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Chemical Analysis in Environmental and Toxicological Chemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Conceptually the most straightforward kind of quantitative analysis, gravimetric analysis consists of isolating in a pure form a species produced stoichiometrically by the analyte, weighing it, and calculating the percentage of analyte in the sample. Obtaining a pure, weighable product is often a complicated process. Many ways of doing that have been developed. The most common of these is formation of a precipitate by a reaction of the analyte in solution. As an example, the chloride content of a weighed, water-soluble sample can be determined by precipitating the chloride in the dissolved sample with excess silver nitrate solution: Ag+(aq)+NO3-(aq)+Cl-(aq)→AgCl(s)+NO3-(aq)Reagent Analyte Precipitate
Chemical Methods
Published in Jerome Greyson, Carbon, Nitrogen, and Sulfur Pollutants and Their Determination in Air and Water, 2020
Gravimetric analysis requires that the constituent being determined be separated from the sample. This may be accomplished by precipitating a chemical transform of the analyte and separating, drying, and weighing the precipitate. Alternatively, if the analyte can be transformed into a volatile product, it may be separated from the analysate by purge techniques or evaporation and collected on an adsorbent and weighed, or the loss in weight of the residual analysate may be determined.
Nanomaterials in the Work Environment
Published in Małgorzata Pośniak, Emerging Chemical Risks in the Work Environment, 2020
Lidia Zapór, Przemysław Oberbek
Gravimetric analysis is a class of laboratory techniques used to determine the mass and concentration of a substance by measuring mass change. Gravimetric analysis of suspended particulate matter is a standard method used for the determination of mass concentration in the work environment and assessment of occupational exposure. Most commonly, large dust fractions are measured, such as the inhalable fraction (penetrating the upper respiratory tract due to the size of the particles) and the respirable fraction (penetrating the lower respiratory tract), or fine particles (PM2.5, which refers to particles with an aerodynamic diameter of 2.5 µm or less) and coarse particles (PM10, which refers to particles with an aerodynamic diameter of 10 µm or less).
Laboratory determination of gravimetric correction factors for real-time area measurements of electronic cigarette aerosols
Published in Aerosol Science and Technology, 2022
Sinan Sousan, Jack Pender, Dillon Streuber, Meaghan Haley, Will Shingleton, Eric Soule
PM measurements are obtained using gravimetric analysis, which is considered the gold standard for air quality monitoring (Sousan, Regmi, and Park 2021). The method uses filter samples to calculate time-weighted average (TWA) PM mass concentration by weighing the mass difference of PM accumulated on the filter at a specific flow rate and sampling time (Olegario, Regmi, and Sousan 2021). However, gravimetric analysis is time-consuming and requires specialized laboratories to control the temperature within ±1 °C and relative humidity between 30% and 50% with ± 5% variability (Hinds 1999). In addition, gravimetric analysis provides an average concentration value over the sampling time with no temporal information. On the other hand, light scattering monitors provide real-time PM mass concentration and are inexpensive to operate (Sousan et al. 2016b). Optical particle counters (OPCs) use the magnitude of light scattered from particles to count the number of particles per size (e.g. PM2.5) and calculate the mass concentration at different PM sizes. Photometers use light scattering from an assembly of particles passing at a specific angle to estimate mass concentration at a specific PM size based on a linear regression model. However, these devices require on-site filter correction as recommended by the manufacturer (GRIMM. 2010; Sousan et al. 2016a; ThermoFisherScientific 2010). Multiple field and laboratory studies have measured ECIG PM2.5 concentrations in ECIGs discussed in the next paragraph.
Morphological modification of Chromolaena odorata cellulosic biomass using alkaline peroxide oxidation pretreatment methodology and its enzymatic conversion to biobased products
Published in Cogent Engineering, 2018
Augustine O. Ayeni, Michael O. Daramola, Adeola Awoyomi, Francis B. Elehinafe, Ajibola Ogunbiyi, Patrick T. Sekoai, Johnson A. Folayan
Compositional analysis on the raw and pretreated samples was carried out gravimetrically as described elsewhere (Ayeni et al., 2014a; Blasi, Signorelli, Russo, & Rea, 1999; Li, Xu, Liu, Yang, & Lu, 2004; Lin, Yan, Liu, & Jiang, 2010). Gravimetric analysis describes a set of methods for the quantitative determination of a sample or material based on the mass of a solid. Dried solids are weighed with an analytical balance. Accurate weighing of materials can provide precise analysis. Gravimetric analysis provides very little room for instrumental error. It does not require expensive equipment. Extractives were determined by means of the Soxhlet extractor. Acetone of 150 mL was used as the solvent for the extractives on 2.5 g of dried biomass. Solvent extraction was carried out at 70°C for a 4-h run period. The residence time for the rising stage was 25 min. Samples were air-dried at room temperature for few minutes. Constant weight was achieved by drying samples at 105°C in a convection oven. The extractives weight percent, %(w/w) was calculated based on the loss in weight between the dried RB and extracted sample. Mineral components were determined by ashing at 575°C. The hemicellulose content was estimated by placing 1 g of dried biomass from the extractive analysis into a 250-mL Erlenmeyer flask. One hundred and fifty millilitres of 0.5 mol/L NaOH solution was added. The mixture was boiled for 3.5 h with distilled water. Slurry was vacuum filtered after cooling to room temperature and washed (until pH value of solution approached 7). The residue was dried to a constant weight at 105°C in a convention oven after cooling. The difference between the sample weight before and after this treatment is the hemicellulose. Lignin content was estimated by weighing 300 mg of dry biomass in glass test tubes. Three millilitres of a 72% H2SO4 was added to the solid. Acid hydrolysis was made to occur by keeping the samples at room temperature for 2 h with manual mixing of samples every 30 min. Eighty-four milliliters of distilled water was added to each test tube after the 2-h acid hydrolysis step bringing the total volumeto 87 mL. The samples were autoclaved for 1 h at 121°C. After the second weak acid hydrolysis step, the mixtures were cooled to room temperature and filtered through vacuum using a filtering crucible. The acid insoluble lignin was determined by drying the residue at 105°C and accounting for ash by incinerating the hydrolyzed samples at 575°C in a muffle furnace. The acid-soluble lignin fraction was determined by measuring the absorbance of the acid hydrolyzed samples at 320 nm (Sluiter et al., 2008). The cellulose content was calculated by difference, assuming that extractives, hemicellulose, lignin, ash, and cellulose are the only components of the entire biomass. The material balance for the lignin removal (%w/w) and hemicellulose solubilization (%w/w) were estimated based on the following equations: