Evaluation of some metals in Brazilian coffees cultivated during the process of conversion from conventional to organic agriculture

Abstract

Available metals in soil Nutrients and toxic elements a b s t r a c tThe aim of this study was to evaluate the presence of nutrients and toxic elements in coffees cultivated during the process of conversion, on organic agriculture, in southwest Bahia, Brazil. Levels of the nutrients and toxic elements were determined in samples of soils and coffee tissues from two transitional organic farms by atomic absorption spectrometry (FAAS). The metals in soil samples were extracted by Mehlich1 and USEPA-3050 procedures. Coffee samples from both farms presented relatively high levels of Cd, Zn and Cu (0.75, 45.4 and 14.9 lg g À1 , respectively), but were still below the limits specified by the Brazilian Food Legislation. The application of statistical methods showed that this finding can be attributed to the addition of high amounts of organic matter during the flowering tree period which can act on the bioavailability of metal ions in soils.

Determination of the Elemental Composition of Coffee Using Instrumental Methods

“…Flame atomic absorption spectrometry (FAAS) with a deuterium lamp background corrector or intermittently with a Zeeman effect background corrector (Filho et al 2007) is quite often used for selective determinations of different major (Ca, K, Mg, Na), minor (Cu, Fe, Mn, Zn) and trace (Cd, Co, Cr, Ni, Pb) elements of coffee (Krivan et al 1993;Onianwa et al 1999;Anthemidis and Pliatsika 2005;Filho et al 2007;Grembecka et al 2007;dos Santos et al 2009dos Santos et al , 2010Ashu and Chandravanshi 2011). High-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS) can also be used for this purpose (Ca, Fe, K, Mg, Mn, and Na) (Oliveira et al 2012).…”

“…Samples of green, roasted, or instant coffees require to be appropriately prepared before measurements by the digestion and the mineralization of their organic matrix. The calibration of FAAS is commonly carried out using simple standard solutions (Onianwa et al 1999;Suseela et al 2001;Anthemidis and Pliatsika 2005;Filho et al 2007;Grembecka et al 2007;dos Santos et al 2009dos Santos et al , 2010Ashu and Chandravanshi 2011;Oliveira et al 2012). Exceptionally, in case of measurements of K and Na, a solution of CsCl 3 can be added to standards and samples as an ionization buffer (chemical suppressor) (Grembecka et al 2007;Oliveira et al 2012).…”

“…Solid standards can also be prepared by drying standard solutions on ashless filter papers or directly in measurement capsules (Krivan et al 1993;Zaidi et al 2006). Krivan et al 1993;Martin et al 1998aMartin et al , 1999Onianwa et al 1999;Dos Santos and de Oliveira 2001;Suseela et al 2001;Anderson and Smith 2002;Vega-Carrillo et al 2002;Anthemidis and Pliatsika 2005;Tagliaferro et al 2006Tagliaferro et al , 2007Zaidi et al 2006;Filho et al 2007;Grembecka et al 2007;Bertrand et al 2008;Santos et al 2008;Dos Santos et al 2009;Frankova et al 2009 Although a certified standard reference material (CRM) of organic green coffee was under the development, it has been found that such matrix can be homogeneous only for some selected elements, i.e., Ca, Co, Cs, K, and Sc (Tagliaferro et al 2006). For other important elements (Br, Fe, Na, Rb, and Zn), a high degree of inhomogeneity in this CRM candidate has been observed.…”

“…Green arabica and robusta coffee beans are directly taken from coffee plantations or coffee plantation cooperatives (Krivan et al 1993;Martin et al 1998aMartin et al , 1999Filho et al 2007;Oleszczuk et al 2007;Bertrand et al 2008;dos Santos et al 2009dos Santos et al , 2010. In a laboratory, coffee beans can be washed at first with tap water, followed by a neutral detergent, a diluted HCl solution and finally de-ionized water to remove soil particles and dust (dos ).…”

“…Ratios of the sample mass (in grams) to the volume of reagents (in milliliter) applied can be 1:6.5 (dos de Oliveira 2001), 1:10 (Rajwanshi et al 1997;Anderson and Smith 2002;Anthemidis and Pliatsika 2005), 1:12.5 (Filho et al 2007), 1:15 (Castro et al 2009), 1:15.5 (Krivan et al 1993), 1:16 (Fernandes et al 2005;Oleszczuk et al 2007), 1:17.5 (Krejcova and Cernohorsky 2003), 1:24 (dos ), 1:30 (dos Santos et al 2010, 1:31.5 (Ribeiro et al 2003), 1:32 (Santos et al 2008;Castro et al 2009), 1:33.3 (Frankova et al 2009), or even 1:100 (Magalhaes et al 1999). Residues after the digestion are diluted with water to 15 (Castro et al 2009), 20 (Castro et al 2009), 25 (Krivan et al 1993;Krejcova and Cernohorsky 2003;Anthemidis and Pliatsika 2005;Fernandes et al 2005;Filho et al 2007;Oleszczuk et al 2007;Santos et al 2008;dos Santos et al 2010), 50 (Rajwanshi et al 1997; dos Santos and de Oliveira 2001;Ribeiro et al 2003;dos Santos et al 2009;Ashu and Chandravanshi 2011), or 100 mL (Magalhaes et al 1999).…”