); cbl is the concentration, in milligrams per litre, of the blank solution; m Vt is the mass of the sample, in grams, taken for the extraction, and corrected for water content; is the total volume, in litres, of water added to the test portion for extraction Method B: Determination by alkaline digestion and ion chromatography with spectrophotometric detection 6.1 Principle 6.1.1 Digestion Cr(VI) is digested from the sample by an alkaline solution To quantify the content of Cr(VI) in a solid matrix, the following three criteria shall be satisfied: a) the digestion solution shall solubilize all species of Cr(VI); b) the conditions of the digestion shall not induce reduction of native Cr(VI) to Cr(III); c) the method shall not cause oxidation of native Cr(III) contained in the sample to Cr(VI) The alkaline digestion described in this document meets these criteria for a wide spectrum of solid matrices Under the alkaline conditions, neglect able reduction of Cr(VI) or oxidation of native Cr(III) is expected The addition of Mg2+ in a phosphate buffer to the alkaline solution prevents air oxidation of trivalent chromium (see [7], [8] and [9]) NOTE Background on methods for the determination of Cr(VI) in solid samples is given in EN 15192:2006, Annex D and [10], [11], [8] 6.1.2 Determination The quantification of Cr(VI) in the alkaline digestion solution should be performed using a suitable technique with appropriate accuracy For this purpose, ion chromatography is used to separate Cr(VI) from interferences Following this ion chromatographic separation, Cr(VI) is measured spectrophotometrically either at 365 nm (direct UV detection) or after post-column derivatization with 1,5-diphenylcarbazide in acid solution at 540 nm Post-column derivatization involves reaction of 1,5-diphenylcarbazide with Cr(VI) to produce trivalent chromium and diphenylcarbazone These then combine to form a trivalent chromium-diphenylcarbazone complex containing the characteristic magenta chromagen (λmax = 540 nm) NOTE The choice of detection method is based upon the required sensitivity Direct UV detection is less sensitive than detection after post-column derivatization with 1,5-diphenylcarbazide Hyphenated methods with ion chromatographic separation and detection techniques, such as inductively coupled plasma-mass spectrometry (ICP-MS) or inductively coupled plasma-atomic BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) emission spectroscopy (ICP-AES), may be used once validation of the chosen analytical method has been performed 6.1.3 Interferences and sources of error Use of ion chromatography is necessary for the separation of Cr(VI) from possible interferences in the alkaline digestion solution from solid material [12] (see also EN 15192:2006, D.3) For waste materials or soils, where the Cr(III)/Cr(VI) ratio is expected to be high, Cr(VI) results may be biased due to method-induced oxidation This can be particularly expected in soils high in Mn content and amended with soluble Cr(III) salts or freshly precipitated Cr(OH)3 [10] (see also EN 15192:2006, D.2) Cr(VI) can be reduced to Cr(III) during digestion from the sample due to reaction with reducing agents such as e.g divalent iron This problem is minimized in the described procedure using alkaline digestion solution [8] (see also EN 15192:2006, D.2) Cr(III) can be oxidized to Cr(VI) in hot alkaline solutions This problem is minimized in the described procedure by adding magnesium to the alkaline digestion solution [8], [9], [10], [13] (see also EN 15192:2006, D.2) Overloading the analytical column capacity with high concentrations of anionic species (e.g chloride) may cause underestimation of Cr(VI) [6] 6.2 Reagents Use only reagents of recognized analytical grade, and water as specified in 6.2.1 6.2.1 Water, according to EN ISO 3696, grade (electrical conductivity max 0,1 mS × m-1 equivalent to resistivity greater than 0,01 MΩ⋅m at 25 °C) It is recommended that the water used is obtained from a purification system that delivers ultrapure water having a resistivity greater than 0,18 MΩ⋅m 6.2.2 6.2.3 Sulfuric acid, concentrated, ρ(H2SO4) ≈ 1,84 g/ml, w(H2SO4) ≈ 98 % 6.2.4 Sodium carbonate, anhydrous, w(Na2CO3) > 99,9 % 6.2.5 Acetone 6.2.6 Methanol 6.2.7 Potassium dichromate, w(K2Cr2O7) > 99,9 % 1,5-Diphenylcarbazide, !w((C6H5NHNH)2CO) > 98 %" Dry to constant weight at 110 °C, cool and store in a desiccator 6.2.8 6.2.9 Sodium hydroxide, w(NaOH) > 99 % Magnesium chloride hexahydrate, w(MgCl2.6H2O) > 99 % 6.2.10 Dipotassium hydrogenphosphate, w(K2HPO4) > 99 % 6.2.11 Potassium dihydrogenphosphate, w(KH2PO4) > 99 % 6.2.12 Lead chromate, w(PbCrO4) > 99 % 10 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) 6.2.13 Diphenylcarbazide