Arsenic speciation in rice, straw, soil, hair and nails samples from the arsenic-affected areas of Middle and Lower Ganga plain

Abstract

In the present study, pressurised liquid extraction and ultrasound probe sonication, for the latter in combination with a mixed enzymatic treatment in case of rice and straw samples, were applied as sample preparation prior to arsenic speciation analysis by high pressure liquid chromatography coupled to inductively coupled plasma mass spectrometric detection (HPLC-ICP-MS). A significant number of samples as different as rice, straw, soil, nail and hair, all coming from the heavily arsenic-contaminated Middle and Lower Ganga plain area, could be investigated with validated methods, supported by high speed extraction methods. For rice and paddy samples, inorganic arsenic counted up to 70–98% of the total arsenic content, being the major species As (III). The levels of arsenic obtained from straw and soil samples are significantly higher than the background levels, being the major species As (V), thus increasing human exposure to arsenic via the soil-plant-animal-human pathway. Concentrations found in hair and nails were significantly higher than their background levels: 39- and 20-fold for hair and nails, respectively. These samples contained mainly inorganic arsenic in its tri- and pentavalent forms. Results indicate that, under the local frame conditions, arsenic mainly enters into the food chain via its more problematic inorganic forms. Arsenic speciation analysis proves to be a powerful tool for a complete analytical assessment in epidemiological studies covering the endemic areas.

Keywords:

• Arsenic poisoning
• Ganga plain
• arsenic speciation
• ultrasound probe sonication
• pressurised liquid extraction

Acknowledgments

This work has been carried out with the economical support of the CICYT project Ref. CTQ-2005-02281. The authors gratefully acknowledge the Spanish Ministry of Science and Technology for the Ramón y Cajal contract of Riansares Muñoz-Olivas. A special thank to Prof. Chakraborti, who proposed us for the participation in this special issue concerning the dramatic situation that India and Bangladesh are undergoing.

Notes

^a Total arsenic concentration data kindly provided by Dr. D. Chakraborti, School of Environmental Studies, Jadavpur University, Kolkata, India

^a Total As is total As extracted

^b This recovery is calculated as (As measured/As certified value) × 100.

^c This recovery is calculated as (Sum of As species/Total As extracted) × 100.

^a Total As is total As extracted.

^b This recovery is calculated as (As measured/As certified value) ×100.

^c This recovery is calculated as (Sum of species) /Total As extraced) ×100.