I found several articles with detectors being used ELSD or Refractive Index. I have DAD in my lab. Can we use it for analysis of triglycerides in vegetable oils?
Triglycerides in vegetable oils are best separated by HPLC and detected by gradient elution with an ELSD. A literature search will turn up plenty of application notes and papers demonstrating this use, including some of my own.
Note: These are NOT universal detectors. Their response is dependent on the type of sample (chemical characteristics), the mobile phase used, the detector settings and the operator's experience and skill using this detector.
You can't detect saturated fatty acids by DAD, that's why people use ELSD or RI. With DAD you you'd detect some of the TAG with unsaturated fatty acids, but you'd miss some, and it would be tough to be quantitative.
Consider that double bonds need to be conjugated to show absorbance in UV. Conjugated dienes absorb at about 220-230 nm wavelenght. Non-conjugated double bonds have maximum absorbance below 200 nm wavelenght and below lower range limits of most DAD. As regards saturated fatty acids, they do not absorb in UV, as stated by Michael
If that is the only detector, you may use a reversed UV detector technique by adding a small amount of UV absorbing compound in the mobile phase (acetone). You will have high level of baseline reading. When your compound is eluted, it will reduce the absorbance of mobile phase and give you a negative peak. Of course, it will works better with isocratic elution where you have constant level of the baseline.
Triglycerides in vegetable oils are best separated by HPLC and detected by gradient elution with an ELSD. A literature search will turn up plenty of application notes and papers demonstrating this use, including some of my own.
Note: These are NOT universal detectors. Their response is dependent on the type of sample (chemical characteristics), the mobile phase used, the detector settings and the operator's experience and skill using this detector.
Mahesha, the best option for you is to prepare their methly esters and analyse by GC-FID or GC-MLS
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