Experimental procedure instrumental analysis

Dupuy and coworkers have reported a direct gas chromatographic procedure for the examination of volatiles in vegetable oils (11). peanuts and peanut butters (12, 13), and rice and com products (14). When the procedure was appTTed to the analysis of flavor-scored samples, the instrumental data correlated well with sensory data (15, 16, 17), showing that food flavor can be measured by instrvmental means. Our present report provides additional evidence that the direct gas chromatographic method, when coupled with mass spectrometry for the identification of the compounds, can supply valid information about the flavor quality of certain food products. Such information can then be used to understand the mechanisms that affect flavor quality. Experimental Procedures... 

The enthalpies of solution were measured with a LKB 8700-1 precision calorimetry system. The experimental procedure and test of the instrument have been given before (6,7). EC (Fluka, purissimum) was distilled under reduced pressure and the middle fraction was stored over molecular sieves (4 A) for at least 48 hr. ACN (Merck, pro analysis) was dried over molecular sieves and used without further purification. The purity of both solvents (determined shortly before use), as deduced from GLC, was always better than 99.8%. The volume fraction of water, determined by K. Fischer titration (8) was always less than 3.10-4. The mixed solvents were prepared by weight as shortly as possible before the measurements. AH° of Bu4NBr in W-ACN mixtures have been measured at 25°C while those in W-EC are at 45°C, which is above the melting point of pure EC. 

In this section the instrumentation and the experimental procedure to determine the Cd, Cu and Pb total dissolved concentration is described in some detail. Several reviews regarding the general theoretical and experimental aspects of anodic stripping voltammetry and its application in sea water (or natural water) analysis can be found in the literature (15 17, 41, 59, 62, 67, 68). Details of the speciation procedure are reported below. 

An automated system for clinical analysis consists of the instrument (hardware), the reagents, and the experimental conditions (time, temperature, etc) required for each determination. The reagents plus the experimental conditions are sometimes referred to as the chemistry of the system. The chemistry employed is generally similar to that used in manual assays because most automated assay methods have been adapted from the manual ones. However, automated analyzers rarely afford the flexibility of experimental procedure that is possible in manual analysis. 

Several solid surfaces, such as filter paper, sodium acetate, and silica gel chromatoplates with a polyacrylate binder, have been used in solid-surface luminescence work (1,2). Experimentally it is relatively easy to prepare samples for analysis. With filter paper, for example, a small volume of sample solution is spotted onto the surface, the filter paper is dried, and then the measurement is made. In many cases, an inert gas is passed over the surface during the measurement step to enhance the RTF signal. For powdered samples, the sample preparation procedure is somewhat more involved. Commercial instruments can be readily used to measure the luminescence signals, and a variety of research instruments have been developed to obtain the solid-surface luminescence data (1,2). 

Anyway, using data from different instruments increases the experimental effort, time, and costs of analysis. For this reason, although fusion is always an elegant data-processing procedure, for practical applications the real benefit/cost balance should be carefully evaluated. 

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