Analytica Chimica Acta 537 (2005) 271–278 On-line emulsion formation and multi-element analysis of edible oils by inductively coupled plasma atomic emission spectrometry A.N. Anthemidis ∗ , V. Arvanitidis, J.A. Stratis Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University, Thessaloniki 54124, Greece Received 7 October 2004; received in revised form 4 January 2005; accepted 4 January 2005 Available online 15 February 2005 Abstract A novel simple on-line emulsion formation system for multi-element analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) was developed. A laboratory made magnetic-stirring micro-chamber was used for continuous edible emulsification with Triton X-100 and for subsequent introduction of the emulsion into ICP-AES. The optimum concentration of oil in emulsion for maximum sensitivity was 50% (v/v). The performance of the system was demonstrated for Ag, Al, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, Mg, Mn, Ni, Pb, Tl and Zn determination in olive, sunflower and corn oil. Good agreement was found between calibration curves for oil emulsion and aqueous ones for the most of the investigated spectral lines. The calibration curves for each element were linear at least up to 1.0 mg l -1 and the correlation coefficients were ranged between 0.991 and 0.999. The proposed method was applied to the analysis of olive oil sample and compared with ETAAS-wet digestion method. No significant differences were observed between the two methods. © 2005 Elsevier B.V. All rights reserved. Keywords: Inductively coupled plasma atomic emission spectrometry; On-line; Emulsion; Edible oil; Multi-element analysis 1. Introduction The quality of edible oils with regard to freshness, stora- bility and toxicity can be evaluated by the determination of metals. Trace levels of metals like Fe, Cu, Ca, Mg, Co, Ni and Mn are known to increase the rate of oil oxidation while other elements such as Cr, Cd, and Pb are very important on account of their toxicity and metabolic role. Thus, the de- velopment of rapid and accurate analytical methods for trace elements determination in edible oil has been a challenge in quality control and food analysis. Various techniques like electrothermal atomic absorp- tion spectrometry (ETAAS) [1], inductively coupled plasma atomic emission spectrometry (ICP-AES) [2] or mass spec- trometry (ICPMS) [3,4] and voltammetry [5] have been em- ployed for analysis of edible oils. However, sample pretreat- ment procedures like: wet or dry digestion, microwave di- ∗ Corresponding author. Tel.: +30 2310 997707; fax: +30 2310 997719. E-mail address: anthemid@chem.auth.gr (A.N. Anthemidis). gestion, dilution with organic solvent and some extraction methods are required, in order to eliminate the organic ma- trix. These techniques are usually difficult to be automated, time consuming, laborious and prone to contamination and losses. On the other hand, direct analysis of samples with high content of organic matrix by ICP techniques encoun- ters many drawbacks and usually causes plasma to be ex- tinguished. Another negative effect is the injector blocking due to carbon deposition from incomplete oxidation of or- ganic matrix [6]. An alternative technique for introduction of oil samples directly into inductively coupled plasma (ICP) is the on-line emulsification [2,7], which also offers some other advantages like using aqueous standards solutions for cali- bration and quantification, reduction of matrix interference, higher sampling frequency and lower cost of analysis. Direct introduction of oil samples in the form of emulsion into ICP considerable simplifies the spray chamber and plasma torch because no extra oxygen or complicated desolvation device is needed. In this case, the use of stable emulsions with proper surfactant concentration is very important. The on-line prepa- 0003-2670/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2005.01.035