Identification of sample components

The time required by a given analyte to migrate under the sole influence of the applied electric field across the capillary tube from the injection end of the capillary to the detection windows (migration distance) is defined as the migration time (tj and, similarly as the retention time in HPLC, is used for identification of sample components. It is given by... 

Marker. A reference component which is chromatographed with the sample to aid in the identification of sample components. 

There are a variety of techniques currently in use to aid in the identification of sample components. Most techniques, such as spiking and the enzyme peak shift method, are used to confirm the identities of components thought to be in the sample. If, however, the identity of the sample is truly unknown, a combination of techniques is needed to provide a unique fingerprint. ... 

There are a variety of techniques available to aid in the identification of sample components matching retention times, standard addition, internal standard, isotopic labeling, enzyme peak shift, and UV and mass spectral libraries. 

Techniques in clinical analysis have undergone many advances in the last few decades. The basic needs in clinical chemistry are unambiguous analyte-specific assays that provide both identification of sample components and their concentration levels. The importance of this is self-evident, since most substances analyzed are part of a multicomponent biological fluid. Advances in enzyme and immunochemical assay techniques provide ideal systems for component... 

Identification of sample components based solely on migration time in capillary electrophoresis (CE) requires reproducibilities not normally obtained. These are caused, mainly, by two effects temperature effects and electro-osmotic affects. Migration times in CE are determined by the electro-osmotic velocity Ueof and effective electrophoretic migration velocity Ueef the net migration velocity Vt is the vector sum of both velocities ... 

The coupled TLC-FAB-MS, without the prior recovery of analyte from the TLC plate, provides a powerful tool for the unambiguous identification of sample components. The use of tandem MS-MS represents a further refinement of this approach, enabling identification to be performed even when the separated components are incompletely resolved from each other or are subject to background interference. 

First one component is fed into the reactor column in a pulsed maimer, then a second one after a certain interval. The reaction proceeds during the time interval when the second component overtakes the first one in the column. The use of this method as applied to the qualitative identification of sample components has been described elsewhere [41]. The application of the method for determining the kinetic characteristics was proposed by Berezkin [55]. The method was developed in earlier work [61 ]. 

The desirable features of the flame photometer are sensitivity, stability, and relatively large linear dynamic range. FPDs also require very little maintenance, and are ready to use in a very short time. An FPD s response to phosphorous is a first-order relationship, while its response to sulfiir components is second order because sulfur is detected as Sj. Analysis by an FPD without a GC column is considered real-time detection. Unfortunately, without GC involvement, the detector cannot provide possible compound identification due to its generic nature. The addition of GC capability permits identification of sample components that contain targeted elements, and reduces the false alarm rate. 

Validation of true extraction efficiency normally requires the identification and quantitation of field-applied radiolabeled analyte(s), including resulting metabolites and all other degradation products. The manufacturer of a new pesticide has to perform such experiments and is able to determine the extraction efficiency of aged residues. Without any identification of residue components the calculation of the ratio between extracted radioactivity and total radioactivity inside the sample before extraction gives a first impression of the extraction efficiency of solvents. At best, this ratio is nearly 1 (i.e., a traceability of about 100%) and no further information is required. Such an efficient extraction solvent may serve as a reference solvent for any comparison with other extraction procedures. 

Thermal-programmed solid insertion probe mass spectrometry (TP-SIP-MS) has been proposed [247,248], in which the solid insertion probe consisting of a water-cooled microfumace enters the mass spectrometer via an airlock. The sample is contained in a small Pyrex tube (i.d. 1 mm, length 20 mm). The TIC trace gives a characteristic evolved gas profile for each compound in a mixture of materials, and the mass spectra associated with each TIC peak give a positive identification of that component as it is vaporised. TP-SIP-MS is appropriate for analysis of small solid particles which are volatile, or produce volatile decomposition products. The technique is a form of evolved gas analysis. 

So-called street drugs for identification of principal components, impurities, adulterants, and cutting agents in order to establish the method of synthesis, to compare the samples seized from users with those from dealers, as well as for comparative analysis or so-called profiling to find out the source of the material. 

Hyphenated methods can be divided into two types those that do and those that do not destroy the sample in the process of analysis. Spectrophotometric methods, thermal conductivity, and refractive index methods of detection do not destroy the sample. Chromatographic methods using flame ionization and similar detection methods destroy the sample as it is detected. Any hyphenated method that involves MS or thermal analysis (TA) will also destroy the sample. In most cases, the identification of the components in soil is most important, so the destruction of the analyte is of less importance. 

Another approach is to separate the solvent from the sample before a spectrum is obtained. Because HPLC is often used with a combination of volatile eluents and organic compounds that are not volatile, the solvent can be removed and the isolated component analyzed by FTIR [13]. FTIR is not particularly useful for the identification of inorganic components, particularly ions. 

Retention distance (or time) is normally used to aid the identification of a component of a mixture, provided that a known sample of the component has been subjected to separation under identical conditions. Because of the variations that can occur in the retention time due to technical factors, e.g. fluctuations in flow rate, condition of the column, the relative retention or selectivity factor (a) is sometimes used. This expresses the test retention time as a ratio of the retention time of another component or reference compound when both are injected as a mixture ... 

F1PLC has found applications in a wide variety of studies concerning the marine environment [295], It has been employed for the identification of the components of microphy-tobenthic communities [296], for the investigation of the change in phytoplankton communities [297] in many sampling sites such as the Mediterranean Sea [298], Equatorial Pacific [299], Mississipi River-influenced continental shelf [300], etc. 

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