Sample dialysis

Notwithstanding the excellent analytical features inherent in molecular phosphorimetric measurements, their use has been impeded by the need for cumbersome cryogenic temperature techniques. The ability to stabilize the "triplet state" at room temperature by immobilization of the phosphor on a solid support [69,70] or in a liquid solution using an "ordered medium" [71] has opened new avenues for phosphorescence studies and analytical phosphorimetry. Room-temperature phosphorescence (RTF) has so far been used for the determination of trace amounts of many organic compounds of biochemical interest [69,72]. Retention of the phosphorescent species on a solid support housed in a flow-cell is an excellent way of "anchoring" it in order to avoid radiationless deactivation. A configuration such as that shown in Fig. 2.13.4 was used to implement a sensor based on this principle in order to determine aluminium in clinical samples (dialysis fluids and concen-... 

The flow-through sensor shown in Fig. 5.17.B, developed for the determination of aluminium in real samples (dialysis fluids and concentrates), is... 

Most of the electrophoresis systems are sensitive to ionic strength ( salt content ) of samples. Dialysis of the sample against a 100-fold volume of sample buffer for 30 min or protein precipitation by TCA and dissolving of the pellet in sample buffer obviate this problem. 

The ideal system for sample preparation in a chromatographic method is that the operation of all the steps between sample dissolution and chromatography is done through a SIA technique (Fig.l). The first part of the system will consist of a sample dialysis (unit 1) and the outlet will be channeled into the second unit consisting of concentration or dilution steps and extraction of the analyte. It is always assumed that the concentration, dilution, and derivatization steps can be done by extraction — in most cases, it is absolutely necessary. 

Peroxyni trite Biological samples Dialysis (for sampling) CL 1 x 1CU11 and 1 x 1CT10 mol L 1 for systems without and with dialysis Flow injection system permselective cellulose acetate membrane sampler [544]... 

Therefore, it is crucial to check the blank of the samples (dialysis water and the pool of blood and urine) used to assess quality control procedure and method validation. 

This demonstration procedure should be performed on distilled water (where no interferences should be present) and then on matrix samples (dialysis water, urine, and/or blood) to evaluate the weight of matrix effect on the reliability of the method. 

In order to avoid loss of analytes during collection and storage, 2 mL of the sample (dialysis water, and/or urine and/or heparinized blood) should be immediately transferred to 4.0-mL SPME glass vials containing 1.0 g of NaCl. 

Illustration of a dialysis membrane in action. In (a) the sample solution is placed in the dialysis tube and submerged in the solvent, (b) Smaller particles pass through the membrane, but larger particles remain within the dialysis tube. 

The microdialysis sampling process which allows the monitoring of small molecules in circulation within an animal, is an example. An artificial capillary is placed in the tissue region of interest, and a sample is coUected via dialysis. In the case of a laboratory animal such as a rat, a probe is placed in the jugular vein under anesthesia. Elow rates ate of the order of 1 p.L/min. 

A. Farjam, N. C. van de Merbel, A. A. Nieman, H. Lingeman and U. A. Th Brinkman, Determination of aflatoxin Ml using a dialysis-based immunoaffinity sample pretreat-ment system coupled on-line to liquid cliromatography , ]. Chromatogr. 589 141-149(1992). 

R. Herraez-Heruandez, A. J. H. Eouter, N. C. van de Merbel and U. A. Th Brinkman, Automated on-line dialysis for sample preparation for gas cliromatogruphy determination of benzodiazepines in human plasma , 7. Pharm. Biomed. Anal. 14 1077-1087 (1996). 

The solution was then dialyzed through a cellophane membrane against 4 iiters of water for 10 hours, with stirring. The dialysis was repeated 2 additional times, with fresh amounts of water. To the dialyzed solution there was added 2 mi of 1 N hydrochloric acid, whereupon polyestradiol phosphate was precipitated as a white bulky precipitate. This was centrifuged off and washed repeatedly with 0.1 N hydrochloric acid. Thereafter it was dried in a vacuum desiccator. The yield was 3 g of polyestradiol phosphate. The analysis shows 0.65% of water, 1.35% of pyridine and 9,3% of phosphorus (calculated on a dry sample). 

Prevention of clotting in arterial and heart surgery, in blood transfusions and dialysis procedures, and in blood samples for laboratory purposes ... 

Inhibitors should be removed from sample. An example is urinary phosphate, which can be removed by dialysis prior to measuring the urinary alkaline phosphatase activity (18). 

Figure 4.8 Noradrenaline concentration in dialysis samples from probes implanted in the rat frontal cortex. Spontaneous efflux of noradrenaline is stable throughout a 4h sampling period ( extended basals ) but is increased markedly when either the noradrenaline reuptake inhibitor, desipramine (5 pM), or the a2-adrenoceptor antagonist, atipamezole (0.5 pM), is infused into the extracellular fluid via the microdialysis probe ( retrodialysis )...

AE was purified from orange peels. After homogenization, precipitation with 30 - 60% (NH4)2S04 followed by dialysis, the sample was applied to a cation exchange column (CM-Sepharose CL-6B). AE binds strongly to a cation exchange column material at pH 6.8... 

This assay system developed by Chaires [136] is a new, powerful and effective tool based on the fundamental thermodynamic principle of equilibrium dialysis for the discovery of ligands that bind to nucleic acids with structural and sequence selectivity. Here, identical concentrations of various nucleic acid samples are dialysed in dispodialysers against a common ligand solution. At equilibrium, the contents of the ligand bound to each nucleic acid are determined and this is correlated directly to the ligand s specificity to a particular sequence. 

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