FT-IR-cPAS—New Photoacoustic Measurement Technique for Analysis of Hot Gases: A Case Study on VOCs

This article describes a new photoacoustic FT-IR system capable of operating at elevated temperatures. The key hardware component is an optical-readout cantilever microphone that can work up to 200 °C. All parts in contact with the sample gas were put into a heated oven, incl. the photoacoustic cell. The sensitivity of the built photoacoustic system was tested by measuring 18 different VOCs. At 100 ppm gas concentration, the univariate signal to noise ratios (1σ, measurement time 25.5 min, at highest peak, optical resolution 8 cm−1) of the spectra varied from minimally 19 for o-xylene up to 329 for butyl acetate. The sensitivity can be improved by multivariate analyses over broad wavelength ranges, which effectively co-adds the univariate sensitivities achievable at individual wavelengths. The multivariate limit of detection (3σ, 8.5 min, full useful wavelength range), i.e., the best possible inverse analytical sensitivity achievable at optimum calibration, was calculated using the SBC method and varied from 2.60 ppm for dichloromethane to 0.33 ppm for butyl acetate. Depending on the shape of the spectra, which often only contain a few sharp peaks, the multivariate analysis improved the analytical sensitivity by 2.2 to 9.2 times compared to the univariate case. Selectivity and multi component ability were tested by a SBC calibration including 5 VOCs and water. The average cross selectivities turned out to be less than 2% and the resulting inverse analytical sensitivities of the 5 interfering VOCs was increased by maximum factor of 2.2 compared to the single component sensitivities. Water subtraction using SBC gave the true analyte concentration with a variation coefficient of 3%, although the sample spectra (methyl ethyl ketone, 200 ppm) contained water from 1,400 to 100k ppm and for subtraction only one water spectra (10k ppm) was used. The developed device shows significant improvement to the current state-of-the-art measurement methods used in industrial VOC measurements

Human hair in the identification of cocaine abuse with cantilever-Enhanced photoacoustic spectroscopy and principal component analysis

In this study, a novel approach combining different techniques, including Fourier transform infrared (FT-IR) spectroscopy, photoacoustic spectroscopy (PAS) with an interferometric cantilever microphone, and principal component analysis (PCA) along with a proper data preprocessing procedure, have been used in the investigation of hair samples for cocaine abuse. Hair fibers from cocaine-overdose patients have been measured using a simple procedure involving cantilever-enhanced photoacoustic Fourier transform infrared spectroscopy. In addition, a reference group of hair samples from subjects with no cocaine abuse has been measured. We present a first approach to discriminate the cocaine users from the reference group with the photoacoustic method and PCA. With proper data preprocessing methods, the two groups were successfully separated according to their spectra. The results were confirmed with two different classification methods independent of the principal component data analysis. </jats:p

Adsorption of As(V), Cd(II) and Pb(II), in multicomponent aqueous systems using activated carbons

This paper studies the use of two activated carbon samples made of cocoa pod husk (CPH-AC) and one commercial activated carbon sample in the adsorption of As(V), Cd(II) and Pb(II) from multicomponent synthetic solutions and from the Puyango-Tumbes River water, a river located in northwest Peru. The characterization of the activated carbon samples was conducted. The CPH-AC samples exhibited a specific surface area (SBET ) between 709 and 1117 m2/g and a pH point of zero charge (pHPZC) between 4.4 ± 0.2 and 5 ± 0.2, while the commercial material gave an SBET value of 775 m2/g and a pHPZC value of 7.6 ± 0.1. All the evaluated samples displayed the capacity to adsorb As(V), Cd(II) and Pb(II) from both aqueous systems. The adsorption efficiency for Pb was outstanding reaching the value of 89%. A pseudo-second order kinetic model was satisfactorily applied for most of the activated carbon samples.Web of Science89985584

Producción de biocarbón a partir de biomasa residual y su uso en la germinación y crecimiento en vivero de Capparis scabrida (Sapote)

Se produjeron biocarbones a partir de tres tipos de biomasa residual: coronta de maíz, cáscara de café y exoesqueleto de langostino, para estudiar la influencia de diferentes dosis de los mismos en la germinación y crecimiento en vivero de semillas de la especie forestal Capparis scabrida (Sapote). Se realizó una exhaustiva caracterización de los biocarbones obtenidos en base a sus propiedades texturales, morfológicas, estructurales y química superficial. Semillas viables de sapote fueron colocadas en sustratos con dosis de 0, 15 y 30 %wt de cada uno de los tres tipos de biocarbones obtenidos y se colocaron en bolsas de 2 kg en condiciones de vivero. Se evaluaron los parámetros de germinación: tiempo y % de germinación; y de crecimiento de las plántulas: crecimiento de raíz y tallo, engrosamiento de tallo, incremento de masa de raíz y parte aérea y la carga microbiana en la raíz. Se determinó que el tipo de biocarbón tuvo influencia solamente en el tiempo de germinación y la dosis de biocarbón tuvo influencia en el incremento de masa de parte aérea durante el crecimiento de las plántulas. El resto de parámetros evaluados no fueron afectados ni por el tipo ni por la dosis de biocarbón

Effect of ultrafiltration on anthocyanin and flavonol content of black currant juice (Ribes nigrum L.)

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Two unconventional precursors to produce ZnCl₂‐based activated carbon for water treatment applications

Abstract Two unconventional raw materials, the seeds from Spondias purpurea L. (red mombin) and Inga edulis (ice cream bean), were characterized and used as precursors to produce good‐quality zinc chloride‐activated carbons for potential use in water treatment applications. The red mombin seed was significantly more porous than the ice cream bean seed, while the activated carbons prepared from red mombin seed and ice cream bean seeds showed both a very well‐established microporous‐mesoporous structure. Equilibrium as well as kinetic adsorption experiments were conducted with methylene blue, methyl orange, and As(V). It was revealed that both seeds are unconventional, renewable, cheap, and suitable agro‐precursors for production of activated carbons with potential application in wastewater treatment