Determination of thallium in water samples via solid sampling HR-CS GF AAS after preconcentration on chromatographic paper

A method for determining thallium in water samples via solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (SS HR-CS GF AAS) after preconcentration using chromatographic filter paper as a solid support was proposed. The effects of pH, stirring time, and sample volume in the analyte preconcentration step were studied. The presence of potential interferences in the sample and the type of masking agent were also examined. In the proposed procedure, the sample was placed in contact with the solid phase in a polypropylene tube, and after stirring for 3 min, thallium determination was performed via HR-CS GF AAS directly on chromatographic filter paper. A preconcentration factor of 55, a precision of 9.4% (n = 10; 10 μg L-1), a limit of detection of 0.018 μg L-1, and a limit of quantification of 0.059 μg L-1 were achieved. Analyte addition and recovery tests were performed, and the results ranged from 91% to 110%. The accuracy of the method was evaluated by analyzing a water reference material. The procedure was used to determine thallium in water samples collected in Barreiras, Bahia, Brazil. The results were compared with those obtained using inductively coupled plasma‒mass spectrometry (ICP‒MS). Thallium concentrations in the analyzed samples ranged from <0.059 to 0.80 μg L-1.

Comparison of the performance of atmospheric pressure glow discharges operated between a flowing liquid cathode and either a pin-type anode or a helium jet anode for the Ga and In determination by the optical emission spectrometry

Novel atmospheric pressure glow discharge (APGD) microplasma systems, sustained between a miniaturized flowing liquid cathode (FLC) and either a pin-type anode or a He nozzle jet were investigated for the determination of Ga and In by the optical emission spectrometry (OES). The most influential working parameters, i.e., solution flow rate, acid concentration, discharge current, and He flow rate, were optimized for both studied systems. Furthermore, the effect of the addition of low molecular weight organic compounds (LMWOCs) into the FLC solution on the signals intensity of Ga and In was investigated. Subsequently, the impact of concomitant ions on the signals intensity of Ga and In was thoroughly studied and it was established that both studied methods are relatively resistant to matrix effects. Under the optimized conditions, the detection limits (DLs, assessed on the basis of the 3σ criterion) of the studied elements were similar for both discharges and ranged between 1.8 and 2.3 μg L^-1 for Ga and 0.37-0.40 μg L^-1 for In. The received DLs were therefore better than those obtained for other spectrometric methods being premised upon microplasma systems and comparable with those obtained by currently employed large-scale instrumentation. The system with the pin-type anode was successfully applied for the Ga and In determination in four leachates of solders and electronic scrap as well as river water, using external calibration with simple standard solutions. The received results were compared to those obtained from ICP-OES or ICP-MS measurements and their recoveries were fallen within the range of 98-114%, confirming the excellent accuracy and reliability of the developed FLC-APGD-OES method.

Determination of bongkrekic acid and isobongkrekic acid in rice noodles by HPLC-Orbitrap HRMS technology using magnetic halloysite nanotubes

The existing extraction and detection methods of bongkrekic acid (BKA) and isobongkrekic acid (IBKA) are complex, time-consuming and solvent-consuming. In this work, a simple and fast pre-concentration procedure based on Fe₃O₄/HNTs was developed for the determination of BKA and IBKA in rice noodles using HPLC-Orbitrap HRMS. The structure and morphology of Fe₃O₄/HNTs was characterized by means of XRD, SEM, FT-IR and VSM. Parameters affecting the extraction efficiency including adsorbent amount, pH, extraction time, type and volume of eluent were investigated by employing the response surface method. Results indicated that the proposed method had favorable linearity in the concentration range of 2-200 μg/L with a correlation coefficient >0.998. Method LOD and LOQ were 0.3 μg/kg and 1.0 μg/kg, respectively. Finally, the method was successfully applied to determine BKA and IBKA in rice noodle samples from southern China with recoveries ranging from 79.8% to 102.6% and relative standard deviation (RSD) of 4.2%-7.1%.