Mobile Phase Recyclers

[Paladin]

Does anyone have any experience with mobile phase recylcers such as Supelco, Brinkmann, etc with an Agilent 1100/1200 LC? If so, which brand would you recommend?

[alwelch]

Axxiom Chromatography offers HPLC solvent recyclers and we have customers who use them with Agilent 1100 systems.

You can see them at

http://www.axxiomchromatography.com/solventtrak.htm

Al Welch

[HPLCCONSULT]

I will assume you are running isocratic and are NOT in a regulated environment. If you are performing any type of work where you are measuring sample concentrations, performing calibrations or looking for unknowns, then I would not recommend the use of any mobile phase recycler. Since you are re-using the mobile phase over and over again, some compounds may get through and contaminate your results. The devices usually operate by monitoring a connection to another detector (usually UV at a wavelength that you specify) and divert the waste flow back to your primary reservoir when a user specified threshold is met OR divert flow based on a timetable value window that you select. *I have used several models in the past (Alltech and others) where we only used them to test operation of a particular system and NOT actually perform method development or analysis of any real samples. IMHO: I would never use them for "real-world" analysis. How would you document such use ? How would you quantitate the material that is recycled back into your system ? Are you going to analyze the "used" mobile phase by HPLC/GC separately before you use it again ? Don't waste your time...

A far better and less expensive way to save money on solvent purchase and disposal costs is to use narrow bore columns in your HPLC / SFC system. If you keep all parameters linear, moving from the same length 4.6 mm ID column to a 2.1mm ID column will reduce your flow rate (and solvent consumption) by a factor ~ 5. I have preached this approach for twenty some years and it still is true. Most research grade modern HPLC systems are easily capable of running at 200 ul/min with a 2.1 mm ID column and no change in method is usually needed (flow of course).

[alwelch]

There is no concern for contamination of the supply reservoir.

SolventTrak does not depend on absolute baseline threshold as other recyclers do. SolventTrak employees a proprietary peak detection algorithm which can cope with drifting baselines. Once it has bee set up with expected peak width and transit delay volume time you can generally leave it alone to handle day to day drifts in the analysis.

SolventTrak automatically extends the time the valve is in the waste position by an extra ½ peak width. So for a one minute wide peak the valve would direct the peak to waste for 1 ½ minutes. Each waste cycle is delayed by the expected transit time from the detector flow cell to the recycler valve. For 36 inches of tubing this might be 20 seconds. So if a start of peak is detected a few second up the front side it is an easy thing to reduce the Delay time by a few seconds and be sure that you will divert the entire peak to waste.

Every SolventTrak unit is equipped with output signals which can be used to validate the units operation. There is an analog signal with tick marks added to show how the peaks are being detected. An additional analog signal indicates when the valve is in the waste and recycle positions.

SolventTrak also provides an RS232 digital output which provides complete peak detection activity codes as well as periodic time markers. The time markers serve to confirm the unit is working and communications is being maintained between the unit and the logging (LIMS) program. Should there be a loss of power the marks cease to be sent. When power is resumed, the logging program can command the unit to start sending codes again. In this way a LIMS system can create logs of how the SolventTrak system is operating.

[greenlab]

Hi Paladin,

I recommend you the SolventTrak because is the only recycler designed to eliminate the components (peaks) from the mobile phase even if chromatographic baseline has positive or negative drift. I have used the SolventTrak with different HPLC brans as Waters, Shimadzu, Agilent, and Dionex with excellent results.

In terms of the questions or concerns generated by HPLCCONSUL, you can visit the following link for the answers http://www.greenlab.ws/linked/mobile%20 ... oncern.pdf

Contact me if you want more information.

Regards;
GreenLab

[HPLCCONSULT]

Greenlab: Question, what wavelength is used or recommended to monitor the signal ? I assume it is only one. Samples often contain many compounds which absorb to different degrees at different wavelengths. If the user chooses a wavelength of say 254nm, then they could recyle mobile phase and sample(s) from compounds which do not absorb strongly at that wavelength. The recycler system requires a response (voltage) to measure and track the baseline with so if it can not "see" the real response wouldn't it assume that nothing is there ?

[greenlab]

Hi HPLCCONSULT!

First of all, it seems to me that it is necessary to explain how the SolventTrak works. SolventTrak continuously monitors the chromatogram baseline generated by any HPLC detector; no matter what detector type, detector parameters selected by your chromatographic method, or wavelength in case of UV detector. If signal received from detector exceeds the slope and width parameters set in the SolventTrak, a peak is considered detected and (mobile phase + peak) leaving the detector are sent to waste otherwise mobile phase is considered clean and sent it to be re-used.

In general, HPLC methods are developed to identify or quantify components of interest in a solution and do not pretend to identify or quantify all components in the solution. In this sense is possible to have undetected components, coming from sample solution, in the re-used mobile phase. System suitability test can be used to determine the impact of those possible components in the re-used mobile phase. If system suitability test meets the method specifications it means that the HPLC system (Equipment + Re-used mobile phase) is adequate for the analysis. Also is a good laboratory practice to re-evaluate the expiration date of the re-used mobile phase before use.

Please let me know if you have any other concern or questions…

Regards;
Greenlab

[HPLCCONSULT]

Greenlab, thank you for the better explaination.

