Compounds quantification

Chromatographic peak areas are calculated automatically by the data system by reference to the response obtained from certain specified, compound-dependent ions. From the peak areas of the target compounds, quantification is achieved by comparison with the internal standards, which are present in known concentration. The laboratory responsible for the analysis must report the target compounds and all tentatively identified (nontarget) compounds. Standard EPA forms must be completed and submitted. A laboratory is said to be in compliance when it has satisfied all aspects of its CLP contract. 

Organotin compounds enriched from a diethylether extract of a snow sample collected from the city of Gdansk, Poland and analyzed are shown in Fig. 22 b, c [286]. Gas chromatography with atomic emission detection (GC-AED) run in the chlorine and tin channels, respectively, revealed the presence of tributyltin chloride and this was subsequently confirmed by GC-MS and GC-AED analyses of an internal standard solution (e.g., 1-chlorooctane) of that compound. Quantification was based on the response to chlorine (wavelength 479 nm) in the AED system, and a detection limit of 0.5-1 ng/1 was achieved for all the reference substances. 

The limitations of MS, UV detection, ELSD, and CLND in terms of compound quantification, especially when combined with the requirement of high throughput, make the task of quantitative analysis of libraries very difficult. From our point of view the key to quantitative analysis of libraries is in using reference standard compounds and in making conclusions based on a combination of results from several techniques whenever possible. 

Measuring organic compounds, quantification can make use of internal and external standards. Different examples are described in this book. There is no general advice on the various organic compounds in soil that can be quantified. Due to the complex composition of soil, which influences the extractability, it is not customary to correct measured values for the incomplete extraction. There can be a high extraction efficiency for one soil and a lower extraction... 

The next step was to develop technology to rapidly quantify each such that the load could be accepted/rejected in an acceptable time frame. Kupina (1984) developed a high-performance liquid chromatographic (HPLC) method that simultaneously quantified each of the msgor metabolites in 11 min. Briefly, the procedure involves chromatographing a composite filtered juice sample on a HPLC column which separates the three components from each other and other matrix compounds. Quantification is accomplished by comparing the component peak areas to those of a standard solution chromatographed in the same way. 

In addition to compound quantification, an exhaustive statistical analysis is applied to the data. The classification and/or verification of samples are major objectives. Our approach is, first, to exactly identify the sample by cascading classification models and, second, to validate the sample with respect to its most qualificatory group (e.g., rediluted apple juice concentrate from Poland). This reduces the variance of the validation models and, therefore, increases their discriminatory power. The foundation of the statistical analyses is... 

The mass spectrometer is used to perform many tasks including, identification of unknowns, trace-level analysis, target compound quantification, and accurate mass measurements, to name a few. Each of these analyses has a number of specific instrumental requirements, including a preferred scanning mode. 

Selective and accurate compound quantification using the MS/MS mode... 

Although GC is a good method for compound quantification, it is only semiquantitative at best when peaks are unresolved. Refined GC-MS methods are available which will overcome this difficulty. 

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