In this study, a procedure was developed to determine short-chain alkane monocarboxylic acids (SCMAs) in aqueous samples using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography (GC) coupled with mass spectrometry (MS). A Stabilwax-DA capillary column (30 m × 0.32-mm inner diameter, 0.50-μm film thickness) was used for GC separation and a 60-μm poly(ethylene glycol) fiber was used to isolate SCMAs from water and introduce them into the gas chromatograph. Parameters of HS-SPME, analyte desorption, and GC-MS analysis were selected and an analytical procedure was proposed. Limits of quantitation were on the order of about 0.2 mg L-1. As an example of the application of the procedure, SCAMs were determined in municipal wastewater at different steps of treatment.
Low molecular mass carboxylic acids (LCAs) occur in many environmental compartments due to natural processes and human activity. They are an important group of organic pollutants of waste water that mainly includes, volatile fatty acids, and also dicarboxylic, aromatic, hydroxy-and ketoacids. LCAs are present in the environment at concentrations between 1 to 5000 ppm and different methods have been reported for their determination [1]. When volatile and nonvolatile acids are to be monitored then liquid chromatography, including ion chromatography is the method of choice. At high pH the acids are in ionized form and can be separated as carboxylates by means of anion exchange chromatography. LCAs can also be separated at low pH by ion exclusion chromatography or by reverse phase chromatography. Using Dionex-3000 instrument with an Acclaim Organic Acid, OA column dedicated to separation of organic acids the method has been developed to identify selected LCAs. With this analytical tool formic, acetic, propionic, butyric and also citric, malonic, and oxalic acids were measured in waste water from swine and cattle livestock farms.
Abstract-This paper presents overviews the capabilities of capillary electrophoretic techniques to determine low molecular mass organic acids in a variety of aqueous, gas and solid samples. It mainly focuses on short -chain carboxylic acids containing one or more carboxylic groups and possibly some other functional groups (hydroxyl, keto-, amino-etc.). Finally the procedures applied to the determine the acids in different matrices are shortly characterized.The principles of capillary electrophoresis its advantages over gas and liquid chromatographic separation and detection modes are briefly discussed. Finally, the brief overview of the technique is followed by characterization of CE based procedures for the analysis of a variety of samples such as food, environmental, biological etc. for the content of organic acids, mainly those with carboxylic groups.Index Terms-Capillary electrophoresis, low molecular mass organic acids.
Short-chain monocarboxylic acids (SCMAs) (C2-C5) formed in the process of aerobic biodegradation of larger organic molecules should often be monitored to optimize wastewater biological treatment and study the processes of converting organic waste matter into methane, etc. Gas chromatography (GC) seems a method of choice for such a task. Majority of samples require clean up before they can be injected into GC system. In this work a special refluxing apparatus is applied to concentrate and clean up the troublesome environment samples before injection into GC. To optimize separation of SCMAs in aqueous sample a special arrangement of two capillary columns, of very different polarity was used. The operational parameters of sample preparation were optimized and enrichment factors determined. The procedure developed was applied to determine SCMAs in troublesome aqueous and solid samples of wastewater treatment origin.
A research was done to develop procedure of determination of volatile fatty acids (VFAs) in heavily polluted wastewaters using an automated static headspace (HS) unit combined with gas chromatograph (GC) with flame ionization detector (FID). Separation conditions were determined under which VFAs with 2-8 carbon atoms in a molecule separate well on a Stabilwax capillary column. Factors such as sample volume, and time and temperature of sample-HS conditioning have been selected for acetic, propionic, iso-and n-butyric, isoand n-valeric and n-capronic acids in the concentration range 0.1-1000 mg/L. HS conditions were: maintaining the system at 95 o C for 30 min, 2mL sample volume placed in 15 mL extraction vial, acidified to pH 2 and salted out with 0.75 g NaCl. In quantitation better results were obtained when was calibration curve divided to the part close to detection limit and to the part for higher concentrations. Validation process has been started.
In order to determine volatile fatty acids (short chain monocarboxylic acids with 2 to 6 carbon atoms in a molecule) in leachates formed in organic waste piles a procedure based on static headspace (HS) coupled with gas chromatography (GC) have been proposed and optimized. The conditions of HS extraction and sample introduction into a gas chromatograph as well as of chromatographic separation were considered. Using flame ionization detection LODs were of the order of 0.02-0.37 mg/L. The analyzed leachate collecting on and close to a zoo organic waste pile contained VFAs (Volatile Fatty Acids) at a concentration ranging from 5.5 mg/L to 0.88 g/L and from below LOD to 10.1 mg/L for pool water at some distance from the pile, respectively.
Abstract-Solidphase microextraction (SPME) fundamentals, characteristics and application are described. The special stress is put on characteristics of sorbents used as SPME fiber coatings. Description of commercially available fibers and the present-day trends in development of new sorbents for SPME are given. Discussion is focused on possibility of application of ionic liquids (IL) and polymeric ionic liquids (PIL) as SPME fiber coatings. An example of application of PIL coating to determine volatile fatty acids in water is given.Index Terms-Environmental trace organic analysis, chromatography, solid phase microextraction, ionic liquids, polymeric ionic liquids.
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