Sample handling extraction

Albro PW. 1979. Problems in analytic methodology Sample handling extraction and cleanup. In Nicholson WJ, Moore JA, eds. Annals of the New York Academy of Sciences, Health Effects of Halogenated Aromatic Hydrocarbons International Symposium, New York, NY, USA, June 24-27, 1978. New York, NY New York Academy of Sciences, 320 19-27. 

Development of suitable sample handling, extraction, and HPLC/diode array detector (DAD) based methods for the analysis of flavonoids and their conjugates in four varieties of onions were described (125). The predominant flavonoids in onions (white, brown, red, and pink varieties) were quercetin mono- and diglucosides, which accounted for approximately 80% of the total flavonol fraction. 

The number of potential future applications of biosensors in food and environmental monitoring is clearly very large, and few examples are given in Table 7.6. There are great opportunities for the exploitation of the unique features that sensors may provide, to solve complex analytical problems. It is our view that a combination of optimized sample handling/extraction, judicious selection of the sensor format, the... 

Owing to the light and air sensitivity of the carotenoids and retinoids, sample handling is a critical issue. It is recommended to conduct extraction of these materials with peroxide-free solvents, to store biological samples at —70° C under argon and in the dark, to perform the analysis under yellow light, and to use reference compounds of high purity (57). 

The tissue to be analyzed is placed directiy onto the gel. Using the tissue itself and not tissue extracts has advanced the study of proteins that are difficult to extract from tissue, or are damaged by the extraction procedure. Dtif is an important advancement in the area of sample handling and appHcation where direct appHcation of a soHd to a gel matrix may actually enhance resolution. 

LC-GC, therefore, shows promise for forensic science applications, reducing sample handling and preparation steps by essentially using an on-line LC column in place of one or more extraction steps. This is followed by a traditional high resolution GC analysis. The methods described here for pesticides and hormones could be readily adapted to a variety of analyses, especially those involving fatty matrices. Such as tissues, food or blood. 

Reliable analytical methods are available for determination of many volatile nitrosamines at concentrations of 0.1 to 10 ppb in a variety of environmental and biological samples. Most methods employ distillation, extraction, an optional cleanup step, concentration, and final separation by gas chromatography (GC). Use of the highly specific Thermal Energy Analyzer (TEA) as a GC detector affords simplification of sample handling and cleanup without sacrifice of selectivity or sensitivity. Mass spectrometry (MS) is usually employed to confirm the identity of nitrosamines. Utilization of the mass spectrometer s capability to provide quantitative data affords additional confirmatory evidence and quantitative confirmation should be a required criterion of environmental sample analysis. Artifactual formation of nitrosamines continues to be a problem, especially at low levels (0.1 to 1 ppb), and precautions must be taken, such as addition of sulfamic acid or other nitrosation inhibitors. The efficacy of measures for prevention of artifactual nitrosamine formation should be evaluated in each type of sample examined. 

It is the difficult task of the analytical chemist to select the sample preparation technique best-suited for the problem at hand. The more tools there are in the toolkit, the larger the chances of finding a sample preparation technique that offers the desired characteristics. The goal of any extraction technique is to obtain extraction efficiency for the analyte which meets the analytical requirements in the shortest possible time. In some analytical procedures little sample handling is needed [46-49]. 

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]. 

No sample handling between extraction and separation (no contamination)... 

The popularity of this extraction method ebbs and flows as the years go by. SFE is typically used to extract nonpolar to moderately polar analytes from solid samples, especially in the environmental, food safety, and polymer sciences. The sample is placed in a special vessel and a supercritical gas such as CO2 is passed through the sample. The extracted analyte is then collected in solvent or on a sorbent. The advantages of this technique include better diffusivity and low viscosity of supercritical fluids, which allow more selective extractions. One recent application of SFE is the extraction of pesticide residues from honey [27]. In this research, liquid-liquid extraction with hexane/acetone was termed the conventional method. Honey was lyophilized and then mixed with acetone and acetonitrile in the SFE cell. Parameters such as temperature, pressure, and extraction time were optimized. The researchers found that SFE resulted in better precision (less than 6% RSD), less solvent consumption, less sample handling, and a faster extraction than the liquid-liquid method [27]. 

The advantages of MAE are short extraction times (10 min), extraction of many samples at one time (up to 14, depending on the system), and less organic solvent consumed. In one recent study [29], MAE was used to extract paclitaxel from Iranian yew trees. The needles of the tree were air-dried and ground. The needles were covered with methanol-water and placed in the MAE apparatus. Extractions took 9-16 min. The extracts were filtered and analyzed by HPLC. Further optimization of the method resulted in less than 10% RSDs for precision and greater than 87% recovery. The overall benefits of the MAE method are reduced extraction times (15-20 min versus 17 h), minimal sample handling, and 75-80% reduction in solvent consumption [29]. 

One of the most widely used techniques across all disciplines is solid-phase extraction (SPE). A simple approach to SPE is shown in Fig. 2.3. These columns provide rapid extraction, minimize emulsion problems, and eliminate most sample handling. 

In the past two decades quite a few new techniques have emerged for the treatment of aqueous samples prior to organic analysis. Perhaps the most important development is that of solid-phase extraction (SPE), which has successfully replaced many off-line steps. This technique can be considered to have introduced a genuine new era in sample handling [1]. The many varieties in which the technique is available and can be applied have made it the key step in handling of aqueous samples. Among the successful varieties are solid-phase microextraction (SPME), matrix solid-phase dispersion, disk extraction and immunosorbent extraction. Several reviews covering these topics have appeared in the literature in the past decade (see e.g. Refs. [2,3] for nonylphenol... 

Strategies for sample handling strongly depend on the nature of the analytes and matrices involved, and on the concentration levels of the analytes [1]. In addition, the method of detection will set specific requirements to the sample treatment procedures applied, in order that the final extract is compatible with the method s ways of sample introduction. 

A variety of sample handling techniques is available, which can be divided into four types Soxhlet extraction, steam distillation, soni-cation and accelerated solvent extraction (ASE) [3]. 

In this chapter, all four types of sediment and sludge sample handling techniques for non-ionic surfactants will be discussed and compared. Most of the studies published on non-ionics focus on APEOs and their degradation products, viz. the alkylphenols, but some extraction methods for alcohol ethoxylates (AEOs) and coconut diethanol amides will also be discussed. 

Performance of sample handling techniques for the extraction of non-ionic surfactants from solid matrices... 

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