An efficient method for measuring dissolved VOSCs in wastewater using GC-SCD with static headspace technique

Volatile organic sulfur compounds (VOSCs) are important sources of unpleasant odor in wastewater systems. However, the study of VOSCs is usually hindered by their complicated measurement method and highly reactive nature. In this work, a static headspace method utilising gas chromatography (GC) with a sulfur chemiluminescence detector (SCD) was developed to quantitatively analyze VOSCs in wastewater matrices. The method has low detection limits and requires no pre-concentration treatment. Three typical VOSCs, namely methanethiol (MT), dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), were chosen as examples for this study. The calibration curves of all three compounds covering a wide range from 0.5 ppb to 500 ppb showed good linearity (R-2 > 0.999). The method detection limits (MDL) were 0.08, 0.12 and 0.21 ppb for MT, DMS and DMDS, respectively. The reproducibility (relative standard deviation) was approximately 2%. The recovery ratio of MT, DMS and DMDS in spiked wastewater samples were 83 +/- 4%, 103 +/- 4% and 102 +/- 3%, respectively. Sample preservation tests showed that VOSCs in wastewater samples could be preserved in vials without headspace under acidified conditions (pH similar to 1.1) for at least 24 h without significant changes

Volatile Compounds in Honey: A Review on Their Involvement in Aroma, Botanical Origin Determination and Potential Biomedical Activities

Volatile organic compounds (VOCs) in honey are obtained from diverse biosynthetic pathways and extracted by using various methods associated with varying degrees of selectivity and effectiveness. These compounds are grouped into chemical categories such as aldehyde, ketone, acid, alcohol, hydrocarbon, norisoprenoids, terpenes and benzene compounds and their derivatives, furan and pyran derivatives. They represent a fingerprint of a specific honey and therefore could be used to differentiate between monofloral honeys from different floral sources, thus providing valuable information concerning the honey’s botanical and geographical origin. However, only plant derived compounds and their metabolites (terpenes, norisoprenoids and benzene compounds and their derivatives) must be employed to discriminate among floral origins of honey. Notwithstanding, many authors have reported different floral markers for honey of the same floral origin, consequently sensory analysis, in conjunction with analysis of VOCs could help to clear this ambiguity. Furthermore, VOCs influence honey’s aroma described as sweet, citrus, floral, almond, rancid, etc. Clearly, the contribution of a volatile compound to honey aroma is determined by its odor activity value. Elucidation of the aroma compounds along with floral origins of a particular honey can help to standardize its quality and avoid fraudulent labeling of the product. Although only present in low concentrations, VOCS could contribute to biomedical activities of honey, especially the antioxidant effect due to their natural radical scavenging potential

Taking ethanol quality beyond fuel grade: A review

Ethanol production in the United States approached 15 billion gal/year in 2015. Only about 2.5% of this was food‐grade alcohol, but this represents a higher‐value product than fuels or other uses. The ethanol production process includes corn milling, cooking, saccharification, fermentation, and separation by distillation. Volatile byproducts are produced during the fermentation of starch. These include other alcohols, aldehydes, ketones, fatty acids and esters. Food‐grade ethanol is generally produced by wet milling, where starch and sugars are separated from the other corn components, resulting in much smaller concentrations of the impurities than are obtained from fermentation of dry‐milled corn, where cyclic and heterocyclic compounds are produced from lignin in the corn hull. Some of these volatile byproducts are likely to show up in the distillate and these fermentation byproducts in ethanol could cause unpleasant flavours and affect human health if used for human consumption. There is some interest in improving ethanol quality, since human consumption represents a higher value. Advanced purification techniques, such as ozone oxidation, currently used for drinking water and municipal wastewater treatment, offer possibilities for adaptation in ethanol quality improvement. The development of analytical techniques has enabled the detection of low‐concentration compounds and simple quality assurance of food‐grade alcohol. This review includes the most recent ethanol production methods, potential ethanol purification techniques and analytical techniques. Application of such techniques would aid in the development of simplified alcohol production

Optical portable instrument for the determination of CO2 in indoor environments

A portable device based on a colorimetric sensor to determine the atmospheric level of CO2 gas is presented in this work. The system is based on a low-cost, low-power System on a Chip (SoC) microcontroller with integrated Wi-Fi. A user-friendly application was developed to monitor and log the CO2 measurements when the system is connected to a Wi-Fi network. The sensing membrane is directly deposited on the surface of the colour detector, thus reducing the complexity of the system. This sensing membrane is formed by a pH indicator α-naphtholphthalein, tetramethylammonium hydroxide pentahydrate, 1-ethyl-3-methylimidazolium tetrafluoroborate, Tween 20 and hydroxypropyl methylcellulose as the hydrophilic polymer. The system has been fully characterized, obtaining response and recovery times of 1.3 and 2.5 s, respectively, a limit of detection of 51 ppm, and an average resolution of 6.3 ppm. This portable device was applied for the in-situ determination of CO2 gas in the atmosphere inside classrooms in several secondary schools. The measurements were taken during complete workdays and the results were statistically compared with the same measurements taken using a commercially available non-dispersive infra-red (NDIR) device. No significant statistical differences were found between the results obtained using both devices. A complete statistical treatment of the measurements made with the proposed portable device was carried out. The obtained results show that the concentration of CO2 gas in some schools was higher than the desired concentration, with regard to influencing the student's health, safety, productivity and comfort. This demonstrates the need to control this parameter to ensure appropriate indoor environmental quality (IEQ)

