Sample handling techniques

To obtain useful spectrograms of the samples, the spectroscopist must do a careful and frequently a lengthy job of sample preparation. The care and effort expended on this phase of the analysis are the biggest contributions to obtaining good results. Even for routine samples, where handling is the same for sample after sample, the prescribed procedures must be carefully followed to obtain the maximum in results. 

There are always a number of single-component samples, and occasionally some mixtures, where the sample can be put into a cell or taped to the spectrophotometer and run as is. Usually, however, the sample must have some chemical or mechanical work done on it prior to its being run. 

Separation of mixtures into their components is usually the lengthiest and most difficult part of the sample-handling problem. These separations can be accomplished by one or more of a variety of techniques, such as extractions, distillations, or chromatography a discussion of these separation techniques does not belong here. However, it should be remembered that during these separations it is possible that changes in the chemical entity of the material may occur, and also that unwanted residues from solvents may be added to the sample. These problems are not necessarily disastrous unless the spectroscopist is unaware of their occurrence. 

This chapter will discuss various techniques by which a sample can be run, assuming that the necessary preliminary separations mentioned above have been completed. The spectroscopist should be aware of the possibility that the same sample run by several different techniques may not show identical spectra. In practice, small variations by the operator in processing the sample may produce differences in spectra obtained from the same original sample. 

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Classical LLEs have also been replaced by membrane extractions such as SLM (supported liquid membrane extraction), MMLLE (microporous membrane liquid-liquid extraction) and MESI (membrane extraction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]. 

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... 

One of the most important factors in the selection of the sample handling technique is to attempt to analyze the sample, as it exists, without any form of chemical or physical modification. For gases and certain liquids, simple transmission cells, often with a flow-through configuration meet these requirements. 

Successful results in CE often depend on the use of appropriate sample handling techniques. This requires knowing the nature of the analytes and their behavior under various conditions. For example, the main difference between the analysis of inorganic species in CE and FIPLC is the size or... 

This chapter aims to provide a step-by-step guide for practitioners involved in the collection of contaminated samples by reviewing current groundwater sampling techniques and procedures and highlighting the major sources of uncertainty associated with sample collection. On-site water-quality measurements, quality assurance procedures and sample handling techniques designed to maintain the representativeness of the sample from field to laboratory are also discussed. 

The versatility of the atomic absorption method has long been obvious. The applications in air sampling and analysis treated here represent only those methods already widely accepted as reproducible in many laboratories. Developments in this field are occurring with great rapidity, and futher methods with simpler, more direct sample handling techniques are expected to cover an even greater range of applications. 

Fig. 1 shows the infrared spectrum of halothane (Ayerst Laboratories Inc. Batch No. 1CKB). The spectrum is that of undiluted halothane in a 0.104 mm. potassium bromide cell vs. a potassium bromide plate. Also, because some of the absorption bands are quite intense, Fig. 1 shows the spectrum of a 4.0 volume percent solution of halothane in carbon disulfide, in a 0.104 mm. potassium bromide cell, vs. a 0.1 mm. cell filled with carbon disulfide. A Beckman Model IR-12 instrument was used. Considering the variety of sample handling techniques used, this spectrum and other published spectra (1-3) are the same. 

In Section 8B-6 we described various automated sample handling techniques including discrete and continuous flow methods. In this section, we explore the instrumentation and two applications of flow-injection analysis with photometric detection. 

Products/technologies The mixing routine of the FAMOS microsampling HPLC workstation enables automated method development for sample handling techniques of single beads to produce combinatorial libraries high-throughput is achieved by multiple analysis per vial. 

Price, W. J. (1972). Sample handling techniques. In Laboratory Methods in Infrared Spectroscopy (R. G. J. Miller and B. C. Stace, eds.). Heyden and Sons, London, pp. 97-128. 

Nicolet 200SXV FI far IR spectrometer. The vacuum infrared cell, and sample handling techniques used have been described in detail in a recent review of this subject.(4)... 

Barcelo, D. and Hennion, M. C., Sample Handling Techniques (extraction and cleanup of samples). Trace Determination of Pesticides and their Degradation Products in Water, Elsevier, Amsterdam, NL, pp. 249-349, 1997. 

K. Wolf and P. J. Worsfold, Flow Injection Analysis as a Sample Handling Technique for Diode Array Spectroscopy. Anal. Proc., 23 (1986) 365. 

Infrared spectrophotometry is a familiar established analytical technique which provides identification of compounds by fingerprint spectra, of which a vast library is available. Both liquid and gaseous samples may be easily analysed and therefore modifications of established sample handling techniques have enabled both GC and HPLC instruments to be readily interfaced. Ideally, scan times of less than 1 s are required to be able to record each peak and peak shoulders. Instrument sensitivity is sufficient so that on the fly recording of spectra can be obtained from GC and HPLC eluants which contain nanograms of sample per ml mobile phase, for example, 10 ng sample in 100 pi GC-IR sample cell. Fourier transform infrared (FTIR) instruments are able to meet these criteria but until recently the instrumentation and computer system have been too expensive for routine use. The new generation of... 

Several sample-handling techniques are employed for SERS, In one technique, colloidal silver or gold particles are suspended in a dilute solution (usually aqueous) of the sample. The solution is then held or flowed through a narrow glass tube while it is excited by a laser beam. In another method, a thin film of colloidal metal panicles is deposited on a glass slide and a drop or two of the sample solulion spotted on the film. The Raman spectrum is then obtained in the usual manner. Alternatively, the satnple may be deposited electrolytically on a roughened metal electrode, which is then removed from the solulion and exposed to the laser excitation source. 

Infrared spectroscopy underwent tremendous advances after the second world war and after 1950 with improvements in instrumentation and electronics, which put the technique at the center of chemical research and later in the 80 s in the biosciences in general with new sample handling techniques, the attenuated total reflection method (ATR) and of course the interferometer [13]. The Fourier TransformIR spectrophotometry is now widely used in both research and industry as a routine method and as a reliable technique for quality control. 

To recognize the different methods of sample preparation and sample handling techniques which are used for preparing samples in infrared spectroscopy. 

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