查看更多>>摘要：A new sample introduction method of nebulized film dielectric barrier discharge (NFDBD) assisted chelate vapor generation coupled with inductively coupled plasma mass spectrometry (ICP-MS) for trace rare earth elements (REEs) determination in environmental water was developed in this work. Using 2,2,6,6-tetramethyl-3,5-heptanedione (DPM) as chelating reagent, the volatile and stable chelates of REE-DPM were effectively vaporized in NFDBD sampling system, leading to 8-9 folds enhancement of REEs sensitivity compared with solution nebulization sampling system, with the sample introduction efficiencies between 51.9% and 66.0%. The enhancement mechanism and the experimental parameters for REEs determination including the DPM concentration, the carrier solution concentration, the input discharge voltage and the argon flow rate were evaluated in detail. The interferences from sample matrix at 10 mg L-1 level and the degradation product of DPM at 0.5 mmol L-1 were also found negligible for trace REEs determination in NFDBD sampling system. Under optimized conditions, the relative standard deviations for 15 REEs were between 0.3% and 2.5% at the concentration of 0.5 mu g L-1 and the detection limits for 15 REEs were between 0.0009 and 0.11 ng L-1, which were 1-2 orders of magnitude lower than other sampling systems such as solution nebulization, membrane desolvation, ultrasonic nebulization and electrothermal vaporization and 2-4 folds lower than NFDBD vapor generation system without chelate. This proposed method not only can be used for trace REEs determination directly in freshwater samples, but also is promising for seawater determination without column separation.
Borduchi, Luis Carlos LevaMilori, Debora Marcondes Bastos PereiraVillas-Boas, Paulino Ribeiro
8页
查看更多>>摘要：The time control of signal acquisition in laser-induced breakdown spectroscopy (LIBS) is critical to the quantification of elements in samples. Upon interacting with the laser pulse, the plasma expands and then cools rapidly in tens of microseconds, undergoing temperature variations of over 50,000 K. In the LIBS technique, the signal acquisition is controlled with the delay time, which is the time between the emission of the laser pulse and the reading of the spectrum, and the gate width, which is the integration time of the spectrometer. Although the relationship of the delay time with the measured plasma temperature and electron density is well-known in the literature, little is known about how these parameters vary with different gate widths. Thus, the objective of this work was to evaluate how the measured plasma parameters and the signal-to-noise ratio (SNR) of an atomic line change with different values of delay time and gate width. For this study, two sets of samples were prepared: i) pure NaCl and ii) NaCl with 20 wt% H3BO3, and at concentrations of 1 and 3 wt% Ca. TiO2 and CuSO4 were also added to these samples to facilitate plasma temperature and electron density calculations, which were carried out using a Saha-Boltzmann plot corrected with the one-point calibration method. The results of this study indicated that the measured plasma parameters did not vary with the gate width, even though the SNR of the Ca I line at 643.9 nm increased as the gate width did. Furthermore, the use of the concept of local thermodynamic equilibrium was verified even with long gate widths (>= 20 mu s), except for the 4 mu s delay time. Studies with other samples and other combinations of LIBS system parameters, e.g., at sub atmospheric pressure, should be done to confirm and expand these findings.
NSTL
Elsevier