SIST EN 16320:2013
(Main)Fertilizers - Determination of trace elements - Determination of mercury by vapour generation (VG) after aqua regia dissolution
Fertilizers - Determination of trace elements - Determination of mercury by vapour generation (VG) after aqua regia dissolution
This European Standard specifies a method for the determination of the content of mercury in fertilizers after extraction with aqua regia and the detection of mercury by vapour generation (VG) coupled to an atomic absorption spectrometer or an inductively coupled plasma-atomic emission spectrometer. A limit of quantification of 0,01 mg/kg is to be expected.
Düngemittel - Bestimmung von Elementspuren - Bestimmung von Quecksilber mit Verdampfungstechnik (VG) nach Königswasseraufschluss
Diese Europäische Norm legt ein Verfahren zur Bestimmung von Quecksilber in Düngemitteln mittels Verdampfungstechnik (VG), gekoppelt mit Atomabsorptionsspektrometer oder Atomemissionsspektrometer, mit induktiv gekoppeltem Plasma nach Königswasseraufschluss fest. Die Bestimmungsgrenze ist bei 0,01 mg/kg zu erwarten.
Engrais - Dosage des éléments traces - Détermination du mercure par génération de vapeur (VG) après digestion à l'eau régale
Cette norme européenne spécifie une méthode permettant de déterminer, après extraction à l’eau régale, la teneur en mercure dans les engrais par détection de mercure par génération de vapeur (VG) couplée à un spectromètre d’absorption atomique ou un spectromètre d’émission atomique avec plasma à couplage inductif. Une limite de quantification de 0,01 mg/kg doit être attendue.
Gnojila - Določevanje elementov v sledovih - Določevanje živega srebra s tehniko hladnih par po raztapljanju v zlatotopki
Ta evropski standard določa metodo za določevanje vsebnosti živega srebra v gnojilih po ekstrakciji z zlatotopko in določevanje živega srebra s tehniko hladnih par (VG) z atomskim absorpcijskim spektrometrom ali atomskim emisijskim spektrometrom z induktivno sklopljeno plazmo. Pričakuje se meja kvantifikacije 0,01 mg/kg.
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Düngemittel - Bestimmung von Elementspuren - Bestimmung von Quecksilber mit Verdampfungstechnik (VG) nach KönigswasseraufschlussEngrais - Dosage des éléments traces - Détermination du mercure par génération de vapeur (VG) après digestion à l'eau régaleFertilizers - Determination of trace elements - Determination of mercury by vapour generation (VG) after aqua regia dissolution65.080GnojilaFertilizersICS:Ta slovenski standard je istoveten z:EN 16320:2013SIST EN 16320:2013en,fr,de01-december-2013SIST EN 16320:2013SLOVENSKI
STANDARDSIST-TS CEN/TS 16320:20121DGRPHãþD
SIST EN 16320:2013
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 16320
October 2013 ICS 65.080 Supersedes CEN/TS 16320:2012English Version
Fertilizers - Determination of trace elements - Determination of mercury by vapour generation (VG) after aqua regia dissolution Engrais - Dosage des éléments traces - Détermination du mercure par génération de vapeur (VG) après digestion à l'eau régale
Düngemittel - Bestimmung von Elementspuren - Bestimmung von Quecksilber mit Verdampfungstechnik (VG) nach Königswasseraufschluss This European Standard was approved by CEN on 29 August 2013.
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
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 16320:2013: ESIST EN 16320:2013
EN 16320:2013 (E) 2 Contents Page Foreword . 3 1 Scope . 4 2 Normative references . 4 3 Terms and definitions . 4 4 Principle. 4 5 Sampling and sample preparation . 4 6 Reagents . 4 7 Apparatus . 5 8 Procedure . 6 8.1 General . 6 8.2 Preparation of the test solution . 7 8.2.1 General . 7 8.2.2 Preparation . 7 8.3 Preparation of the test solution for the correction of matrix effects by spike recovery . 7 8.4 Preparation of the blank test solution . 8 8.5 Preparation of the calibration solutions . 8 8.5.1 Calibration solutions for the analysis of mercury . 8 8.5.2 Calibration standards. 8 8.6 Determination of mercury . 8 8.6.1 General . 8 8.6.2 Determination by VG-AAS . 8 8.6.3 Spectrometer settings of VG-AAS . 9 8.6.4 Determination by VG-ICP-AES . 9 9 Calculation and expression of the results . 10 9.1 External calibration . 10 9.2 Correction for spike recovery . 10 9.3 Standard addition method . 11 9.4 Calculation of the element content in the sample . 12 10 Precision . 12 10.1 Inter laboratory tests . 12 10.2 Repeatability . 12 10.3 Reproducibility . 12 11 Test report . 13 Annex A (informative)
Results of the inter-laboratory test . 14 Bibliography. 15
SIST EN 16320:2013
EN 16320:2013 (E) 3 Foreword This document (EN 16320:2013) 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 April 2014, and conflicting national standards shall be withdrawn at the latest by April 2014. 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 supersedes CEN/TS 16320:2012. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. The following changes have been made to the former edition: a) the CEN Technical Specification has been adopted as a European Standard; b) the document has been editorially revised. According to the CEN-CENELEC Internal Regulations, the national standards organisations 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 16320:2013
EN 16320:2013 (E) 4 1 Scope This European Standard specifies a method for the determination of the content of mercury in fertilizers after extraction with aqua regia and the detection of mercury by vapour generation (VG) coupled to an atomic absorption spectrometer or an inductively coupled plasma-atomic emission spectrometer. A limit of quantification of 0,01 mg/kg is to be expected. 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 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 ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696) 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999 apply. 4 Principle Mercury is extracted from the sample with aqua regia and conventional boiling. The concentration of mercury in the extract is measured by (cold) vapour generation (VG) coupled to a suitable detector, such as an atomic absorption spectrometer (AAS) or an inductively coupled plasma-atomic emission spectrometer (ICP-AES). 5 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. Sample preparation shall be carried out in accordance with EN 1482-2. 6 Reagents Use only reagents of recognised analytical grade. Commercially available stock solutions shall be replaced according to the specifications from the supplier or after one year if prepared in the laboratory from available salts. Standard solutions shall be renewed monthly as a general rule.
6.1 Water, conforming to grade 2 of EN ISO 3696. 6.2 Hydrochloric acid, c(HCl) = 12 mol/l; 37
≈ 1,18 g/ml. 6.3 Nitric acid, c(HNO3) = 16 mol/l; not less than 65 % volume fraction, ρ ≈ 1,42 g/ml. SIST EN 16320:2013
EN 16320:2013 (E) 5 6.4 Mixed acid solution of 0,8 mol/l nitric acid and 1,8 mol/l hydrochloric acid. Mix 150 ml of hydrochloric acid (6.2) and 50 ml nitric acid (6.3) to 1,0 l of water (6.1). 6.5 Standard stock solution, mercury standard stock solution, e.g.
= 1 000 mg/l. Use suitable stock solutions. Single-element stock solutions with adequate specification stating the acid used and the preparation technique are commercially available. It is recommended to use commercially available standard stock solutions for mercury. 6.6 Working standard solutions. Depending on the scope, different working standard solutions may be necessary. In general, the stability of mercury working standard solutions should be checked. 6.6.1 Working standard solution I,
= 10 mg/l for mercury.
Dilute 1,00 ml of the standard stock solution for mercury (6.5) to 100,0 ml with the mixed acid solution (6.4). This solution is used to prepare 200 µg/l mercury working standard solution.
6.6.2 Working standard solution II,
= 200 g/l for mercury. Dilute 2,00 ml of the 10 mg/l mercury working standard solution I (6.6.1) to 100,0 ml with the mixed acid solution (6.4). This solution is used to prepare spiked test solutions and calibration solutions. 6.7 Reducing agents. 6.7.1 General. Tin(II) chloride or sodium borohydride may be used as the reducing agent, but it is not advisable to use the two reagents alternately. Observe the instructions of the manufacturers of the apparatus. 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. 6.7.2 Tin(II) chloride solution, (SnCl2·2H2O) = 100 g/l. Dissolve 50 g of tin(II) chloride in approximately 100 ml of hydrochloric acid (6.2) in a 500 ml volumetric flask and dilute to the mark. Prepare a fresh solution daily. 6.7.3 Sodium borohydride solution, e.g.
