Extraction from environmental matrices

The examples described in this section 10.6.1 constituted the first report ever of ill situ reaction-extraction work involving foodstuffs. We had reported earlier on a related approach in a different field, namely a derivatisation-extraction procedure whereby phenols and methylated phenols were acetylated-extracted from environmental matrices in a one-step MAP procedure (15). The latter procedure, however, was performed under much harsher conditions that could not be used with foodstuffs where the potential of creating artefacts is a prime concern. This approach of one-pot, multiple-step procedures opens the avenue to numerous applications of direct interest to the food analysts and are especially versatile and valuable when using microwave-assisted extraction performed in open-vessel systems. This, along with solvent-less extraction (such as MAP gas-phase applications ) is believed... 

As in other techniques, SF extracts are not always free of unwanted matrix components. A number of clean-up methods have been used with and after the extraction step to overcome this problem. Sample clean-up is mandatory with fat-soluble analytes. On the other hand, neat supercritical CO, extracts from environmental samples are often clean enough for direct injection into a gas chromatograph [17]. 

From sx the 95% confidence interval on the estimate may be determined by multiplication by the appropriate /-value (/o.o5",n-2)-Standard addition is used when there are potential interferents that would lead to a systematic error that is proportional to concentration. Calculation of the concentration by the standard addition method causes these errors in the measurements to cancel. It is also useful if the analyte cannot be extracted from its matrix, and there is not a matrix matched calibrant available. This may be the case in environmental analysis. Note, however, that standard addition does not compensate for a constant additive interferent. 

Prior to their separation by GC, organolead compounds need to be extracted from the sample matrix and, if necessary, derivatized into a volatile and thermally stable form. Volatile nonpolar tetraalkyl compounds can be extracted from environmental samples with nonpolar solvents such as benzene or hexane and injected directly onto the gas chromatograph. The case of nonvolatile, ionic alkyl compounds (R2Pb and RsPb ) is more complex. They should first be extracted and preconcentrated in the presence of NaCl and sodium diethyldithiocarbamate and then derivatized into a volatile form. The most widespread derivatization methods are of two distinct types those based on the use of tetraalkylborates that can be directly performed in the aqueous solution (ethylation and propylation) and those applying... 

Like plasma and urine, matrixes from plant or environmental sources contain a vast diversity of components. Thus, achiral-chiral LC-LC is also useful for analysis involving samples from these sources. Stalcup et al. (1991) studied the enantiomeric purity of scopolamine extracted from Datura sanguinea in both homogenized plant leaves and commercial extracts. A reverse-phase separation on a C j g column separated the scopolamine from other alkaloid and matrix components while the enantiomeric separation (also in the reverse-phase mode) was carried out on two coupled [3-cyclodextrin columns or a single acetylated (3-cyclodextrin column. The single... 

The qualitative determination of anionic surfactants in environmental samples such as water extracts by flow injection analysis coupled with MS (FIA-MS) applying a screening approach in the negative ionisation mode sometimes may be very effective. Using atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI), coupled with FIA or LC in combination with MS, anionic surfactants are either predominantly or sometimes exclusively ionised in the negative mode. Therefore, overview spectra obtained by FIA—MS(—) often are very clear and free from disturbing matrix components that are ionisable only in the positive mode. However, the advantage of clear... 

Soxhlet, sonication, supercritical fluid, subcritical or accelerated solvent, and purge-and-trap extraction have been introduced into a variety of methods for the extraction of contaminated soil. Headspace is recommended as a screening method. Shaking/vortexing is adequate for the extraction of petroleum hydrocarbons in most environmental samples. For these extraction methods, the ability to extract petroleum hydrocarbons from soil and water samples depends on the solvent and the sample matrix. Surrogates (compounds of known identity and quantity) are frequently added to monitor extraction efficiency. Environmental laboratories also generally perform matrix spikes (addition of target analytes) to determine if the soil or water matrix retains analytes. 

Concentration Methods. The GCMS analysis of an environmental sample starts with the isolation of the organic compounds from the matrix (air, water, food, etc.) into a form suitable for introduction into the GCMS instrument, typically a solution in a volatile solvent. This concentration step includes essentially three major methods vapor stripping, solvent extraction, and lipophilic adsorption. We have recently reviewed the detailed operation of these methods (Ij, (See also Bellar, Budde and Eichel-berger, this volume) but their general features will be outlined here. 

