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In this work, we present the development of a method for the determination of acetate and formate in vegetable oils by ion chromatography with conductometric detection following their extraction from samples using a diluted KOH solution. The extraction procedure was optimized using a multivariate approach. The application of a 2 4 full factorial design showed that the mass of sample, extraction time, and KOH concentration presented significant influence on the extraction of both acetate and formate, whereas the temperature presented little influence on the process. As a result, we set the extraction temperature at 22 °C and performed the multivariate optimization of the other variables using a Doehlert design. The optimum conditions were: 4.8 g of sample, 8 mmol L -1 KOH solution and 19 min extraction time. Six samples of vegetable oils (soybean, corn, canola, sunflower and olive) were analyzed and recovery tests provided recovery percentages in the range of 82-118%., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A 'missing source' of atmospheric formic acid is consistently observed during model-measurement comparisons, and evidence from multiple environments suggests a near-surface source. Soil emissions are considered to be a small formic acid source, but estimates are based on a single study from a tropical site. Here, we investigate soil emissions of organic acids from two soils - a ponderosa pine forest (Manitou Experimental Forest Observatory), and a managed lawn (Colorado State University) using a laboratory chamber. Both soils are a source of formic and acetic acids. Under ambient conditions, formic acid emissions are 0.11 (pine forest) and 0.15 (lawn) nmol m-2 s-1, and acetic acid emissions are 0.05 (pine forest) and 0.71 (lawn) nmol m-2 s-1. Only acetic acid emissions from the forest site correlate with CO2 fluxes, but all formic and acetic acid emissions increase exponentially with temperature. Increasing soil moisture only enhances acetic acid emissions from the forest. Considering this temperature and moisture dependence, we hypothesize that while equilibrium partitioning may contribute to the forest emissions, organic acid emissions from the lawn are likely driven by microbial activity. Lactic acid was emitted from both soils, but not quantified. The observed formic acid emissions are higher than previous measurements, but still low enough that soils are unlikely the 'missing source' of atmospheric organic acids, although the variability in the soil source is substantial. We contrast observations to previous parameterizations used in models, and present recommendations for modified parameterizations for formic and acetic acid emission.

Spatial trends of acetate (Ac - ) and formate (Fo - ) were determined in surface snow samples along a coastal-inland transect (180km) in the ice cap region at Princess Elizabeth Land and along a coastal transect in the Amery Ice Shelf (130km), East Antarctica. Variations in both Ac - and Fo - seem to be unrelated to the acidity of snow. Ionic balance determined for the snow samples indicate the availability of HNO 3 that could undergo photolysis to produce hydroxyl radical (OH), one of the major reactants involved in oxidation reactions with organic matter. The strong positive correlations between Ac - and NO 3 - in snow from both regions indicate that NO 3 - mediated OH-oxidation of organic compounds in snow could be an important source of Ac - within the snowpack. On the other hand, negative correlation between Fo - and NO 3 - might indicate that sources other than OH-oxidation of organic matter may be dominant in the case of Fo - . Higher Ac - concentrations in the ice cap compared to the ice shelf correspond with long-range transport of biomass burning emissions to the ice cap region. Interaction of Ac - and Fo - with alkaline minerals could lead to their stability in the snowpack and minimize their loss from the snow surface. Resident microbial communities could also influence the budget of the carboxylic acids in snow., (Copyright © 2017. Published by Elsevier B.V.)

