Methods For Determination Of Degree Research Articles

High-throughput vibrational spectroscopy methods for determination of degree of acetylation for chitin and chitosan

The rising demand for chitin and chitosan in chemical, agro-food, and healthcare industries is creating a need for rapid and high-throughput analysis. The physicochemical properties of these biopolymers are greatly dependent on the degree of acetylation (DA). Conventional methods for DA determination, such as LC-MS and 1H NMR, are time-consuming when performed on many samples, and therefore efficient methods are needed. Here, high-throughput microplate-based FTIR and FT-Raman methods were compared with their manual counterparts. Partial least squares regression models were based on 30 samples of chitin and chitosan with reference DA values obtained by LC-MS and 1H NMR, and the models were validated on an independent test set of 16 samples. The overall predictive accuracy of the high-throughput methods was at the same level as the manual methods and the well-established LC-MS and 1H NMR methods. Therefore, high-throughput FTIR and FT-Raman DA determination methods have great potential to serve as fast and economical substitutes for traditional methods.

Methods for Determination of the Degree of Iron Oxidation in LiFePO4

The disposal of LiFePO4 (LFP) cathode material through oxidation in an air atmosphere is explained by its high chemical activity and high surface area (especially for nanoparticles). In this article, new methods for the determination of the degree of iron oxidation in LFP (oxidation degree) are taken into consideration, specifically those which do not require complicated hardware support. The proposed methods are based on electrochemical oxidation (coulometric method) and chemical oxidation (chemical oxidation in alkaline and acidic solutions). As an arbitration method for analyzing the iron state, the method of Mössbauer spectroscopy (being the most proven and reliable method) was chosen. With respect to the proposed methods for determination of the oxidation degree, the most reliable and quick approach is the titrimetric method (oxidation in an acidic medium), which is in good correlation with Mossbauer spectroscopy. The coulometric method is also able to determine the material oxidation degree (with some approximation), but it requires a number of conditions in order to eliminate errors.

1D NMR methods for determination of degree of cross-linking and BDDE substitution positions in HA hydrogels

Hyaluronic acid polymers cross-linked with BDDE are today among the most used hydrogels for biomedical applications. The physical properties of the hydrogels depend, among other parameters, on the degree of cross-linking of HA. Another parameter likely to affect the physical properties is the substitution position of the linker on the HA functional groups. A NMR-based method for the determination of these parameters in hyaluronic acid hydrogels is presented. The method is based on the degradation of HA cross linked hydrogels by chondroitinase ABC followed by one-dimensional 1H and 13C NMR analysis. The necessary structural information to obtain both the degree of cross-linking and the substitution positions can be obtained from the same NMR sample and no chromatographic separation step is required prior to NMR analysis.

Methods for determination of degree of reaction of slag in blended cement pastes

To measure the degree of reaction of slag in blended pastes, five methods were studied. Selective dissolution and differential scanning calorimetry are shown to be unreliable, SEM-BSE-IA-mapping is time consuming, but does provide good results with a reasonable degree of precision. The difference in cumulative calorimetry and chemical shrinkage curves of slag blends in comparison to blends with inert filler shows potential to isolate the reaction of the slag. These methods have the advantage of being continuous, techniques with good precision, but the absolute heat of hydration, or contribution to chemical shrinkage of any particular slag is not known. Calibration of the calorimetry technique with SEM-BSE-IA-mapping seems to be a promising method to understand and quantify the degree of reaction of slag.

Simple Determination Method of Degree of Substitution for Starch Acetate

Abstract To develop a simple method to determine the degree of substitution (dS) for starch ester, we prepared starch acetate with various dS values (0—3) and examined the mode of starch-iodine complex formation for the starch acetate by monitoring the ultraviolet-visible (UV-vis) spectra and their Fourier-transform infrared (FT-IR) spectral changes. The effect of acetylation on the formation of the starch-iodine complex was investigated by monitoring the decrease in absorbance at 680 nm (blue value). The blue value decreased by increasing the standard dS value determined by NMR for starch acetate, but two different correlations between the blue values and the dS values were observed for the low- and highly-substituted starch acetate. The FT-IR spectra for starch acetate particles were measured using a diffuse reflection method. The peak areas and absorbances of the bands assigned to the acetyl group showed a poor correlation with standard dS values from the NMR. On the other hand, the FT-IR peaks assigned to sodium acetate produced by saponification of the starch acetate could be detected using the ATR (attenuated total reflection) method; they showed a good correlation with the standard dS values from the NMR. From these results, it was concluded that the ATR method should be available for the dS determination of starch acetate.