Extraction robustness

A target purity of 99 % was established for both extract and raffinate. According to the simulation results, one can predict that a variation of the feed concentration range between 7.5 and 11 g will meet the required purity. The system was designed for a feed concentration equal to 10 g The influence of change in feed concentration on the purity of both extract and raffinate illustrates the robustness of SMB, and that the process tolerates fluctuations when critical parameters are stressed during process validation. 

In the past decade, new sample extraction techniques have been introduced to meet stricter criteria in the areas of food and agriculture, for example, enviromnentally friendly, non-toxic, fast, automated, robust, and cost-efficient techniques. Accelerated solvent extraction (ASE) and pressurized liquid extraction (PEE) are two methods developed for the extraction of chemicals of interest " and provide high yields and efficiency from a wide range of botanical, - animal, and biological samples. ASE and PLE combine solvents at elevated temperatures (40 to 200°C)... 

Membrane Types Key membrane properties include their size rating, selectivity, permeability, mechanical robustness (to allow module fabrication and withstand operating conditions), chemical robustness (to fabrication materials, process fluids, cleaners, and sanitizers), low extractibles, low fouling characteristics, high capacity, low cost, and consistency. 

Crops with high acid content have to be tested separately, to demonstrate the robustness of methods with regard to changes in pH. In such cases, where extractions are performed at pH values which are lower than those of acidic crops (e.g., <3), the influence of sample acidity is not significant. It is assumed that under such circumstances an expert statement should be sufficient and may replace validation experiments with representative commodities of this matrix group. 

Solid-phase microextraction (SPME) consists of dipping a fiber into an aqueous sample to adsorb the analytes followed by thermal desorption into the carrier stream for GC, or, if the analytes are thermally labile, they can be desorbed into the mobile phase for LC. Examples of commercially available fibers include 100-qm PDMS, 65-qm Carbowax-divinylbenzene (CW-DVB), 75-qm Carboxen-polydimethylsiloxane (CX-PDMS), and 85-qm polyacrylate, the last being more suitable for the determination of triazines. The LCDs can be as low as 0.1 qgL Since the quantity of analyte adsorbed on the fiber is based on equilibrium rather than extraction, procedural recovery cannot be assessed on the basis of percentage extraction. The robustness and sensitivity of the technique were demonstrated in an inter-laboratory validation study for several parent triazines and DEA and DIA. A 65-qm CW-DVB fiber was employed for analyte adsorption followed by desorption into the injection port (split/splitless) of a gas chromatograph. The sample was adjusted to neutral pH, and sodium chloride was added to obtain a concentration of 0.3 g During continuous... 

It is often difficult to define where sample extraction ends and cleanup procedures begin. Sample extracts may be injected directly into a gas or liquid chromatograph in certain cases, but this will be dependent on the analyte, sample matrix, injection, separation and detection system, and the limit of determination (LOD) which is required. It is also more likely that matrix-matched calibration standards will be needed in order to obtain robust quantitative data if no cleanup steps are employed. 

The development of a robust analytical method is a complex issue. The residue analyst has available a vast array of techniques to assist in this task, but there are a number of basic rules that should be followed to produce a reliable method. The intention of this article is to provide the analyst with ideas from which a method can be constructed by considering each major component of the analytical method (sample preparation, extraction, sample cleanup, and the determinative step), and to suggest modern techniques that can be used to develop an effective and efficient overall approach. The latter portion emphasizes mass spectrometry (MS) since the current trend for pesticide residue methods is leading to MS becoming the method of choice for simultaneous quantitation and confirmation. This article also serves to update previous publications on similar topics by the authors. ... 

The ICl-CaC03 procedure required a filtration to remove insoluble, inorganic by-products prior to biphasic extraction. In an effort to develop a homogeneous process for the iodination step, a pH control protocol was later implemented in the manufacturing process. The pH-controlled iodination was run in a single phase in a MeOH-water system by simultaneous addition of the aqueous IC1 solution and 1M NaOH. Citric acid was added to increase the buffer capacity to the optimal pH (5-5.5) for robust operation. Under these conditions, the iodoaniline 28 was typically obtained in >99 A% with <1% of diiodoaniline 32. Residual... 

After the flue gas leaves the combustion chamber, most furnace designs extract further heat from the flue gas in horizontal banks of tubes in a convection section, before the flue gas is vented to the atmosphere. The temperature of the flue gases at the exit of the radiant section is usually in the range 700 to 900°C. The first few rows of tubes at the exit of the radiant section are plain tubes, known as shock tubes or shield tubes. These tubes need to be robust enough to be able to withstand high temperatures and receive significant radiant heat from the radiant section. Heat transfer to the shock tubes is both by radiation and by convection. After the shock tubes, the hot flue gases flow across banks of tubes that usually have extended surfaces to increase the rate of heat transfer to the flue gas. The heat transferred in the radiant section will usually be between 50 and 70% of the total heat transferred. 

After performing the mild and effective extraction process the carotenoids must be separated in order to make structural assignments. Robust and reproducible separations of air and UV-sensitive... 

There are a number of procedures described in the literature dealing with the extraction of emerging contaminants from solid matrices. For extractions of solid samples, Soxhlet is widely accepted as a robust liquid-solid extraction technique. 

This technology lends itself to continuous, rather than batch, processing and has been proven robust since first applied for the extraction of uranium in the early 1940s.10 The types of extractant used can be classified according to the types of reactions involved in phase transfer.111... 

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