Reaction chromatogram

Figure 10. Reaction chromatograms for A, Amstel river water and B, Amstel river water fortified with 3 ng of aldicarb (peak 1) 3 ng of methomyl (peak 2) 5 ng of propoxur (peak 3) 5 ng of carbaryl (peak 4) and 10 ng of methiocarb (peak 5). Conditions 150-mm X 4.6-mm i.d. column packed with Spherisorb ODS mobile phase of 50% water and 50% methanol (v/v) at a flow rate of 1.0 mL/min 60-mm X 4.6-mm i.d. reactor column packed with Aminex A-28 reaction temperature of 100 °C OF A reagent flow rate of 30 pL/min detection with Perkin-Elmer Model 204A fluorescence spectrometer excitation wavelength of 340 nm emission wavelength of 455 nm. (Reproduced with permission from reference 46. Copyright 1983 Elsevier Scientific Publishers.)...

C4 peak on the shot reaction chromatogram, making measurement difficult. The estimated probable error has been indicated by bars in Figure 3. (A typical peak is shown in Figure 5, d the dashed line shows the peak width for a shot passed through the analytical column alone.) There was also a loss of material in the shot reactions—i.e., the difference between the initial and final quantities of thiophene (upper curve, Figure 3) was greater than the C4 produced (middle curve). Presumably the loss was due to irreversible adsorption of either butene or thiophene, possibly as a polymer. 

Figure 1. Typical HPLC chromatograms of the OPA-NAC (II) derivitized amino acids detected from the spark discharge reactions. Chromatograms labeled with roman numerals I.) Amino acid standard, II.) CO2/N2 not sparked, III.) CO2/N2 + CaCOs, sparked, hydrolyzed- ascorbate. IV.) CO2/N2, sparked, hydrolyzed - ascorbate V.) CO2/N2, sparked + CaCOs, hydrolyzed + ascorbate. Amino acids I.) DL aspartic acid 2.) DL glutamic acid 3.) DL serine 4.) glycine 5.) P-alanine 6.) DL alanine 7.) a-amino isobutyric acid 8.) DL norleucine (internal standard). The D and L enantiomers of glutamic acid and serine are not separated under these chromatographic conditions.

Fig. S.5S. Reaction chromatogram of the photoreaction of stilbene using the microprocessor control set-up given in Fig. 4.29 and correcting for the dilution according u> Fig 4.30. The differott dironratograms absorbance E versus retention time t afta distinct pbotoreaction...

In Fig. 5.56 the even more complex photoreaction of diphenyloctatetraene is discussed [187,188]. The reaction chromatogram allows the elucidation of the mechanism with respect to consecutive and parallel photoreactions, which is interesting in comparison with other diphenyl substituted alkene chains. 

Cinnamic alcohol and its derivatives are starting materials for the synthesis of coumarin dyes used in food industries and as laser dyes. By irradiation at 254 nm cinnamic acid or the alcohol exhibits an extremely complex reaction spectrum using UWVis-spectroscopy. A comparison of the reaction chromatograms for different irradiation conditions in various solvents... 

In Section 5.6.1.1 quantitative results for the partial photochemical quantum yields of the photoreaction of stilbene-1 were given. A photoisomerisation was assumed to be the mechanism as a first step. This proposal is supported by a reaction chromatogram of the photodegradation reaction of this laser dye. The two parts of the diagram (see Fig. 5.58) prove a photo-reversible isomerisation as a first step [190]. This information was used for the evaluation mentioned. 

Fig. 5.57. Cinnamic alcohol irradiated at 254 nm in methanol reaction chromatogram with...

The inlet peak area is expressed by an internal standard being completely separated from the reaction chromatogram and inert with respect to the reaction. Then... 

Thede, R. Pscheidl, H. Haberland, D. Analysis of the first absolute statistical total moment of reaction chromatograms for determining the rate constants of first-order irreversible reactions. Z. Phys. Chem. 1985, 266 (6), 1089-1105. 

The purity of the product was determined by the checkers by GLC analysis using the following column and conditions 3-nm by 1.8-m column, 5% free fatty acid phase (FFAP) on acid-washed chromosorb W (60-80 mesh) treated with dimethyldichlorosilane, 90 C (1 min) then 90 to 200 C (15°C per rain). The chromatogram showed a major peak for methyl 2-methyl-l-cyclohexene-l-carboxylate preceded by two minor peaks for methyl 1-cyclohexene-l-carboxylate and l-acetyl-2-methylcyclohexene. The areas of the two impurity peaks were 5-6% and 0.5-2% that of the major peak. The purity of the product seems to depend upon careful temperature control during the reaction. The total amount of the two impurities was 14-21% in runs conducted at about -15 to -20°C or at temperatures below -23°C. 

Microchemical reactions These can be carried out either with universal reagents [11] or with such substances which react with particular functional groups (group-characterizing reagents). If the separation process ensures that only one component occurs at a particular spot on the chromatogram, then this can be detected sub-stance-specifically . But specificity in an unequivocal sense can only be produced by a combination of the separation and the detection process. (The same is true of other forms of detection.)... 

