Selected ion chromatograms and tandem mass spectrometry for detection of trace polycyclic aromatic hydrocarbons in diesel exhaust

Polycyclic aromatic hydrocarbon (PAH) measurements are essential for scientists and engineers who investigate these anthropogenic compounds. Diesel engines contribute to the problem, so analysts are measuring PAHs from these sources. However, diesel exhaust presents special problems for precise analytical measurements. The exhaust matrix is very complex; consequently, PAH detection sensitivity deteriorates, especially for trace PAHs in the exhaust. Yet, these are conditions and amounts that exist in real samples. Nonetheless, selected ion chromatogram (SIC) and tandem mass spectrometry (MS/MS) techniques improve trace PAH detection; ion trap technology makes both mass techniques possible. The purpose of this investigation was to evaluate SIC and MS/MS for applications to measure PAHs in diesel exhaust samples. The signal-to-noise ratio for accurate quantitation improves, relative to traditional mass techniques, because these techniques ignore or eliminate interfering components. On a VF-5MS chromatographic column, these techniques improve sensitivity and reproducibility. They produce a superior limit of detection in the useful range for PAH samples extracted from actual engine exhaust, 10-30 pg for the smaller PAHs and 1-6 ng for the larger PAHs. The results with SIC and MS/MS are reproducible, so analysts can report PAH amounts with defined statistical confidence intervals. SIC and MS/MS improve detection for trace PAHs in convoluted diesel exhaust samples.     

Voluntary GHG management using a life cycle approach. A case study

Voluntary GHG management is a primary issue for many organizations. To support organizations with this activity, authoritative bodies have published many different guidelines. Nevertheless, these guidelines show limitations in identification of the direct and indirect processes that have a major impact on climate change, which should be considered in GHG management.In this paper, a life cycle approach is used to identify the processes of an organization and its supply chain that have major impacts on climate change. The results show that this approach is compatible with the current ISO standards and that in the case study the greatest emissions come from the organization’s indirect processes.     

Comparison of different methods for extraction of polycyclic aromatic hydrocarbons (PAHs) from Sicilian (Italy) coastal area sediments

This paper describes a work aimed at improving the conditions of an extraction method, coupling GC-MS determination, for the analysis without cleanup phase, of polycyclic aromatic hydrocarbons (PAHs) from sediment samples. The automatic Soxhlet extraction in warm mode (using Extraction System B-811 Standard, Büchi) has demonstrated advantages for automation, reduced extraction time, and lower solvent use than for conventional Soxhlet extraction. Under these conditions, the recoveries are very good as they resulted greater than 85 % and, in most of the cases, near 100 %. The repeatability is also satisfactory (relative standard deviation less than 15 %). The detection limits are also acceptable and ranged from 0.001 to0.01 μg/kg dry weight. Fifty-four sediment samples were collected. The total concentration of the 17 compounds investigated, in samples of sediments collected from three Sicilian coastal areas, expressed as the sum of concentrations, varies from 99 to 11,557 μg/kg of dry matrix; concentrations of total PAHs in the sediments of Cala are two to three times higher than the other stations.     

Noninvasive prenatal diagnosis in a family at risk for Fraser syndrome

The front cover image is based on the Research Letter Noninvasive prenatal diagnosis in a family at risk for Fraser syndrome by Aldesia Provenzano et al., https://doi.org/10.1002/pd.5700 .

     

OPTIMAL MANAGEMENT AND DESIGN OF HYDRAULIC SYSTEMS1

ABSTRACT: A possible methodology is developed to deal with the problem of designing complex pipeline systems, when they are subject to different rates of demand, and when a hypothesis of the flow distribution in different branches is not allowed. The mathematical algorithm used in linear programming. The problem, which is not linear, is dealt with by means of an iterative method; that is, by starting with a possible solution and inserting at each iteration the solution found in the preceding iteration. By taking as variables of the problem the piezometric heads of the ends for each branch of the network, the piezometric gradients and flows, and by thus considering the diameter as a derived variable, it is possible to isolate the nonlinearity in the cost function of the network. The latter is linearized each time close to the solution found in the preceding iteration.