Determination of lysine content based on an in situ pretreatment and headspace gas chromatographic measurement technique.

This work reports on a simple method for the determination of lysine content by an in situ sample pretreatment and headspace gas chromatographic measurement (HS-GC) technique, based on carbon dioxide (CO2) formation from the pretreatment reaction (between lysine and ninhydrin solution) in a closed vial. It was observed that complete lysine conversion to CO2 could be achieved within 60 min at 60 °C in a phosphate buffer medium (pH = 4.0), with a minimum molar ratio of ninhydrin/lysine of 16. The results showed that the method had a good precision (RSD < 5.23%) and accuracy (within 6.80%), compared to the results measured by a reference method (ninhydrin spectroscopic method). Due to the feature of in situ sample pretreatment and headspace measurement, the present method becomes very simple and particularly suitable to be used for batch sample analysis in lysine-related research and applications. Graphical abstract The flow path of the reaction and HS-GC measurement for the lysine analysis.

Determination of 3-chloro-1,2-propanediol in polyamideamine epichlorohydrin resin solution by reaction-based headspace gas chromatography.

We report on a headspace gas chromatographic method for determining the content of 3-chloro-1,2-propanediol in polyamideamine epichlorohydrin resin solution. It was based on quantitatively converting 3-chloro-1,2-propanediol to formaldehyde by periodate oxidation in a closed headspace sample vial at a room temperature for 10 min, and then to methanol by borohydride reduction at 90°C for 40 min followed by the headspace gas chromatographic measurement. The results showed that the present method has an excellent measurement precision (relative standard deviation < 2.60%) and accuracy (recoveries from 96.4-102%) in 3-chloro-1,2-propanediol analysis. The limit of quantitation was 0.031 mg/mL. It is simple and suitable for determining the 3-chloro-1,2-propanediol content in polyamideamine epichlorohydrin resin solution.

Simultaneous Determination of the Degree of Deacetylation and Substitution on Carboxymethyl Chitosan by Headspace Gas Chromatography.

This study reported a new headspace gas chromatography (HS-GC) for simultaneously determining the degree of deacetylation (DD) and the degree of substitution (DS) in carboxymethyl chitosan (CMCS), which were based on HS-GC measuring the amounts of CO2 released from both the bicarbonate decomposition suppressed by -NH2 and the reaction between the bicarbonate and the acidified carboxymethyl and amino groups in CMCS. The results showed that the present method has a good measurement precision (RSD < 2.55%) and accuracy (relative differences <5.90%). Compared with the current titration-based method, the present HS-GC techniques provide a more reliable testing in the quantification of amino and carboxymethyl contents in CMCS. Moreover, since the HS-GC can perform an automated sample reaction equilibration and measurement, it could be much more efficient than the existing methods in the batch sample analysis.

A Zero-Valent Pd/Fe Loaded and Nanofibrillated Cellulose-Reinforced Carboxymethyl Cellulose Hydrogel for Dechlorination of 2,4,6-Trichlorophenol.

A full-cellulose derived hydrogel, composed of carboxymethyl cellulose (CMC) and nanofibrillated cellulose (NFC), was successfully manufactured and immobilized with Pd/Fe bimetallic nanoparticles for the dechlorination of 2,4,6-trichlorophenol. The NFC-reinforced CMC hydrogels with or without loading of bimetallic nanoparticles were characterized by Fourier transform infrared spectroscopy, Transmission electron microscopy, Scanning electron microscopy-energy dispersive X-ray, and X-ray diffraction analyses. The effect of amounts of NFC on the loading capacity of Pd/Fe, mechanical properties and specific Brunauer-Emmett-Teller surface areas of NFC-reinforced CMC hydrogel was also investigated. The experimental results showed that Pd/Fe bimetallic nanoparticles were dispersed and fixed in the hydrogel matrix with the nanosize spherical shape. The hydrogel would protect the Pd/Fe nanoparticles from oxidation, and thus providing long-term stability in comparison with only NFC-coated Pd/Fe nanoparticles. The hydrogel loaded with Pd/Fe nanoparticles, as a soft material catalytic system, was investigated to dechlorinate 2,4,6-trichlorophenol and was found to be very effective.

Kinetic research on dechlorinating dichlorobenzene in aqueous system by nano-scale nickel/iron loaded with CMC/NFC hydrogel.

In this study, we reported on the nano-scale nickel/iron particles loaded in carboxymethyl/nanofibrillated cellulose (CMC/NFC) hydrogel for the dechlorination of o-dichlorobenzene (DCB) in aqueous solution. The biodegradable hydrogel may provide an ideal supporting material for fastening the bimetallic nano-scale particles, which was examined and characterized by TEM, SEM-EDX, FT-IR and BET. The performance of the selected bimetallic particles was evaluated by conducting the dechlorination of DCB in the solution under different reaction conditions (e.g., pH, dosage of nickel/iron nanoparticles and temperature). The results showed that about 70% of DCB could be dechlorinated at 20 °C in 8 h, which indicated that the immobilized reactive material had a high reduction activity when Ni/Fe loading dosage in the hydrogel (18 wt%) was considered. Moreover, the reduction behavior agreed to the pseudo-first order reaction, in which the dechlorination rate was irrelative to the pH aqueous solution. A kinetic model for predicting the concentration of DCB during the reduction reaction was established based on the experimental data.

Determination of chlorinated volatile organic compounds in polyamine epichlorohydrin solution by headspace gas chromatography.

This study demonstrated a headspace gas chromatographic (HS-GC) method for the determination of residual epichlorohydrin (ECH) and the by-product 1,3-dichloro-2-propanol (DCP) in polyamine epichlorohydrin (PAE) solution. It was based on the vapor-liquid phase equilibrium of these analytes at 60°C for 30min in a closed headspace sample vial before GC measurement. It was found that matrix of the PAE solution had the effect on the headspace equilibrium of these species and therefore a standard addition must be applied in the method validation. The results showed that the present method has a good measurement precision (RSD <2.90%) and accuracy (recoveries from 93.6 to 105%), and the limit of quantitation (LOQ) is 3.75mg/L for ECH and 0.8g/L for DCP. The present method is suitable to be used for analyzing the chlorinated volatile organic compounds in the commercial PAE resin solutions.

Determination of the content of alkyl ketene dimer in its latex by an ionic-liquid assisted headspace gas chromatography.

This paper reports on an ionic-liquid assisted headspace gas chromatographic (HS-GC) for the determination of the content of alkyl ketene dimer (AKD) in its latex samples, in which the GC system was equipped with a thermal conductivity detector (TCD). The method was based on the AKD hydrolysis conducted in 1-butyl-3-methylimidazolium chloride (ionic-liquid) added medium at 100°C for 10min in a closed headspace sample vial, and the measured CO2 (the resulting product of the hydrolysis) by HS-GC. The results showed that the present method has a good measurement precision (RSD <2.3%) and accuracy (recoveries from 96 - 105%), and the limit of quantitation (LOQ) is 0.9%. The present method is very suitable to be used for the routine check of AKD content in its latex sample in mill applications. The study also showed that the content of AKD in the tested commercial latex samples were in the range of 3.5-12%.