Wet Chemical Sample Research Articles

Dielectric Barrier Discharge of Moist Nitrogen: A Methodology for Exclusive NO Generation

Chemical transformations of moist nitrogen in dielectric barrier discharge cold plasma into NO, NO2, and NO2− in conjunction with the control for exclusive NO generation are reported. Initial gas-phase products NO and NO2 were identified and estimated spectrophotometrically at respective absorption $\lambda _{{{\text {max}}}}$ taking the set of three closely spaced peaks around 204, 214.5, and 226 nm in case of the former, while at 400 nm for latter. Other products NO2− and H2O2 were identified and estimated by wet-chemical sampling methods followed by colorimetric analyzes, respectively, at 540 and 350 nm. NO, NO2, and NO2− yields increased continuously, with increase in gas residence time inside the plasma zone, applied voltage between two electrodes, and the moisture concentration in the gas stream. Typical G values estimated are: NO, $3.98 \times 10^{-3}$ ; total NO2 and NO2−, $6.30 \times 10^{-3}$ ; and H2O2, $2.7 \times 10^{-3}~\mu \text {mol}\cdot \text {J}^{-1}$ . In the product mixture, employing NO2 and NO2− absorber solution, 50–750 ppm level NO was obtained as an exclusive product with 0.05–24 kHz ac power supplies.

NitroMAC: An instrument for the measurement of HONO and intercomparison with a long-path absorption photometer

NitroMAC (French acronym for continuous atmospheric measurements of nitrogenous compounds) is an instrument which has been developed for the semi-continuous measurement of atmospheric nitrous acid (HONO). This instrument relies on wet chemical sampling and detection using high performance liquid chromatography (HPLC)-visible absorption at 540nm. Sampling proceeds by dissolution of gaseous HONO in a phosphate buffer solution followed by derivatization with sulfanilamide/N-(1-naphthyl)-ethylenediamine. The performance of this instrument was found to be as follows: a detection limit of around 3ppt with measurement uncertainty of 10% over an analysis time of 10min. Intercomparison was made between the instrument and a long-path absorption photometer (LOPAP) during two experiments in different environments. First, air was sampled in a smog chamber with concentrations up to 18ppb of nitrous acid. NitroMAC and LOPAP measurements showed very good agreement. Then, in a second experiment, ambient air with HONO concentrations below 250ppt was sampled. While NitroMAC showed its capability of measuring HONO in moderate and highly polluted environments, the intercomparison results in ambient air highlighted that corrections must be made for minor interferences when low concentrations are measured.

Analytical Approaches Based on Gas Chromatography Mass Spectrometry (GC/MS) to Study Organic Materials in Artworks and Archaeological Objects.

Gas chromatography/mass spectrometry (GC/MS), after appropriate wet chemical sample pre-treatments or pyrolysis, is one of the most commonly adopted analytical techniques in the study of organic materials from cultural heritage objects. Organic materials in archaeological contexts, in classical art objects, or in modern and contemporary works of art may be the same or belong to the same classes, but can also vary considerably, often presenting different ageing pathways and chemical environments. This paper provides an overview of the literature published in the last 10years on the research based on the use of GC/MS for the analysis of organic materials in artworks and archaeological objects. The latest progresses in advancing analytical approaches, characterising materials and understanding their degradation, and developing methods for monitoring their stability are discussed. Case studies from the literature are presented to examine how the choice of the working conditions and the analytical approaches is driven by the analytical and technical question to be answered, as well as the nature of the object from which the samples are collected.

Acid Emission Automatic Real-Time Sampling Monitoring System

This paper introduces a novel on-line real-time monitoring system for acidic emission produced by acid pickling, which has been one of the greatest contaminant and major harness content. The system can monitor the HCL concentration in exhaust fumes on-line, and realize the real-time analysis and transmission of the acquisition data. HCL wet chemical sampling system form the whole on-line monitoring system. HCL wet chemical sampling system consists of integrated air velocity transducer, chloride ion analyzer, wet chemical sampling device and liquid level measurement device. It aims to collect HCL fog sample and convert the sampling analogue signal to digital data that can be analyzed. The system overcomes the influence by high temperature, high humidity and high concentration of dust. It realizes the monitoring, storage, analysis, warning and transmission of HCL concentration data in the exhaust. It is beneficial in practical industrial field and environmental protection.

