Helena Stecka

Determination and Fractionation of Metals in Honey

The composition of metals in honey is correlated with the type of plant species from which resources (nectar, pollen, propolis, honeydew) are collected and ripened by honey bees into honey. However, the botanical origin is strictly attributed to the geographical locality of an apiary, because the soil composition and the climatic conditions determine the presence of certain melliferous flowers and trees harvested by bees. The environmental pollution or other anthropogenic processes and effects should also be considered as an additional source of metals in honey, namely Cd, Cr, Cu, Fe, Ni, Pb and Zn. These metals may condemn the quality and food safety of honey, and exhibit a potential hazard to human health. The present literature survey reviews original works of the last decade which relate to the atomic and mass spectrometric analysis of honey on the presence of major, minor and trace metals. Different aspects of such analysis are treated in detail, including the methods of choice, calibration strategies, sample treatments, and preparation procedures applied. The suitability of the metals content for the classification of honey according to the botanical and geographical origins or indication and control of the environmental pollution are discussed.

Different Aspects of the Elemental Analysis of Honey by Flame Atomic Absorption and Emission Spectrometry: A Review

The elemental composition of honey is correlated with the botanical provenience of nectar, pollen, and honeydew that are collected and ripened by bees. In addition to this, the geographical origin related to the locality of an apiary, the soil composition, and climatic conditions may contribute to the origin of elements in honey. The environmental pollution or other anthropogenic processes and activities also have an effect on the quality and the safety of honey since they may be accompanying sources that lead to its contamination and the presence of various trace elements (Cd, Cr, Cu, Fe, Ni, Pb, and Zn). This review article covers the literature devoted to the analysis of honey carried out by the most popular and commonly utilized flame atomic absorption and emission spectrometry, which was published from 1999 to 2011. Various aspects of such analysis are treated in detail, including ways of the sample preparation, the calibration, and the quality assurance of results. In addition, methods and results related to the fractionation analysis of elements in honey by means of chromatographic and non-chromatographic approaches are described.

Solid phase extraction and sequential elution for pre-concentration of traces of Mn and Zn in analysis of honey by flame atomic absorption spectrometry

A pre-concentration procedure based on solid phase extraction and two-step elution was developed for the determination of the total concentrations of traces of food safety relevant elements (Mn and Zn) in ripened honeys. Accordingly, 10% (m/v) solutions of analyzed honeys (100 ml) were passed at 20 ml min−1 through resin beds of Dowex 50W × 8–400 to retain Mn and Zn ions and separate them from the glucose and fructose matrix. Afterwards, 20 ml of a 0.5 mol l−1HNO3 solution was used to elute K and Na, easily ionized interfering metals. Finally, Mn and Zn were recovered prior to measurements by flame atomic absorption spectrometry (FAAS) using 5 ml of a 2 mol l−1HCl solution. This procedure was applied in the analysis of six honeys and resulted in the determination of 0.2–13.6 μg g−1 of Mn and 0.2–1.2 μg g−1 of Zn with the precision (n = 3) within 3–10% and an accuracy better than 5%. Detection limits of Mn and Zn with this pre-concentration/separation procedure and the FAAS detection were 4 and 3 ng g−1, respectively.

Pre-concentration of lithium prior to its determination in honey by flame optical emission spectrometry

A procedure based on solid phase extraction with a strongly acidic cation-exchanger Dowex 50W×8-200 was proposed to pre-concentrate and determine ultra-traces of Li in different floral honeys. When loading 10% (m/v) honey solutions onto columns packed with the cation-exchanger, Li+ ions were retained on the resin along with K+ and Na+, while simple sugars were passed through columns and were entirely found in effluents. In turn, columns were washed with water and eluted with a 1.0 mol L-1 HCl solution to strip Li+ that was subsequently determined in respective eluates by flame optical emission spectrometry (FOES). The proposed method was characterized by a limit of detection (LOD) of 0.05 ng g-1 of Li and later used for analysis of several raw and commercial mono- and multi-flower honeys. It enabled to determine from 0.4 to 5.3 ng g-1 of Li with precision being within 8-11%. Accuracy of this sample pre-treatment procedure and analysis method was assessed applying spike recovery tests. Recoveries of added Li were found to be within 98 to 106%, demonstrating trustworthiness of results achieved.

