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Inorganic arsenic - SPE HG-AAS method for RICE tested in-house and collaboratively
Rasmussen, Rie Romme; Qian, Yiting; Sloth, Jens Jørgen
Publication date: 2013 Document Version Early version, also known as pre-print Link back to DTU Orbit
Citation (APA): Rasmussen, R. R., Qian, Y., & Sloth, J. J. (2013). Inorganic arsenic - SPE HG-AAS method for RICE tested inhouse and collaboratively. Poster session presented at 6th International Symposium on Recent Advances in Food Analysis, Prague, Czech Republic.
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INORGANIC ARSENIC
Rasmussen RR Qian Y Sloth JJ
[email protected]
SPE HG-AAS RICE METHOD TESTED IN-HOUSE AND COLLABORATIVELY Extraction 0.5 g (dry weight) sample extracted for 60 minutes at 90 °C with 10 ml of a dilute acidic mixture (0.1 M HNO3 and 3% H2O2)
INTRODUCTION Internationally
accepted
validated
Water bath extraction
method(s) are needed for establish-
SPE separation
ment of a maximum level (ML) for
Detection Pre-reduction; AsV AsIII by mixing eluate with KI, HCl and ascorbic acid Hydride generation; HCl, NaOH and NaBH4 Instrument settings; heated cell (900° C), As lamp (193.7 nm wave length, 0.5 nm slit width)
inorganic arsenic (iAs) in rice as recently emphasised by the European
SPE SEPARATION
Food Safety Authority (2009), the World Health Organization (2011) and Codex Alimentarius (2012).
The charge of the arsenic species depends on pH pH 5-7
Rice contains most often three forms of the trace element arsenic; iAs and the
iAsV
Sequential elution:
3. Load buffered sample: pH 5.0-7.5
of less toxicological importance.
As H H
OH iAsIII
volatile
OH
As CH3
O
As CH3
OH
CH3
MAV
DMAV
SPE HG-AAS vs HPLC-ICP-MS A comparison of the results from the
5. Elute SPE, 0.4 M HNO3
two methods (Fig. 3) showed good agreement. SPE fractions
Organic arsenic
25,000
20,000
0.9 0.8 HPLC-ICP-MS (mg kg-1)
CONCLUSION
1.0
Load Wash Eluate
DMAV
15,000
Inorganic arsenic (V)
This SPE HG-AAS method enables selective determination of inorganic arsenic in rice and rice products by use of inexpensive instrumentation (HGAAS) and is a candidate method for future control.
10,000
5,000
MAV
0.7 0.6 0.5 0.4 Day 1
0.3
Day 2
0.2
0 0
1
2
3
4
6
5
Time (min)
Day 3 Day 4
0.1
y=x
0.0
Figure 1. Overlaid HPLC-ICP-MS chromatogram of 3 SPE fractions (load, wash and eluate) of a rice sample (NIST1568a) containing both inorganic and organoarsenic species.
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 SPE HG-AAS (mg kg-1)
Figure 3. Determination of inorganic arsenic by two different methods; HPLC-ICP-MS and SPE HG-AAS. In total results for 84 spiked and natural incurred rice samples analysed on four different days. The correlation is y=x (99% confidence interval regression analysis by Excel 2010).
VALIDATION RESULTS In-house validation was satisfying
Table 1. In-house validation Spiked rice samples
Rice reference materials
Low
Medium
High
IMEP-107
NIST1568a
0.30
0.55
0.80
0.107*
0.096*
9
9
9
8
7**
105
106
106
101
103
Repeatability RSDir (%)
5
3
4
6
5
Reproducibility RSDIR (%)
7
9
8
7
7
(Tab 1.) and was in accordance with Target level (mg·kg-1)
previous results for marine samples (Rasmussen et. al 2013). The LOD (0.02
Hydrides
4. Wash SPE, 0.5 M CH3COOH
intensity 75As (cps)
mg·kg-1)
-
O
special
DMA and MA are generally considered
As OH
H
OH
(DMAV). Dietary intake of iAs is of carcinogenicity to humans, whereas
As OH
Pre-reduction
SPE strong anion exchange
2. Equilibrate SPE, 35 mM (NH4)2CO3, 0.05 M HNO3, 1.5% H2O2
its
OH
iAsV
acid (MAV) and dimethylarsinic acid to
O
is negatively charged
1. Pre-condition of SPE, MeOH
due
OH
O
methylated species monomethylarsonic
concern
HG-AAS detection
was below the proposed
maximum levels (0.2-0.3 mg·kg-1).
Observations (N) Mean recovery (%)
*) Consensus mean values: IMEP-107 (de la Calle MB et al., 2011 TrAC 30:641– 651) and NIST1568a (Raab A et al., 2009 J Environ Monit 11:41–44). **) One outlier result discarded (0.048 mg·kg-1).
RICE SAMPLES The iAs concentration determined by SPE HG-AAS in 36 rice samples purchased on the Danish retail market varied (0.03–0.60 mg·kg-1), with the
Collaborative test of the SPE separation method on a wholemeal rice meal sample
highest concentration found in a red
gave a satisfactory HorRat value of 1.6 among 10 laboratories.
rice sample.
References Codex (2012) Proposed draft maximum levels for arsenic in rice (at step 3). European Food Safety Authority (2009) EFSA Journal 7(10), 1351:1-199 Rasmussen et al (2013), ABC, doi 10.1007/s00216-013-6936-8 World Health Organization (2011) WHO Technical Report Series 959
Funding was received from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 211326 www.conffidence.eu
