Quantitative Determination of Arsenate in Dried Shrimp by Spectrophotometric Measurement of Its Heteropoly Blue Charuwan Suitcharit Faculty of Science and Technology, Songkhla Rajabaht University, Songkhla, 90000, Thailand charuwan.su@mail.skru.ac.th Keywords: Arsenate. Heteropoly blue. Spectrophotometric method. Dried shrimp. Abstract. A cost-effective and sensitive spectrophotometric method for the determination of arsenate in dried shrimp has been developed using molybdenum blue as a chromogenic reagent. The method is based on arsenate conversion to arsenomolybdate heteropoly blue having an absorbance maximum at 870 nm. The effects of pH, time, temperature and light on its complex formation were investigated. The optimal complex formation condition at pH 4 in 90 min at 15+1 o C was obtained and the blue color was favorable developed in daylight. The proposed method has been successfully applied for the determination of arsenate in samples with the addition of DTPA to eliminate the interferences resulting in increased selectivity. The standard addition calibration graph was constructed with the linear range extended to 40 µgL -1 (r 2 = 0.9987). The detection limit (S/N = 3) of 3.21 µgL -1 , and the precision of 3.13% (RSD) were obtained. The method has good recovery of 95% for the determination of arsenate. The amounts of arsenate in dried shrimp samples compared with those obtained from ICP-OES were shown to be in good agreement (r = 0.998). Introduction Arsenic (As) has long been recognized as toxicants and it is considered a human carcinogen [1-2]. Nowadays, arsenic contamination is widespread in the environment, especially in dust, soil and natural waters. However, the human exposure of arsenic is mainly from foods and drinking water [2]. In foods, especially in seafood, arsenic is mostly found in shrimp, fish, mussel, etc. [3-4]. The accumulation of arsenic in seafood is due to both natural anthropogenic sources such as agricultural and industrial applications [5]. The toxicity and availability of arsenic depended on its chemical forms. For inorganic forms of arsenic, arsenite (As(III)) and arsenate (As(V)) are dominant. As(III) is most toxic, whereas the toxicity of As(V) is 25-60 times lower than that of As(III), due to the phosphate replacement in ATP by As(V) [2]. Therefore, the accurate measurement of arsenic in foods is absolutely required. Several methods for the measurement of arsenic have been proposed; such as hydride generation atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma-optical emission spectroscopy, and differential pulse anodic stripping voltammetry [2], but none of them are suitable for use as on-site analysis [2, 6] due to a comparatively expensive instrument, skilful operators, heavy instrumentation, and toxicity of mercury. According to drawback of such techniques, the sensitive and inexpensive spectrophotometric method is then considered. It is well known that As(V) is able to form molybdoheteropoly anions of [AsMo 12 O 40 ] 3- formula [7] which is of some importance for the analysis of As(V). That is; it serves for a qualitative detection of As(V). In this study, the spectrophotometric method has been applied to determine the arsenate in dried shrimp based on molybdenum blue method. For the determination, when the arsenomolybdate was formed with subsequent reduction by ascorbic acid to liberate colored molybdenum blue, arsenate can be determined spectrophotometrically [2, 5-6]. In addition, the effect of masking agents on the removal of interferences was also studied. Advanced Materials Research Vol. 705 (2013) pp 9-14 Online available since 2013/Jun/13 at www.scientific.net © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.705.9 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 202.29.16.249-10/07/13,07:51:32)