Analysis of Liquids and Solutions

The quantitative analysis of a component in solution can be successfully carried out given that there is a suitable band in the spectrum of the component of interest. The band chosen for analysis should  

We will illustrate the process of simple quantitative analysis by using the example of aspirin dissolved in chloroform. The best peak to choose in this example is the C=0 stretching band of aspirin observed at 1764 cm because it is an intense peak and lies in a region where there is no interference from the chloroform spectrum. 

The next step is to draw a calibration plot of absorbance versus aspirin concentration. A series of chloroform solutions of known (aspirin) concentrations yere therefore prepared. The infrared spectrum of each solution was recorded by using a O.lmmNaCl transmission cell. The intensity of the 1764 cm i band was measured for each solution, with the results obtained being listed in Table 5.5a. 

Infrared spectroscopy can be used to measure the number of functional groups in a molecule, e.g. the number of —OH or —NH2 groups. It has been found that the molar absorptivity of the bands corresponding to a particular group is proportional to the number of groups that are present, i.e. each group has its own intensity which does not vary drastically from molecule to molecule. 

Solid mixtures can also be analysed by using infrared spectroscopy. However, solids are more susceptible to errors because of scattering effects. Such analyses are usually carried out with KBr discs or with mulls. The problem here is the difficulty in measuring the pathlength. However, this measurement becomes unnecessary when an internal standard is used. Addition of a constant known amount of an internal standard is made to all samples and calibration standards. 

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Sham TK, Yang BX, Kirz J, Tse JS (1989) -edge near-edge X-ray-absorption fine structure of oxygen-and carbon-containing molecules in the gas phase. Phys Rev A 40 652-669 Siegbahn H (1985) Electron spectroscopy for chemical analysis of liquids and solutions. J Phys Chem 89 897-909... 

H. Siegbahn Electron spectroscopy for chemical analysis of liquids and solutions. J. Phys. Chem. 89, 897 (1985)... 

One type of chemical approach to the analysis of liquid and solid hydrocarbons that will probably see considerable development is that involving reaction or complex formation to yield precipitates that can be separated from the unreacted mass and subsequently be treated to regenerate the hydrocarbons or class of hydrocarbons so precipitated. This field is certainly not extensively developed. In fact very few examples come to mind but among these are Gair s (21) determination of naphthalene by precipitation with picric acid determination of benzene by Pritzker and Jungkunz (52) by an aqueous solution of specially prepared nickel ammonium cyanide Bond s (8) nitrous acid method for styrene and more recently the determination of normal alkanes in hydrocarbons of more than 15 carbon atoms by adduct formation with urea as described by Zimmerschied et al. (71). 

Because X-ray powder diffraction deals with solid samples, the analytical variables are different from those associated with the analysis of liquid or solution samples. Principle among these are particle size effects, uniform sample surface, crystallinity and X-ray absorption. Although particle size and a non-uniform sample surface are serious problems, their... 

The analysis of liquid and solid samples very often requires some form of solvent extraction to isolate organic constituents. Conventional solvent extraction can be used, and the pH may be adjusted to achieve some selectivity, for example, extracting from acid solution to prevent basic compounds from extracting. More efficient means of extraction are commonly employed today, such as microwave-assisted or accelerated solvent extraction for solid samples (Chapter 19). See... 

Polymer IR sample cards are available as an inexpensive disposable sample substrate for qualitative analysis of liquids or solutions. These usually consist of a polymer or crystal film held by a cardboard frame that can be mounted for transmission measurement. The most used polymers are PTFE and Polyethylene, due to their relatively flat IR spectra. PTFE has absorption peaks at 1,100-1,300 and 400-750 cm while Polyethylene at 2,800-3,000 and 1,400-1,500 cm . Some companies also offer these cards with crystal films of NaCl, KBr, and KCl. 

Dg remains constant over a wide range of resin to liquid ratios. In a relatively short time, by simple equilibration of small known amounts of resin and solution followed by analysis of the phases, the distribution of solutes may be followed under many different sets of experimental conditions. Variables requiring investigation include the capacity and percent cross-linkage of resin, the type of resin itself, the temperature, and the concentration and pH of electrolyte in the equilibrating solution. 

Preparing the Sample Flame and plasma sources are best suited for the analysis of samples in solution and liquid form. Although solids can be analyzed by direct insertion into the flame or plasma, they usually are first brought into solution by digestion or extraction. 

An instrument known as a refractometer has been used for many years to measure the refractive index of liquids and liquid solutions for the purpose of both quantitative and qualitative analysis (see Chapter 15). A refractometer measures the degree of refraction (or bending) of a light beam passing through a thin film of the liquid. This refraction occurs when the speed of light in the sample is different from a reference liquid or air. The refractometer measures the position of the light beam relative to the reference and is calibrated directly in refractive index values. It is rare for any two liquids to have the same refractive index, and thus this instrument has been used successfully for qualitative analyses. 

Consider what is termed the sample. A sample is a small portion of a large bulk system that is acquired and taken into the analytical laboratory in lieu of the entire system. For example, it is not practical to bring the entire contents of a 5000-gallon tank of liquid sugar solution used in a pharmaceutical preparation into the analytical laboratory for analysis. The small portion of the solution, perhaps a small vial, that is obtained for the analysis is called the sample, and that is what is taken into the laboratory for analysis. Flow well a sample represents the entire bulk system, and what fundamental issues of quality are involved when obtaining the sample are important questions and will be dealt with in Section 6. The process of obtaining the sample is referred... 

The gas-liquid chromatography with mass spectrometric detection (GLC-MS) analysis of the electrolyzed solution has shown that thiophenol is the only reduction product and the S—S bond cleavage is quantitative. Such a mechanism of bond breaking was confirmed by electrochemical studies. In cyclic voltammograms, anodic and cathodic peak potentials were the same for thiophenol and diphenyl disulfides thus the same species were participating in these processes. Electrode reactions of diphenyl disulfide are given by the following equations [166] ... 

Whitehead, J. A., Lawrance, G. A. and Mccluskey, A., Analysis of gold in solutions containing ionic liquids by inductively coupled plasma atomic emission spectrometry. Australian ]. Chem., 57,151, 2004. 

The basic principles employed in the preparation of parenteral products do not vary from those widely used in other sterile and non-sterile liquid preparations. However, it is imperative that all calculations are made in an accurate and most precise manner. Therefore, an issue of a parenteral solution scale-up essentially becomes a liquid scale-up task, which requires a high degree of accuracy. A practical yet scientifically sound means of performing this scale-up analysis of liquid parenteral systems is presented below. The approach is based on the scale of agitation method. For singlephase liquid systems, the primary scale-up criterion is equal liquid motion when comparing pilot-size batches to a larger production-size batches. 

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