Aqueous matrices

Hobbins, W. B. Direct Determination of Phosphorus in Aqueous Matrices by Atomic Absorption Varian Instruments at Work, Number AA-19, Eebruary 1982. 

Hummel D, Loffler D, Fink G, Temes TA (2006) Simultaneous determination of psychoactive drugs and their metabolites in aqueous matrices by liquid chromatography mass spectrometry. Environ Sci Technol 40 7321-7328... 

To date most of the work which has been done with supercritical fluid extraction has concentrated on the extraction of analytes from solid matrices or liquids supported on an inert solid carrier matrix. The extraction of aqueous matrices presents particular problems [276-278]. The co-extraction of water causes problems with restrictor plugging, column deterioration, and phase separation if a nonpolar solvent is used for sample collection. Also, carbon dioxide isay have limited extraction efficiency for many water soluble compounds. 

Classical LLEs have also been replaced by membrane extractions such as SLM (supported liquid membrane extraction), MMLLE (microporous membrane liquid-liquid extraction) and MESI (membrane extraction with a sorbent interface). All of these techniques use a nonporous membrane, involving partitioning of the analytes [499]. SLM is a sample handling technique which can be used for selective extraction of a particular class of compounds from complex (aqueous) matrices [500]. Membrane extraction with a sorbent interface (MESI) is suitable for VOC analysis (e.g. in a MESI- xGC-TCD configuration) [501,502]. 

Whereas SPE is a sample cleanup method, SPME is essentially a solvent-free sampling method. Stir bars in hyphenated SBSE-TDS-CGC configuration for product control analysis are a powerful tool for the extraction and analysis of organic compounds in aqueous matrices. 

Several analytical methodologies have been developed and implemented in the past few years to determine the levels of these substances in diverse aqueous matrices, e.g., wastewater and surface water [5-21], Studies in this line have been performed so far in the United States [5,10,15,22,23] and in several European countries such as Italy [9, 18, 21, 24, 25], Switzerland [9, 25], the United Kingdom[21, 25-28], Belgium [29, 30], Ireland [8], Germany [14], and Spain [6, 7, 12, 13, 19, 31-34],... 

The frequency of detection of each investigated analyte in the different aqueous matrices and the levels at which the studied classes of illicit drugs and metabolites... 

Fig. 2 Frequency of appearance of each investigated illicit drug and metabolite in the various studied aqueous matrices...

Fig. 4 Range of concentrations determined for each analyte in the different investigated aqueous matrices. For those analytes detected only once in a specific matrix (e.g., nor-LSD and cannabi-noids), the concentration range expands from the method limit of determination to the only positive value reported...

The trend of discovering the analytical field of environmental analysis of surfactants by LC-MS is described in detail in Chapters 2.6-2.13 and also reflected by the method collection in Chapter 3.1 (Table 3.1.1), which gives an overview on analytical determinations of surfactants in aqueous matrices. Most methods have focused on high volume surfactants and their metabolites, such as the alkylphenol ethoxylates (APEO, Chapter 2.6), linear alkylbenzene sulfonates (LAS, Chapter 2.10) and alcohol ethoxylates (AE, Chapter 2.9). Surfactants with lower consumption rates such as the cationics (Chapter 2.12) and esterquats (Chapter 2.13) or the fluorinated surfactants perfluoro alkane sulfonates (PFAS) and perfluoro alkane carboxylates (PFAC) used in fire fighting foams (Chapter 2.11) are also covered in this book, but have received less attention. 

The present chapter provides an overview of methods currently used for extracting and concentrating surfactants from aqueous matrices. Some of the techniques will be addressed only briefly, because they are discussed elsewhere in this book more extensively. 

With the aim of minimising the time taken in the preconcentration, and extending the chemical analysis of surfactants to more complex aqueous matrices in which very low detection limits are required, preconcentration techniques using solid-liquid extraction with various adsorbent materials, such as XAD [27] and anionic exchange resin [28] have been developed. 

