efsa-opinion-chromium-food-drinking-water
efsa-opinion-chromium-food-drinking-water
efsa-opinion-chromium-food-drinking-water
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Chromium in <strong>food</strong> and <strong>drinking</strong> <strong>water</strong><br />
speciation analysis allowing the determination of both species simultaneously should be treated with<br />
caution (Novotnik et al., 2013).<br />
A large number of papers are dealing with methods of analysis of <strong>chromium</strong> species in <strong>water</strong>.<br />
Chromium can be separated from interfering materials by precipitation, chelation extraction, or ion<br />
chromatography. The purified <strong>chromium</strong> can then be quantified by a variety of techniques. The most<br />
established ones are briefly summarized in Appendix A.<br />
Spectrophotometric and colorimetric methods are still widely used for <strong>chromium</strong> speciation in <strong>water</strong><br />
samples (Swietlik, 1998; Kotaś and Stasicka, 2000; Namiesnik and Rabajczyk, 2012; Water Research<br />
Foundation, 2012). Both methods are mainly based on determination of Cr(VI) as a coloured complex<br />
with 1,5-diphenylcarbazide. Cr(III) can be similarly measured as the diphenylcarbazide complex after<br />
oxidation to Cr(VI). Despite its simplicity, the 1,5-diphenylcarbazide method suffers from the<br />
presence of interfering compounds which can react with 1,5-diphenylcarbazide, resulting in the<br />
formation of complexes that absorb at the same analytical wavelength. Ion chromatography (IC) can<br />
be used to separate Cr(VI) from these positive interferences before the derivatization with<br />
1,5-diphenylcarbazide (LOD ranging from 1 ng/L to 0.3 µg/L for Cr(VI)) (U.S. EPA 218-7, 2011;<br />
Water Research Foundation, 2012). Some recent methods also based on colorimetric reactions used<br />
different reagent solutions with similar LOD (range 0.2 ng/L to 1 µg/L) (Li et al., 2006; Jamaluddin<br />
and Reazul, 2011; Amin and Kassem, 2012; Kanwal et al., 2012).<br />
Electroanalytical methods are also employed for the direct determination of Cr(VI) or Cr(III). The<br />
most common method is differential pulse adsorptive stripping voltammetry (DPAdSV) or catalytic<br />
adsorptive stripping voltammetry (CAdSV), because of their low cost and high sensitivity. LOD<br />
varied between 2 μg/L without preconcentration and 2-16 ng/L when using a deposition step in which<br />
the target analyte is preconcentrated on to the working electrode (Swietlik, 1998; Dominguez and<br />
Arcos, 2002; Bobrowski et al., 2004; Lin et al., 2005; Zhu et al., 2007; Abbasi and Bahiraei, 2012).<br />
Atomic spectrometric techniques such as FAAS, ETAAS and ICP-AES have been used for <strong>chromium</strong><br />
speciation after a separation or isolation technique that provides selectivity for one species relative to<br />
the other (Vercoutere et al., 1996; Kotaś and Stasicka, 2000; Namiesnik and Rabajczyk, 2012). For<br />
samples with low levels of <strong>chromium</strong>, the use of a preconcentration technique with ETAAS (LOD of<br />
0.021 µg/L) (Liang and Sang, 2008) is more suitable than FAAS detection (LOD of 0.2-6.1 µg/L)<br />
(Cespon-Romero et al., 1996; Tuzen and Soylak, 2006; Duran et al., 2007; Aydin and Soylak, 2007;<br />
Saygi et al., 2008; Bulut et al., 2009; Matos et al., 2009; Uluozlu et al., 2009; Zeng et al., 2012).<br />
Many of the methods mentioned above have the disadvantage that one of the species is determined as<br />
the difference between total Cr (often obtained after reduction or oxidation) and the other chemical<br />
form of the element. So, on-line separation often coupled with UV-Vis (LOD of 5 ng/L for Cr(III) and<br />
7-20 ng/L for Cr(VI)) (Kaur and Malik, 2009), chemiluminescence (LOD of 0.05 μg/L for Cr(III) and<br />
0.1 μg/L for Cr(VI)) (Beere and Jones, 1994), FAAS (LOD of 30 μg/L for Cr(III) and 20 μg/L for<br />
Cr(VI) or 0.5 µg/L for Cr(VI) with a preconcentration technique) (Posta et al., 1993), ICP-AES (LOD<br />
of 1000 μg/L for Cr(III) and 2000 μg/L for Cr(VI)) (Byrdy et al., 1995) are increasingly used in order<br />
to minimize contamination and losses of Cr species or redox conversion (Swietlik, 1998; Sarzanini,<br />
1999; Cornelis et al., 2003). In recent years, owing to its high sensitivity and selectivity, ICP-MS has<br />
received most attention as a detection technique for <strong>chromium</strong> (Sarzanini, 1999). Coupled to ICP-MS,<br />
ion chromatography is the most widely used separation method. Anion-exchange columns and anion<br />
exchange columns having also cation exchange capacities have been explored to separate Cr(III) and<br />
Cr(VI) species, with ICP-MS detection limits ranging from 0.1 to 1.0 µg/L (Byrdy et al., 1995;<br />
Barnowski et al., 1997; Pantsar-Kallio and Manninen, 1997; Donais et al., 1999; Seby et al., 2003).<br />
The use of complexing agents, high salt concentration and eluents with carbon or chlorine generate<br />
ArC and ClOH polyatomic interferences that may disturb measurement of the most abundant<br />
<strong>chromium</strong> isotopes 52 Cr and 53 Cr. To overcome the spectral interferences caused by carbon, most<br />
interferences can be removed by using an ICP-MS equipped with a CCT (LOD of about<br />
0.010-0.050 µg/L for Cr(III) and Cr(VI)) (McSheehy et al., 2006; Sakai and McCurdy, 2007; Agilent,<br />
2011; Wolf et al., 2011). Another advantage of using ICP-MS is to correct analytical biases by<br />
SIDMS. The method developed by Ma and Tanner, (2008) in natural <strong>water</strong>s indicated that the<br />
EFSA Journal 2014;12(3):3595 29