Formic and acetic acids are ubiquitous in the environment and in many biological processes. Analysis of the stable carbon isotope composition (δ(13)C) of formic and acetic acids is important to understanding their biogeochemical cycles. However, it has been faced with poor accuracy and high detection limits due to their low carbon number, high hydrophilicity, and semi-volatility. Here we developed an analytical technique by needle trap and gas chromatography-isotope ratio mass spectrometry (GC-IRMS). The organic acids in aqueous solution were extracted using a NeedlEx needle through purge-and-trap and were analyzed by GC-IRMS for δ(13)C. The procedures incur no isotope fractionation. Defined as the point at which the mean δ(13)C is statistically the same as the given value and the analytical error starts rising, the method's detection limits are 200 and 100 mg/L for formic and acetic acids, respectively, with an uncertainty of approximately 0.5‰ in direct extraction and analysis. They were lowered to 1 mg/L with precision of 0.9‰ after samples were subjected to preconcentration. The method was successfully applied to natural samples as diverse as precipitation, vinegars, ant plasma, and vehicle exhaust, which vary considerably in concentration and matrix of the organic acids. It is applicable to the organic acids in not only aqueous solution but also gaseous phase., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Formic and acetic acids are ubiquitous in the environment, food, and most of the natural products. Extraction of the acids from aqueous solution is required for their isotope analysis by the gas chromatography-isotope ratio mass spectrometry. To this objective, we have previously developed a purge-and-trap technique using the dynamic solid-phase microextraction technology, the NeedlEX. The extraction efficiency, however, remains unexamined. Here, we address this question using the flame ionization detector and isotope ratio mass spectrometer while comparing it with that of the CAR/PDMS fiber. The results show that the NeedlEX is applicable at a wide range of concentration through coordination of purge volume given the minimum amount 3.7 ng and 1.8 ng of formic and acetic, respectively, is extracted. The efficiency of NeedlEX was 6-7 times lower than the fiber at 1000 μg/mL depending on the analyte. It is, however, superior to the latter at 10 μg/mL or less owing to its lower detection limit. The extraction efficiency of both acids is equivalent in molar amount. This is, however, disguised by the different response of the flame ionization detector. The isotope ratio mass spectrometor overcomes this problem but is compromised by relatively large errors. These results are particularly useful for isotopic analysis of carboxylic acids., (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

To investigate the concentrations of organic acids in precipitation in China and their contributions to the total acidity of precipitation, samples were taken at 14 stations of regional representativeness in 2007 and analyzed for acetate and formate using ion chromatography. In this paper, data of acetate and formate in precipitation at 14 stations are presented, wet depositions of these organic acids are calculated, and contributions of them to the total free acidity (TFA) of precipitation are estimated. Based on the measurements, the mean concentrations of formate at different stations were in the range of 0.96-3.43 micromol/L, and those of acetate in the range of 0-5.13 micromol/L, close to the levels at remote sites in other countries and at the lower ends of concentration ranges from previous measurements in China. Comparisons indicate that the concentrations of the organic acids at remote sites are lower than those at sites in the vicinity of urban areas. The annual wet depositions of formate and acetate were estimated to be in the ranges of 0.38-4.18 mmol/(m2 x a) and 0.06-5.87 mmol/(m2 x a), respectively, with larger depositions in southern China and smaller depositions in northern China. The relative contributions of the two organic acids to the TFA of precipitation were estimated to be in the range of 0.02%-51.6%, with an overall average of 2.95%. This suggests that although acid rain in China is mainly caused by emissions of sulfur and nitrogen oxides, organic acids can significantly contribute to the acidification of precipitation in some regions and during some periods, hence need to be included in observational studies of acid rain.

A combined method of dynamic headspace-needle trap sample preparation and gas chromatography for the determination of formic and acetic acids in aqueous solution was developed in this study. A needle extraction device coupled with a gas aspirating pump was intended to perform sampling and preconcentration of target compounds from aqueous sample before gas chromatographic analysis. The needle trap extraction (NTE) technique allows for the successful sampling of short chain fatty acids under dynamic conditions while keeping the headspace (HS) volume constant. Two important parameters, including extraction temperature and effect of acidification, have been optimized and evaluated using the needle trap device. The method detection limits for the compounds estimated were 87.2microg/L for acetic acid and 234.8microg/L for formic acid in spite of the low flame ionization detection response for formic acid and its low Henry's law constant in aqueous solution. Precision was determined based on the two real samples and ranged between 4.7 and 10.7%. The validated headspace-needle trap extraction method was also successfully applied to several environmental samples.