Z. Wang, M. Ashraf-Khorassani and L.T. Taylor, On-line coupling of supercritical C02 extraction with reversed-phase liquid chromatography for the quantitative analysis of analytes in aqueous matrices. J. Chromatogr.A 1033 (2004) 221-227. 

Young and Weber [397] presented an equilibrium and rate study of analyte-matrix interactions in SFE in aqueous matrices, while correlation of SFE with supercritical fluid chromatography (SFC) in aqueous media has been reported by Yu et al. [398]. Tena et al. [399] screened PAHs in soil by on-line fiber-optic-interfaced SFE spectrometry. 

Bauer S, Solyom D. 1994. Determination of volatile organic compoimds at the parts per trillion level in complex aqueous matrices using membrane introduction mass spectrometry. Anal Chem 66(24) 4422-4431. 

Cadmium in acidified aqueous solution may be analyzed at trace levels by various instrumental techniques such as flame and furnace atomic absorption, and ICP emission spectrophotometry. Cadmium in solid matrices is extracted into aqueous phase by digestion with nitric acid prior to analysis. A much lower detection level may be obtained by ICP-mass spectrometry. Other instrumental techniques to analyze this metal include neutron activation analysis and anodic stripping voltammetry. Cadmium also may be measured in aqueous matrices by colorimetry. Cadmium ions react with dithizone to form a pink-red color that can be extracted with chloroform. The absorbance of the solution is measured by a spectrophotometer and the concentration is determined from a standard calibration curve (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). The metal in the solid phase may be determined nondestructively by x-ray fluorescence or diffraction techniques. 

It is a little difficult to relate these observations of phosphorescence in low-temperature matrices (which in both cases are composed of molecules which at room temperature photoreact with the pyrimidines) to the observed photochemical reactions. The fluorescence of the pyrimidines in frozen aqueous matrices may be weak because the excited molecules are quenching each other reactively—an argument strengthened by the observation110 that addition of ethanol to the solution strengthens the phosphorescence but prevents dimer formation.29 No clear-cut conclusions can yet be provided by these studies. 

Quantitative extraction of di- and tributyltin compounds from aqueous matrices is demonstrated for the first time (Alzaga and Bayona, 1993). 

Solid waste matriees Solvent extraction or direct injection (with azeotropic distillation) into capillary GC column GC/FID 9-21 pg/L (aqueous matrices) 0.08-0.20 mg/kg (solid matrices) Environmental Protection Agency (1996a) [Method 8015B]... 

In order to investigate hole and electron transfer we have employed a number of techniques to produce holes and electron adducts within DNA [7]. These trapped ion radical species of DNA are produced by y- or UV-irradia-tion at 77 K of DNA in various aqueous matrices. Each technique employed produces specific radical species. 

Supercritical fluids, in general, are inexpensive, contaminant-free, and less costly to dispose of safely than conventional organic solvents. Extracts are obtained under mild conditions that minimize thermal degradation, they are usually solvent-free or in a concentrated form, and no evaporation steps are needed prior to the final assay. However, the disadvantages of SFE should not be also ignored. As with all extraction methods, there are analytes and matrices for which SFE is not suitable. Some compounds are insoluble and may need solvent extraction. Aqueous matrices can cause problems and samples may need to be freeze-dried. Like all single-step extractions, SFE has only limited selectivity, but some distinction can be made between analytes by careful selection of temperature and pressure. 

Porschmann, J., Z. Zhang, F.-D. Kopinke, and J. Pawliszyn, Solid-phase microextraction for determining the distribution of chemicals in aqueous matrices , Anal. Chem., 69, 597-608 (1997). 

M Company (2001a) Kow (Solubility in Water, Natural Seawater, An Aqueous Solution of 3.5% Sodium Chloride, and n-Octanol with Subsequent Calculation of the n-Octanol Water Partition Coefficient (Kow) of PFOS for each of the Aqueous Matrices). USEPA Docket No. AR226-1030a031... 

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