CEN/TS 16731:2014
(Main)Foodstuffs - Determination of hydride-reactive arsenic compounds in rice by atomic absorption spectrometry (Hydride-AAS) following acid extraction
Foodstuffs - Determination of hydride-reactive arsenic compounds in rice by atomic absorption spectrometry (Hydride-AAS) following acid extraction
This Technical Specification describes a screening procedure for the determination of nitric-acid extractable inorganic arsenic in rice with hydride generation-AAS.
The method has been developed and validated for the application of analysis in rice. It has been validated in an interlaboratory study according to ISO 5725 [2] on parboiled rice and brown rice having an inorganic arsenic content of 0,092 mg/kg and 0,191 mg/kg.
Lebensmittel - Bestimmung von Hydrid-bildenden Arsen-Verbindungen in Reis nach Säureextraktion mit Atomabsorptionsspektrometrie (Hydrid-AAS)
Diese Technische Spezifikation beschreibt ein Screening-Verfahren zur Bestimmung von mit Salpetersäure extrahierbarem anorganischem Arsen in Reis mit Hydrid-AAS.
Dieses Verfahren wurde für die Anwendung bei Reis entwickelt und validiert. Es wurde in einem Ringversuch mit Parboiled Reis und Vollkornreis, mit einem Gehalt an anorganischem Arsen von 0,092 mg/kg und 0,191 mg/kg, nach ISO 5725 [2] validiert.
Détermination de composés arséniés réactifs aux hydrures dans le riz par spectrométrie d’absorption atomique (SAA-Génération d’Hydrures) après extraction acide
Živila - Določevanje hidridno-reaktivnih arzenovih spojin v rižu z metodo atomske absorpcijske spektrometrije (hidridna-AAS) po kislinski ekstrakciji
Ta metoda opisuje postopek za določevanje anorganskega arzena v rižu z metodo atomske absorpcijske spektrometrije (hidridna-AAS) po ekstrakciji z dušikovo kislino. Ta metoda je bila zasnovana in validirana za analize riža.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-januar-2015
äLYLOD'RORþHYDQMHKLGULGQRUHDNWLYQLKDU]HQRYLKVSRMLQYULåX]PHWRGRDWRPVNH
DEVRUSFLMVNHVSHNWURPHWULMH KLGULGQD$$6 SRNLVOLQVNLHNVWUDNFLML
Foodstuffs - Determination of hydride-reactive arsenic compounds in rice by atomic
absorption spectrometry (Hydride-AAS) following acid extraction
Lebensmittel - Bestimmung von Hydris-AAS-reaktiven Arsen-Verbindungen in Reis nach
Säureextraktion
Ta slovenski standard je istoveten z: CEN/TS 16731:2014
ICS:
67.060 äLWDVWURþQLFHLQSURL]YRGLL] Cereals, pulses and derived
QMLK products
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
TECHNICAL SPECIFICATION
CEN/TS 16731
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
October 2014
ICS 67.060
English Version
Foodstuffs - Determination of hydride-reactive arsenic
compounds in rice by atomic absorption spectrometry (Hydride-
AAS) following acid extraction
Détermination de composés arséniés réactifs aux hydrures Lebensmittel - Bestimmung von Hydrid-bildenden Arsen-
dans le riz par spectrométrie d'absorption atomique (SAA- Verbindungen in Reis nach Säureextraktion mit
Génération d'Hydrures) après extraction acide Atomabsorptionsspektrometrie (Hydrid-AAS)
This Technical Specification (CEN/TS) was approved by CEN on 9 September 2014 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.
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
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 16731:2014 E
worldwide for CEN national Members.
Contents Page
Foreword .3
1 Scope .4
2 Normative references .4
3 Principle .4
4 Reagents .4
5 Apparatus .5
6 Procedure .6
6.1 Sample preparation .6
6.1.1 General .6
6.1.2 Extraction .6
6.1.3 Pre-reduction of reference, blank and sample solution .7
6.2 Atomic absorption spectrometry (Hydride generation AAS) .8
6.2.1 Operating conditions for the hydride generation AAS .8
6.2.2 AAS measurement .9
7 Evaluation .9
8 Precision .9
8.1 General .9
8.2 Repeatability .9
8.3 Reproducibility . 10
9 Test report . 10
Bibliography . 12
Foreword
This document (CEN/TS 16731:2014) has been prepared by Technical Committee CEN/TC 275 “Food
analysis - Horizontal methods”, the secretariat of which is held by DIN.
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.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: 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.
1 Scope
This Technical Specification describes a screening procedure for the determination of nitric-acid extractable
inorganic arsenic in rice with hydride generation-AAS.
The method has been developed and validated for the application of analysis in rice. It has been validated in
an interlaboratory study according to ISO 5725 [2] on parboiled rice and brown rice having an inorganic
arsenic content of 0,092 mg/kg and 0,191 mg/kg.
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 13804, Foodstuffs — Determination of elements and their chemical species — General considerations and
specific requirements
3 Principle
Organic and inorganic arsenic compounds are extracted from the rice using diluted nitric acid. When
determining the arsenic by hydride generation technique, only reducible forms of arsenic react. Of the organic
arsenic compounds only a low proportion of dimethylarsinic acid reacts to form a hydride and methylarsonic
acid is typically not present in rice. The gaseous hydride is transferred into a heated measuring cell (quartz
cuvettes or coated graphite tube), by a stream of carrier gas, and decomposed. The absorption line of arsenic
at 193,7 nm serves as a measure of the arsenic concentration [3], [4].
The procedure is exclusively applicable to rice [5].