So it does in fact only monitor one input signal and switch to waste based on established slope thresholds being exceeded. In general, I would not want to use such a system in my lab for method development, but if you had a well qualified application where no "new" compounds were to be present (still, I would check using a DAD and/or MS on a scheduled basis to confirm) and were running at a low UV wavelength which also resulted in saving >80% of the solvent, then it might be useful.

For method development of Pharmaceuticals (what I do) which often have unknowns, I would go back to my original statement. To save solvent, use mini-bore or narrow bore columns. This is the safest way to reduce solvent consumption (usually by a factor of 5 or an 80% savings) w/o changing hardware. It also does not require any re-use of solvent or checking of re-used solvent on a periodic basic so saves time and is easier to validate overall.

[greenlab]

Hi HPLCCONSULT,

Reduce the diameter and particle size of the column, the use of UPLC system, and the use of the mobile phase recycler among others, are excellent strategies to save solvents and be more cost-effective during the HPLC analysis. However the strategy selection or no selection will depend of the nature of the business, necessity, priority, philosophy, vision, economic status, or available resources among other factors.

SolventTrak advantages:

1. Cheaper alternatives
2. Quick and easy implementation
3. It can be used in any isocratic HPLC method
4. No change to the actual method
5. Decrease analysis cycle time since less preparation of mobile phase is required
6. It will save still more solvent
a. After isocratic HPLC method has been developed, considering column size (Good method), you can save still more solvent using the SolventTrak.

7. Less HPLC waste will be generated
8. Less disposition costs related to the HPLC waste

Mobile phase recycling is not recommended when:

1. Gradient methods
2. MS detector
3. Suppressor device
4. Two different detectors in parallel

Regarding to spend time when checking the re-used mobile phase:
In general terms, a system suitability test is required before start the chromatographic run. If quality of the re-used mobile phase is determined during the system suitability test (as I do and recommend), there will be no wasted time.

[Devchem]

Hi greenlab,

I am investigating the possibility of introducing solvent recycling in my lab. I do not plan on using a solvent reclycing system but plan to recycle all of the flow back into the mobile phase resevoir.

Can you please explain how I can test the re-used mobile phase. Assuming that over time recycling the baseline may continue to rise and potentially begin to decrease the peak height of my active (as the active will be accumulating in the mobile phase resevoir and become the baseline).

Do I just make an injection of the reused mobile in the system suit and assess any peak interfering at the active component retention time?
Or
Do I inject a clean mobile phase and determine if a negative peak forms at the active component retention time?

Is there any other checks I need to do in the system suit check to ensure the re-used mobile is suitable for use?

Thanks!

[HW Mueller]

So these recyclers would happily recycle a mobile phase that has a continuum of matrix gunk emerging from the column, as happened after some time of running even three step analyses of cortisol in blood in my lab.
Also, did I understand correctly that the SolventTrack recycler is not bothered by drifting baselines? It doesn´t care that there is ever more junk coming off the column, as one example?
I see an enormous problem of repeatability of a published method if it is forgotten to mention that a recycler was used.
Also, I wonder whether a recycler has a lifetime that would allow its amortization in regard to ecology.

[greenlab]

Hello Devchem,
Thanks for your interest in this topic.
Since you are planning to use recycled mobile phase without the SolventTrak you should know that:

1. Quality of your re-used mobile phase will be affected by the following factors:
• Sample composition
• Component concentration
• Component response factor
• Sample injection volume
• Number of sample injections
• Mobile phase reservoir volume

2. Quality of your re-used mobile phase could affect the following method parameters:
• Limit of Detection (LOD)
• Limit of Quantitation (LOQ)
• Linearity
• Range
• Precision
• Accuracy
• Specificity
• Ruggedness
Note: Above method parameters should be re-evaluated, based on the intended use of your method.
Quality of your re-used mobile phase should be determined during the method re-validation process. This re-validation process will determine when quality of your re-used mobile phase is acceptable or unacceptable.

If the above method parameters are not affected after the re-validation process, considering the worst case scenario, then you can determine the quality of your re-used mobile phase using the results obtained from the system suitability test.
A pass result after system suitability test indicates that your chromatographic system (Injector + mobile phase + column + detector + acquisition system) is suitable to be used in your method. Make sure no atypical peak or unknown peaks are observed during the system suitability test.

My suggestion is to use the SolventTrak system to eliminate components from the recycled mobile phase and improve the quality of your re-used mobile phase.

Regards;
GreenLab

[greenlab]

Hello HW Mueller,

Thanks for your interest in this topic.

Yes the SolventTrak performance is not affected by positive or negative baseline drift, its part of the design. Refer to www.greenlab.ws for more information.

If the junk coming off the column (peaks) were considered during the validation then the SolventTrak will eliminate them from the re-used mobile phase. Also as I have mentioned, you can perform a system suitability test to verify the quality of your re-used mobile phase before use.

See my response to Devchem regarding to method validation or refer to www.greenlab.ws for more information about SolventTrak topic.

Regards;
Green Lab

[HW Mueller]

I was not talking about junk coming off the column in form of peaks, but as a continuum, when there is an equilibrium between sample matrix absorption and desorption or if drifting baselines are not caused by air.

[greenlab]

Hello HW Muller,

The SolventTrak is designed to eliminate peaks from the mobile phase no matter if there is positive or negative drift baseline situations.

Regards;
Green Lab