Analysis of Powdered Coffee and Milk by ICP OES after Sample Treatment with Tetramethylammonium Hydroxide

Determination of the Elemental Composition of Coffee Using Instrumental Methods

“…Soluble powdered instant coffees (pure or chicoryblended) have also been analyzed (dos Santos and de Oliveira 2001;Suseela et al 2001;Vega-Carrillo et al 2002;Krejcova and Cernohorsky 2003;Ribeiro et al 2003;Fernandes et al 2005;Zaidi et al 2006;Grembecka et al 2007;Oliveira et al 2012). …”

“…Samples of laboratory roasted and ground green coffee beans, natural powdered, or soluble coffees (0.1-5.0 g) are commonly wet digested in pressurized closed vessel microwave assisted systems (Krejcova and Cernohorsky 2003;Fernandes et al 2005;Filho et al 2007;Oleszczuk et al 2007;Santos et al 2008;Castro et al 2009;Frankova et al 2009;dos Santos et al 2010), pressurized sealed vessels, i.e., Parr bombs (Anthemidis and Pliatsika 2005;Castro et al 2009), a Berghof apparatus (Krivan et al 1993), and open vessel systems with hot plates or heating blocks (Magalhaes et al 1999;Martin et al 1998aMartin et al , 1999Anderson and Smith 2002;Ribeiro et al 2003;Filho et al 2007), or a Kjeldahl apparatus (Ashu and Chandravanshi 2011). When samples of soluble coffee are digested, higher sample amounts (1-5 g) can be taken (dos Santos and de Oliveira 2001).…”

Improvement of Determination of Trace Amounts of Arsenic and Selenium in Slim Coffee Products by HG-ICP-OES

“…It was established that when the recommended pre-reduction step with HCl prior to the Se determination by HG-ICP-OES in sample solutions prepared was applied, a solid residue was formed in these conditions that particles possibly could retain the volatile element species and/or tend to its decay. Although the sample preparation procedure using TMAH for soluble coffee prior to its elemental analysis (including the Se content) was previously proposed in one work (Ribeiro et al 2003), the conventional PN was applied there for elements' measurements by ICP-OES. Simple coffee samples dissolutions in diluted HNO 3 (P5) or water (P6) were unsuitable.…”

“…Accordingly, there have been only few reports on the concentration of aforementioned elements (Vega-Carrillo et al 2002; Jose dos Santos and de Oliveira 2001;Ribeiro et al 2003;Asfaw and Wibetoe 2005). In general, the analysis of coffee on the content of As and Se are performed using inductively coupled plasma optical emission spectrometry (ICP-OES) with PN (Ribeiro et al 2003) or HG (Jose dos Santos and de Oliveira 2001;Asfaw and Wibetoe 2005) after the previous sample total decomposition by means of the wet digestion in closed vessel microwave (MW)-assisted (Jose dos Santos and de Oliveira 2001;Asfaw and Wibetoe 2005) or open vessel (Ribeiro et al 2003) systems in the presence of concentrated oxidative reagents, particularly mixtures of HNO 3 +H 2 O 2 . The direct analysis of solid coffee samples is also possible, carried out by the INNA method (Vega-Carrillo et al 2002).…”

“…To our best knowledge, there is no work on the evaluation of optimal conditions being suitable for the determination of total As and Se in soluble coffee products by the HG-ICP-OES hyphenated system with as little sample treatment as possible. So far, an alkaline solubilisation of instant coffee in tetramethyl ammonium hydroxide (TMAH) solution has been proposed by Ribeiro et al (Ribeiro et al 2003) for ICP-OES multi-element measurements, including Se. Asfaw and Wibetoe (Asfaw and Wibetoe 2005) have tested the dissolution in a 0.36 mol l −1 HNO 3 solution and the solubilisation in aqua regia to determine hydride (Se) and non-hydride forming elements by ICP-OES using a dual-mode sample introduction system (MSIS) in various beverages (e.g., instant coffee).…”