Inorganic arsenic

(Tab 1.) and was in accordance with previous results for marine samples (Rasmussen et. al 2013). The LOD (0.02 mg·kg-1) was below the proposed maximum...

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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