Analyte addition technique

Welz, B. Abuse of the analyte addition technique in atomic absorption spectrometry. Fresen. Z. Anal. Chem. 325, 95-101 (1986)... 

Reactions of the analyte with the tube material (graphite) or the purge gas are not normally considered to be interferences because they influence the analyte in the sample and in the standard to the same degree. A nonspectral interference is in many instances best detected by the use of the analyte addition technique. An interference exists if the slope of... 

Analytic equations or group additivity techniques when applicable. 

To avoid different interpretations, a list of analytical techniques, regarded as commonly available, is given in the guidance document SANCO/825/00. Other techniques may also be powerful tools in residue analysis the acceptance of these additional techniques as part of enforcement methods will be discussed at appropriate intervals by governmental experts. Therefore, whilst not wishing to prevent... 

It is important to note that the ion series observed by the API-MS method may not be representative of all the products present, not the quantities thereof. Cleavage of the ethoxylate chain removes the capacity of silicone surfactants to be ionised and therefore detected by these methods. As such, for example, the cleaved silicone head group [M(D/CH2CH2CH2OH)M, 3] was never observed by API-MS. The nature of the API-MS process is such that competition between analytes for ionisation occurs, and as such compounds with higher surface activity and EO content can be expected to dominate in the resulting spectra. Suppression effects may thus preclude observation rather than confirm absence. As a consequence, the use of additional techniques such as FTICR-MS, GC-MS, HPLC and NMR to provide complementary data was also necessary. Furthermore, the high number of possible structures for each ion series observed, rendered it difficult to assign structures with confidence. Consequently simplified M2D-C3-0-(E0)n-R... 

The response of vertebrates to olfactory stimulation is affected by previous experience but behaviour can be specifically affected by odours (pheromones) (4). The olfactory system has been shown to detect specific components within complex mixtures and analytical chemistry techniques have been used to identify these active components (5). We have assessed the application of these methods to the problems of agricultural odours in an attempt to develop techniques applicable to both slurries and air samples. The identification of the odorous components might allow specific treatment methods to be developed. In addition, the designation of a range of indicator compounds might be useful in practice for monitoring abatement of odour nuisances. 

During the last few years, a number of specific monographs for different pharmaceutical products have appeared in pharmacopoeias in which CE is prescribed as one of the analytical procedures. Several comparative studies have been reported in which established analytical procedures described in pharmacopoeial monographs were compared with capillary electrophoretic methods or in which CE was evaluated as a valuable additional technique.Based on the results, some analytical procedures have been replaced by CE-based alternative methods in a number of monographs. For other products, CE has been included in the monograph from the initial version onwards. In addition, CE has been applied... 

In addition techniques, the test substance concentration is determined from the difference in the ISE potentials obtained before and after a change in the sample solution concentration. The main advantage Ues in the fact that the whole measurement is carried out in the presence of the sample matrix, so that results with satisfactory accuracy and precision can be obtained even if a substantial portion of the test substance is complexed. Several addition techniques can be used, namely, single, double or multiple known addition methods, in which the sample concentration is increased by additions of a test substance standard solution single, double or multiple known subtraction methods, in which the sample concentration is decreased by additions of a standard solution of a substance that reacts stoichiometrically with the determinand and analyte addition and subtraction methods, in which the sample is added to a test substance solution or to a reagent solution. 

The contents of the book are intended to help a newcomer in the field, as well as to provide current information including developing technologies, for those who have practiced process analytical chemistry and PAT for some time. The main spectroscopic tools used for PAT are presented NIR, Raman, UV-Vis and FTIR, including not just the hardware, but many apphcation examples, and implementation issues. As chemometrics is central for use of many of these tools, a comprehensive chapter on this, now revised to more specifically address some issues relevant to PAT is included. In this second edition many of the previous chapters have been updated and revised, and additional chapters covering the important topic of sampling, and the additional techniques of NMR, fluorescence, and acoustic chemometrics are included. 

A major consequence of using regulatory limits based on degradant formation, rather than absolute change of the API level in the drug product, is that it necessitates the application and routine use of very sensitive analytical techniques [ 10]. In addition, the need to resolve both structurally similar, as well as structurally diverse degradants of the API, mandates the use of analytical separation techniques, for example, HPLC, CE, often coupled with highly sensitive detection modes, for example, ultraviolet (UV) spectroscopy, fluorescence (F) spectroscopy, electrochemical detection (EC), mass spectroscopy (MS), tandem mass spectroscopy (MS-MS) and so forth. 

A selection of the most successful CSPs, chiral particles and chiral additive techniques used for analytical and preparative enantioseparation by LC is discussed in the following sections with respect to molecular recognition and experimental application. As additional sources of background information recent books and review articles2-16, which contain numerous relevant references and examine the most important aspects of the field of liquid chromatographic enantioseparation, should be consulted. 

Another calibration technique - standard addition - minimizes matrix effects because analytes with well defined increasing concentrations are added to a set of sample solutions to be analyzed. The measured calibration curve in the standard addition mode plots the measured ion intensities of analytes versus the concentration added to the sample solution. The concentration of analytes in the undoped sample is then determined by extrapolation of the calibration curve with the x-axis. Matrix matching is subsequently performed and the matrix effects (signal depression or interference problems) are considered. An example of the standard addition technique is described in Section 6.2.6 using solution based calibration in LA-ICP-MS. 

Organic FDR detection is a useful additional technique, despite the fact that single-based propellant constituents cannot be reliably detected. The current system uses GC/TEA as a rapid screening technique for NG and 2,4-DNT, and only positive samples need to be subjected to the SPE cleanup/ concentration procedure. The method is flexible in that the extract can be analyzed by a range of analytical instrumentation. There does not appear to be good correlation between the detection of organic and inorganic FDR which emphasizes the need for combined instrumentation, that is, GC/TEA, GC/MS, and SEM/EDX. Details of the method devised are as follows. 

The organic analytical techniques covered here may be considered those commonly found in routine (commercial) analytical laboratories. Some laboratories that also perform research and method development may use other techniques in addition to the ones mentioned in this chapter. These additional techniques often involve spectroscopy methods like infrared spectroscopy, nuclear magnetic resonance, and X-ray diffraction and microscopy. 

The content of aroma compounds is, in general, low, and compositions of these compounds are often complex. Therefore, at the dawn of analytical chemistry, aroma compounds were extracted from a huge mass of raw material. Fractionation was carried out by means of distillation, and various other classical procedures (e.g., crystallization, pH control in extraction, derivatization) were employed. Quite obviously, compounds revealed using these procedures were inevitably restricted to a set of major constituents, if any. Occasionally, before the 1950s, additional techniques like UV-IR spectroscopy and open-column chromatography were employed and were helpful to some extent. 

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