离子色谱法测定“地沟油”中钠离子和氯离子的含量及其比例关系
摘要
By reference to edible oil using process as well as hogwash oil refining technology, a method is presented to determine the contents of the sodium and chloride in hogwash oil based on ion chromatography. The molar ratio of the sodium and chloride was analyzed in order to determine whether the sample contained hogwash oil. A hogwash oil sample was extracted by deionized water before analysis. The ion chromatographic separation of the chloride was carried out on an AS19 column (250 mm × 4 mm) at 30 ℃, using 20 nmol / L KOH solution as mobile phase at a flow rate of 1 mL / min and suppressor current of 112 mA. The ion chromatographic separation of the sodium was carried out on a CS12 column (250 mm × 4 mm) at 30 ℃, using 20 nmol / L methanesulfonic acid (MSA) as mobile phase at a flow rate of 1 mL / min and suppressor current of 59 mA. The injection volume was 25 μL and the detector was an electron capture detector (ECD). The external standard method was used to quantify chloride and sodium. The detection limits of this method were 0.005 mg / L for chloride and 0.001 mg / L for sodium. The linear range was from 0 to 5 mg / L with r^2 =0.999988 for chloride and r^2 = 0.999926 for sodium. The average recoveries and relative standard deviations were 94.2% and 2.4% for chloride and 92.5% and 2.7% for sodium, respectively. The molar ratio of sodium and chloride in edible oil was approximately 1, while that in hogwash oil was more than 4. The determination of the contents and molar ratio of the chloride and sodium in hogwash oil can be used as an important basis for the judgment of hogwash oil.