reagent solution Dissolve 0,125 g of 1,5-diphenylcarbazide (6.2.4) in 25 ml of acetone (6.2.5) or methanol (6.2.6) in a 250 ml volumetric flask Fill 125 ml of water (6.2.1) into a separate container, slowly add ml of concentrated sulfuric acid (6.2.2), swirl to mix and allow to cool Degas with, e.g helium or argon, for to 10 prior to adding to the 1,5-diphenylcarbazide solution After combining the solutions, fill up to the mark with water (6.2.1) and degas additionally for to 10 The reagent solution is stable for five days 6.2.14 Eluent solution Use an eluent solution appropriate to separate chromate over the ion chromatographic column (6.3.7) 6.2.15 Alkaline digestion solution, sodium hydroxide, c(NaOH) = 0,5 mol/l, sodium carbonate, c(Na2CO3) = 0,28 mol/l Dissolve 20,0 g of sodium hydroxide (6.2.8) in approximately 500 ml of water (6.2.1) Add 30,0 g of sodium carbonate (6.2.3) and swirl to mix Quantitatively transfer the solution into a l volumetric flask Dilute to the mark with water (6.2.1) The pH-value of the digestion solution shall be checked before use The pH-value shall be 11,5 or higher Store in a polyethylene bottle at room temperature and prepare fresh monthly 6.2.16 Calibration solutions of Cr(VI) 6.2.16.1 Cr(VI) standard stock solution, 000 mg/l Cr(VI) Dissolve 0,282 g of potassium dichromate (6.2.7) in 75 ml of water (6.2.1) in a 100 ml volumetric flask Dilute to the mark with water (6.2.1), close and mix thoroughly Store the solution in a polypropylene bottle for a maximum period of one year Alternatively, a commercial standard solution with a certified Cr(VI) concentration traceable to national standards may be used Observe the manufacturer's expiration date or recommended shelf life 6.2.16.2 Cr(VI) working standard solution, 10 mg/l Cr(VI) Accurately pipette 10,0 ml of the Cr(VI) standard stock solution (6.2.16.1) into a l volumetric flask, dilute to the mark with water (6.2.1), close and mix thoroughly Prepare this solution fresh monthly 6.2.16.3 Cr(VI) calibration solutions Prepare a set of at least five calibration solutions by diluting the Cr(VI) working standard solution with a + diluted alkaline digestion solution (6.2.15) Add 25 ml of the alkaline digestion solution (6.2.15) into a 50 ml volumetric flask, pipette accurately the appropriate volume of Cr(VI) working standard solution (6.2.16.2) into the volumetric flask and dilute to the mark with water (6.2.1), close and mix thoroughly Prepare these calibration solutions fresh daily 6.2.16.4 Cr(VI) spiking solutions The Cr(VI) working standard solution (6.2.16.2) may be used to spike samples 6.2.17 Phosphate buffer solution, 0,5 mol/l dipotassium hydrogenphosphate (K2HPO4)/0,5 mol/l potassium dihydrogenphosphate (KH2PO4), pH Dissolve 87,09 g K2HPO4 (6.2.10) and 68,04 g of KH2PO4 (6.2.11) in approximately 700 ml of water (6.2.1) and swirl to mix Transfer the solution into a l volumetric flask Dilute to the mark with water (6.2.1) 11 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) 6.2.18 Magnesium chloride solution Dissolve 85,4 g MgCl2.6H2O (6.2.9) in a 100 ml volumetric flask, dilute to the mark with water (6.2.1), close and mix thoroughly 6.2.19 Chromium chloride hexahydrate, w(CrCl3.6H2O) > 96 % 6.2.20 Cr(III) spiking solution Use a commercial standard solution with a certified Cr(III) concentration, e.g 000 mg/l Cr(III) traceable to national standards Observe the manufacturer's expiration date or recommended shelf life Alternatively, dissolve 512 mg of chromium chloride hexahydrate (6.2.19) in water (6.2.1) in a 100 ml volumetric flask, dilute to the mark with water (6.2.1), close and mix thoroughly Store the solution in a polypropylene bottle for a maximum period of one year Before using, determine the Cr concentration of the spiking solution 6.3 Apparatus 6.3.1 Common laboratory glassware 6.3.2 Analytical balance, capable of weighing to an accuracy of mg 6.3.3 Digestion equipment: — hotplate with a magnetic stirrer, thermostatically controlled with a digestion vessel of 250 ml covered with a watch glass; or — heating block with a magnetic stirrer, thermostatically controlled with a digestion vessel of 250 ml covered with a watch glass Other thermostatically controlled digestion equipment with a magnetic stirrer may be used once validation has been performed 6.3.4 6.3.5 Filtration equipment, suitable for using 0,45 μm membrane filters 6.3.6 Ion chromatographic system Membrane filters, 0,45 μm pore size, chemically inert All components which come into contact with the sample or eluent stream shall be comprised of inert materials, e.g polyether ether ketone (PEEK), as shall all connecting tubing (see EN 15192:2006, Annex B) 6.3.7 Ion chromatographic column, suitable for