Trace-level screening of dichlorophenols in processed dairy milk by headspace gas chromatography

Chai

2017

We report a new headspace analytical method in which multiple headspace extraction is incorporated with the full evaporation technique. The pressure uncertainty caused by the solid content change in the samples has a great impact to the measurement accuracy in the conventional full evaporation headspace analysis. The results (using ethanol solution as the model sample) showed that the present technique is effective to minimize such a problem. The proposed full evaporation multiple headspace extraction analysis technique is also automated and practical, and which could greatly broaden the applications of the full-evaporation-based headspace analysis.

A_{n} = A_{n - 1} 10^{- b}

where b , A n and A n –1 represent a ratio constant of the headspace extraction, the GC peak area of the n th and the ( n− 1)th MHE‐GC measurements, respectively.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Method for improving accuracy in full evaporation headspace analysis

Chai

2017

“…The total weight of water in the vial can be expressed as [14,23] w = s + g = s + g g (2) where m w is the total weight of water added in the wheat flour sample. w and V g represent the weight of the wheat flour and the volume of the vapor phase in the sealed vial.…”

Section: Methodsmentioning

confidence: 99%

“…Wheat flour is a powder made from the grinding of wheat and has been widely used as a human food source as it mainly consists of starch, protein, sugars, and water [1][2][3][4][5][6][7]. Water absorption capacity in wheat flour is defined as the ratio of the weight of absorbed water/wheat flour sample, which is one of the major factors that affect the quality of wheat flour [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Measurement of water absorption capacity in wheat flour by a headspace gas chromatographic technique

Gong

2018

The purpose of this work is to introduce a new method for quantitatively analyzing water absorption capacity in wheat flour by a headspace gas chromatographic technique. This headspace gas chromatographic technique was based on measuring the water vapor released from a series of wheat flour samples with different contents of water addition. According to the different trends between the vapor and wheat flour phase before and after the water absorption capacity in wheat flour, a turning point (corresponding to water absorption capacity in wheat flour) can be obtained by fitting the data of the water gas chromatography peak area from different wheat flour samples. The data showed that the phase equilibrium in the vial can be achieved in 25 min at desired temperature (35°C). The relative standard deviation of the reaction headspace gas chromatographic technique in water absorption capacity determination was within 3.48%, the relative differences has been determined by comparing the water absorption capacity obtained from this new analytical technique with the data from the reference technique (i.e., the filtration method), which are less than 8.92%. The new headspace gas chromatographic method is automated, accurate and be a reliable tool for quantifying water absorption capacity in wheat flour in both laboratory research and mill applications.

“…Headspace (HS) GC has been proven an effective tool that can minimize the impact from nonvolatile substances in complex liquid or solid samples and has been widely used to quantify the volatile compounds in samples without or with less pretreatment . HS‐GC can also be used as an alternative way to quantify some of nonvolatile compounds if they can be quantitatively transferred to some related volatile substances by some related reactions .…”

Section: Introductionmentioning

confidence: 99%

Quantification of anhydride groups in anhydride‐based epoxy hardeners by reaction headspace gas chromatography

Gong

Yu³

2017

We demonstrate a reaction headspace gas chromatographic method for quantifying anhydride groups in anhydride-based epoxy hardeners. In this method, the conversion process of anhydride groups can be realized by two steps. In the first step, anhydride groups in anhydride-based epoxy hardeners completely reacted with water to form carboxyl groups. In the second step, the carboxyl groups reacted with sodium bicarbonate solution in a closed sample vial. After the complete reaction between the carboxyl groups and sodium bicarbonate, the CO formed from this reaction was then measured by headspace gas chromatography. The data showed that the reaction in the closed headspace vial can be completed in 15 min at 55°C, the relative standard deviation of the reaction headspace gas chromatography method in the precision test was less than 3.94%, the relative differences between the new method and a reference method were no more than 9.38%. The present reaction method is automated, efficient and can be a reliable tool for quantifying the anhydride groups in anhydride-based epoxy hardeners and related research.