New sorbents for desulfurization of diesel fuels via Π-complexation

Desulfurization of a commercial diesel fuel by different adsorbents was studied in a fixed-bed adsorber operated at ambient temperature and pressure. In general, the adsorbents tested for total sulfur adsorption capacity at breakthrough followed the order: AC/Cu(I)-Y > Cu(I)-Y > Selexsorb® CDX (alumina) > CuCl/Γ-Al 2 O 3 > activated carbon > Cu(I)-ZSM-5. The best adsorbent, AC/Cu(I)-Y (layered bed of 15 wt % activated carbon followed by Cu(I)Y), is capable of producing 30 cm 3 of diesel fuel per gram of adsorbent with a weighted average content of 0.15 ppmw-S, and about 20 cm 3 of diesel fuel per gram of adsorbent with a weighted average content of 0.06 ppmw-S. These low-sulfur fuels are suitable for fuel cell applications. The added layer of carbon not only delayed the sulfur breakthrough significantly but also sharpened the sulfur wavefronts. GC-FPD results showed that the Π-complexation sorbents selectively adsorbed highly substituted thiophenes, benzothiophenes, and dibenzothiophenes from diesel, which is not possible with conventional hydrodesulfurization (HDS) reactors. The high sulfur selectivity and high sulfur capacity of Cu(I)Y were because of Π-complexation. © 2004 American Institute of Chemical Engineers AIChE J, 50: 791–801, 2004Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34251/1/10074_ftp.pd

Granica izlaganja formaldehidu u alkoholnim pićima

Formaldehyde has been classified as carcinogenic to humans (WHO IARC group 1). It causes leukaemia and nasopharyngeal cancer, and was described to regularly occur in alcoholic beverages. However, its risk associated with consumption of alcohol has not been systematically studied, so this study will provide the first risk assessment of formaldehyde for consumers of alcoholic beverages. Human dietary intake of formaldehyde via alcoholic beverages in the European Union was estimated based on WHO alcohol consumption data and literature on formaldehyde contents of different beverage groups (beer, wine, spirits, and unrecorded alcohol). The risk assessment was conducted using the margin of exposure (MOE) approach with benchmark doses (BMD) for 10 % effect obtained from dose-response modelling of animal experiments. For tumours in male rats, a BMD of 30 mg kg-1 body weight per day and a “BMD lower confi dence limit” (BMDL) of 23 mg kg-1 d-1 were calculated from available long-term animal experiments. The average human exposure to formaldehyde from alcoholic beverages was estimated at 8·10-5 mg kg-1 d-1. Comparing the human exposure with BMDL, the resulting MOE was above 200,000 for average scenarios. Even in the worst-case scenarios, the MOE was never below 10,000, which is considered to be the threshold for public health concerns. The risk assessment shows that the cancer risk from formaldehyde to the alcohol-consuming population is negligible and the priority for risk management (e.g. to reduce the contamination) is very low. The major risk in alcoholic beverages derives from ethanol and acetaldehyde.Formaldehid je kancerogen za ljude te je klasificiran u skupinu 1 prema WHO IARC-u. Uzrokuje leukemiju i nazofaringealni karcinom, a navodi se i kao redoviti sastojak alkoholnih pića. Međutim, rizik od izlaganja formaldehidu konzumacijom alkoholnih pića nije sustavno istražen pa će ovo istraživanje pružiti prvu takvu procjenu rizika. Količina formaldehida koju ljudi unose alkoholnim pićima u Europskoj je uniji procijenjena temeljem podataka Svjetske zdravstvene organizacije o konzumaciji alkohola i literature o sadržaju formaldehida u različitim skupinama alkoholnih pića (pivo, vino, jaka alkoholna pića i neregistrirani alkohol). Procjena rizika obavljena je korištenjem pristupa granice izlaganja (eng. margin of exposure, MOE) i graničnih doza (eng. benchmark doses, BMD) za 10 %-tni učinak koji se postiže modeliranjem odnosa doza-odgovor u ispitivanjima provedenima na životinjama. BMD od 30 mg kg-1 tjelesne težine na dan i BMD s nižom granicom pouzdanosti (BMDL) od 23 mg kg-1 d-1 izračunati su za tumore kod mužjaka štakora temeljem raspoloživih dugotrajnih ispitivanja provedenih na životinjama. Prosječno izlaganje ljudi formaldehidu u alkoholnim pićima procijenjeno je na 8·10-5 mg kg-1 d-1. U usporedbi s BMDL vrijednošću krajnji MOE je iznosio više od 200.000 u prosječnim situacijama. Čak i u najlošijim situacijama MOE nije nikada bio niži od 10.000, što se smatra graničnom vrijednošću za zdravlje ljudi. Procjena rizika pokazuje da je rizik od nastanka karcinoma uslijed izlaganja formaldehidu iz alkoholnih pića zanemariv te da je prioritet upravljanja rizikom u takvim slučajevima (npr. kako bi se smanjila kontaminacija) vrlo nizak. Najveći rizik proizlazi iz etanola i acetaldehida koji se također nalaze u alkoholnim pićima