UNCORRECTED PROOF 1 2 Assessment of toxic metals in raw and processed milk samples 3 using electrothermal atomic absorption spectrophotometer 4 Tasneem Gul Kazi a,1 , Nusrat Jalbani b, * , Jameel Ahmed Baig a,1 , Ghulam Abbas Kandhro a,1 , 5 Hassan Imran Afridi a,1 , Bilal Mohammad Arain a,1 , Mohammad Khan Jamali a,1 , Abdul Qadir Shah a,1 6 a National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro 76080, Sindh, Pakistan 7 b Pakistan Council Scientific and Industrial Research Laboratories, Karachi, Pakistan 8 10 article info 11 Article history: 12 Received 3 April 2009 13 Accepted 28 May 2009 14 Available online xxxx 15 Keywords: 16 Raw and processed milk 17 Microwave 18 Toxic metals 19 Multivariate 20 21 abstract 22 Milk and dairy products have been recognized all over the world for their beneficial influence on human 23 health. The levels of toxic metals (TMs) are an important component of safety and quality of milk. A sim- 24 ple and efficient microwave assisted extraction (MAE) method has been developed for the determination 25 of TMs (Al, Ni, Cd and Pb), in raw and processed milk samples. A Plackett–Burman experimental design 26 and 2 3 + star central composite design, were applied in order to determine the optimum conditions for 27 MAE. Concentrations of TMs were measured by electrothermal atomic absorption spectrometry. The 28 accuracy of the optimized procedure was evaluated by standard addition method and conventional 29 wet acid digestion method (CDM), for comparative purpose. No significant differences were observed 30 (P > 0.05), when comparing the values obtained by the proposed MAE method and CDM (paired t-test). 31 The average relative standard deviation of the MAE method varied between 4.3% and 7.6% based on ana- 32 lyte (n = 6). The proposed method was successfully applied for the determination of understudy TMs in 33 milk samples. The results of raw and processed milk indicated that environmental conditions and man- 34 ufacturing processes play a key role in the distribution of toxic metals in raw and processed milk. 35 Ó 2009 Published by Elsevier Ltd. 36 37 38 1. Introduction 39 Dairy products provide a great sense of eating pleasure due to 40 their flavor and characteristics smooth taste. In fresh milk, flavor 41 and off-flavor compounds could likely be created through cow’s 42 metabolism and be transferred from feed systems to milk via the 43 rumen (Badings, 1991). In addition, off-flavors occur in milk 44 through a variety of mechanisms such as action of native milk or 45 bacterial enzymes and chemical changes catalyzed by light or hea- 46 vy metals (Zurera-Cosano et al., 1994). Milk is known as an excel- 47 lent source of Ca, and it can supply moderate amounts of Mg, 48 smaller quantity of Zn and very small contents of Fe and Cu (Pen- 49 nigton et al., 1995). On the other hand, due to the growing environ- 50 mental pollution it is also necessary to determine and monitor the 51 levels of toxic metals (TMs) in milk, because they can significantly 52 influence the human health (Steijns, 2001; Licata et al., 2004). 53 Many reports indicate the presence of heavy metals in milk and 54 other food products (Caggiano et al., 2005; Soylak et al., 2005; 55 Tuzen et al., 2008). 56 The TMs in milk are of particular concern because milk is largely 57 consumed by infants and children (Jeng et al., 1994; Kazi et al., 58 2009) and the determination of TMs level in milk is particularly 59 attended by international organizations (Codex, 2003). The deter- 60 mination of trace inorganic constituents in milk is not a minor task 61 due to their complex emulsion like matrices and low concentration 62 levels of the metal ions. Most proposed procedures involve a step 63 of digestion to eliminate the organic matrixes, which may involve 64 several steps and contamination can become a serious obstacle for 65 obtaining accurate data of trace quantities of elements (Karimi 66 et al., 2008; Tuzen and Soylak, 2007). 67 Many digestion procedures to oxidize organic matrixes of dif- 68 ferent samples have been reported in literature (Mingorance, 69 2002; Arain et al., 2007; Shah et al., 2009). The acid digestion pro- 70 cedures are the most popular sample pre-treatment for elemental 71 determination in biological and environmental samples, and the 72 acid digestion induced by microwave energy is a well-established 73 method (Jalbani et al., 2007; Demirel et al., 2008). 74 Even though the use of microwave digestion, which is fast and 75 effective digestion operation, requires the participation of concen- 76 trated acids, contamination risks as result of the intensive sample 77 handling, and a large cooling times required before opening the 78 low or high-pressure bombs (Lorentzen and Kingston, 1996; Afridi 0278-6915/$ - see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.fct.2009.05.035 * Corresponding author. Q2 E-mail addresses: tgkazi@yahoo.com (T.G. Kazi), nussaratjalbani21@yahoo.com (N. Jalbani), jab_mughal@yahoo.com (J.A. Baig), gakandhro@yahoo.com (G.A. Kandhro), hassanimranafridi@yahoo.com (H.I. Afridi), bilal_ku2004@yahoo.com (B.M. Arain), mkhanjamali@yahoo.com (M.K. Jamali), aqshah07@yahoo.com (A.Q. Shah). 1 Tel.: +92 0222 771379; fax: +92 0222 771560. Food and Chemical Toxicology xxx (2009) xxx–xxx Contents lists available at ScienceDirect Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox FCT 4943 No. of Pages 7, Model 5G 13 June 2009 Disk Used ARTICLE IN PRESS Please cite this article in press as: Kazi, T.G., et al. Assessment of toxic metals in raw and processed milk samples using electrothermal atomic absorption spectrophotometer. Food Chem. Toxicol. (2009), doi:10.1016/j.fct.2009.05.035