基于电导率的地沟油快速鉴别方法的改进

Improvement on the Rapid Detection Method of Waste Oil Based on Electrical Conductivity

摘要: 以合格食用油和地沟油为样品，探究油脂种类、温度、水油比例对电导率检测影响，找出能更准确更快的检测油脂电导率的条件。本实验采用的方法是取油样10 ml时，加正己烷25 ml，去离子水30 ml，70℃恒温水浴振荡30 min，分离油、水相，再将水相置于70℃水浴中测其电导率。在此条件下，由于去离子水的增加，分离出更多更清澈的水相使检测时水相能将电极完全淹没，减小了由于电极不能完全淹没在水中而产生的误差；升高振荡时的水浴温度，振荡后不用静止马上就能分离出清澈的水相，缩短了实验时间，水相清澈减小了由于水相中含有油珠而对电导率检测产生的影响，而且升高振荡时的水浴温度使油脂中的杂质或离子能尽可能全部溶解到水中，更准确的反映油脂中含杂质或离子情况；升高检测时的水相温度使合格油与地沟油间的电导率差距变大，减小了把电导率处于中间的合格油判为地沟油或把地沟油判为合格油的可能。同时，保持检测时水相的温度与分离油、水相时的温度一致，能更准确的反应分离时杂质或离子在水相中的溶解情况。因此该方法不但大大提高了检测电导率的准确性，还提高分离速度。

Abstract: Using the qualified edible oil and waste oil for sample, we explore the influence of oil types, temperature, the ratio of water and oil for electrical conductivity, to find out a test condition which can faster and more accurately detect grease conductivity. This method adopted in the experiment is that inject n-hexane 25 ml, 30 ml deionized water, then vibrate 30 min in 70˚C thermostatic water bath to separate the oil and water phase, then put the water phase in 70˚C thermostatic water bath measuring the conductivity when the 10 ml of sample is taken. On this condition, it can extract clearer water which can make the pole be completely submerged when detection, thus it reduces the error because the pole can not be completely submerged in water. Because the water bath temperature has risen higher, the clear water can be fleetly separated from mixture sample after vibration, hence it shortens the time of experiment. Clear water reduced the influence of oil droplets for conductivity detection, and the rising bath temperature of vibration can make impurities or ions in oil dissolve in water as much as possible, thereby, the measuring result can more accurately reflect the condition of impurities or ions in oil. Rising the bath temperature of detection increased the conductivity gap of qualified oil and waste oil, thus the possibility of mis-judgement was reduced, meanwhile, keeping water temperature of detection and separation the same can more accurately reflect the condition of impurities or ions in water when separation. Therefore, this method not only boosts veracity of conductivity detection, but also increases speed of separation.