Evaluation of Sample Preparation Methods for the Determination of Ca, Cu, Fe, K, and Na in Milk Powder Samples by ICP-OES

Abstract

In this paper, a comparative study between three acid decomposition procedures of milk powder samples for the determination of Ca, Cu, Fe, K, and Na by optical emission spectrometry with inductively coupled plasma is presented. Utilizing a reflux system, it was possible to increase the temperature of the digester block above the boiling point of the reaction medium, avoiding the loss of analyte and the excessive evaporation of the acids during the heating. Conditions of acidity (10 mL HNO 3 /H 2 SO 4 ), temperature (350°C), and decomposition time (4 h) were defined by evaluation of residual carbon content. Acid digestion in an open system with a cold finger was compared with a conventional open system (4 h ate 120°C), as well as with microwave digestion (heating ramp to 180°C by the time 45 min), for four commercial samples of milk powder. For the three sample preparation procedures, the values of the analyte concentrations in all analyzed samples were similar. The accuracy of the acid digestion procedures for Ca, Cu, Fe, K, and Na was assessed by the analysis of a certified reference material of milk (infant formula), and good agreement between the certified values and the measured value was obtained. The limits of quantification for the acid digestion with reflux system for Ca, Cu, Fe, K, and Na, in milligram per kilogram, were 7. 48, 0.31, 1.0, 8.20, and 25.81, respectively, and for the microwave digestion were 14.0, 0.57, 1.78, 14.65, and 46.08, respectively. The decomposition procedure using a cold finger in an open system is effective, presenting the lowest residual carbon content (6 %), good accuracy, and relative standard deviation lower than 5 %, and appears to be a suitable procedure for sample preparation for routine analysis.

Use of MIP OES and F AAS/AES for determination of Ca, K, Na and Mg in brazilian cream cheese

“…26 The variable H 2 SO 4 volume was not significant, however, in the preliminary tests it was observed that the decomposition carried out with mixture of acids (HNO 3 and H 2 SO 4 ) has better analytical signals in the determination of the four elements compared with the use of only HNO 3 . The same was verified by Oreste et al 17 by using the mixture in order to determine Ca, Cu, Fe, K and Na milk powder samples.…”

“…Its applicability has been shown in the preparation of different types of matrices for subsequent determination of metals by different analytical techniques. [16][17][18] Another simple and efficient alternative used for the preparation of organic samples employs solubilization with tetramethylammonium hydroxide (TMAH). Samples treated with TMAH provides a solution with characteristics similar to a suspension, with a low dilution factor and remaining stable for months at room temperature.…”

Evaluation of the Concentration of Cu, Zn, Pb and Cr in Different Fish Species from the São Gonçalo Channel in Pelotas-RS, Brazil

“…The cold finger is inserted into a digestion vessel for sample preparation, using an open system with conventional heating. Our research group has applied a new design of cold finger for sample preparation with a reflux system, which has demonstrated a high efficiency in decomposing different samples, as can be observed in the published papers on the determination of Hg in biological samples; 33 Cd, Pb and Sn in meat; 34 Ca, Cu, Fe, K and Na in milk powder; 35 As, Cd, Pb, and Se in rice 36 and Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Pb and Zn in yerba mate. 37 Thus, this study aims to determine the concentrations of Cu, Zn, Cr and Pb in different species of fish from estuarine and limnic portions of the São Gonçalo channel, in different seasons of 2013 and 2014.…”

Analytical advances in the determination of calcium in bovine milk, dairy products and milk-based infant formulas

“…This solution is preferred over open systems offering reduced risk of analyte loss. Sample preparation through such device was adopted to determine calcium and other minerals in milk powders and MIF (n = 4) by inductively coupled plasma optical emission spectrometry (ICP-OES) (Oreste, de Souza, Pereira, Lisboa, Cidade et al, 2016). Results fitted well (at 99% confidence level) with those obtained by conventional open-vessel heating system.…”