= 2 g/l. Dissolve 2 g of sodium hydroxide pellets in water, add 2 g of sodium borohydride and dilute to 1 000 ml with water (6.1). Prepare a fresh solution daily and, when necessary, filter before use. When the analysis procedure is of a longer time, it is recommended to cool the sodium borohydride solution (i.e. with ice around the flask) during its use in the vapour generation ICP-AES or AAS measurement. 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. 7 Apparatus 7.1 Common laboratory glassware. 7.2 Analytical balance, capable of weighing to an accuracy of 1 mg. SIST EN 16320:2013
EN 16320:2013 (E) 6 7.3 Inductively coupled plasma-atomic emission spectrometer, with axial or radial viewing of the plasma and with suitable background correction. The settings of the working conditions (e.g. gas flows, RF or plasma power, sample uptake rate, integration time, number of replicates) shall be optimised according the manufacturer’s instructions. Radial viewing of the plasma may be used if it can be shown that the limit of quantification for mercury is below the required legal limit value. 7.4 Atomic absorption spectrometer, equipped with a heated quartz cuvette or a mercury absorption cell, or optionally with an amalgamation system. 7.5 Vapour generation equipment. 7.5.1 Continuous flow or flow-injection cold-vapour system.
7.5.2 Element-specific lamp for mercury. 7.6 Dilutor. Instrument used for automated volumetric dilutions or other appropriate equipment (e.g. pipettes and volumetric glassware) to perform dilutions. The precision and accuracy of this type of equipment for volumetric dilutions shall be established, and controlled and documented regularly.
7.7 Ash-free filter paper, i.e. Whatman 589/2®1) or equivalent quality. 8 Procedure 8.1 General Calibrations by standard additions with several standards or by matrix matching are very powerful calibration techniques and can be used to accurately correct for matrix effects from easy-ionisable elements (multiplicative matrix effects). Additive matrix effects (i.e. spectral interferences) are not corrected for with standard additions calibration. For matrix matching, additive matrix effects will be corrected for when the added matrix is the cause of the matrix effect. The main drawback of calibration by standard addition with several standards is the requirement for a calibration function for each sample type, which is a time consuming process. For matrix matching, a profound knowledge of the sample matrix is needed, which is not always necessarily available. These two techniques may thus not be practical to use in routine fertilizer laboratories. It is therefore suggested that calibrations are to be performed by means of external calibration and correction of matrix effects by addition of one known spike of a standard solution (spike recovery). The method of external calibration and correction for spike recovery allows for the analysis of fertilizers with unknown matrix composition or with a matrix that cannot be easily imitated synthetically. This calibration technique may not be as precise as calibration by standard additions with several standards but the increased uncertainty is small compared to the total uncertainty of the method, if the total analyte concentration is in the linear working range after the spike and the added spike corresponds to at least a doubling of the analyte concentration. Many matrix errors can be compensated for by this procedure, if they are not additive (e.g. spectral interferences). Aliquots of the sample solution are analysed by the means of external calibration and then one aliquot is spiked with known concentrations of the analytes without changing the matrix of the sample solution. The calculated spike recovery is then used to correct the concentration calculated from the external calibration function. The concentration of the spikes shall be in the linear working range of the analytical detection tec
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Düngemittel - Bestimmung von Elementspuren - Bestimmung von Quecksilber mit Verdampfungstechnik (VG) nach KönigswasseraufschlussEngrais - Dosage des éléments traces - Détermination du mercure par génération de vapeur (VG) après digestion à l'eau régaleFertilizers - Determination of trace elements - Determination of mercury by vapour generation (VG) after aqua regia dissolution65.080GnojilaFertilizersICS:Ta slovenski standard je istoveten z:FprEN 16320kSIST FprEN 16320:2013en,fr,de01-maj-2013kSIST FprEN 16320:2013SLOVENSKI
STANDARD
kSIST FprEN 16320:2013
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
FINAL DRAFT
FprEN 16320
February 2013 ICS 65.080 Will supersede CEN/TS 16320:2012English Version
Fertilizers - Determination of trace elements - Determination of mercury by vapour generation (VG) after aqua regia dissolution Engrais - Dosage des éléments traces - Détermination du mercure par génération de vapeur (VG) après digestion à l'eau régale
Düngemittel - Bestimmung von Elementspuren - Bestimmung von Quecksilber mit Verdampfungstechnik (VG) nach Königswasseraufschluss This draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the Technical Committee CEN/TC 260.
