Laboratory extractions, liquid

Robandt PV, Klette KL, Sibum M (2009) Automated solid-phase extraction-liquid chromatography-tandem mass spectrometry analysis of 1 l-nor-Delta9-tetrahydrocannabinol-9-car-boxylic acid in human urine specimens application to a high-throughput urine analysis laboratory. J Anal Toxicol 33(8) 456 f60... 

In the tenth official proficiency test, the presence of bis(2-hydroxyethyl) sulfone) (BHES, CAS 2580-77-0) in the decontamination solution sample D2 was missed by one laboratory. The laboratory performed liquid-liquid extraction of the aliquots with dichloromethane and benzene, concentrated the organic extracts, and silylated them. One aliquot of the organic extract was evaporated to dryness, dissolved, methylated, evaporated to dryness, and dissolved again. Evaporation of the water phase to dryness and silylation of the residue was not reported, and the failure to do this might be the reason why the laboratory did not identify BHES using GC-based methods for analysis. 

Sample preparation represents a formidable challenge in the chemical analysis of the real-world samples. Not only is the majority of total analysis time spent in sample preparation, but also it is the most error-prone, least glamorous, and the most labor-intensive task in the laboratory. The components to be separated from the matrix are usually taken up with an auxiliary substance such as a carrier gas, an organic solvent, or an adsorbent. These separation processes can be regarded as extraction procedures (i.e., liquid-liquid extraction, liquid-solid extraction, Soxhlet extraction, solid-phase extraction, supercritical fluid extraction, solid-phase microextraction, etc.). 

The residues must be soluble in the extraction liquid, whereas as few as possible of the interfering substances should be soluble. Possibilities to purify and reuse the solvents by distillation and chromatographic techniques in the laboratory are advantageous. If the extract has to be concentrated, a low boiling point is important. 

We present here some experimental data on gas solubilities in liquids obtained in our laboratory. The liquid previously degassed is saturated by the unreacted gas, in a thermostated autoclave, provided with a mechanically bladed stirrer under a solute partial pressure p. After saturation attainment, a sample of the saturated liquid is taken via a syringe of high precision and injected into a gas-chromatograph in order to extract the solute dissolved in a known volume of the liquid sample V. By the way of calibration gas of known solute mole fraction, the number of... 

The different uses of liquid-liquid extraction, liquid membranes, and solvent impregnated materials make the subject important for university students of chemistry, metallurgy, hydrometallurgy, and chemical and mineral processing technology. Some universities offer special courses on separation processes in which those techniques are minor topics in more comprehensive courses. Laboratory experiments on liquid-liquid and liquid membranes are common in chemical and mineral processing engineering curricula. Because of the breadth of the subject, the treatment in such courses is often scarce, and more comprehensive text is difficult to find in a form suitable for use directly with students. 

In order to give an idea of the care with which such methods have to be developed several detailed examples are given of previously unpublished methods developed in the Author s laboratories for the determination of particular types of extractables in extraction liquids, e.g., dilaurylthiodipropionate, Nonox Cl, antioxidants and Ethylon (lauric diethanolamide). 

The sodium fusion and extraction, if performed strictly in accordance with the above directions, should be safe operations. In crowded laboratories, however, additional safety may be obtained by employing the follow ing modification. Suspend the hard-glass test-tube by the rim through a hole in a piece of stout copper sheet (Fig. 69). Place 1 -2 pellets of sodium in the tube, and heat gently until the sodium melts. Then drop the organic compound, in small quantities at a time, down — =. the tube, allowing the reaction to subside after each addition before the next is made. (If the compound is liquid, allow two or three small drops to fall at intervals from a fine dropping-tube directly on to the molten sodium.) Then heat the complete mixture as before until no further reaction occurs. 

The theory of the process can best be illustrated by considering the operation, frequently carried out in the laboratory, of extracting an orgaiuc compound from its aqueous solution with an immiscible solvent. We are concerned here with the distribution law or partition law which, states that if to a system of two liquid layers, made up of two immiscible or slightly miscible components, is added a quantity of a third substance soluble in both layers, then the substance distributes itself between the two layers so that the ratio of the concentration in one solvent to the concentration in the second solvent remains constant at constant temperature. It is assumed that the molecular state of the substance is the same in both solvents. If and Cg are the concentrations in the layers A and B, then, at constant temperature ... 

The Analysis of Trihalomethanes in Drinking Water by Liquid Extraction US Environmental Protection Agency, Environmental Monitoring and Support Laboratory, Cincinnati, OH, 9 Sept. 1977. 

An equihbrium, or theoretical, stage in liquid-liquid extraction as defined earlier is routinely utilized in laboratory procedures. A feed solution is contacted with an immiscible solvent to remove one or more of the solutes from the feed. This can be carried out in a separating funnel, or, preferably, in an agitated vessel that can produce droplets of about 1 mm in diameter. After agitation has stopped and the phases separate, the two clear liquid layers are isolated by decantation. 

The general proportions may be varied from one end of the tower to the other to accommodate changing liquid volumes and physical properties. These towers have been used in diameters ranging from a few inches for laboratory work up to 2.4 m (8 ft) in diameter by 12.2 m (40 ft) tall for purposes of deasphalting petroleum. Other commercial services include furfural extraction of lubricating oils, desulfurization of gasoline, phenol recoveiy from wastewaters, and many others. Columns up to 4.5 m in diameter and up to 50 m in height have been constructed. 

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