On-line microwave digestion of slurry samples with direct flame atomic absorption spectrometric elemental detection

Abstract

A flow injection (FI) system for on-line microwave digestion of slurried samples with direct elemental determinations by flame atomic absorption spectrometry is described. Organically based elemental reference samples were prepared as slurries in 5% v/v HN03 and the system was optimized for slurry mass, acid strength and tube and microwave cavity geometry. Bubble formation during digestion was controlled by post-digestion cooling and pressure regulation. Comparison of direct and FI calibrations indicated no apparent loss in sensitivity. Various samples were examined and elemental recoveries for Car Fe, Mg and Zn were typically found to be in the range 94-107% with precisions of less than 4.5% relative standard deviation.The major source of error was found t o be in the dispersion of solids (<I80 pm) as slurries in dilute HN03. The throughput of samples in the system developed was found t o be 1-2 min per sample.

Modern Strategies for Environmental Sample Preparation and Analysis

“…This is a closed system where sample and reagents can be pumped continuously through the flow system or maintained to be irradiated in stopped-flow conditions. As examples of very interesting works regarding a continuous flow system and environmental samples we must mention the papers published by Karanassios et al (1991), Haswell and Barclay (1992), Welz et al (1992), Tsalev et al (1992a), Carbonell et al (1992), Hanna and McIntosh (1995), Arruda et al (1997) and Almeida et al (1997). These papers deal with metal determinations by using atomic spectroscopy techniques for samples such as waters, wastewaters, botanic, biological tissues, sludge, sediments, and rocks, respectively.…”

Automatic flow-injection system for the determination of heavy metals in sewage sludge by microwave digestion and detection by inductively coupled plasma-atomic emission spectrometry (MW-ICP/AES)

“…Many of these problems can be avoided or at least alleviated if the process is carried out by the flow injection methodology (FIA) [18]. Several authors have achieved satisfactory results using the FIA methodology to combine the microwave sample treatment with atomic spectrometric detection (i.e., FAAS, ICP/AES) [19][20][21][22][23][24][25][26][27]. Burguera et al [19] used an FIA flow-merging manifold for the FAAS determination of Cu, Zn and Fe in blood.…”

“…Burguera et al [20] also used the combination MW-FAAS for the determination of Zn and Cd in biological tissues treated with 5 ml of 1.0 mol/l HNO , at 200 W power for 8 min. More recently, Haswell and Barclay [22] applied this same combination to different biological samples, reaching quantitative recoveries in about 2 min with a microwave power (P) of 525 W. Gluodenis and Tyson [24] compared three digestion systems (conventional acid digestion, MW digestion in closed vessels and MW digestion on-line) by determining Cu and Fe in a cocoa powder sample. The mean values obtained for both elements were similar in all three cases, whereas the dispersion of the values was greater for the on-line system.…”

Semiautomatic determination of ferrous iron in iron ore using a flow-injection technique

“…In order to speed up analysis, analytical chemists have made great effort to investigate approaches for on-line sample preparation and its successful applications to liquid samples coupled with ICP-atomic emission [2], flame [3][4][5], cold vapor [6,7] and hydride generation [8,9] atomic absorption spectrometry. This demonstrated the extensive applications of FI techniques to on-line preparation of liquid samples.…”