efsa-opinion-chromium-food-drinking-water

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