If this draft becomes a European Standard, 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.
This draft European Standard was established by CEN 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. FprEN 16320:2013: EkSIST FprEN 16320:2013
FprEN 16320:2013 (E) 2 Contents Page Foreword .3 1 Scope .4 2 Normative references .4 3 Terms and definitions .4 4 Principle .4 5 Sampling and sample preparation .4 6 Reagents .4 7 Apparatus .5 8 Procedure .6 8.1 General .6 8.2 Preparation of the test solution .7 8.2.1 General .7 8.2.2 Preparation .7 8.3 Preparation of the test solution for the correction of matrix effects by spike recovery .7 8.4 Preparation of the blank test solution .8 8.5 Preparation of the calibration solutions .8 8.5.1 Calibration solutions for the analysis of mercury .8 8.5.2 Calibration standards .8 8.6 Determination of mercury .8 8.6.1 General .8 8.6.2 Determination by VG-AAS .8 8.6.3 Spectrometer settings of VG-AAS .9 8.6.4 Determination by VG-ICP-AES .9 9 Calculation and expression of the results . 10 9.1 External calibration. 10 9.2 Correction for spike recovery . 10 9.3 Standard addition method . 11 9.4 Calculation of the element content in the sample . 12 10 Precision . 12 10.1 Inter laboratory tests . 12 10.2 Repeatability . 12 10.3 Reproducibility . 12 11 Test report . 12 Annex A (informative)
Results of the inter-laboratory test . 14 Bibliography . 15
kSIST FprEN 16320:2013
FprEN 16320:2013 (E) 3 Foreword This document (FprEN 16320:2013) has been prepared by Technical Committee CEN/TC 260 “Fertilizers and liming materials”, the secretariat of which is held by DIN. This document is currently submitted to the Unique Acceptance Procedure. This document will supersede CEN/TS 16320:2012. The following changes have been made to the former edition: a) The CEN Technical Specification has been adopted as a European Standard; b) The document has been editorially revised. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. kSIST FprEN 16320:2013
FprEN 16320:2013 (E) 4 1 Scope This European Standard specifies a method for the determination of the content of mercury in fertilizers after extraction with aqua regia and the detection of mercury by vapour generation (VG) coupled to an atomic absorption spectrometer or an inductively coupled plasma-atomic emission spectrometer. A limit of quantification of 0,01 mg/kg is to be expected. 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 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 ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696) 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999 apply. 4 Principle Mercury is extracted from the sample with aqua regia and conventional boiling. The concentration of mercury in the extract is measured by (cold) vapour generation (VG) coupled to a suitable detector, such as an atomic absorption spectrometer (AAS) or an inductively coupled plasma-atomic emission spectrometer (ICP-AES). 5 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. Sample preparation shall be carried out in accordance with EN 1482-2. 6 Reagents Use only reagents of recognized analytical grade. Commercially available stock solutions shall be replaced according to the specifications from the supplier or after one year if prepared in the laboratory from available salts. Standard solutions shall be renewed monthly as a general rule.
6.1 Water, conforming to grade 2 of EN ISO 3696. 6.2 Hydrochloric acid, c(HCl) = 12 mol/l; 37 % volume fractio ≈ 1,18 g/ml. 6.3 Nitric acid, c(HNO3) = 16 mol/l; not less than 65 % volume fraction, ρ ≈ 1,42 g/ml. kSIST FprEN 16320:2013
FprEN 16320:2013 (E) 5 6.4 Mixed solution of 0,8 mol/l nitric acid and 1,8 mol/l hydrochloric acid. Mix 150 ml of hydrochloric acid (6.2) and 50 ml nitric acid (6.3) to 1,0 l of water (6.1). 6.5 Standard stock solution, mercury standard stock solution, e.g.
= 1 000 mg/l. Use suitable stock solutions. Single-element stock solutions with adequate specification stating the acid used and the preparation technique are commercially available. It is recommended to use commercially available standard stock solutions for mercury. 6.6 Working standard solutions. Depending on the scope, different working standard solutions may be necessary. In general, the stability of mercury working standard solutions should be checked. 6.6.1 Working standard solution I,
= 10 mg/l for mercury.
