Determination of mercury in mosses by novel cold vapor generation atmospheric pressure glow microdischarge optical emission spectrometry after multivariate optimization

Abstract

A novel atmospheric pressure glow microdischarge system coupled with chemical vapor generation was applied to the optical emission spectrometry determination of Hg in samples of mosses (Pleurozium schreberi) from parks and surrounding forests of Wroclaw (Poland). The design of experiment (DOE) was used to optimize the operating parameters of the microdischarge system combined with a reaction/ separation unit used for chemical vapor generation. Seven experimental factors were examined, i.e., concentrations of NaBH 4 and HCl, the discharge current and flow rates of reagents, the jet-supporting gas, the shielding gas and the liquid cathode solution on the intensity of the Hg I 253.7 nm emission line and the standard deviation of the background in its vicinity. The optimized operating conditions allowed us to obtain a detection limit of 0.066 mg L À1 for Hg, which was close to the predicted value with a fitted model.To separate Hg species from moss samples, a 2-step extraction procedure with a 5.0 mol L À1 HCl solution was carried out instead of complete wet digestion with concentrated HNO 3 . To validate the reliability of results, the spike-and-recovery experiment was performed. The obtained results were close to 100% proving the good accuracy of the methodology proposed. The average concentration of Hg in mosses in the urban area of Wroclaw was high (0.37 mg g À1 ) but no specific source of contamination was found.

Pump- and Valve-Free Flow Injection Capillary Liquid Electrode Discharge Optical Emission Spectrometry Coupled to a Droplet Array Platform

“…Figure shows that the specific molecular emissions are significantly increased, while emissions from Hg and Cd are increased about 50-fold compared to those obtained under open-air conditions. These significant improvements can be attributed to the fact that the water vapor produced from the thermal vaporization of sample solution is efficiently flushed out of the discharge zone and thus enhance the energy of the system. − Additionally, Figure b reveals that the intensity of NO molecule emission bands (230–270 nm) is significantly suppressed in the absence of air and the background arising from the Ar plasma is more stable than that from the air plasma, which agrees well with the previous works and suggest that the Ar plasma is beneficial for the determination of trace elements in real samples. Unfortunately, a drop of liquid appeared close to the end of the capillary (see Figure S2 and Movie S1), resulting in an unstable discharge generated between the drop and the tungsten electrode.…”

The application of tetramethylammonium hydroxide for generating atmospheric pressure glow discharge in contact with alkalized flowing liquid cathode solutions – evaluation of the analytical performance

“…The Box–Behnken response surface design, which comprised 15 runs and included 3 center points, was used for this purpose. 41 The measured response of the system was the SBRs of the analytical lines. A quadratic model was chosen for describing the influence of the investigated operating parameters on the SBR values, nonetheless, insignificant terms (at the significance level α > 0.15, meaning the confidence level <85%) were removed from it.…”

The sensitive determination of Ag, Pb and Tl as well as reduction of spectral interferences in a hanging drop cathode atmospheric pressure glow discharge excitation microsource equipped with a Dove prism system

“…This approach was previously used to assess the effect of several factors on the multi-response in different analytical and technological systems; such factor settings were selected that followed the compliance criteria for all individual responses and provided the best compromise conditions contributing to a desirable joint multi-response. 14,15 The Box-Behnken design used in the present work comprised 15 runs (including 3 center points), and it was related to the number of the studied experimental factors and the combinations of their settings at 3 different levels, i.e., À1, 0 and +1. To describe the main effects, the interactions, and the curvature of the experimental factors on the measured analytical response, a quadratic model was chosen.…”