Pre-concentration of traces of cadmium, cobalt, nickel and lead in natural honeys by solid phase extraction followed by their determination using flame atomic absorption spectrometry

A simple and fast sample preparation procedure for the determination of traces of Cd, Co, Ni and Pb in honeys was proposed. It included the preparation of acidified sample solutions of honeys, the retention of elements of interest on resin beds of a strongly acidic gel cation exchanger Dowex 50W×8-400, and their elution with a 3.0 mol L-1 HCl solution prior to measurements by flame atomic absorption spectrometry (FAAS). The method provided the precision and the accuracy better than 4.5% and detection limits of 0.005 µg g-1 (Cd), 0.015 µg g-1 (Co, Ni) and 0.073 µg g-1 (Pb). The reliability of results obtained with the developed procedure and FAAS was validated by the recovery test and the comparison with results achieved using the wet digestion and inductively coupled plasma optical emission spectrometry. The method was applied for the analysis of sixty nine samples of honeys originated from the Lower Silesia region (southeast Poland). It was found that Cd, Co and Pb were under detection limits, while Ni was determined in nine honeys at the level of 0.19-0.93 µg g-1.

Elemental Composition of White Refined Sugar by Instrumental Methods of Analysis

This overview deals with an important issue for the sugar industry, the elemental analysis of white refined sugar by atomic absorption spectrometry and other instrumental methods, including inductively coupled plasma optical emission spectrometry, neutron activation analysis, and stripping voltammetry. Strong and weak points of these methods in terms of determinations of major and trace elements in sugar samples are featured. Different sample preparation procedures applied in sugar analysis, with their advantages and disadvantages, are discussed. The importance of quality assurance and control of results are highlighted. Separate sections are focused on sources of elements in white refined sugar and various food safety and technological aspects related to their presence.

Fast and interference free determination of calcium and magnesium in honeys by solid phase extraction followed by flame atomic absorption spectrometry

A sample preparation procedure based on the solid phase extraction and the two-step elution was developed for the determination of the total concentrations of Ca and Mg in bee honeys. The honey samples were treated as follows: the 5.0% (m/v) sample solutions (50 mL) were passed at the flow rate of 20 mL min-1 through the resin beds of Dowex 50W×8-400 to retain the Ca(II) and Mg(II) ions and separate them from the matrix of glucose and fructose in addition to the anionic minerals. Afterwards, 20 mL of a 0.5 mol L-1 HNO3 solution was used to remove the K and Na ions. Finally, Ca and Mg were eluted prior to the measurements of their concentrations by flame atomic absorption spectrometry (FAAS) using 5 mL of a 2.0 mol L-1 HCl solution. The proposed sample preparation procedure was fast (30 min) and enabled to measure the concentrations of Ca and Mg in honey with the precision of 1-5% and the accuracy of 1-3%. The limits of detection of 24 ng g-1 of Ca and 4.4 ng g-1 of Mg were obtained for FAAS with this procedure.

Application of Ion Exchangers in Speciation and Fractionation of Elements in Food and Beverages

A relationship between different species of elements in dietary products and their bioavailability from that source is very important to human safety and wholesomeness. Analytical methods outlined in this report are based on solid phase extraction with polymeric ion exchange resins and other nonionic sorbents can be applied for fractionation analysis of elements in a number of food products and beverages. Their attractiveness mostly lies in simplicity of solid phase extraction operation, versatility, and diversity of available sorbents and possibility of insight into chemical nature of element forms due to different sorption mechanisms served by these sorbents. This article surveys two main means of partitioning of elements by solid phase extraction, including procedures with single sorbents or two coupled sorbents. Attention is also drawn to operational character of fractions of species distinguished and evaluation of possible groups of species of elements. Sample pretreatment and quality assurance and control of results of fractionation analysis achieved using the mentioned solid phase extraction schemes are highlighted.