Dipping solutions

Tire Cord. Melamine resins are also used to improve the adhesion of mbber to reinforcing cord in tires. Textile cord is normally coated with a latex dip solution composed of a vinylpyridine—styrene—butadiene latex mbber containing resorcinol—formaldehyde resin.. The dip coat is cured prior to use. The dip coat improves the adhesion of the textile cord to mbber. Further improvement in adhesion is provided by adding resorcinol and hexa(methoxymethyl) melamine [3089-11 -0] (HMMM) to the mbber compound which is in contact with the textile cord. The HMMM resin and resorcinol cross-link during mbber vulcanization and cure to form an interpenetrating polymer within the mbber matrix which strengthens or reinforces the mbber and increases adhesion to the textile cord. Brass-coated steel cord is also widely used in tires for reinforcement. Steel belts and bead wire are common apphcations. Again, HMMM resins and resorcinol [108-46-3] are used in the mbber compound which is in contact with the steel cord to reinforce the mbber and increase the adhesion of the mbber to the steel cord. This use of melamine resins is described in the patent Hterature (49). 

Fig. 38 Companson of manual dipping (A) with mechanized dipping (B) on the basis of scans and calibration curves [114] — 1 = cM-diethylstilbestrol, 2 = traw-diethylstilbestrol, 3 = ethinylestradiol Scanning curve 2 ng of each substance per chromatogram zone = 313 nm, /n > 390 nm Dipping solution water — sulfuric acid — methanol (85 + 15 + 1)...

The dipping solutions described in Part II of this book are usually less concentrated than the corresponding spray solutions. The solvents employed are specially chosen for their suitability to the special requirements of dipping solutions. Water, which on the one hand, can sit on the surface of RP plates and not penetrate them and, on the other hand, can cause disintegration of water-incompatible layers is usually replaced by alcohol or other lipophilic solvents. 

Fig. 51 Fluorescence intensities of porphyrins as a function of the concentration of the paraffin oil dipping solution mesoporphynn, coproporphynn, pentaporphynn...

Liquid paraffin aflatoxins 3 to 4-fold dipping solution, 33% in n-hexane, investigation of fungal nutrients [239]... 

Liquid paraffin estnol as dansyl derivative 10-fold dipping solution, 67% m n-hexane [247]... 

Liquid paraffin aimlonde 80% increase dipping solution, 33% in cyclohexane, human plasma investigation [250]... 

Liquid paraffin fluphenazine enhancement dipping solution, 5% in toluene, plasma investigation [251]... 

Liquid paraffin piroxicam enhancement dipping solution, 10% in n-pentane, unne, tissue and plasma investigations [252]... 

Liquid paraffin gentamycins, netilmicin 50 to 65 /o enhancement dipping solution, 15% m n-hexane [253]... 

Liquid paraffin gentamycins stabilization dipping solution, 33% m n-hexane [254]... 

Polyethylene glycol 400 cysteine adducts of a-, -unsaturated aldehydes as dansyl hydrazones stabilization and enhancement dipping solution, 25% in chloroform [268]... 

Polyethylene glycol 400 compounds with alcoholic OH groups 20 to 25-fold dipping solution, 10% in methanol [269]... 

Polyethylene glycol primary amines, indole derivatives, sympathomimetics stabilization and enhancement dipping solution, 20% in methanol [270]... 

Polyethylene glycol 4000 flavonoide glycosides no information dipping solution, 5% in ethanol, phytochemical investigations [273]... 

Polyethylene glycol 4000 primary, secondary, tertiary alcohols as anthracene-urethane denvatives stabilization and enhancement saturated dipping solution in methanol [275]... 

Polyethylene glycol 4000 cetanol after reaction with 8-bromomethyl-benzo-d-pyndo( 1,2-a)pynmidin-6-one stabilization > 15 d dipping solution, 10% in chloroform [291]... 

Triton X-100 testosterone dansyl hydrazone > 25-fold dipping solution, 20% in chloroform [232]... 

Dioctyl sulfo-succinate codeine, morphine, monoacetyl-mor-phine, heroin stabilization dipping solution, 20% in ethanol [94]... 

Dipping solution II Dissolve 4 g potassium hexacyanoferrate(Ill) in 50 ml water and make up to 100 ml with ethanol. 

The dipping solution and spray solution 1 can be stored in the refrigerator for about 1 week. 

Dipping solution Dissolve 1 g 4-aminobenzoic acid in 18 ml glacial acetic acid and add 20 ml water and 1 ml 85% phosphoric acid immediately before use dilute with acetone in the ratio 2 + 3 [2],... 

Dipping solution Carefully mix equal volumes of solutions I and II immediately before the dipping process. 

Note The dipping solution, which can also be used as a spray solution, can be employed with silica gel, kieselguhr, cellulose, RP, NH2 and CN phases. Sugars (exceptions include, for example, fructose, melezitose and raffinose) yield brilliantly colored zones on an almost colorless background when the spray solution is employed. Aldohexoses appear brown, aldopentoses bright red and hexuronic acids orange in color [3]. The detection limit differs for different substances it ranges from 10 ng (pyridoxal) over 100 ng (cinnamaldehyde) up to 2 pg (citral). 

Dipping solution Dissolve 0.2 g 4-atninohippuric acid and 3 g phthalic acid in 50 ml ethanol and dilute with 50 ml toluene. 

Dipping solution I Dissolve 1 g ammonium thiocyanate (ammonium rhodanide) in 100 ml acetone. 

Dipping solution II Dissolve 50 mg iron(III) chloride in 100 ml acetone. 

The reagent can be employed on silica gel, kieselguhr, polyamide and cellulose layers. Only dipping solution I can be employed on amino phases. 

The well-dried chromatogram (1 h at 105°C if acidic or basic eluents have been employed) is immersed in the dipping solution for 1 s or homogeneously sprayed with the spray solution and then dried in a stream of cold air. Acids yield blue zones on a colorless or pale blue background [1] which gradually darkens. 

The chromatogram is freed from mobile phase and immersed in the dipping solution for 3 s or the solution is sprayed on homogeneously the chromatogram is then heated to 90 —140°C for 5 —10 min. Brown zones are produced on a beige-grey background. 

Detection and result The chromatogram was freed from mobile phase and immersed for 3 s in the dipping solution and heated to 125°C for 5 — 10 min. The carboxylic acids terephthalic acid (tiRi 5), succinic acid (fiRi 50 — 55), phthalic acid (hRf 55 — 60), suberic acid (tiRi 60 — 65), sebacic acid (fiRi 65 — 70), benzoic acid (tiRi 75 — 80) and salicylic acid (hRf 80 — 85) yielded brown zones on a light brown background. The detection limit was 2 pg acid per chromatogram zone. 

Note If a dipping solution was employed for detection whose concentration was reduced to 1/10th that given above the acids appeared as white zones on a light brown background. 

Dipping solution Dissolve 2 g diphenylamine and 2 ml aniline in 80 ml acetone. 

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. 

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