Determination Of Primary Amino Groups Research Articles

Silk grafting with chitosan and crosslinking agents

Chitosan grafting onto silk was tested with three crosslinking agents: trifunctional epoxy resin Araldite DY-T, PEG400 dimethacrylate, and glutaraldehyde in acetic as well as in tartaric acid solutions. Operating conditions were studied to obtain a significant silk weighting with satisfactory graft yields. With the epoxy crosslinker the weight gain was in the range from 1.8 to 8.8 % with graft yield from 8 to 23 %. In the case of PEG400DMA weight gain was 8–12 % with 22–24 % graft yield. With glutaraldehyde in tartaric acid solution a maximum weight gain of 8.4 % with 27.6 % graft yield was obtained. Results of determination of primary amino groups on the grafted silk showed that with epoxy and glutaraldehyde, unlike PEG400DMA, the amino groups of chitosan were only partially involved in crosslinking. Results of DSC analyses suggested that the modification of fibroin structure in chitosan-grafted silk was stronger with glutaraldehyde than with epoxy or dimethacrylate. FTIR-ATR spectra of grafted fibers were found very similar to that of control silk with an additional weak peak ascribable to chitosan in 1180–1080 cm−1 range. Surface investigation through AFM showed clear morphology differences between chitosan-grafted silk with epoxy or dimethacrylate and that crosslinked with glutaraldehyde; the latter appears uneven and scale-like, the others slightly rougher than the original silk.

Determination of ammonia and primary amine compounds and Kjeldahl nitrogen in water samples with a modified Roth's fluorimetric method

A method for the simultaneous determination of primary amino groups and ammonium ion has been proposed. The method is based in solution derivatization with o-Phthaldialdehyde/ N-acetyl-cisteine (OPA/NAC) and fluorescence measurement of the formed isoindols. Analytical characteristics and description of the developed procedure have been provided. The calibration graphs for ammonium (up to 1.44 mg L −1 of N) and methylamine as primary amino model compound (up to 0.282 mg L −1 of N), were obtained. Bivariate and multivariate calibration models have been tested. The limits of detection were 0.07 mg L −1 of N and 0.004 mg L −1 of N for ammonium and amine, respectively. The procedure was first applied directly to standard solutions containing ammonium and amines and secondly to digested solutions by Kjeldahl method. The results obtained allowed to establish the best digestion conditions in order to perform the total amine conversion into ammonium. This procedure has been also applied to real samples (irrigation ditch, residual and fountain waters) and the concentrations of primary amine groups and ammonium have been evaluated. The results obtained after Kjeldahl digestion allowed to estimate the total Kjeldahl N contained in the samples. The samples were also analysed by Nessler method and similar results were obtained.

Rapid fluorimetric assay for primary amine groups in water samples.

Bond Elut C(18) solid-phase extraction cartridges were used for pre-concentration followed by derivatization with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) of primary amines in water. Optimal conditions were: conditioning the cartridges with borate buffer pH 10.4, retention of the primary amines, addition of the OPA-NAC(3.7 mmol L(-1)) 1:1 molar ratio and borate buffer pH 8, elution of the isoindol with MeOH-borate buffer (9:1) pH 10.2 and fluorescence measurement. The equations of the calibration graphs for methylamine, ethylamine, propylamine, butylamine, pentylamine, and beta-phenylethylamine at lambda(excitation)=330 nm and lambda(emission)=440 nm, in the optimal conditions are presented. The solid-phase extraction procedure improved ten times the detection limits of the solution derivatization. Those values are in the 0.01-0.06 mg L(-1) interval in function of the amine. Also, it is possible to estimate the total primary aliphatic amine concentration in water, expressed as molar concentration of -NH(2) group or -NH(2)-N mg L(-1). On the basis of these studies, the method was applied for the determination of primary amino groups in tap, ground, factory and source water samples.

Rapid determination of primary amino groups on soluble polymers

A method for the rapid determination of primary amino groups on soluble polymers is described and discussed. After reaction of the amino groups with fluorescamine, the relative fluorescence is measured. The calibration and application of the procedure in practice is demonstrated for two copolymers of 1-vinyl-2-pyrrolidinone with alanine vinylester or allylamine.

Determination of Primary Amino Groups by Reaction Chromatography

Abstract A gas chromatographic method is described for the assay of primary amino groups. The technique is a modification of the Van Slyke method, in which the N2 liberated by the reaction of primary amino groups with nitrous acid is measured by GC. The assay of amino acids, monosodium glutamate, Shake'n Bake and Adolph's Sugar Substitute is described.

Microdetermination of primary amino groups

Summary In the gasometric determination of primary amino groups, crystalline silver permanganate is recommended as a solid absorbent for the complete removal of nitric oxide, the formation of which always occurs to some extent from the decomposition of nitrous acid. Elimination of the wash solutions reduces both the number of connections in the apparatus and its internal resistance, which may give rise to leaks. The time required for the complicated procedure of purging the apparatus free of air is appreciably minimized.

Determination of primary amino groups by gas chromatography

Determination of primary amino groups by gas chromatography