Zhixia Zhuang

Flow injection–electrochemical hydride generation technique for atomic absorption spectrometry. Invited lecture

A flow injection–electrochemical hydride generation technique for atomic absorption spectrometry has been developed in order to avoid the use of sodium tetrahydroborate, which is capable of introducing contamination. A specially designed thin-layer electrolytic flow cell for hydride generation was used in a normal flow injection system coupled to an electrically heated T-tube atomizer for the atomic absorption measurements. About 200 µl of sample were injected into the electrolyte carrier stream flowing to the electrolytic cell, where hydride-forming elements were reduced to gaseous hydrides. The effects of various factors, e.g., electrode material, electrolyte, current density and carrier stream flow rate, on rate of formation of the hydride and interferences have been studied. The technique has been applied to the determination of As, Se and Sb in various samples. The detection limits for these elements in aqueous solutions were 0.45, 0.62 and 0.92 ng ml–1, respectively, with precisions of 1.2–1.8%.

On-line flow injection cobalt–ammonium pyrrolidin-1-yldithioformate coprecipitation for preconcentration of trace amounts of metals in waters with simultaneous determination by inductively coupled plasma atomic emission spectrometry

The technique of on-line flow injection (FI) cobalt-ammonium pyrrolidin-1-yldithioformate (Co–APDC) coprecipitation for the preconcentration of trace amounts of the heavy metals Cd, Cu, Fe, Ni, Pb and Zn in rain water samples with simultaneous determination by inductively coupled plasma atomic emission spectrometry (KP-AES) has been developed. A precipitate collector system, consisting of a poly(tetrafluoroethylene)(PTFE) membrane on a polypropylene support filtering device combined with a 1.5 m reaction coil, was selected. An inorganic solution of concentrated nitric acid and hydrogen peroxide was applied as the dissolution reagent. The technique is characterized by high retention efficiency (which ranged from 77 to 99% for the six elements of interest), good enrichment factors (ranging from 10 to 50 for 100 s preconcentration depending on the elements studied) and satisfactory accuracy and precision (recoveries from two standard additions to a rain sample ranged from 92 to 104%, with relative standard deviations ranging from 1.9 to 5%). The sample throughput is 20 per hour.

Thermospray nebulizer as sample introduction technique for microwave plasma torch atomic emission spectrometry

Abstract A thermospray nebulizer was used as a sample introduction device for microwave plasma torch (MPT) atomic emission spectrometry (AES). Experimental parameters, including the power supplied to the MPT, the flow rates of support and carrier gases, the observation height, the sample uptake rate, the thermospray working temperature, the temperature of the aerosol spray chamber and cooling water were optimized. Under optimum conditions, the relative standard deviation (RSD) of 10 measurements for 21 elements is in the range 0.3–2.0%. The detection limits were improved in comparison with the ultrasonic nebulizer as sample introduction technique for MPT–AES. The inclusion of 20% methanol into the MPT showed there is no effect on the stability of MPT discharge. The technique can thus be held to have the potential for interface to reverse-phase HPLC systems.

Preliminary study on the use of palladium as a chemical modifier for the determination of silicon by electrothermal atomic absorption spectrometry

This paper describes the use of palladium salt as chemical modifier for the determination of silicon by electrothermal atomic absorption spectrometry. It is found that the optimal atomization temperature of silicon appeared to be flat above 2500 °C and that the sensitivity was significantly improved in the presence of palladium. The method was validated by the analysis of National Bureau of Standards (now National Institute for Standards and Technology) Standard Reference Materials 361, 362 and 363 Low Alloy Steels.

High-resolution spectra of selected rare earth elements and spectral interferences studied by inductively coupled plasma-atomic emission spectroscopy (ICP-AES)

The rare earth elements (REEs) play very important roles in industrial manufacturing, technology development and biological processes. Due to their complex emission spectra, trace levels of REEs are difficult to analyze by conventional ICP-AES techniques. The present study investigates possible spectral interferences of matrices (rare earth oxides of Ce, Pr, Nd, Sm and Dy) on the analytical lines (± 0.1 nm) of a target REE. Detailed and well-resolved spectra for selected REEs are presented, and procedures used to rectify the problem of spectral interferences caused by REE matrices are discussed. A computer-assisted system (CAS) for spectral recognition has been developed and used to assist in the study of matrix interference. To determine directly trace rare earth elements in REE matrices without sample pre-separation, the application potential is demonstrated with a one meter sequential instrument retrofitted with a 3600 grooves/mm grating.

Development of transient data acquisition system for hyphenated techniques coupled with inductively coupled plasma atomic emission spectrometry

Abstract A transient data acquisition system for flow injection analysis (FIA), high performance liquid chromatography (HPLC), and electrothermal vaporization (ETV) combined with ICP-AES multi-element instrumentation was developed and successfully applied to the analysis of different types of samples, including human serum, human hair and tea, for simultaneous multi-element determinations. The accuracy of the method was verified with hair reference material. Good agreement between the experimental results and certified values, and also satisfactory recoveries from standard additions, were achleved.