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- Posts: 10
- Joined: Tue Jan 06, 2009 5:43 pm
A colleague of mine posed an interesting question:
An existing method using direct injection GC/FID with a FFAP column is capable of analyzing low molecular weight free fatty acids (C2 - C7) in water down to the low ppm range. The chromatography, as you might expect, is not fantastic, but the method is suitable. Note that this is in fairly clean water. I believe the pH is adjusted down to 3 and the water samples are injected and analyzed vs. an external calibration.
Now they are looking to do the same type of analyses, but on a much more complicated matrix. Problem 1; there is high salt/conductivity. Lots of ppm of various cations and lots of chloride. Problem 2; Could also be some other, higher MW organics present as well.
As you might expect, even when they dilute these samples quite heavily with water the results are not good. The liner and the head of the column suffer, the reproducibility and recovery are quite poor.
Any ideas on sample clean up, etc. that might be useful? Also, complicating the issue is that the desired LOQ are requested to be ~ 10 ppm as each individual acid. I know....a real mess.
Any thoughts you might have are greatly appreciated. There could be many samples of this type for my colleague to analyze, and they could keep coming in. Not a pretty scenario, but I thought I would try to help. Obviously another method would be better, or a drastically improved version of the one he's got.
Regards,
Tim McGinnis
An existing method using direct injection GC/FID with a FFAP column is capable of analyzing low molecular weight free fatty acids (C2 - C7) in water down to the low ppm range. The chromatography, as you might expect, is not fantastic, but the method is suitable. Note that this is in fairly clean water. I believe the pH is adjusted down to 3 and the water samples are injected and analyzed vs. an external calibration.
Now they are looking to do the same type of analyses, but on a much more complicated matrix. Problem 1; there is high salt/conductivity. Lots of ppm of various cations and lots of chloride. Problem 2; Could also be some other, higher MW organics present as well.
As you might expect, even when they dilute these samples quite heavily with water the results are not good. The liner and the head of the column suffer, the reproducibility and recovery are quite poor.
Any ideas on sample clean up, etc. that might be useful? Also, complicating the issue is that the desired LOQ are requested to be ~ 10 ppm as each individual acid. I know....a real mess.
Any thoughts you might have are greatly appreciated. There could be many samples of this type for my colleague to analyze, and they could keep coming in. Not a pretty scenario, but I thought I would try to help. Obviously another method would be better, or a drastically improved version of the one he's got.
Regards,
Tim McGinnis