chromate separation with a sufficient ion exchange capacity 6.3.8 Detection system: — UV-VIS spectrophotometer at 365 nm; or — VIS spectrophotometer at 540 nm after post column derivatization 12 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) 6.4 Alkaline digestion procedure 6.4.1 General Use either the hotplate or heating block method described in 6.3.3 to prepare test solutions for determination of Cr(VI) in fertilizers 6.4.2 Preparation of test solutions using a hotplate or heating block Adjust the temperature setting by preparing and monitoring a temperature blank (a 250 ml vessel filled with 50 ml digestion solution) Maintain a digestion solution temperature of (92,5 ± 2,5) °C Do not allow the solution to boil or evaporate to dryness Transfer (2,5 ± 0,1) g of the test portion weighed to the nearest 0,1 mg into a clean 250 ml digestion vessel NOTE For very high expected concentrations of Cr(VI), a smaller representative test portion can be used Add (50 ± 1) ml of the alkaline digestion solution (6.2.15) to each sample using a graduated cylinder, and also add ml of magnesium chloride solution (6.2.18) and 0,5 ml of phosphate buffer solution (6.2.17) Cover all digestion vessels If using a heating block, reflux condensers may be used Heat the samples to (92,5 ± 2,5) °C while continuously stirring, then maintain the samples at (92,5 ± 2,5) °C for at least 60 with stirring continuously Cool each solution to room temperature Transfer the contents quantitatively to the filtration equipment (6.3.4), rinsing the digestion vessel three times with small portions of water (6.2.1) Filter through a 0,45 μm membrane filter (6.3.5) Rinse the filtration equipment (6.3.4) with water (6.2.1) and transfer the filtrate to a 100 ml volumetric flask and fill up to the mark with water (6.2.1) Alternatively, the sample may be centrifuged or allowed to settle 6.5 Procedure 6.5.1 Instrumental set-up Set up the ion chromatograph in accordance with manufacturer’s instructions Adjust the flow rate of the eluent solution (6.2.14) to a value that is compatible with the columns used (typically 0,3 ml/min to ml/min) In case of post column derivatization, optimize the ratio of eluent solution and reagent flow rates or adjust the sulfuric acid concentration of the diphenylcarbazide reagent solution (6.2.13) to obtain the best signal to background ratio It is important that the ratio between the eluent solution and reagent flow rates is kept constant, that the total flow rate does not exceed the maximum flow rate for the detector and the diphenylcarbazide reagent is present in excess A typical value for the ratio between the eluent solution and reagent flow rates is 3:1 After the flow rates are adjusted, allow the system to equilibrate for 15 In case of direct detection, adjust the UV-VIS detector to measure within a range of 355 nm to 375 nm, preferably at 365 nm In case of measuring after post-column derivatization with 1,5-diphenylcarbazide, adjust the VIS detector to measure within a range of 530 nm to 550 nm, preferably at 540 nm 6.5.2 Calibration Inject a suitable volume (20 μl to 250 μl), e.g 50 μl, of each calibration solution (6.2.16.3) into the ion chromatographic system (6.3.6) 13 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Determine the absorbance for each of the calibration solutions using either peak height or peak area mode Prepare a calibration graph using a linear plot of the peak height or peak area as a function of calibration solution concentration by least squares regression analysis using suitable software 6.5.3 Test solution measurement Inject a suitable volume, e.g 50 μl, of filtered !test solutions" (6.4.2) into the ion chromatographic system (6.3.6) Determine the concentrations of Cr(VI) in the test solutions (6.4.2) by comparison with the calibration graph (6.5.2) If concentrations of Cr(VI) are found to be above the upper calibration solution, dilute the extract with a + diluted alkaline digestion solution (6.2.15) in order to bring them within the linear range and repeat the analysis Take note of the dilution when calculating the mass concentration of Cr(VI) in the material under investigation NOTE For samples expected to have very high concentrations of Cr(VI), it might be necessary to dilute the test solutions before they are first analyzed Otherwise, swamping of the diphenylcarbazide reagent can occur and no colour will develop 6.6 Quality control 6.6.1 General Process quality control (QC) samples with each batch of test samples, as detailed below 6.6.2 Blank test solution To assess glassware contamination and/or reagents, process in parallel at least one blank solution following the same digestion procedure as applied to the test samples but