Compound specific analyzers

Colorimetry, See Analytical techniques Combustion chemistry, 40 products, 41, 42, 502 spontaueous, 18, 41, 43, 214, 216 Communicatious, 427, 428 Compound specific analyzers, 311 Compressed gases colour coding, 271 construction materials, 266 first aid measures, 280 hazards, 265 precautions, 272, 403... 

Renwick (1991, 1993) analyzed interindividual differences of healthy volunteers by comparing the maximum and mean values of pharmacokinetic parameters (7 substances) and pharmacodynamic parameters (6 substances). The data indicated that toxicokinetic differences were slightly greater than toxicodynamic differences. With one exception, the ratios between the maximum and mean value for a substance s kinetic parameter ranged from 1.8 to 4.2 with most values between 3 and 4, and it was concluded that a factor of 3-4 would be sufficient to consider toxicokinetic differences for 99% of the healthy, adult population and for 80% of the substances. The ratios between the maximum and mean value for a substance s dynamic parameter ranged from 1.5 to 6.9 with most values between 1.7 and 2.7. Based on the analyses, Renwick proposed to subdivide the interindividual factor of 10 into a factor of 4 for pharmacokinetic differences and a factor of 2.5 for pharmacodynamic differences. The aim of the subdivision of the 10-fold factor was to allow the incorporation of suitable compound-specific data for one particular aspect of uncertainty. 

Detecting explosives in complex environments requires very sensitive and specific analyzers. Though MS offers excellent detection limits and resolutions (e.g., sensitivity and specificity), general-purpose laboratory instrumentation is not ideally suited for detecting trace levels of explosives in the presence of large abundances of potential interferent compounds. Furthermore MS has traditionally required a skilled operator not only to acquire data but to interpret it. MS developments have tended to focus on the performance issues and less so on the operational issues. 

Unlike clenbuterol, salbutamol is a difficult compound to analyze due to its particular chemical attributes. It is a basic compound subjected to protein binding poor recoveries are obtained especially when protein precipitation techniques are used to prepare the extracts (145). In addition, salbutamol is charged at all pH values and does not readily lend itself to simple, specific back-extracting procedures. This severely restricts the options of sample cleanup. However, a Subtilisin protease digestion step followed by acid clarification and solid-phase extraction has been suggested (146) as an adequate extraction and cleanup procedure prior to the end-point determination of salbutamol by an enzyme immunoassay (139) based on the cross-reactivity of anticlenbuterol antibodies. 

The last part of the book is devoted to the development of simple integrative models of organic chemicals in real environmental systems. The compound-specific tools derived in Parts II and III will be combined with the modeling tools of Part IV. As before, the aim of the discussion is not to compete with the many rather sophisticated models of environmental systems which can be found in the literature, but to concentrate on the simple models which can be analyzed by hand or with desk calculators. 

When [M-H] serves as a precursor ion for MS/ MS, [M-H-CO2] and [M-H-141] were generated as product ions (listed in Table 2), and they are very useful for the confirmation of penicillins. After a series of detailed examinations, the other MS/MS conditions including the compound-specific parameters were selected. To provide the applicability of the present method, the fortified bovine tissues, at a concentration of 0.05 mg/kg of each six penicillins, were analyzed. As shown in Fig. 2 left, all six penicillins from the liver sample appeared as separate peaks on the mass chromatograms monitored at [M-H-141] under ESI LC/MS/MS conditions. Fig. 2 right shows the tandem mass spectra of the penicillins recorded at the top of each peak on the mass chromatograms shown in Fig. 2 left. All of these mass chromatograms and tandem mass spectra of fortified samples were almost the same as for the respective standards. Based on the results of the analyses of the fortified samples at 0.02 mg/kg, the lower limit of confirmation of the present method for muscle sample was estimated to be 0.02 mg/kg for all six penicillins, and those for kidney and liver were between 0.02 and 0.03 mg/kg. 

Identified by Sullivan et al. (1959), Stoll et al. (1967), and Stoffelsma et al. (1968). Merritt et al. (1963, 1970) identified it in roasted but not in green coffee. Guyot and Vincent (1990) found traces when specifically analyzing volatile sulfur compounds (see Q.4). 

