Sample Treatment Procedures

The method employed for sample pretreatment prior to IC analysis is dependent on the sample type and the particular analytes under study. The determination of alkali metals in liquid samples, such as blood, plasma, and urine, is usually straightforward and requires only that the sample be 

TABLE 1. Detection Limits Attainable for Some Metal Ions Using Postcolumn Reaction with PAR  

Metal ion Detection limit (ng) Metal ion Detection limit (ng) 

When detection limits are inadequate for the levels of analyte present in the prepared sample, some form of sample preconcentration becomes necessary. The most widely used approach to trace enrichment in IC involves the use of a precolumn designed to trap trace levels of solutes from a large volume of sample. The precolumn method is popular because it is simple and convenient to apply, is amenable to automation, offers high enrichment factors, and is less prone to sample contamination effects than other methods. 

Sample preconcentration using two pumps—a single high-pressure switching valve and a concentrator column. EP, eluent pump SP, sample pump C, analytical column D, detector. The concentrator column is indicated by the hatched area and flow paths are shown by the solid lines. Note that the sample pump is turned off for the final analysis stage. 

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The development of analytical strategies for the regulatory control of dmg residues in food-producing animals has also been reviewed (128). Because of the complexity of biological matrices such as eggs (qv), milk, meat, and dmg feeds, weU-designed off-line or on-line sample treatment procedures are essential. 

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. 

For PBDEs and PBBs, sample treatment procedures have typically been based on protocols previously established for trace classic POPs. 

When HPLC was the preferred analytical method for a pesticide, the choice of sampling device and sample treatment procedure was... 

In food analysis, sensitivity is not the only requirement for analytical method development. Besides confirmation of the identity of pesticides, the identification of nontarget analytes is also important. One powerful tool is LC/MS, especially when it is combined with appropiate sample-treatment procedures it allows one to obtain detection limits adequate for trace-level analysis. Liquid chromatography-MS has demonstrated that it is an effective way to obtain both qualitative and quantitative information. 

This chapter presents an overview of sample treatment procedures [e.g., decomposition, digestion, mineralization, oxidation, ultraviolet (UV) decomposition, and ozonation] and discusses a range of analytical techniques for the mineralization of natural aquatic systems. Other samples, such as effluents and sewage sludge, are beyond the scope of this contribution and will not be discussed here. 

Sample treatment procedures are similiar to those cited for creams and ointments [3, pp. 466, 686, 758]. Acetone and a mixture of chloroform and methanol (1 2) [3, p. 196] have been used to dilute lotions prior to assay. For assuring batch-to-batch uniformity a diffusion-cell system has been developed [54]. 

The advances in sample fractionation methods, sample derivatization approaches, and the instrumentation of GC and GC/MS, in particular, are fundamental to metabolic profile research. Biological variation that is inherent to the samples of physiological fluids or tissues should not be obscured by an excessive imprecision of measurement techniques. Thus, reliable sampling and sample treatment procedures (including as much automation as is feasible) should precede the use of sophisticated GC and GC/MS techniques. 

For atomic absorption, plasma atomic emission, and atomic fluorescence spectrometric analysis the sample is normally introduced in the liquid form. The pretreatment of the sample depends on the sample type, element to be determined, and its concentration, as well as the analysis technique used. Any general sample preparation which would fit all kinds of samples cannot be employed. Sometimes the sample can be analysed without any pretreatment, sometimes complex sample treatment procedures are needed. 

Water is an essential resource for all living species, including man, and it is necessary to analyze a range of natural waters (e.g., seawater, rainwater, surface water, and groundwater), polluted waters (e.g., industrial water and sewage water), and purified waters (e.g., potable water and distilled water). This article presents an overview of sampling and sample treatment procedures and discusses a range of analytical techniques used for the quantification of major, minor, and trace constituents. 

The aim of this chapter is to present the state of the art on UHPLC-MS(/MS) analysis of pesticides in food. It includes a selection of the most relevant papers recently published regarding instrumental and column technology focusing on UHPLC analysis with sub-2 pm and novel porous shell particle-packed columns. Sample treatment procedures such as QuEChERS, MIPs, and online SPE will also be addressed. MS strategies for the analysis of pesticide residues as well as to guarantee confirmation and identification such as the use of HRMS or alternative confirmation strategies will be discussed with relevant application examples. 

This is followed, in Chapter 3, by the description of the analytical procedures used for monitoring the presence of uranium in the environment air, water, soil, and plants. As there is a large variety of sample types, there is no universal procedure for all environmental samples. Therefore, we present a myriad of sample treatment procedures and preparation methods as well as some separation and preconcentration techniques. Several examples of analytical procedures, based on the sample preparation methods, are described to demonstrate the diversity required for characterizing environmental samples. 

Once these samples are collected, an arsenal of the analytical procedures for the determination of uranium is available. Some of these were described in this chapter, but given the variation in the types of samples, in the sample treatment procedures and in the analytical methods, there is no universal routine for all. In order to report meaningful results for the uranium content in vegetation and food... 

The boom in microanalysers started aroimd 1994. Laborious sample treatment procedures and other peripheral operations were performed in reactor columns connected upstream or downstream from the central part. Highly efficient instruments, like a miniature mass spectrometer, became available. Amperometric detectors became the standard device for flow systems since they could be miniaturized easily. They are foimd primarily in liquid chromatographic /i-TASs as well as in such systems which work on the principle of capillary electrophoresis. 

The direct analysis of flavonoids is not possible due to the high complexity of the sample matrices. Sample pretreatment is a requirement in all flavonoid analysis to remove possible interferences, to increase the concentration of the analyte and hence the sensitivity of the analytical method, to adapt the analyte to the detection method, and to provide a more reproducible and robust analysis method. The selection of the proper sample treatment procedure depends on the type of flavonoids and the sample matrix (plant, food, or liquid sample such as biological fluids and drinks). Solid samples are normally lyophilized and homogenized before extraction liquid samples are normally filtered and/or centrifuged before the isolation or extractive procedure. 

In an effort to understand this lack of distinctive behavior of the alloys at acid pH, some additional sample treatment procedures were introduced. Samples of A and B alloys were heat-treated at 900°C, and quenched in cold water. One heat-treated sample for each alloy was then annealed at 500°C for 100 h. These treatments were intended to determine if the two alloys exhibited different corrosion behaviors as a result of a heat-treatment procedure that would alter the distribution of impurities at the grain boundaries. The original high-temperature heat treatment would be expected to cause. sensitizing impurities (such as B) to diffuse away from the boundaries an anneal at a lower temperature, on the other hand, would result in impurities drifting back to the boundaries if there were no structure in the bulk alloy capable of trapping the impurities. The latter condition is believed to be relevant to alloy B. where the phase composition (see Table 2) is close enough to the pha.se boundary to affect the solubilities of many impurities. 

Sampling Treatment Procedures Used to Enhance Contrast... 

Table 2. Absolute recoveries obtained by the SPE with disposable cartridges, CS and IT-SPME sample treatment procedures (values established at a concentration of 5.0 ng/mL in the SPE-LC-FLD and CS-capillary LC-DAD methods, and 1.0 ng/mL in the IT-...

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