Rapid method for monitoring chitosan coagulation using low-field NMR relaxometry.
Time-domain NMR relaxometry was proposed as a simple, rapid method to monitor chitosan (CS) coagulation as a function of pH. The longitudinal (T1) and transverse (T2) relaxation times of three CS concentrations (0.022, 0.22, and 2.2gL(-1)) were simultaneously measured by CP-CWFPx-x pulse sequences in a 0.47T spectrometer. T1 and T2 were shown to be independent of pH as well as to assume values similar to the relaxation time of water (2.7s) at the lowest tested CS concentration. At the highest concentration, T1 increased whereas T2 decreased as pH varied from 6.0 to 7.0. This indicates a remarkable effect of CS on water relaxation at pH values higher than the pKa of CS amino groups (6.5). Therefore, CS reduced the water mobility at the highest CS concentration and greatest pH values, suggesting a CS supramolecular structure (gel) that entraps the solvent in confined regions. The method proposed here can be further used to study the coagulation of other polysaccharides.
Instituto de Química de São Carlos, Universidade de São Paulo, Avenida Trabalhador São Carlense 400, 13566-590 São Carlos, São Paulo, Brazil.
Flávio Vinicius Crizóstomo
FV
Kock
Embrapa Instrumentação, Rua XV de Novembro 1452, 13560-970 São Carlos, São Paulo, Brazil. Electronic address: luiz.colnago@embrapa.br.
Luiz Alberto
LA
Colnago
D048271:Chitosan / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D013997:Time Factors; D014867:Water / Q000737:chemistry
D014867:Water; D048271:Chitosan
Chitosan; Coagulation; Relaxometry