Analytica Chimica Acta 547 (2005) 237–242 Determination of arsenic(III) and total inorganic arsenic in water samples using an on-line sequential insertion system and hydride generation atomic absorption spectrometry Aristidis N. Anthemidis ∗ , George A. Zachariadis, John A. Stratis LaboratoryofAnalyticalChemistry,DepartmentofChemistry,AristotleUniversity,Thessaloniki54124,Greece Received 21 March 2005; received in revised form 16 May 2005; accepted 17 May 2005 Available online 24 June 2005 Abstract A simple and robust on-line sequential insertion system coupled with hydride generation atomic absorption spectrometry (HG-AAS) was developed, for selective As(III) and total inorganic arsenic determination without pre-reduction step. The proposed manifold, which is employing an integrated reaction chamber/gas–liquid separator (RC-GLS), is characterized by the ability of the successful managing of variable sample volumes (up to 25ml), in order to achieve high sensitivity. Arsine is able to be selectively generated either from inorganic As(III) or from total arsenic, using different concentrations of HCl and NaBH 4 solutions. For 8 ml sample volume consumption, the sampling frequency is 40 h -1 . The detection limit is c L = 0.1 and 0.06 gl -1 for As(III) and total arsenic, respectively. The precision (relative standard deviation) at 2.0 gl -1 (n = 10) level is s r = 2.9 and 3.1% for As(III) and total arsenic, respectively. The performance of the proposed method was evaluated by analyzing the certified reference material NIST CRM 1643d and spiked water samples with various concentration ratios of As(III) to As(V). The method was applied for arsenic speciation in natural waters samples. © 2005 Elsevier B.V. All rights reserved. Keywords: Arsenic speciation; Hydride generation atomic absorption spectrometry; Sequential; Gas–liquid separator 1. Introduction The occurrence of arsenic in aquatic environment arises mainly from biogeochemical cycles and anthropogenic pro- cesses. The concentration ratio of As(III) to As(V) can be used as a chemical indicator of the red-ox status of underground-water systems [1]. Inorganic compounds of arsenic are far more toxic than the organic ones, and As(III) and As(V) are the most important species released in the envi- ronment from mineral deterioration. Because of the different toxicity of the inorganic arsenic species (arsenite > arsenate), their determination in the environment has generated consid- erable interest. Undoubtedly, hydride generation atomic absorption spec- trometry (HG-AAS) is currently the most popular technique for routine determination of trace amounts of arsenic, sele- ∗ Corresponding author. Fax: +30 2310997719. E-mailaddress: anthemid@chem.auth.gr (A.N. Anthemidis). nium, bismuth and other elements, which generate volatile hydrides [2,3]. In this technique, the signal response obtained from As(V) is about 40% lower than that obtained from As(III), thus a pre-reduction of As(V) to As(III) before the formation of the arsine, is recommended [2,4]. Usually, two procedures are demanded for the discrimination of the As(III) content from the total arsenic one; a selective procedure for As(III) and another one, including a pre-reduction step for total arsenic. However, complete volatilization of arsenate in the absence of pre-reducing step could be achieved by using higher HCl and NaBH 4 concentrations [5–8]. It is well known that manual (batch) methods, may lead to operator errors particularly when a considerable number of reagents and repetitive steps is involved and a large num- ber of samples have to be analyzed. Continuous flow (CF) [9,10], flow injection (FI) [8,11], and recently sequential injection or insertion (SI) [12–16] systems were reported in order to decrease or eliminate the above drawbacks, by automated handling of reagents, which also improves the pre- 0003-2670/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2005.05.039