Conductivity and Detergent Concentration

Question:
How is conductivity used to determine how much detergent concentrate to add to a cleaning solution to restore cleaning performance?

Answer:
Part of the technical information Alconox, Inc supplies for its brands are detergent concentration versus conductivity curves. By adapting these curves to your conditions and measuring the conductivity, detergent depletion and dilution can be determined. This determination can be used to figure out how much detergent to add to the cleaning solution to restore cleaning performance.

Keep in mind that, the bath will ultimately reach a point where it forms sludge (or where some other failure occurs). At that point, the bath must be dumped and a complete batch of new cleaner made up. The time to dump the bath, and start over, is generally determined using some sort of cleanliness measurement and defined in terms of number of parts cleaned or time period of bath use. Conductivity does not typically detect the point of cleaning failure, but only detects concentration of cleaner present, whether depleted or not. The following table gives specific examples of concentration vs. conductivity for several Alconox-brand cleaners. Use this data to derive the concentration of detergent from measured conductivity. Note that, conductivity is temperature dependent. Detergent solutions do not have the same slope as many default settings on temperature-correcting conductivity meters. For best results, allow hot detergent solutions to cool to a consistent temperature for comparison.

Conductivity Controller in a Machine Washer

Question:
How does a conductivity controller regulate a dosing pump in a machine washer?

Answer:
A conductivity probe would need to be set up in the sump of a machine washer. The conductivity recorded is sent to the conductivity controller that regulates the pump (usually a peristaltic pump) that dispenses the detergent into the sump. The pump dispenses until the correct conductivity is reached for the desired concentration. Typically a concentration of 0.5% or 0.1% detergent is desired. For example, for a 0.5% Solujet concentration, enough detergent concentrate is pumped into solution until the sump reaches 2.45 mS at 22 deg C (Alconox, Inc has conductivity VS concentration curves available for each brand at 22 deg C). Once the correct concentration has been reached, the wash cycle starts.

Since conductivity is temperature dependent if hot water is used a new conductivity curve must be generated that reflects the higher temperature. If the customer provides the Alconox Technical Team the higher working temperature then a curve could be generated. Alternately, if the customer has access to a conductivity meter they could simply generate the appropriate curve for their working temperature.

Washers with Non-Standard Connectors

Question:
It is not unusual for lab/glassware-washer manufacturers to make custom connectors specific that link their brand of detergent (with unique bottle dimensions) to the machine. This is strategic on the lab/glassware-washer manufactures’ part, as their customers are locked into using their detergent. These custom molded bottles are expensive and generally make the product more expensive than Alconox brands that have standard bottles. So how does Alconox suggest adjusting for the standard bottle with these types of connector set ups?

Answer:
Unfortunately we are usually unable to supply a bottle that fits the connections because the bottles are made from custom molds that are not commercially available. The way some customers use our cleaners in these washers is to pour our detergents out of their original bottles into some of the custom bottles that fit the special washer fittings. This is of course somewhat time consuming and hazardous and there must be adequate cost savings and performance improvements to justify this. In some cases, washers can be fitted with peristaltic pumps and controllers that dose in the detergent correctly from a tube that is dipped in to one of our bottles and bypass the custom fitting bottles. This would typically require an outside contractor with experience in how to retro-fit the washers, or good in-house engineering capability by the customer. We do not have this expertise. We can supply conductivity curves to a contractor or engineer to allow them to program a conductivity controller that regulates the dosing pump.

Cleaning Stainless Steel Weldments

Question:
We need recommendations for cleaning stainless steel weldments. A Walter weld cleaning machine is being used. Currently we have tried using Luminox but sometimes it does not produce satisfactory results.

Answer:
Luminox is a very light duty cleaner used to remove light oils and tiny particulates from delicate substrates. Generally, stainless steel is not considered a delicate substrate. In this case the recommendation would be 2% Citrajet at 60 deg C for 10 minutes followed by a water rinse. Citrajet is a mild organic acid cleaner (pH 2.5) that is good at removing heat scale and discoloration around weld joints as well as being a good general purpose cleaner. The cleaning results with Citrajet will be much better than luminox.

Note, if for some reason you need to use Luminox and are satisfied with the light duty cleaning it gives, I would recommend using it at a 3% concentration at 60 deg C for 10 minutes but I would not expect it to clean as well as Citrajet.

