Continuous ultrasound-assisted extraction of cadmium from legumes and dried fruit samples coupled with on-line preconcentration-flame atomic absorption spectrometry

Green Sample Preparation Methods

Sample preparation is the stage of the analytical process where greenness-related issues can likely play the most important role. With the exception of direct methods for solid sample analysis, for most analytical methods it is necessary to carry out a certain number of operations to make the sample amenable to the instrument. These operations, which may include digestion, extraction, dissolution, preconcentration and clean-up, typically require the use of large amounts of acids, organic solvents, and in general, chemicals that can often be persistent, bioaccumulative and toxic (PBT) as well as operating conditions that can become unsafe and energy-consuming. Therefore, sample preparation stages should be targeted as a priority when green chemistry principles are to be adapted to analytical activities. This chapter is devoted to the discussion of most relevant sample preparation strategies that approach the fulfilment of the green chemistry principles. Thus, digestion and extraction strategies from solid samples for both inorganic and organic analysis are approached using microwaves and ultrasound, followed by a discussion of modern extraction techniques, such as microwave-assisted extraction, supercritical fluid extraction, pressurized liquid extraction and solid-phase extraction for trace organic analysis. Microextraction techniques also deserve a place here, since a high degree of greenness is achieved when they are implemented in analytical methodology. Finally, application of surfactants in techniques such as cloud point extraction or membranes that allow minimizing the use of organic solvents for analysis of liquid samples are discussed.

Trace element levels in some dried fruit samples from Turkey

Trace element levels in nine different dried fruit samples from Kayseri, Turkey were determined by flame atomic absorption spectrometry after dry and wet digestion methods. Good accuracy was assured by the analysis of standard reference material (NIST-SRM 1515-Apple Leaves). The contents of trace elements in the samples were determined in the ranges of 1.68-4.52, 0.6-9.4, 5.5-12.4, 6.76-64.1, 4.74-25.5, 0.2-1.78, 0.8-6.17 and 0.1-0.81 microg/g for copper, nickel, lead, iron, manganese, cobalt, chromium and cadmium, respectively. The highest copper content was 4.52 microg/g in black grape, highest nickel content was 9.4 microg/g in black plum, highest lead content was 12.4 microg/g in apricot, highest iron content was 64.1 microg/g in apricot, highest manganese content was 25.5 microg/g in rose hip, highest cobalt content was 1.81 microg/g in white mulberry, highest chromium content was 6.17 microg/g in yellow plum and highest cadmium content was 0.8 microg/g in apricot and rose hip. The results were compared with the literature values.

Trace metal contents in chewing gums and candies marketed in Turkey

Cu, Ni, Pb, Fe, Mn, Cr and Cd contents were determined in 17 different brands of chewing gum and candy samples available in local markets of Kayseri, Turkey. Concentration of selected trace metals were estimated using flame atomic absorption spectrometer after dry and wet digestion methods. Out of 17 brands of chewing gums and candies analysed, four were cocoa based, two were sugar based and other were of fruit based. Copper level ranged from 0.219 to 2.455 microg/g with an average of 1.390 microg/g. Nickel ranged from 0.120 to 2.588 microg/g with an average of 0.846 microg/g. Lead level ranged from 0.031 to 2.46 microg/g with an average of 0.746 microg/g. Iron level ranged from 3.963 to 9.863 microg/g with an average of 6.618 microg/g. Manganese level ranged from 1.872 to 5.067 microg/g with an average of 3.196 microg/g. Chromium ranged from 0.740 to 6.265 microg/g with an average of 2.473 microg/g and cadmium level ranged from 0.027 to 0.825 microg/g with an average of 0.296 microg/g. Cocoa based samples were found to have higher contents of the analysed metals than sugar and fruit based samples.

On-line sorption-based systems for determination of cadmium with atomic spectrometry detectors

Determination of cadmium is often required in various environmental, biological and food samples as it is recognized worldwide as a toxic metal. However, these analysis with atomic spectrometry detectors are often difficult due to relatively low content of cadmium and complex matrices. Several preconcentration/separation procedures to determine cadmium have been devised, among them the methods based on sorbent extraction are the most popular. They can be easily implemented and controlled in flow injection (FI) or sequential injection (SI) systems to perform appropriate sample pretreatment. This work reviews the papers, published from 1990, concerning procedures based on sorption principles for on-line determination of cadmium. They were compared using experimental enhancement factor (EF) and concentration efficiency (CE) values.