Isolation techniques automated procedures

Due to the numerous drawbacks of L-L extraction procedures, Liquid-Solid (L-S) methods using very low volumes of solvent were introduced since the beginning of the 1980s. These include SPME and SPE, and currently the emphasis is on automation of the whole SPE procedure. The ideal methodology for sample preparation is fast, accurate, precise, and consumes little solvent. Furthermore, it is easily adapted for fieldwork, and requires less costly materials. The SPE method may be the isolation technique capable of meeting all these expectations. ... 

The chromatographic procedure intially investigated was reverse-phase liquid chromatography (RPLC) using Cig-bonded silica gel. This technique has been used previously for the preconcentration of trace metals from seawater prior to analysis by atomic absorption spectrophotometry (23, 24) and for the isolation of organically bound copper from seawater (4). These methods were modified and adapted for automation. 

We have developed an automated parallel synthesis methodology that permits the rapid and detailed Investigation of hydrothermal systems. The general procedure is as follows automatic dispensing of reagents into autoclave blocks followed by synthesis, product isolation and automated structure analysis with X-ray diffractometry. Here we describe the application of this technique to the exploration of the aluminophosphate synthesis field. The effects of template, template concentration, A1 sources as well as mixed template systems are investigated. Emphasis is put on the study of cooperative structure direction effects. 

Previous work by Assem (1977) had suggested that the leucocyte histamine release test was a particularly useful diagnostic tool in patients who developed reactions to muscle relaxants. In that work, it was essential to assay the histamine released by a non-biological method (i.e., not on isolated guinea-pig ileum) because of the interference by muscle relaxants with the bioassay. The assay procedure used was chemical, using an automated spectrofluorometric technique (Technicon). Good... 

Chromatographic techniques require various procedures to isolate the drugs from biological matrices. In the reviewed methods, two distinct approaches are applied liquid-liquid extraction and direct injection into a chromatographic system. Diethyl ether and ethyl acetate,chloroform,toluene, benzene, methyl r-butyl ether, and n-butyl chloride are used as solvents to obtain recoveries well over 80% for all considered compounds. However, manual sample preparation can be labor and time intensive. Therefore, direct injection is used as a highly automated methodol-ogy. The direct injection of complex samples, however, may lead to contamination of columns, thereby impairing their performance. Contamination often persists, even when a precolumn is used to protect the analytical column. A summary of these chromatographic methods for determination of sulfonylureas is presented in Table 1. 

Because of their therapeutic advantages, the above-discussed oral antidiabetic drugs are more and more frequently used in therapy and are extensively examined by analytical procedures. Especially, the methods for pharmacokinetic studies and for quantification of potential impurities in bulk drug substances are continually being developed. Most favored, in terms of a number of publications, are the HPLC techniques, although TLC methods are also represented. In HPLC, a RP technique with Ci8 columns is more prevalent than the alternative phases. Isolation steps are almost evenly distributed between conventional liquid—liquid extraction and SPE procedures. The UV detection can serve as a reliable tool for determination of most of these antidiabetics. However, new prospects are represented by the MS/MS detection. Sensitive and automated HPLC techniques with column switching are also more and more frequently applied. 

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