When running chemistry on an FS3700 system, (or any flow analysis system) one important aspect that can often get neglected is post-run flushing and cleaning.
The exact procedure varies depending on the chemistry but there are some over-arching themes that are worth discussing.
Here at EZkem we recommend a daily procedure that involves a 10-30minute rinse/flush using DI water and startup solution with specified surfactant. The lower end of that scale is for chemistries that don’t have a heater, with a heater the rinse process is at least 15-20minutes and for chemistries with a UV module the rinse should be at least 30minutes. We find that this daily procedure is often enough to prevent any issues. However, in some cases difficult samples or matrices can necessitate a more thorough cleaning procedure. In these cases, the general procedure we recommend is to flush for 10-30 minutes with 1 Normal Sodium hydroxide or 1 Normal Sulfuric acid in opposing pH to the analyte (A basic analyte like Ammonia would be flushed with acid and an acidic analyte like Cyanide would be flushed with base, or in some cases both an acidic and basic flush may be needed). This cleaning procedure will also strip any surfactants from the system and may leave trace acid or base in the system so a follow up rinse using your normal DI water/Startup solution with specified surfactant for 10-30 minutes is required to restore lubricity in the pump tubes and debubbler.
There are other schools of thought on flushing and maintenance, often in methods* you will see a recommendation for a weekly cleaning procedure using Kleenflow acidic and/or Kleenflow basic. This is a reasonable approach particularly if one neglects the daily rinsing/flushing procedure. However, at EZkem we have found that consistent following of the daily DI water/Startup solution with specified surfactant rinsing procedure usually precludes the need for these weekly cleanings.
*Kleenflow Acidic is used in Ammonia, Hardness, Phenol, and Total Kjeldahl Nitrogen.
*Kleenflow Basic is used in Alkalinity, Chloride, Fluoride, Cyanide, PKU, Nitrate, Nitrite, Orthophosphate, Total Phosphate, and Galactose.
Additionally, Kleenflow acidic and basic both contain alcohol, which is a much more severe cleaning procedure, which in some cases can be required particularly in labs dealing with heavy soil samples, and matrices. However, we have found that it can be hard on the system as alcohol can affect some materials negatively and requires much more care in follow up treatment and restoration of surfactants.
At the end of the day system maintenance is an important aspect of flow analysis that needs to be considered carefully. So, take the time to research and come to a decision that is tailored to the specific needs of your lab.
