| Corn, belonging to coarse food grain, is an evident effective health product.lt contains a large number of nutritional substances,not only carbohydrates, protein, fat, and carotene,but also riboflavin, vitamin B1, vitamin B2, vitamin E, nicotinic acid,trace elements such as selenium and magnesium and so on.Corn has been proved to be the prevention of heart disease, cancer and have anti-aging effect,with its obvious benefit to human health.Sweet potato is a versatile agricultural products, having edible, medicinal and forage use value.Not only rich in starch and soluble sugar, but also higher fatty acid, protein,and aminophenol content,sweet potato is a widely eaten food.In recent years,edible portion of sweet potato has changed from the root to the leaves and buds,which have become high-grade vegetables on the table.The leaves and buds of sweet potato are described as "Queen of vegetables" in the West because of the rich nutritional components they containing.The protein, fat, sugar, calcium, phosphorus, iron and other content of the leaves and buds are higher than other leafy vegetables, and its vitamin content of is also ranked the highest in vegetables.Corn and sweet potato are nutritious and rich in fatty acids. There are few literatures analysing the methods of measuring the fatty acid in recent decades, especially the fatty acids in the fermentation broth.In this article,we used ion-exchange chromatography-gas chromatography coupled as a detection method, ion chromatography valve switching as a pre-treatment, detected acetic acid, propionic acid, butyric acid, isobutyric acid, n-valeric acid, isovaleric acid.In the article, the determination of acetic acid, propionic acid, butyric acid, valeric acid, isobutyrate and isovalerate in straw fermentation broth by the off line of ion-exchange chromatography and gas chromatography are established. In the range of50-200mg/L,linear equations of acetic acid and propionic acid have higher linearity, and the clinearly dependent coefficient are0.9809and0.9908.In the range of10-200mg/L, linear equations of butyric acid, valeric acid, isobutyrate and isovalerate have higher linearity, and the linear correlation coefficient are within0.9903-0.9988.The recovery of the fatty acid was77.65%-96.92%.(i) The switching valve conditions of ion-exchange chromatography had been optimized as follows. Style of Ion chromatographic column was IonPac AS11-HC analytical column (4mm x250mm I.D) and IonPac AG11-HC column (4mm x50mm I.D). The mobile phase was6mmol KOH,which flow rate was1.2mL/min.Column temperature was30℃.Detector was conductivity detector. Sample volume was200μL. Valve switching time was in2minutes and54seconds to5minutes. The fatty acids sample were collected.(ii)The gas chromatographic conditions were optimized as follows. Chromatographic column was CP WAX58CB and capillary column. Inlet temperature was220℃.The detector temperature was260℃. Split ratio acted as10:1.The equilibrium time of column oven temperature was0.5min,and the carrier gas speed was300mL/min. nitrogen speed was30mL/min, and hydrogen speed was29mL/min. The carrier gas flowed in a constant current mode for1mL/min.The gradient temperature program:stayed at100℃for three minutes, and rose to150℃in speed of30℃/min, then rose to180℃in speed of15℃/min,and kept for5minutes, lastly rose up to240℃in speed of20℃/min and hold for4minutes.(iii) The fatty acid in fermentation broth of corn in different times were determined. Based on the comparison between the available content changes of6kinds of fatty acid in15days, we can see the changes of anaerobic activity index.(iv)The fatty acid in fermentation broth of sweet potato in different times were determined. Based on the comparison between the available content changes of6kinds of fatty acid in36days, we can see the changes of anaerobic activity index. |
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