Sample liquid samples

Field Measurement Conditions Those gathering samples must be aware of the temperature, pressure, flamm ihty, and toxic characteristics of the samples for which they will be responsible. This is particularly important when samples are taken from unfamihar locations. Sample ports will have to be blown down to obtain representative samples. Liquid samples will have to be vented. Temperatures above... 

Loading and Compression Media. The loading procedures of the DAC depend on the thermodynamic properties and chemical characteristic of the sample. Liquid samples at ambient conditions are generally easy to be loaded, because a droplet can be positioned in the sample chamber to completely fill the gasket hole. Solid samples can be crumbled and cut in the desired dimensions and then positioned in the gasket hole. Powders as well can be loaded in the same way. 

Liquid Samples. Liquid samples such as plasma or milk are shell-frozen in the lyophilizer flasks using a mixture of crushed dry ice and 2-propanol. They are then dehydrated in the same way as the solid samples. The resulting material, which is brittle and spongy and easily broken up, is then pressed into cans and sealed. No preservative is added to the dried materials they can be stored indefinitely at room temperature. Approximately 2 liters of fresh milk can be dried and compressed into one can. 

Sample preparation for color analysis will depend on the type of food sample. Liquid samples such as beverages can be filtered through a 0.45 /rm pore membrane filter and injected directly in the HPLC. Carbonated beverages are degassed. Beverages containing suspended solids are filtered or centrifuged to eliminate suspended solids (143,156,160). 

Solid Scintillation Counting of f3 Emissions. To avoid some of the problems associated with liquid scintillation counting, a method has been developed for measuring /T radioactivity by scintillation of solid samples. Liquid samples containing the radioactive material to be counted are placed in small... 

The selection of an extraction procedure depends primarily on the class of compounds of interest as well as the type and physical state of the sample. Liquid samples generally do not require extraction prior to analysis however liquid-liquid extraction may be performed to isolate a certain class of compounds. Extraction of antioxidants from solid plant materials is most commonly done using aqueous mixtures of organic solvents. This is based on the principle that, upon extraction. 

Table 1 Management of large compound collections by three interconnected samplehandling systems. The three systems are used for automated storage and retrieval of powder samples, liquid samples, and liquid aliquots, respectively...

The extraction technique depends on the sample. Liquid samples may be extracted with an organic solvent or with a sorbent where compounds of interest are easily sorbed and desorbed. Solid-phase extraction, solid-phase... 

Samples. Liquid samples are diluted with water to contain from 0.5 to 2.5 Mg- per milliliter of terramycin. Dry samples of the free base, which are not readily soluble in water, are more easily handled by first being dissolved in a small amount of 0.1 IV HCl and then brought to the required dilution with water. 

Gaseous samples Liquid samples Solid samples... 

Now using a hydrocarbon component, say ethane, as an example, let us consider the other parameter, volume, using a plot of pressure versus specific volume (i.e. volume per unit mass of the component, the inverse of the density). The process to be described could be performed physically by placing the liquid sample into a closed cell (PVT cell), and then reducing the pressure of the sample by withdrawing the piston of the cell and increasing the volume contained by the sample. 

It is especially useflil for liquid samples in flat cells, which may extend through tlie entire height of the cavity. In the cylindrical cavity a TEq mode is frequently used because of its fairly high g-factor and the very strong along the sample axis. 

The vibration frequencies of C-H bond are noticeably higher for gaseous thiazole than for its dilute solutions in carbon tetrachloride or tor liquid samples (Table 1-27). The molar extinction coefficient and especially the integrated intensity of the same peaks decrease dramatically with dilution (203). Inversely, the y(C(2jH) and y(C(5(H) frequencies are lower for gaseous thiazole than for its solutions, and still lower than for liquid samples (cf. Table 1-27). 

Although the terms solute and solution are often associated with liquid samples, they can be extended to gas-phase and solid-phase samples as well. The actual units for reporting concentration depend on how the amounts of solute and solution are measured. Table 2.4 lists the most common units of concentration. 

Typical examples of liquid samples include those drawn from containers of commercial solvents beverages, such as milk or fruit juice natural waters, including from lakes, streams, seawater, and rain bodily fluids, such as blood and urine and, suspensions, such as those found in many oral medications. 

Sample Preservation Once removed from its target population, a liquid sample s chemical composition may change as a result of chemical, biological, or physical processes. Following its collection, samples are preserved by controlling the solu-... 

Solid-Phase Extractions In a solid-phase extraction the sample is passed through a cartridge containing solid particulates that serve as the adsorbent material. For liquid samples the solid adsorbent is isolated in either a disk cartridge or a column (Figure 7.17). The choice of adsorbent is determined by the properties of the species being retained and the matrix in which it is found. Representative solid adsorbents... 

Selected Adsorbents for Solid-Phase Extraction of Liquid Samples... 

A technique for separating volatile analytes from liquid samples in which the analytes are subsequently trapped on a solid adsorbent. 

Liquid-liquid extractions using ammonium pyrrolidine dithiocarbamate (APDC) as a metal chelating agent are commonly encountered in the analysis of metal ions in aqueous samples. The sample and APDC are mixed together, and the resulting metal-ligand complexes are extracted into methyl isobutyl ketone before analysis. 

Liquid samples are analyzed in one of two ways. For nonvolatile liquids a suitable sample can be prepared by placing a drop of the liquid between two NaCl plates, forming a thin film that typically is less than 0.01 mm thick. Volatile liquids must be placed in a sealed cell to prevent their evaporation. 

Atomization and Excitation Atomic emission requires a means for converting an analyte in solid, liquid, or solution form to a free gaseous atom. The same source of thermal energy usually serves as the excitation source. The most common methods are flames and plasmas, both of which are useful for liquid or solution samples. Solid samples may be analyzed by dissolving in solution and using a flame or plasma atomizer. 

Porro, T. J. Pattacini, S. C. Sample Handling for Mid-Infrared Spectroscopy, Part 1 Solid and Liquid Sampling, Spectroscopy 1993, 8(7), 40-47. 

For most samples liquid-solid chromatography does not offer any special advantages over liquid-liquid chromatography (LLC). One exception is for the analysis of isomers, where LLC excels. Figure 12.32 shows a typical LSC separation of two amphetamines on a silica column using an 80 20 mixture of methylene chloride and methanol containing 1% NH4OH as a mobile phase. Nonpolar stationary phases, such as charcoal-based absorbents, also may be used. 

Under these conditions, the flow of sample liquid is predicted to be shown and this is similar to the flows observed with concentric nebulizers. 

The liquid sample flows into the nozzle and coats the inside walls. The sample stream arrives at the orifice (the nozzle outlet is about 0.01 cm diameter), where it meets the argon stream and is nebulized. 

Finally, in yet another variant, the sample liquid stream and the gas flow are brought together at a shaped nozzle into which the liquid flows (parallel-path nebulizer). Again, the intersection of liquid film and gas flow leads to the formation of an aerosol. Obstruction of the sample flow by formation of deposits is not a problem, and the devices are easily constructed from plastics, making them robust and cheap. 

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