The chromatogram is observed and documented as soon as the spots are readily visible. The iodine can then be allowed to evaporate from the chromatogram (fume cupboard ). The chromatogram can then be subjected to further reactions or processes after this reversible reaction. 

When undertaking quantitative investigations it should be checked that the reaction on the TLC plate is complete — or at least stoichiometric and reproducible. In all cases it is also useful to apply reagent and sample solutions separately on neighboring tracks in order to be able to determine where the starting products appear in the chromatogram under the reaction conditions. In this way it is possible to decide whether additional by-products are produced. 

Fig. 36 Dependence of the area of the chromatogram zone at constant amount of applied substance (1 pg) on the reagent employed, top relief representation, below zone areas projected on one another Iodine vapor reacts least sensitively here, aniline-phthalate most sensitively and the GOD reaction (glucose oxidase reaction) most specifically [2161...

Hotplates (Fig. 45) are coming into increasing use for heating chromatograms. They have the advantage that it is possible to follow the reaction visually and the... 

Enzymatic determinations of the detection limit where the chromatograms are first sprayed with an enzyme solution Then after appropriate incubation the enzymatically altered components are detected by reaction with a suitable reagent... 

The chromatogram is freed from mobile phase and evenly sprayed with the spray solution or immersed for 1 s in the dipping solution. After drying the TLC plate is heated to 85 —120°C normally for 10 to 15 min but in exceptional cases for 60 min. It is advisable to observe the chromatogram during the reaction period, because the temperature and duration of heating strongly affect color development. 

The mechanism of the reaction has not been elucidated. Berberine is probably enriched in the lipophilic chromatogram zones which then fluoresce more intensely than the environment. 

Folic acid is detected by irradiating the chromatogram with broad-spectrum UV light for 30 min before reaction with Bratton-Marshall reagent (detection limit 200ng)[12]. 

Aminoglycoside antibiotics and / -substituted indoles are stained red. Pyrrole derivatives with free / -positions react at room temperature to yield blue-colored zones [11]. Exposure to the vapors of aqua regia deepens the colors. This reaction sometimes produces fluorescence [3]. The detection limit for monomethylhydrazine is 200 pg per chromatogram zone [3]. 

Note The pre- and post-treatment of the chromatograms with the basic tri-ethylamine solution, which can be replaced by an alcoholic solution of sodium hydroxide [1,4] or a phosphate buffer solution pH = 8.0 (c = 0.2 mol/1) [5], serves to stabilize the fluorescence of the amino derivatives [2]. A final spraying with methanolic hydrochloric acid (chci = 5 mol/1) or 70% perchloric acid renders the detection reaction highly specific for histamine [4] and for catecholamines and indolamines [5]. 

Detection and result The chromatogram was dried in a stream of warm air for 10 min, immersed in the reagent solution for 3 s and then subjected to intense UV radiation (high pressure lamp, A = 365 nm) for up to 10 min. Terephthalic (hRf 0 - 5), pimelic (hRf 55), suberic (hRf 60), sebacic (hRf 65 — 70) and benzoic acids (hRf 70 — 75) together with sorbic, malic, adipic, citric, tartaric, lactic and fumaric acids only exhibited a reaction on silica gel layers at higher concentrations. 4-Hydroxybenzoic, salicylic and acetylsalicylic acids fluoresced light blue after irradiation. The detection limit per chromatogram zone was 0.5 pg for salicylic acid and more than 5 pg for benzoic acid. 

Note The detection limits per chromatogram zone arc ca. 1 pg substance in the case of aryl-substituted thioureas [4], but even at 50 pg per zone diallate and triallate did not produce any reaction [6]. The reagent should be employed undiluted (cf. Procedure Tested , Fig. 2). 

The reaction is based, on the one hand, on the oxidative cleavage of vicinal diols by lead(IV) acetate and, on the other hand, on the reaction of dichlorofluorescein with lead(IV) acetate to yield a nonfluorescent oxidation product. The dichlorofluorescein only maintains its fluorescence in the chromatogram zones where the lead(IV) acetate has been consumed by the glycol cleavage reaction [1],... 

Reaction usually occurs immediately or occasionally after heating briefly to 140°C, to yield red-violet chromatogram zones on a pale yellow-beige background. 

Note The reaction for barbiturates according to variant I is increased in sensitivity if the chromatogram is exposed to direct sunlight or UV light after it has been sprayed this causes the background coloration to fade almost completely and the blue zones stand out more distinctly [4]. 

Note The reagent can be employed on silica gel, kieselguhr, cellulose and polyamide layers. When left exposed to air the whole chromatogram is slowly colored blue because of the formation of the blue cation (3) (see Reaction). The detection limits for patulin, moniliformine and penicillic acid are ca. 50 ng per chromatogram zone. 

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