Absoiption analysis

However, the use of IR spectra is limited for the analysis of food because sample preparation is more complicated in comparison with NIR. Dehydration, homogenization, dissolution or dispersion of samples is necessary. In addition, to make an IR transmission spectra of liquid samples, it is necessary to use a cuvette with very narrow path length of 0.001 - 0.1 mm because the absoiptivities are very high, which causes a sample loading... 

Fluorescence microspectrophotometry typically provides chemical information in three modes spectral characterization, constituent mapping in specimens, and kinetic measurements of enzyme systems or photobleaching. All three approaches assist in defining chemical composition and properties in situ and one or all may be incorporated into modem instruments. Software control of monochrometers allows precise analysis of absoiption and/or fluorescence emission characteristics in foods, and routine detailed spectral analysis of large numbers of food elements (e.g., cells, fibers, fat droplets, protein bodies, crystals, etc.) is accomplished easily. The limit to the number of applications is really only that which is imposed by the imagination - there are quite incredible numbers of reagents which are capable of selective fluorescence tagging of food components, and their application is as diverse as the variety of problems in the research laboratory. 

TNT vapor in air was determined by a colorimetric method involving a Na sulfite-hydroxide color complex (Ref 15). A method is presented for the quant spectrophotometric analysis of polynitroaromatics as their Meisenheimer complexes in ethylene diamine dimethylsulfoxide solns (Ref 32). Detection by formation of colored reaction complexes determined by wavelength absorbances and absoiptivities of the reagent/expl samples are described (Refs 92 132). A semi-quant colorimetric determination... 

A more complex analysis of the effect of laser phase diffusion has been appli fS the case of one-photon vs. three-photon absoiption (i.e., simultaneous absorption 3a)j and third-harmonic generation frqnt>t coi laser. As discussed in Section 3.3.2, current experiments vary the relative ph of two laser beams by passing co3 and co, through a gas. If the laser frequcnc somewhat unstable, then the relative phase of the two beams will acquire a fhtct y ing phase that is a source of phase loss in the system. The phase fluctuations q ... 

In situ quantitation The absoiption-photometric analysis was earned out at / - 378 nm.----------------------------------------------------------------... 

Protein, iron catd labile sufiir analysis Protein was quantified by a modified Lowry assay (12) on triplicate samples at 3 different sample amounts. Iron was analyz by atomic absoiption using deuterium arc background correction by the method of standard additions. AU samples for iron analysis were passed over Chelex resin io>Rad) to remove any unbound iron. Labile sulfur analysis was done according to the method of (13) except that CHQ3 was used for extraction of pigment acidification products. 

The total mass of the system is m, n is the total mass flux (mass flow per unit area) relative to the stem boundaiy at any point, and S is the cross-sectional area nonnal to flow at that same location. The summations extend over all the mass entry and exit locations in the system. The mass flux at any poim is equal to pv, where p is the mass density and o is the velocity relative to the boundary at that point. Equation (2.2-1) can be applied equally well to a countercuirent gas absoiption column or to a lake with input and output streams such as rain l, evaporation, streams flowing to or from the lake, deposition of sediment on the lake bottom, or dissolution of minerals fiom the sides and bottom of the lake. The steady-state version of Eq. (2.2-1) ( 0) is of use in chemical process analysis because it permits calculation of various flow rates once some have been specified. 

The ciystallisation run was as follows. One litre each of 14.7 g L calcium chloride and sodium sulphate solutions were placed in the crystalliser, the impeller was started and the whole system was left to equilibrate to the designated temperatures of 25, 35, and 45 C. A solution sample (which conesponds to t = 0 or zero time) was taken and prepared for the calculation of calcium ion concentration using atomic absoiption spectrometry (AAS) analysis (as discussed later, the gypsum crystallisation process was followed by measuring the decrease of one of the gypsum crystal components, i.e. the Ca. Eight grams of seed crystals (sized 53 to 90 micron) were added and the timer was started. Samples were taken for AAS analysis at 5,10,15,20, 30,40, 60 and 90 minutes respectively after the seed addition. 

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