omitting the test portion If contamination is detected, control your procedure until the level of Cr(VI) is negligible and repeat the digestions Analyze the blank solutions according to a frequency of blank per 20 test portions or at least once in each series of measurement 6.6.3 Verification of method Prepare a Cr(VI) standard solution from a stock standard solution from a different source than that used for preparing the calibration solutions In parallel with processing the test samples, prepare a blank solution spiked with this Cr(VI) standard solution following the same digestion procedure as applied to the test samples but omitting the test portion Process this QC sample within each batch Prepare a Cr(III) standard solution from the Cr(III) spiking solution (6.2.20) In parallel with processing the test samples, prepare a blank solution spiked with this Cr(III) standard solution following the same digestion procedure as applied to the test samples but omitting the test portion Process this QC sample within each batch 6.6.4 Duplicate samples Process duplicate samples to estimate the method accuracy according to a frequency of at least one duplicate sample per 20 test portions or process minimum of duplicate sample per batch 14 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) 6.6.5 Cr(VI) spiked samples Process soluble spikes (e.g K2Cr2O7 (6.2.16.4)) on a routine basis to estimate the method accuracy in relation to possible reduction processes Spiked samples consist of solid material to which known amounts of Cr(VI) have been added Soluble pre-digestion matrix spikes should be analyzed at a frequency of at least spike sample per 20 test portions or per batch The matrix spike is then carried through the digestion process More frequent matrix spikes should be analyzed if the sample characteristics within the analytical batch appear to have significant variability based on visual observation To evaluate the dissolution of all Cr(VI) species during the digestion process, an insoluble spike (e.g PbCrO4 (6.2.12)) may be used The recovery of the Cr(VI) spike can be used to assess the following criteria: — digestion solution shall solubilize all species of Cr(VI); — conditions of the digestion shall not induce reduction of native Cr(VI) to Cr(III) 6.6.6 Cr(III) spiked samples Process the Cr(III) spiking solution (6.2.20) on a routine basis to estimate the method accuracy in relation to the possible oxidation processes, expressed as a percent Cr(VI) recovery relative to the spiked amount of Cr(III) Spiked samples consist of solid material to which known amounts of Cr(III) have been added The recovery of the Cr(III) spike can be used to assess the risk of method induced oxidation of native Cr(III) contained in the sample to Cr(VI) 6.6.7 Interpretation of Quality Control data If the verification procedure performed in 6.6.3 and the recoveries from the spiked samples performed in 6.6.5 and 6.6.6 meet laboratory criteria, the analytical result can be judged to be valid NOTE An acceptable range for Cr(VI) spike recoveries is 75 % to 125 % in soil, sludge, sediments and similar waste materials according to EPA-method 3060 A [5] If the verification procedure performed in 6.6.3 meets the laboratory criteria, but the recoveries from the spiked samples performed in 6.6.5 and 6.6.6 not meet the laboratory criteria, it is appropriate to determine the reducing/oxidizing tendency of the sample matrix NOTE This can be accomplished by characterization of each sample for additional analytical parameters, such as pH, ferrous iron (Fe II), sulfides, organic carbon content and the oxidation potential The analysis of these additional parameters establishes the tendency of Cr(VI) to exist or not exist in the unspiked samples and assists in interpreting QC data for matrix spike recoveries outside conventionally accepted criteria for total metals 6.7 Calculation and expression of results 6.7.1 Calculation Calculate the mass fraction of Cr(VI), wCr(VI), in the fertilizer sample according to Formula (4) wCr(VI) = where wCr(VI) rd × F × 10 m × wdm (4) is the mass fraction of Cr(VI) in the fertilizer sample, expressed in milligrams per kilogram 15 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) ρd m wdm F dry matter; is the concentration of Cr(VI) in the alkaline digested test solution, expressed in micrograms per litre; is the !mass of the test portion", expressed in grams, nominally 2,5 g; is the dry matter content of the test portion, expressed as a percentage; is the dilution factor (F = if the alkaline extraction solution of nominally 100 ml has not been diluted prior to analysis) 6.7.2 Expression of results Values should be rounded to 0,01 mg/kg, only three significant figures