The effect of glucose concentration as a carbon source in the range of 5-20 g/L on the fermentative productions of intra-and extra-cellular ethanol, acetate, formate, oxalate, lactate, and pyruvate, as well as pyruvate decarboxylase in A. orientalis were investigated, depending on the incubation period. Intra-and extra-cellular pyruvate levels increased with rising glucose concentrations up to 15 and 20 g/L of glucose, respectively. In addition, intra-cellular pyruvate levels reached their maximum on the 48th hour in the range of 12.5-20 g/L of glucose, except for 5 and 10 g/L while extra-cellular pyruvate were at the 48th and 60th hours. As a fermentative end product, intra-and extra-cellular ethanol levels increased with increasing glucose concentrations of the growth medium and with incubation period. Activity of pyruvate decarboxylase, one of the key enzymes of the alcoholic fermentation, increased significantly with increasing glucose concentrations up to the 48th hour. Intra-and extra-cellular acetate levels increased significantly with increasing glucose concentrations of the growth medium and reached their maximums on the 48th hour, as was the case also for pyruvate. Intra-cellular formate levels increased up to 15 g/L, while extra-cellular levels increased with increasing glucose concentration. The maximum intra-and extra-cellular lactate levels were determined at 12.5 g/L and 20 g/L of glucose on the 48th hour, respectively. The results suggest that elevated ethanol production suppressed lactate and formate production, supported via possibly formed CO(2). In addition, pyruvate, as well as acetate, were used as carbon sources due to the depletion of glucose contents in the growth medium.

Paenibacillus polymyxa ATCC 12321 produced more acetic acid and less butanediol from xylose than from glucose. The product yields from xylose were ethanol (0.72 mol/mol sugar), (R,R)-2,3-butanediol (0.31 mol/mol sugar), and acetate (0.38 mol/mol sugar) while those from glucose were ethanol (0.74 mol/mol sugar), (R,R)-2,3-butanediol (0.46 mol/mol sugar), and acetate (0.05 mol/mol sugar). Higher acetate kinase activity and lower acetate uptake ability were found in xylose-grown cells than in glucose-grown cells. Furthermore, phosphoketolase activity was higher in xylose-grown cells than in glucose-grown cells. In fed-batch culture on xylose, glucose feeding raised the butanediol yield to 0.56 mol/mol sugar and reduced acetate accumulation to 0.04 mol/mol sugar.

Simultaneous indoor and outdoor measurements of organic acids were made at six residential houses located in a suburban New Jersey area during the summer of 1992. Each house was measured for six days and controlled for ventilation and gas combustion conditions. The study presents the first set of simultaneous measurements of formic and acetic acid in indoor and outdoor air. The concentrations of formic acid were 1.24 +/- 1.17 ppb outdoors and 8.77 +/- 4.67 ppb indoors. The concentrations of acetic acid were 3.05 +/- 3.63 ppb outdoors and 23.97 +/- 16.20 ppb indoors. The higher indoor concentrations indicated the presence of significant indoor sources such as direct emissions and indoor chemical formation. However, the results indicated that organic acids indoors were not likely to be emitted from indoor gas combustion. The study also collected temperature, humidity, ozone, aldehyde, and nitrogen dioxide data, and provided the supporting evidence for indoor chemical reaction pathways leading to organic acid formation.

The dynamics of acid production in 18 strains of bifidobacteria, belonging to 5 different species, has been studied Bifidobacteria have been found to produce 3 acids, lactic, acetic and formic, in the process of their metabolism. The lactic acid/acetic acid quantitative ratio varies, depending on the culture medium on the average, 1:2 in Blaurock medium, 1:5 in milk hydrolysate medium. Various strains have also been found to differ in the dynamics of acid production with respect to the amounts of lactic and acetic acids. The study has shown that, despite the active production of acids for a period of up to 72 hours, a decrease in the pH of the medium is observed for not more than 48 hours. The existence of a specific mechanism permitting bifidobacteria to regulate the acidity of their environment is supposed.

A gas chromatographic (GC) method is presented for the specific determination of acetic acid in air. Air samples are collected in fritted midget bubblers containing aqueous sodium carbonate. Aliquots of the absorbent solution are esterified and GC analysis performed on the headspace. The formation of the ester is directly proportional to the concentration of the acetic acid concentration in the absorbent. The method is applicable to concentrations of acetic acid in air over the range of 2.0 mg/m3 to 75 mg/m3, and can be extended to include higher concentrations by quantitative dilution of samples.