The determination of the inorganic fraction of arsenic requires a determination of arsenic with hydride
generation AAS; direct measurement of the extract by graphite furnace AAS, using ICP-MS or ICP-OES
provides incorrect results.
4 Reagents
Unless stated otherwise, chemicals of analytical grade shall be used and “solution” means aqueous solution.
The water shall be of the corresponding purity.
The arsenic concentration of reagents and water shall be so low that it does not influence the result of the
determination.
1) 2)
4.1 Hydrochloric acid, w = 30 % , ρ = 1,15 g/ml .
4.2 Nitric acid, concentrated, w = 65 %.
3)
4.3 Diluted nitric acid, c = 0,28 mol/l .
Dilute 3,7 ml of nitric acid (4.2) to 200 ml with water.
4.4 Sodium borohydride, w ≥ 96 %.
1) w = mass fraction.
2) ρ = mass concentration.
3) c = substance concentration.
4.5 Sodium hydroxide, w ≥ 98 %.
4.6 Sodium borohydride solution, e.g. ρ = 3 g/l.
Dissolve 1 g of sodium hydroxide pellets (4.5) in water, add 3 g of sodium borohydride (4.4) and dilute to
1 000 ml with water.
Prepare the solution freshly every day of analysis. If the solution contains undissolved fractions, filter before
use.
The mass concentration ρ of the sodium borohydride solution can vary depending on the system being used.
Therefore, follow the manufacturer's instructions.
4.7 Carrier solution, diluted hydrochloric acid, e.g. w = 1,5 %.
Dilute 50 ml of hydrochloric acid (4.1) to 1 000 ml with water.
The mass concentration ρ of the carrier solution can vary slightly depending on the system being used.
Therefore, follow the manufacturer's instructions.
4.8 L-ascorbic acid, w ≥ 99,7 %.
4.9 Potassium iodide, w ≥ 99,5 %.
4.10 Solution of potassium iodide and ascorbic acid:
Dilute 5 g of potassium iodide (4.9) and 5 g of ascorbic acid (4.8) in water and make up to 100 ml. Prepare the
solution freshly daily. The mass concentrations of the potassium iodide and the ascorbic acid can slightly vary
depending on the system being used. Therefore, follow the manufacturer's instructions.
4.11 Arsenic stock solution, ρ = 1 000 mg/l.
The use of a commercial, certified stock solution is recommended.
4.12 Arsenic standard solutions:
Prepare arsenic standard solutions by diluting the arsenic stock solution (4.11) in several steps.
The arsenic standard solutions shall contain sufficient amounts of hydrochloric acid (at least 3 ml of
hydrochloric acid (4.1) per 100 ml, w = 0,9 %).
Example of a dilution series:
1 000 mg/l → 10 mg/l → 0,1 mg/l
An arsenic standard solution with a mass concentration of ρ = 10 mg/l of arsenic in hydrochloric acid (w = 6 %)
is stable for at least one month.
4.13 Antifoaming agent, based on polydimethylsiloxane or silicone oil.
5 Apparatus
In order to minimize any contaminations, pre-treat carefully all apparatus and auxiliary equipment coming into
direct contact with the sample and the solutions being used, in accordance with EN 13804. If the extraction
vessels are used for several times, they should be cleaned by heating to 95 °C for 1 h, using nitric acid
(w = 13 %).
When using glassware (e.g. Erlenmeyer flasks, beakers, graduated flasks, pipettes), ensure that it does not
release any arsenic to the solutions which come into contact with the glassware.
5.1 Atomic absorption spectrometer, comprising a measurement data acquisition system and the
required accessories for the hydride generation technique.
5.2 Element-specific lamp for arsenic, (hollow-cathode lamp or electrode-less discharge lamp).
4)
5.3 Centrifuge, with an acceleration of at least 1 000 g .
5.4 Syringe filter (unit), pore size of 0,45 μm, diameter of 25 mm, compatible for use with diluted nitric acid
(4.3).
5.5 Extraction vessels, e.g. 30 ml or 50 ml tubes of polypropylene, with gas-tight screw closures and
sufficient pressure stability.
Centrifuge tubes with screw closures are suitable.
5.6 Temperature controlled heating apparatus, for an extraction temperature of 95 °C, e.g. heating block
or water bath; the heating block should be provided with an accurately fitting insert for the vessels used. The
vessels should have contact with the wall in order to ensure good heat transfer.
In order to achieve an extraction temperature of 95 °C, the heating block shall be adjustable to a temperature
of at least 120 °C.
5.7 Temperature measuring device, for controlling the temperature in the extraction vessel.
6 Procedure
6.1 Sample preparation
6.1.1 General
Prior to the extraction, the rice shall be finely ground, while avoiding the generation of excess heat. The
particle size should be less than 500 μm.
The measurement should be performed as soon as possible after extraction. If this is not possible, store
extracts in a refrigerator but for not longer than 2 d.
6.1.2 Extraction
Weigh 1 g ± 0,01 g of rice flour into a closable extraction vessel (5.5) and add 10 ml of diluted nitric acid (4.3).
The ratio of 1:10 (test portion/extracting agent) shall be adhered to. Close the extraction vessels tightly and
mix the content intensely using a test tube shaker. There shall be no remaining lumps. Afterwards, place the
vessels in a pre-heated heating block and extract for 90 min at 95 °C (±4 °C). Alternatively, a boiling water
bath can be used for the extraction. The extraction time starts as soon as the temperature in the vessel
reaches 95 °C. Shake the vessel occasionally (one to two times during extraction) without opening. A constant
stirring with a magnetic stirrer can be helpful.
Additionally, prepare a blank value with 10 ml of diluted nitric acid (4.3)
...
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