Since there are no others who wish to tackle this question, I will answer. MS detects everything (almost) in your extract, so you can have >>100's or 1000s of peaks in your extract. A PAD (pulsed amperometric detector) is much more selective since not every molecule gives a suitable response. I assume you are injecting a quantitative extract!

In addition HPAEC (High Performance Anion Exchange Chromatography) is a means of resolving carbohydrates from the other crap by baseline separation and selective retention.

See both the Thermofisher information and article;

https://assets.thermofisher.com/TFS-Assets/CMD/brochures/BR-52119-Carbohydrate-Analysis-HPAE-PAD-BR52119-EN.pdf

Article High-Performance Anion-Exchange Chromatography Coupled with ...

I dont know

Hi Matilde,

"today, the gold working electrodes that are used with carbohydrates are cleaned by a voltage waveform. A waveform is a series of voltage steps that work to charge the electrode, detect the analyte, clean the electrode, and then restore the surface. The entire process takes milliseconds and is ongoing throughout the run. This repeated cleaning and detecting is called pulsing; the process is known as pulsed amperometric detection, or PAD. The pulsing waveform ensures the surface is always clean and the results are reproducible. Because the cleaning takes off the top layer of atoms, the disposable electrode must be replaced about every two weeks. Overall, the current technology has improved dramatically from just a few years ago."

More about the advantages you can read here:

https://americanlaboratory.com/914-Application-Notes/35296-The-Power-of-Pulsed-Amperometric-Detection-Coupled-With-Chromatography-for-Analyzing-Carbohydrates/

https://www.ncbi.nlm.nih.gov/pubmed/30685027

Regards

Markus

I wouldn't say one is better than the other, it depends on what your focus is, what your needs are, and what equipment you have available. I use and have used LC-MS for the detection of saccharides like glycans, sialics acids, carbohydrates, etc., both derivatized and underivatized. It is sensitive and specific, unless you have isobaric compounds that co-elute (which would be a problem in HPAEC-PAD as well). I always got good results with LC-MS, but the equipment is significantly more expensive to buy and maintain, and it is more complicated, requiring more training.

I'm not sure what you mean by autosampling, can you please explain?

I am a bit late in the canon, but let me chime in:

HPAE-PAD is the more selective method, as it combines the high chromatographic selectivity of anion exchange chromatography for carbohydrates at a high pH, with specific detection of amperometry.

Having said that: Nothing wrong in combining HPAE-PAD with MS - you use the best of both worlds. Don't forget to use a suppressor inline with the IC-instrument. As the eluent consists of NaOH and most likely NaOAc, you need this device to bring down the pH. Please keep in mind that the commonly used ESI is a soft ionization approach, and neutral carbohydrates are "notoriously" stable. In other words, you have to add some LiCl to the column effluent and go after the Li-adducts. In the case of anionic carbohydrates - you are fine. After Neutralization: Fire at will.

Not to create the wrong impression: HILIC with and without derivatization of carbohydrates is another approach. Some researchers like it better, as they think it is "easier." My advice: Try it.

Why did I bring this up? Because carbohydrates can be separated by multiple mechanisms, that the selection of the chromatographic conditions needs to fit the properties of the saccharides.

For examples:

Some carbohydrates are sensitive to high pH.

Some oligosaccharides and many polysaccharides precipitate at the high organic solvent concentrations of HILIC.

Though being late - I hope this is of some interest.

Good luck with your research

Detlef.