In a series of papers published throughout the 1980s Colin Poole and his coworkers investigated the solvation properties of a wide range of alkylammonium and, to a lesser extent, phosphonium salts. These ionic liquids were used as stationary phases for gas chromatography and the retention of a variety of probe compounds was analyzed using Abraham s solvation parameter model [6]. Since a wide variety of probe solutes were used any problems associated with the use of a single probe, which will inevitably have its own specific chemistry, were removed. 

The mqor limitation to all pharmacokinetic approaches such as these relate to the large data requirements needed to solve model parameters. A full solution for a multicompartment model requires a series of repheated expmments using a single chranical applied at different doses and experiments tominated at various time points. As mmtioned, in vitro studies would be conducted to obtain specific biophysical parameter estimates. All data are simultaneously analyzed. For many compounds, specific components of the full model may not be required thus, in reality the actual model fitted is simpler. Statistical algorithms are presently und developmrait to select the optimum model for the specific compound studied and collapse the remainder of the model structure into a matrix from which individual rate parameters... 

Because drug testing for controlled substances bears heavily on a person s reputation, the method to detect controlled substance must be accurate and must follow international guidelines, which advocate a method that must include chromatographic separation to isolate the analyte from other matrix components and mass spectrometric detection with either SIM of three compound-specific ions on a single mass analyzer or with selected-reaction monitoring (SRM) of two specified precursor-product reactions. GC/MS and LC/MS methods that follow these guidelines are used routinely to detect and quantify cannabinoids, narcotics, cocaine, amphetamines, and other substances of abuse [57]. 

More than one hundred papers reporting diverse applications to analyse wines were published until know. The majority of the referred methodologies use the headspace mode (HS-SPME) instead of the direct immersion mode (DI-SPME). In terms of performance, SPME showed comparable results to LLE or SPE. However, SPME is simpler and solvent-free, and uses smaller volumes of sample nevertheless, on the other hand, LLE had the possibility of carrying out simultaneously the extraction of several samples (Bohlscheid et al., 2006 Castro et al, 2008). When the interest is to obtain the maximum information about the volatile fraction of a wine, the coating DVB/CAR/PDMS seem to be the most suitable (Tat et al., 2005). On the other hand, for specific applications, the choice of a suitable solid-phase, depends on the class of compounds be analyzed, e.g. CAR/PDMS for volatile sulphides and disulphides (Mestres et al., 1999), on-fibre derivatization (PA) for the determination of haloanisoles and halophenols (Pizarro et al, 2007). 

One of the early in vitro assays that is used as part of the new drug discovery paradigm is the metabolic stability assay. This assay is also referred to as the microsomal stability assay or the hepatocyte stability assay or sometimes simply the in vitro stability assay (Thompson, 2000, 2001 Xu et ah, 2002 Jenkins et ah, 2004 Baranczewski et ah, 2006). As these names suggest, there are various ways to perform the in-life part of the assay some departments prefer to screen with liver microsomes, while others find that hepatocytes provide more meaningful data (Lau et ah, 2002). Regardless of the in-life part of the in vitro stability assay, the analytical part represents a significant challenge because the analyst must have compound-specific methods in order to properly analyze the samples. 

Note an important specific feature of GSC, namely that the retention of compounds depends on the nature of the mobile phase. The replacement of light carrier gases by heavy gases leads to dynamic modification of the adsorbent surface, to a decrease in the coefficients of distribution of the compounds being analyzed in the solid adsorbent-gas system, and, hence, to a decrease in retention times. 

The formation of furans, thiophenes, furanones, thiophenones etc. was investigated in a series of [l(or 6)- C]-glucose and [l- C]-arabinose/ cysteine and methionine model experiments. The labeled compounds were analyzed by capillary GC/MS and NMR-spectroscopy. From their structures the degradation pathways via different reactive intermediates (e.g. 3-deoxyaldoketose, 1-deoxydiketose) and fragmentations were evaluated. Besides the transformations to flavor compounds via identical labeled precursors, major differences in the flavor compounds result from specific Strecker reaction sequences. Major unlabeled compounds e.g. 3-mercaptopropionic acid from cysteine and 4-methylthiobutyric acid from methionine demonstrate transamination/reduction, and the formation of pyruvate and 2-mercaptopropionic acid from [l-i C]-glucose/cysteine indicates B-elimination. 

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