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Can someone explain how the separation of glucose and fructose is achieved using liquid chromatography in the industrial production of high-fructose corn syrup?

I've seen references to ion-exchange chromatography, but both glucose and fructose are primarily neutral molecules, so I am not sure how that would work. Other have stated size-exclusion, which makes even less sense.

I've also come across mentions of simulated moving bed chromatography being used. I'm interested in understanding what the stationary phase is and the exact separation method employed in this process.

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    $\begingroup$ If you add a quote please include the source. $\endgroup$
    – Buck Thorn
    Commented Apr 20, 2023 at 1:53
  • $\begingroup$ Are you citing sciencedirect.com/science/article/abs/pii/S138358661100164X ? $\endgroup$ Commented Apr 20, 2023 at 1:59
  • $\begingroup$ As an example, see the abstract to pubs.acs.org/doi/10.1021/ja01645a051 $\endgroup$
    – Buck Thorn
    Commented Apr 20, 2023 at 2:04
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    $\begingroup$ Chromatography is not used to produce high fructose corn syrup (HFCS): it is only used on a small scale to analyse the product. Bulk production uses an enzyme to convert some glucose to fructose to get the final product. $\endgroup$
    – matt_black
    Commented Apr 20, 2023 at 10:05
  • $\begingroup$ source for quote ChatGPT4, I tried to find where and why it would say, but did not. Problem is that industrial processes used on farms would have been published by scientists in the 1950s. All of the science publications I could find were too new and too narrow focused for industrial scale. $\endgroup$
    – vossman77
    Commented Apr 20, 2023 at 13:11

2 Answers 2

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I am glad that you realized that ion-chromatography is not an effective chromatographic mode for separating neutral molecules. However, we should not forget the backbone of cation or anion exchange resins. It is an aromatic group backbone of ethylene divinyl benzene polymers (among other possibilities). In general these resins can interact strongly with organic compounds. Coming back to sugars. Sugars can be ionized in a special way- if you use an strongly alkaline solution like dilute NaOH. Once ionized by losing the protons of the hydroxyl groups, these sugar anions are amenable to ion chromatography, so the organic backbone, plus their ionized state contributes to retention and infact pretty good peak shapes in alkaline medium.

Search Thermo Fisher's website for separating sugars via ion chromatography. They have dedicated columns This is a general answer which should be good enough to let you search deeper.

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    $\begingroup$ I appreciate the attempt, but I doubt it would be cost effective to purify sugar by jacking up the pH to over 12 using NaOH. Wikipedia says that glucose has a pKa of 12.16, I would think fructose has a similar pKa, but could not find a source. Nonetheless, I think I found my answer, see below. $\endgroup$
    – vossman77
    Commented Apr 20, 2023 at 13:13
  • $\begingroup$ @vossman77, You are right, this is how sugars are analyzed at low concentrations, as we say under "analytical conditions". Your answer is good and this is called preparative chromatography. $\endgroup$
    – AChem
    Commented Apr 21, 2023 at 0:29
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I was surprised, I got feedback so quickly, I thought I was asking into the void.

The production of HFCS-55 goes through this process:

  • Corn kernels are ground into corn starch
  • α-Amylase enzyme hydrolyzes α-bonds in starch, producing oligosaccharides
  • Glucoamylase breaks down oligosaccharides into glucose
  • Xylose isomerase converts glucose to ~42% fructose and ~50% glucose
  • Liquid chromatography purifies fructose to ~90% concentration
  • 90% fructose solution mixed with 42% fructose to create 55% fructose "High Fructose Corn Syrup"

I was really curious about the "liquid chromatography"

I think I finally found the answer when I ran across this PDF document, entitled: AmberLiteTM Uniform Particle Size Ion Exchange Resins - Chromatographic Separation of Fructose and Glucose with AmberLiteTM CR99 Ion Exchange Resins - Technical Manual and the section on "3.1 The Chromatographic Mechanism"

[...] Inside the bead, the dissolved sugars interact with the calcium ions held by the resin. Fructose, glucose and water form weak ligand complexes with the calcium ion. A stronger interaction in the fructose/calcium ion complex than in the glucose/calcium ion complex is the basis of the mechanism of separation of fructose from glucose1. This mechanism of separation is called ligand exchange chromatography.

While technically it is a cation exchange column using Ca2+, the interaction between fructose/glucose and the Ca ions, is an affinity relationship. The footnote from the DuPont technical manual clears this up:

1 Chromatographic separation resins do not “exchange” ions as do the resins used in deashing and mixed bed polishing. They function by adsorbing and “slowing” fructose as it moves down the column. The syrup doesn’t exchange ions in the process.

I also found a nice webpage from PuroLite, that goes through the process.

This sweetener is produced by passing a 42% fructose solution through a calcium form strong acid cation resin to effect a separation and create a 75-90% fructose solution which can be blended back with additional 42% fructose to produce a 55% fructose purity.

and

Owing to a greater number of sites available for hydrogen bonding, the fructose molecule will form a coordination complex with calcium ions fixed onto a strong acid cation resin. This results in a preferential affinity of the resin for the fructose molecule over the glucose molecule and hence a chromatographic separation of the two sweeteners as they pass through the resin bed. From a feed solution containing a purity of 42% fructose by weight, the fructose in the product fraction can reach in excess of 99% purity.

When producing 55% fructose, the optimum productivity and efficiency of the system is achieved by enriching to an 85-90% fructose concentration.

some other highlights:

In the 1970s, the technology was developed for continuous chromatographic separation of fructose utilizing a simulated moving bed (SMB) separation system.

Zones in a Fructose Enrichment SMB Profile

let me know if I missed anything.

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