Quantification Of Chemicals Research Articles

Laboratory‐scale Assessment of Chemical Sprays using Dynamic Olfactometry

Dynamic olfactometry enables odour quantitation. Presentation of odorous air to human panellists necessitates a comprehensive risk assessment to ensure that panellist health and safety is not compromised. Assessment of odour of samples derived from sprayed pesticide formulations required a three-stage process: i. Review of information for all product components to identify health risks; ii. Identification and quantification of volatile chemicals in samples destined fo olfactometry, iii. Determination of odour concentration by dynamic olfactometry. The odour strength of air samples derived from commercially available pesticide materials was assessed following spray application in a spray chamber. Measured odour concentrations were combined with application rates and flushing rates to derive specific odour emission rates, thus enabling comparison of odour strength on the basis of the amount of active ingredient in each material sprayed.

Mass spectrometric strategies for the analysis of polar industrial chemicals and their by-products in wastewater and surface water

Various mass spectrometric techniques, such as gas chromatography (GC)–mass spectrometry (MS) after derivatization, liquid chromatography–electrospray ionization (LC–ESI) MS and ESI-time of flight (TOF)-MS have been applied to the determination of, in general substituted, polar organic sulfonates. Methods were developed for the rapid quantification of such industrial chemicals in wastewater effluents and surface water, as required following spills leading to unusually high emissions into the river Rhine, Germany. Using these methods, the tonnage of methylsulfamido-antipyrin, an intermediate of the pain reliever metamizole synthesis, and 3-nitro-benzenesulfonate could be directly calculated without time-consuming enrichment or clean-up procedures. Thereby a significant increase in sensitivity was achieved by switching a cation suppressor between LC and MS. But still, the evaluation and identification of more complex chemical structures of formerly unknown substituted and halogenated by-products of 2-chlorotoluene methylsulfon-synthesis in wastewater was only possible through the combined interpretation of the GC– and LC–ESI mass spectra and with the additional information obtained from application of ESI-TOF-MS to the samples.

QUANTIFICATION OF 14C-LABELED HYDROPHOBIC ORGANIC COMPOUNDS IN SOIL SAMPLES BY A SCINTILLATION FLUID EXTRACTION METHOD

Hydrophobic organic chemicals labeled with 14C are often used as tracers to study chemical fate and transport in soil. Wet oxidation is the recognized but labor-demanding method used most often to measure the concentration of radioactive organic tracers in the soil. In this study, we test an alternative, simpler method for quantification of 14C-labeled hydrophobic organic chemicals in soil samples. The soil samples were extracted directly with scintillation fluid in glass scintillation vials (Scintillation Fluid Extraction, SFE method) and were subsequently analyzed by liquid scintillation counting. Application of internal standards showed no significant quenching or reduced counts of the 14C-labeled chemical caused by the presence of settled soil particles in the scintillation vials. Hence, the scintillation fluid could be used simultaneously as both scintillation and extraction media. Decreasing the amount of soil containing 14C-labeled chemicals added to the scintillation vial was shown to increase the extraction efficiency of the SFE method. Aging (contact time) and concentration were shown to affect the results of the SFE method. However, in a naphthalene diffusion experiment, where aging varied between almost no contact time and 20 days and concentration of naphthalene varied between ∼0 to 40 μg g−1, the estimated naphthalene diffusion coefficient was shown to be influenced only minimally when using the SFE method compared with the wet oxidation method. We emphasize that the SFE method is applicable only to sterile systems with no degradation or assimilation of 14C-labeled compounds. If this condition is met and there is appropriate consideration of the effects of chemical aging and concentration, the SFE method seems to be a useful and labor-saving alternative to the traditional wet oxidation method for determination of the concentration of 14C-labeled organic chemicals in soil samples.

Quantification of Synthetic Organic Chemicals in Biological Treatment Process Effluent Using Solid-Phase Microextraction and Gas Chromatography

Solid-phase microextraction (SPME), a technique that uses a polymer-coated, fused-silica fiber to selectively extract organic analytes from a sample matrix, followed by gas chromatography (GC), was used to quantify selected synthetic organic chemicals (SOCs) in biological reactor effluent. By selecting an appropriate combination of SPME fiber, GC column, and GC detector, assays to quantify either a suite of SOCs or single selected SOCs were developed. Phenol, 4chlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4,-dinitrophenol, isophorone, m-toluate, m-xylene, and di-n-butylphthalate were quantified simultaneously using an 85- m polyacrylate SPME fiber, a 5% diphenyl–95% dimethyl polysiloxane capillary column, and a flame ionization detector. m-Xylene was quantified using a 100- m polydimethylsiloxane SPME fiber, a 5% diphenyl–95% dimethyl polysiloxane capillary column, and a mass spectrometric detector. Dichloromethane was quantified using an 85- m polyacrylate SPME fiber, a Carbopack B/1% SP-1000 packed column, and an electron capture detector. All three assays enabled detection of the target analytes to low concentrations (g/L) with minimal sample volume and processing requirements.

Identification and quantification of toxic chemicals by use of Escherichia coli carrying lux genes fused to stress promoters.

The luxCDABE bioluminescence genes of the Vibrio fischeri lux system have been used as a reporter system for different stress and regulatory promoters of Escherichia coli. Selected E. coli strains carrying lux genes fused to different promoters were exposed to various toxic chemicals, and the recorded luminescence was used for the characterization of the biologic signature of each compound. Analysis of these data with the aid of a proper algorithm allowed quantitative and qualitative assessment of toxic chemicals. Of the 25 tested chemicals, 23 were identified by this novel strategy in a 3-h procedure. This system can also be adapted for the identification of simple mixtures of toxic agents when the biologic signatures of the individual compounds are known. This biologic recognition strategy also provides a tool for evaluating the degree of similarity between the modes of action of different toxic agents.

Application of a multivariate technique to Raman spectra for quantification of body chemicals

Raman spectroscopy is a highly specific technique for the identification of molecules by way of the associated characteristic spectra. The aim of this feasibility study is to assess the combination of the multivariate calibration technique of Partial Least-Squares with Raman spectroscopy for the estimation of glucose, lactic acid, and urea concentrations in the presence of each other in a water substrate. The instrument is a CCD-based Raman spectrometer utilizing the 514.5 nm argon laser line. The estimates for the analyte concentrations yielded a standard deviation of concentration residuals of 20.71 mg/dL for glucose, 12.92 mg/dL for lactic acid, and 19.07 mg/dL for urea.

The Jülich environmental specimen bank

The environmental specimen bank of the Federal Republic of Germany represents the modern form of a systematically designed archive for the preservative storage of selected environmental specimens. Major aims of environmental specimen banks are: (i) retrospective identification and quantification of environmental chemicals including those not known at the time of storage; (ii) retrospective replicate analysis of samples stored under preservative conditions for the determination of inorganic elements or organic compounds already examined; and (iii) retrospective control of the success of legislative environmental protection measures in handling chemicals regarded as hazardous for man and the environment. Results of the environmental specimen bank at Jülich by the Institute of Applied Physical Chemistry, Research Centre Jülich, KFA, obtaining the initiated legislative regulations providing environmental pollution, are already proved for various compartments.