Detecting and identifying toxic compounds in environmental samples (compounds with unknown structures and properties) require the use of time-consuming, costly methods to isolate them from the matrix, then the application of complex techniques to separate the compounds present in an extract, and finally the determination of their structure (identification). Applying such a procedure to all samples collected from a selected area is very expensive. Samples therefore need to be selected, for example, with the aid of the results of ecotoxicological tests samples with the determined toxicity may contain toxic compounds. 

Steroid hormones are found as pollutants in drinking water, waste water, river and sediments. The major concerns of analytical methodologies for monitoring steroid hormones from environmental samples are extraction techniques from aqueous or solid matrices. Since sample volume or amount is not an issue in most cases, SPE is the method of choice. Both LC-MS/MS and GC-MS technologies are broadly applied for steroid analyses of environmental samples, such as LC-MS/MS analyses of steroid hormones in effluents of wastewater treatment plants [100] and estrogens in water [101,102], and GC-MS analyses of steroid hormones in environmental water [34,45, 78, 79], A study by Grover and colleagues showed that GC-MS was the simplest technique in determination of steroid hormones in environmental water samples, but lack of sensitivity LC-MS/MS was more sensitive than GC-MS, but susceptible to matrix interferences and GC-MS/MS was the recommended technique, because it was more selective and sensitive than GC/MS and LC-MS/MS [103],... 

Ra determination in environmental samples (highly saline thermal waters) by ICP-QMS with ultrasonic nebulization has been described by several working groups. Radium was preconcentrated and isolated from the matrix elements by selective extraction using a radium specific solid phase extraction membrane disk designed for radioactive counting methods as proposed by... 

To investigate the data quality of PFC measurements, a worldwide interlaboratory study was conducted in 2005 involving 38 laboratories from 13 countries [93]. Each laboratory analysed 13 PFCs in three environmental samples and two human samples. Results indicated approximately 65% agreement for PFOS and PFOA in human blood and plasma samples, but agreement for other PFS As and PFCAs was much lower and most laboratories underestimated the PFC concentrations in fish extracts due to matrix effects. The study concluded that additional work is needed to improve the analytical techniques employed for the analysis of PFCs. 

Supercritical fluid extraction has been applied to extract phenolic acids from a variety of plant samples. It uses high-pressure to force carbon dioxide to be a mixture of liquid and gas phases, which is called a supercritical fluid. The liquid and gas phase mixture of carbon dioxide can more readily permeate the sample matrix than only the gas phase of carbon dioxide. The compounds solublized in the liquid phase of carbon dioxide are extracted from the sample matrix and collected after they elute from the outlet of the system. The biggest advantage of supercritical fluid extraction is that there is no, or less, organic solvent involved in the extraction, due to the use of carbon dioxide supercritical fluid as the major solvent.. The carbon dioxide readily evaporates as gas phase at the system outlet. Thus, unlike other solvent extraction methods, there is no evaporation step for the extraction, making this an environmentally friendly method. However, the system is much more expensive and delicate than the other novel technology extraction... 

There are many review articles concerning application of USE in food technology [57] and for isolation of bioactive substances from herbs and other plant materials [58], as well as leaching of heavy metals from environmental and industrial samples [59]. Application of ultrasound during sequential extraction of trace elements significantly shortens the whole procedure however, for satisfactory efficiency it is necessary to increase the temperature and modify the matrix. 

Because the environmental matrix is very rich in various kinds of interferents and the FR concentration is relatively low, there is a need to use various kinds of extraction techniques to separate these compounds from environmental samples and to enrich and purify the samples. Depending on the type of matrix, different techniques can be applied. For water samples, first a pre-cleanup step is needed and then the most common technique used is solid phase extraction (SPE) with different SPE columns (Cig, ENV, HLB, PAD3) and different eluents. To enrich the FRs... 

TCBTs are coextracted with PCBs and other lipophilic substances in standard methods of analyses from different environmental matrixes. Waste oil samples were homogenized by ultrasonic shaking, water removed, sample dried by filtration over anhydrous sodium sulfate, and diluted with n-hexane [85]. Water samples (1000 ml) were mixed with 50 ml hexane by Turrax (11,000 rpm). The hexane phase was then dried with anhydrous sodium sulfate [86]. Laboratory water sample (1000 ml) was extracted with three portions of hexane (100 ml, 60 ml, and 60 ml) [87]. Another water sample (50 ml) from laboratory exposure experiments was liquid-liquid extracted with 9 ml of hexane [88]. 

Another use of trace enrichment for environmental samples, such as soil and sediment, is the concentration of analytes from organic solvents that have been used to extract the solid matrix, such as methanol, acetone, or acetonitrile (water-miscible solvents). Commonly, water-miscible organic solvents may be used to recover analytes from soils and sediments. These polar organic... 

---