should be expressed EXAMPLE wCr(VI) = 0,15 mg/kg wCr(VI) = 15,3 mg/kg ! Precision— Inter-laboratory tests" !Details of inter-laboratory tests on the precision of the method are summarized in Annex A Repeatability and reproducibility were calculated according to ISO 5725-1 [3] and ISO 5725-2 [4] Inter-laboratory tests on the precision of the method analysing different mineral fertilizer matrices have been performed in 2009, 2010 and 2011 and in 2013 analyzing different matrices of liming materials using method A and method B In all samples analyzed, the element Cr(VI) could not be detected Inter-laboratory tests on the precision of method A performed in 2005 by the Technical Group Fertilizers of the German VDLUFA resulted in the statistical data given in Annex A." Test report The test report shall contain at least the following information: a) all information necessary for the complete identification of the sample; b) test method used (method A or method B) with reference to this document (EN 16318); c) test results obtained; d) date of sampling and sampling procedure (if known); e) date when the analysis was finished; f) whether the requirement of the repeatability limit has been fulfilled; g) all operating details not specified in this document, or regarded as optional, together with details of any incidents occurred when performing the method, which might have influenced the test result(s) 16 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Annex A (informative) Results of the inter-laboratory test performed by VDLUFA on method A A.1 Inter-laboratory tests The precision of method A has been determined in the year 2005 in an inter-laboratory trial with nine laboratories participating and carried out on one sample The statistical results are given in Table A.1 A.2 Statistical results for the determination of chromium(VI) by photometry (method A) Table A.1 — Statistical results Parameter Year of the test Number of laboratories Number of laboratories retained after elimination of outliers Number of outliers Mean value, x (mg/kg) Repeatability standard deviation sr (mg/kg) Sample wood ash 2005 9 1,66 0,19 Relative repeatability standard deviation RSDr % 11,28 Reproducibility standard deviation sR (mg/kg) 0,24 Repeatability limit r [r = 2,8 × sr] (mg/kg) Relative reproducibility standard deviation RSDR % Reproducibility limit R [R = 2,8 × sR] (mg/kg) 0,53 14,73 0,67 17 BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Annex B (informative) Results of a validation study on spiked water samples A validation study with spiked water samples was performed by the Landwirtschaftliches Technologiezentrum Augustenberg (LTZ), Germany, in order to investigate possible interferences resulting from high calcium contents in test solutions of mineral fertilizers with the determination of Cr(VI) As can be seen from Table B.1 increasing Ca contents had no interference on the calibration data or the recovery of Cr(VI) from spiked water samples ! Table B.1 — Results of determination of Cr(VI) content in spiked water samples Water sample A B C D Amount of Cr(VI) added to the water sample mg/l 0,05 0,25 18 a Calibration: y = a × x + c c R2 0,157 0,001 0,999 100 0,159 0,002 0,999 Mass concentration ρCa mg/l 10 000 Sample A ρCa = mg/l 0,038 0,241 0,157 0,159 0,002 Amount of Cr(VI) detected in the water sample mg/l 0,999 0,999 Sample B ρCa = 10 mg/l Sample C ρCa = 100 mg/l Sample D ρCa = 000 mg/l 0,26 0,239 0,243 0,044 1,023 1,029 4,095 4,116 3,069 0,001 3,078 0,048 1,022 2,996 4,004 0,032 1,009 2,983 3,854 " BS EN 16318:2013+A1:2016 EN 16318:2013+A1:2016 (E) Bibliography [1] [2] [3] REGULATION (EC) NO 2003/2003 of the European Parliament and of the Council of 13 October 2003 relating to fertilisers, Official Journal L 304, 21/11/2003, p 0001-0194 and amendments available from: http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2003:304:0001:0194:EN:PDF EN 1482-1, Fertilizers and liming materials - Sampling and sample preparation —Part 1: Sampling ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles and definitions [4] ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method [5] Method 3060A, Alkaline digestion for hexavalent chromium, in: EPA SW-846, Test Methods for Evaluating Solid wastes, Physical/Chemical Methods, Update, United States Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC, 1996, available from: http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/3060a.pdf [6] [7] [8] [9] [10] [11] [12] [13] Method 7199, Determination of hexavalent chromium in drinking water, groundwater and industrial wastewater effluents by ion chromatography, in: EPA SW-846, Test Methods for Evaluating Solid wastes, Physical/Chemical Methods, United States Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC, 1996, available from: http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/7199.pdf ZATKA V.J Speciation of hexavalent chromium in welding fumes - Interference by air oxidation of chromium Am Ind Hyg Assoc J 1985, 46 p 327 PETTINE M., CAPRI S Anal Chim Acta 2005, 540 p 231 PETTINE M., MILLERO F.J., LA NOCE T Mar Chem 1991, 34 p 29 VITALE R.J., MUSSOLINE G.R., PRETURA J.C., JAMES B.R Hexavalent Chromium Extraction from Soils: Evaluation of an Alkaline Digestion Method J Environ Qual 1994, 23 pp 1249–1256 JAMES B.R., PETURA J.C., VITALE R.J., MUSSOLINE G.R Hexavalent chromium extraction from soils: a comparison of five methods Environ Sci Technol 1995, 29 pp 2377–2381 PETTINE M., CAPRI S Anal Chim Acta 2005, 540 p 239 EARY L.E., RAL D Kinetics of chromium(III) oxidation to chromium(VI) by reaction with manganese dioxide Environ Sci Technol 1987, 21 p 1187 19 This page deliberately left blank This page deliberately left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British Standards and other standards-related publications, information and services BSI is incorporated by Royal Charter British Standards and other standardization products are published by BSI Standards Limited About us Revisions We bring together business, industry, government, consumers, innovators and others to shape their combined experience and expertise into standards -based solutions Our British Standards and other publications are updated by amendment or revision The knowledge embodied in our standards has been carefully assembled in a dependable format and refined through our open consultation process Organizations of all sizes and across all sectors choose standards to help them achieve their goals Information on standards We can provide you with the knowledge that your organization needs to succeed Find out more about British Standards by visiting our website at bsigroup.com/standards or contacting our Customer Services team or Knowledge Centre Buying standards You can buy and download PDF versions of BSI publications, including British and adopted European and international standards, through our website at bsigroup.com/shop, where hard copies can also be purchased If you need international and foreign standards from other Standards Development Organizations, hard copies can be ordered from our Customer Services team Subscriptions Our range of subscription services are designed to make using standards easier for you For further information on our subscription products go to bsigroup.com/subscriptions With British Standards Online (BSOL) you’ll have instant access to over 55,000 British and adopted European and international standards from your desktop It’s available 24/7 and is refreshed daily so you’ll always be up to date You can keep in touch with standards developments and receive substantial discounts on the purchase price of standards, both in single copy and subscription format, by becoming a BSI Subscribing Member PLUS is an updating service exclusive to BSI Subscribing Members You will automatically receive the latest hard copy of your standards when they’re revised or replaced To find out more about becoming a BSI Subscribing Member and the benefits of membership, please visit bsigroup.com/shop With a Multi-User Network Licence (MUNL) you are able to host standards publications on your intranet Licences can cover as few or as many users as you wish With updates supplied as soon as they’re available, you can be sure your documentation is current For further information, email bsmusales@bsigroup.com BSI Group Headquarters 389 Chiswick High Road London W4 4AL UK We continually improve the quality of our products and services to benefit your business If you find an inaccuracy or ambiguity within a British Standard or other BSI publication please inform the Knowledge Centre Copyright All the data, software and documentation set out in all British Standards and other BSI publications are the property of and copyrighted by BSI, or some person or entity that owns copyright in the information used (such as the international standardization bodies) and has formally licensed such information to BSI for commercial publication and use Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior written permission from BSI Details and advice can be obtained from the Copyright & Licensing Department Useful Contacts: Customer Services Tel: +44 845 086 9001 Email (orders): orders@bsigroup.com Email (enquiries): cservices@bsigroup.com Subscriptions Tel: +44 845 086 9001 Email: subscriptions@bsigroup.com Knowledge Centre Tel: +44 20 8996 7004 Email: knowledgecentre@bsigroup.com Copyright & Licensing Tel: +44 20 8996 7070 Email: copyright@bsigroup.com