Reagent, in mobile phase

SEPARATION OF AMINO ACID ENANTIOMERS ON THE COMMERCIAL PLATES WITH CHIRAL REAGENT IN MOBILE PHASE... 

A method offering the possibility for the separation, identification, and determination of alkyl- and alkylphenol ether carboxylates, even in mixtures with other nonionic and amphoteric substances, is carried out by HPLC using a reverse phase RP18 column and a mixture of methanol, water, and acetonitrile with the addition of an ion-pairing reagent as mobile phase working under isocratic conditions [242]. 

TLC is often used by BP monographs as part of a number of identity tests performed on pure substances. For extra confirmation of identity, more than one solvent system may be used and also different types of spray reagent may be used. Some examples of identity checks based on TLC have been mentioned earlier. Table 13.4 lists a few of the compounds which have their identity checked by TLC and a variety of location reagents and mobile phases are used to illustrate the fact that there is much less uniformity about TLC methodology than there is in the case of HPLC or GLC methodology. 

Heptafluoro- 1-butanol can be added postcolumn to give a final concentration of 0.1 % (v/v) to enhance ionization efficiency during electrospray. Typically, a 2% (v/v) solution in mobile phase is added at 50 pl/min to the HPLC column effluent at 1 ml/min. Addition of this reagent is optional. 

The first two points represent a general motivation for miniaturization in separation science independent of the actual fabrication technology. The benefit of a reduction of the consumption of sample, reagents, and mobile phase in chemical and biochemical analysis is self-evident and does not need to be discussed further (reduced consumption of precious samples and reagents, reduced amounts of waste, environmental aspects). This advantage is, however, sharply contrasted by its severe implications on the detection side, as discussed elsewhere in this volume in detail. The detection of the separated zones of very small sample volumes critically depends on the availability of highly sensitive detection methods. It is not surprising that extremely sensitive laser-induced-fluorescence (LIF) has been the mostly used detection principle for chip-based separation systems so far. 

The chemical composition, structure, and, hence the properties of products with modified surface are determined both by observing the required sequence of operations, and chosen chemico-technological parameters of process the chemical nature of reagents (volatile and solid), temperature (in stages of preparation of surface, chemisorption and desorption), concentration of reagents (in gas phase and functional groups on surfaces of substrate), hydrodynamics of the process (rate of transport and removal of reagents, mobility or stationary condition of disperse solid phase). 

In the second approach, the stationary phase is physically coated with a chelating reagent and then conditioned to remove unstable reagent prior to use with a reagent-free mobile phase (precoated stationary phases) [458,465,466]. Alternatively, the... 

All of the components for mobile phase preparation can be purchased from reputable or approved suppliers and any changes in supplier should be checked thoroughly before materials are used. Additional validation of the method may be required when there has been a change in supplier of a critical reagent. All mobile phases should be filtered and degassed prior to use. Further discussion in relation to mobile phase quality is given in Chapter 12. 

Sample preparation 500 p-L Plasma + 100 p.L 200 p,g/mL tridecanoic acid in ethylene chloride + 200 xL 600 mM sulfuric acid + 3 mL isooctane isopropanol 95 5, extract. Remove the organic layer and evaporate it to dryness, reconstitute the residue in 1 mL 2.4 mg/mL 2-etho y-l-ethoxycarbonyl-l,2-dihydroquinoline (EEDQ) in ethylene chloride, add 5 mL reagent, reflux for 10 min, dilute with 10 mL ethylene chloride, wash with an equal volume of 200 mM NaOH, wash with an equal volume of 1 M HCl, wash with an equal volume of water. Remove the organic layer and diy it over sodium sulfate, evaporate to diyness, reconstitute the residue in mobile phase, ii ject an aliquot. (Prepare reagent by dissolving 5 mg p-nitrobenzylamine hydrochloride in 5 mL 200 mM NaOH, extract... 

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