A Simplified, Accurate and Fast Method for Lithium Isotope Analysis of Rocks and Fluids, and δ7Li Values of Seawater and Rock Reference Materials

We report a new approach to conduct fast and accurate lithium isotope ratio measurements by MC‐ICP mass spectrometry after wet chemical sample preparation. In contrast to most previously published methods our MC‐ICP‐MS set‐up did not use a desolvating system to achieve appropriate ion beam intensities and, therefore, was less affected by matrix‐induced shifts of the instrumental mass bias. As the total lithium background and build‐up in the sample introduction system was low, previous sample residues could be washed out by an extended uptake of the new sample. Elimination of a nitric acid rinse step increased the sample throughput by a factor of two and allowed the instrumental mass bias drift to be tracked more precisely. δ7Li values of powdered silicate rock reference materials and seawater obtained in this study revealed good accuracy and an overall analytical uncertainty of typically 0.5‰ (2s). On the basis of a comparison between our lithium isotope data and compiled literature data, we recommend preliminary average δ7Li values for seawater (+30.8‰) and several silicate rock reference materials (BHVO‐1: +5.0‰; JA‐1: +5.6‰; JB‐2: +4.8‰). The compilation of published δ7Li values for seawater suggests that the observed large lithium isotope differences are due to inter‐method and/or interlaboratory bias. Most recently published δ7Li values for seawater show little variation and confirm a constant lithium isotope composition (at the sub ‰ level) of seawater in well mixed ocean basins.

Wet Chemical Method for Determining Levels of Ammonia in Syngas from a Biomass Gasifier

A wet chemical sampling method using acidic absorbing solutions was used to determine levels of ammonia (NH3) in syngas from a biomass gasifier. Before syngas is bubbled into the absorbing solutions, a quartz thimble filter is used to filter ash from the gas stream at 450 °C followed by heavy tar removal at about 100 °C. When gasifying corn, good precision was observed for multiple samples collected on any given day of testing. Tests on producer gas obtained from gasification of switchgrass revealed important conditions for successfully sampling NH3. During gasification of switchgrass, high solids loading in the syngas caused the primary cyclone at the gasifier exit to plug, resulting in abnormally high ash loading in the thimble filter in the sampling system. While gasifying the switchgrass, the NH3 levels showed a continuous decline throughout the day. It is suspected that NH3 reacts with the ash in the thimble filter, confounding attempts to accurately measure NH3 in the syngas.

A new instrument to measure gaseous nitrous acid (HONO) in the atmosphere.

A new in situ instrument (LOPAP: long path absorption photometer) to measure gaseous nitrous acid (HONO) using wet chemical sampling and photometric detection has been developed. This instrument is aimed to overcome the known problems with current HONO measurement techniques and was designed to be a cheap, sensitive, compact, and continuouslyworking HONO monitorfor ambient air measurements in the troposphere or for measurements of higher concentrations e.g. in smog chambers, in exhaust gases, and in indoor environments. Laboratory investigations were carried outto characterize the instrument components with respect to collection efficiency, optimum dye formation, optimum detection, and interfering species. Detection limits ranging from approximately 3 to 50 pptV have been obtained with response times from 4 to 1.5 min, respectively, using different instrument parameters. The accuracy of the measurements is in the range between +/-(10-15)%. The validation of the instrument was performed in the laboratory for HONO concentrations of 3 and 30 ppbV using ion chromatography and with a DOAS (differential optical absorption spectrometer) instrument in a large outdoor smog chamber in the range from 0.1 to 20 ppbV. The deviations were well within the errors of the measurements; however, when comparing the data with the DOAS instrument systematically higher values were found with the LOPAP instrument.

New and simple method of contact processing characterization using atomic force microscopy

This article reports on the use of atomic force microscopy coupled with a simple wet chemical sample preparation to characterize processes involved in the realization of 0.4 μm metal on silicon contacts. Photolithography and contact etching processes both lead to high aspect ratio topography (≳4). The samples are imaged after a preparation which removes the high aspect ratio and leads to a better image. The main parameters of this new procedure are highlighted in this report, namely contact area for lithography and etching processes and silicon consumption for the etching process. The contact silicidation process is also monitored, and the electrical results are correlated with the silicide thickness formed in the contact.

Study of a toroidal argon MIP and a cylindrical helium MIP for atomic emission spectrometry—II: Combination with graphite furnace vaporization and use for analysis of biological samples

The capabilities of a toroidal argon and a diffuse helium microwave induced plasma (MIP) operated in a TM 010 resonator and in combination with electrothermal vaporization have been studied for atomic emission spectrometry (AES). The 75 W toroidal MIP has been found to improve the power of detection with respect to the filament argon MIP by a factor of 3–10. The detection limits using 50 μl solution aliquots for a large series of elements are between 0.1 and 100 ng ml . With a diffuse helium MIP in combination with graphite furnace vaporization the detection limit for P is 10 ng ml and for Pb 1 ng ml . In the toroidal argon MIP, matrix effects due to alkali elements occur already at concentrations of 10 μg ml of Na and could not be eliminated satisfactorily by the use of NH 4NO 3. In. the helium MIP, also volatilization interferences in the case of Ca and P were found. After separation of the alkali elements by sorption of the trace elements as hexamethylene-dithiocarbamates (HMDC) on acetylated cellulose, MIP-AES with the toroidal argon MIP coupled to electrothermal vaporization has been found to be suitable for multielement determinations in biological samples, subsequent to wet chemical sample decomposition in closed PTFE (Teflon) vessels. This is demonstrated by the determination of Fe, Cu and Zn in the NBS standard reference materials of bovine liver, orchard leaves and tomato leaves.