Dilute 1,00 ml of the standard stock solution for mercury (6.5) to 100,0 ml with the mixed acid solution (6.4). This solution is used to prepare 200 µg/l mercury working standard solution.
6.6.2 Working standard solution II,
= 200 g/l for mercury. Dilute 2,00 ml of the 10 mg/l mercury working standard solution I (6.6.1) to 100,0 ml with the mixed acid solution (6.4). This solution is used to prepare spiked test solutions and calibration solutions. 6.7 Reducing agents. 6.7.1 General. Tin(II) chloride or sodium borohydride may be used as the reducing agent, but it is not advisable to use the two reagents alternately. Observe the instructions of the manufacturers of the apparatus. 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. 6.7.2 Tin(II) chloride solution, (SnCl2·2H2O) = 100 g/l. Dissolve 50 g of tin(II) chloride in approximately 100 ml of hydrochloric acid (6.2) in a 500 ml volumetric flask and dilute to the mark. Prepare a fresh solution daily. 6.7.3 Sodium borohydride solution, e.g.
= 2 g/l. Dissolve 2 g of sodium hydroxide pellets in water, add 2 g of sodium borohydride and dilute to 1 000 ml with water (6.1). Prepare a fresh solution daily and, when necessary, filter before use. When the analysis procedure is of a longer time it is recommended to cool the sodium borohydride solution (i.e. with ice around the flask) during its use in the vapour generation ICP-AES or AAS measurement. 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. 7 Apparatus 7.1 Common laboratory glassware. 7.2 Analytical balance, capable of weighing to an accuracy of 1 mg. kSIST FprEN 16320:2013
FprEN 16320:2013 (E) 6 7.3 Inductively coupled plasma-atomic emission spectrometer, with axial or radial viewing of the plasma and with suitable background correction. The settings of the working conditions (e.g. gas flows, RF or plasma power, sample uptake rate, integration time, number of replicates) shall be optimised according the manufacturer’s instructions. Radial viewing of the plasma may be used if it can be shown that the limit of quantification for mercury is below the required legal limit value. 7.4 Atomic absorption spectrometer, equipped with a heated quartz cuvette or a mercury absorption cell, or optionally with an amalgamation system. 7.5 Vapour generation equipment. 7.5.1 Continuous flow or flow-injection cold-vapour system.
7.5.2 Element-specific lamp for mercury. 7.6 Dilutor. Instrument used for automated volumetric dilutions or other appropriate equipment (e.g. pipettes and volumetric glassware) to perform dilutions. The precision and accuracy of this type of equipment for volumetric dilutions shall be established, and controlled and documented regularly.
7.7 Ash-free filter paper, i.e. Whatman 589/2 or equivalent quality. 8 Procedure 8.1 General Calibrations by standard additions with several standards or by matrix matching are very powerful calibration techniques and can be used to accurately correct for matrix effects from easy-ionisable elements (multiplicative matrix effects). Additive matrix effects (i.e. spectral interferences) are not corrected for with standard additions calibration. For matrix matching, additive matrix effects will be corrected for when the added matrix is the cause of the matrix effect. The main drawback of calibration by standard addition with several standards is the requirement for a calibration function for each sample type, which is a time consuming process. For matrix matching a profound knowledge of the sample matrix is needed, which is not always necessarily available. These two techniques may thus not be practical to use in routine fertilizer laboratories. It is therefore suggested that calibrations are to be performed by means of external calibration and correction of matrix effects by addition of one known spike of a standard solution (spike recovery). The method of external calibration and correction for spike recovery allows for the analysis of fertilizers with unknown matrix composition or with a matrix that cannot be synthetically imitated easily. This calibration technique may not be as precise as calibration by standard additions with several standards but the increased uncertainty is small compared to the total uncertainty of the method, if the total analyte concentration is in the linear working range after the spike and the added spike corresponds to at least a doubling of the analyte concentration. Many matrix errors can be compensated for by this procedure, if they are not additive (e.g. spectral interferences). Aliquots of the sample solution are analysed by the means of external calibration and then one aliquot is spiked with known concentrations of the analytes without changing the matrix of the sample solution. The calculated spike recovery is then used to correct the concentration calculated from the external calibration function. The concentration of the spikes shall be in the linear working range of the analytical detection
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