Citrajet is low foaming like Luminox and probably a low foamer is preferable to use in junction in a large dip tank. If you for some reason have a particularly oily substrates to clean, we do make a high foaming cleaner called Citranox (manuf cat no 1801 for the 1 gal size) that would give the same heat scale and discoloration cleaning while doing a better job on oily residues. I am guessing you do not have particularly oily substrates to clean and that you will be happier with the low foaming version.

Citrajet (manuf cat no 2001 for a 1 gallon size) should be available from whatever dealer you get your Luminox from such as VWR, Thomas, Cole-Parmer or other lab and health supply dealers.

Liquinox in Relation to Alconox

Question:
Is the Alconox powder equivalent to the Liquinox liquid? If these are the same could you please provide me with some sort of documentation saying that Alconox is the powdered form of Liquinox and that they are interchangeable?

Answer:
Liquinox liquid hard surface cleaner concentrate is designed to be the functional equivalent of Alconox powdered hard surface cleaner concentrate. Liquinox was designed as a liquid replacement for Alconox. For each functional ingredient in Alconox, there is a functionally equivalent ingredient present in Liquinox at a concentration designed to give functionally equivalent performance. Of the six ingredients in Liquinox, two are identical to those found in Alconox. The other four are chosen for equivalent cleaning functionality with good shelf life characteristics in a liquid form. If we just made a liquid Alconox, it would have a very poor shelf life measured in weeks.

The key ingredient for cleaning by wetting, emulsifying and dispersing is the surfactant sodium dodecylbenzene sulfonate. This ingredient is identical in both cleaners. The surface tension, which correlates with wetting, emulsifying and dispersant character, is 32 dynes per cm in both Alconox and Liquinox. Cleaning is also assisted by chelating and sequestering agents that tie up calcium, magnesium, iron and other ions that will tend to form insoluble complexes with soils. Alconox and Liquinox both contain chelating and sequestering agents that are effective for this purpose. Alconox relies on polyphosphate chelant/sequesterants, which are perfectly stable as powders, but which do not have long term stability as liquids. In Liquinox, liquid stable organic chelants are used. Alconox and Liquinox are both detectable by total organic carbon (TOC) and other surfactant detection methods. The sodium dodecylbenzene sulfonate, which will test TOC positive, is theoretically the last ingredient to rinse away in both formulations.

Xylene Equivalent

Question:
Currently we are using Xylene to clean equipment that is used with extremely non-polar compounds. Does Alconox have a cleaning product that would be equivalent to Xylene but not as harmful and dangerous to work with? It would have to be a cleaning product with a low polarity index (between 2 and 3).

Answer:
Even extremely non-polar compounds can often be emulsified by polar surfactants.
Alconox and Liquinox both contain polar surfactants that would work well at emulsifying a non-polar compound that has been found to be cleaned by xylene. The rational for this recommendation is due to the non-polar end or hydrophilic end of the surfactant that contains xylene and benzene derivatives. In theory, polar surfactants typically form micelles in aqueous solution, meaning that the hydrophilic "head" regions aggregate in contact with surrounding solvent (aqueous) and the opposite non-polar or hydrophilic ends are sequestered together at the center of the micelle sphere, interacting with the non-polar compound of interest, thus trapping the non-polar compound in the center of the sphere. Due to this nature, the interior of the micelle – hydrophobic- is able to emulsify the non-polar residues.

An initial test to determine if warm 1% Liquinox (liquid concentrate) or Alconox (powder) solution to see if it will clean the non-polar compound. Note that unlike xylene cleaning, you will need to rinse away the detergent solution after cleaning. Xylene evaporates away, detergents rinse away. Our rational for this recommendation is based on the non-polar ends of the surfactants found in Alconox and Liquinox, based on xylene and benzene You do not have to try both, either of them should work. The Alconox is more economical to use, but it is a little messy to dissolve the powder to make a cleaning solution. The Liquinox is easier to handle, dose and mix.

If this fails, then consider using a semi-aqueous cleaning system that is a combination of surfactants and solvents that may be able to act as cosolvents for your non-polar residue. I would recommend trying a 5% Detergent 8 solution, but only if Alconox or Liquinox fails. Detergent 8 is a corrosive liquid that requires wearing rubber gloves and eye protection. Detergent 8 contains surfactants and semi-polar glycol ethers that might be able to solvate non-polar solvents.

EC 648/2004 Compliance

Question:
What Alconox brands are EC 648/2004 compliant?

Answer:
Alconox, Alcotabs, Citrajet, Detojet, Tergajet, Tergazyme