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Especiacao quimica de arsenio em amostras de arroz empregando extracao por fase solida in-situ e determinacao por FI-HG AAS

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Overview

Costa’s doctoral thesis developed an in-situ quaternary-ammonium-salt solid-phase extraction method coupled to flow-injection hydride-generation atomic absorption spectrometry for arsenic speciation in rice matrices. The routeable matrix is rice flour certified reference material, not salt. The method validation measured IRMM-804 Rice Flour at 0.045 +/- 0.007 mg/kg total arsenic (As) versus a certified 0.049 +/- 0.004 mg/kg, with As(III) measured at 0.043 +/- 0.004 mg/kg and DMA not detected.

Key numbers

  • Certified reference material: IRMM-804 Rice Flour.
  • Certified total As concentration: 0.049 +/- 0.004 mg/kg.
  • Proposed method result for IRMM-804:
    • As(III): 0.043 +/- 0.004 mg/kg.
    • DMA: not detected.
    • Total As: 0.045 +/- 0.007 mg/kg.
  • Method accuracy for total As: 92.33% versus the certified value.
  • Preconcentration factor for As(III): 16.76.
  • Detection and quantification limits:
    • As(III): LOD 0.04 ug/L and 0.01 ug/g; LOQ 0.12 ug/L and 0.04 ug/g.
    • DMA: LOD 0.46 ug/L and 0.15 ug/g; LOQ 1.55 ug/L and 0.51 ug/g.
  • Precision: coefficient of variation 5.49% for a 10.0 ug/L As(III) solution.
  • Analytical frequency: 30 samples per hour.

Methods (brief)

The thesis validates in-situ solid-phase extraction using tetra-n-butylammonium perchlorate and APDC complexation, followed by FI-HG AAS detection. Rice flour was solubilized by alkaline decomposition with Universol, and total As determination required pre-reduction of pentavalent arsenic before hydride generation. The method selectively extracts As(III) under the optimized conditions and uses a difference/pre-reduction workflow for total inorganic/total As handling. The source does not report a consumer-market survey of rice samples; it reports a certified-reference-material validation result.

Implications

  • Testing: useful method-validation evidence for rice-flour arsenic speciation by FI-HG AAS.
  • Rice: the only extractable food-matrix value is the IRMM-804 Rice Flour CRM result; treat as analytical validation, not a market occurrence distribution.
  • Standards workbench: do not include as a retail rice or salt occurrence row.
  • Speciation: the thesis distinguishes As(III), DMA, and total As. Do not substitute total As for inorganic arsenic in downstream routing.

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