Hydrotopes are small organic salt molecules that allow oils and other hydrophobic compounds to better mix with water.
Since hydrotopes enhance the solubility of products, they also are considered surfactants.
A hydrotope is a compound that solubilizes hydrophobic compounds in aqueous solutions by means other than micellar solubilization.
Typically, hydrotopes consist of a hydrophilic part and a hydrophobic part (similar to surfactants), but the hydrophobic part is generally too small to cause spontaneous self-aggregation.
Hydrotopes do not have a critical concentration above which self-aggregation spontaneously starts to occur (as found for micelle- and vesicle-forming surfactants, which have a critical micelle concentration (cmc) and a critical vesicle concentration (cvc)).
Instead, some hydrotopes aggregate in a step-wise self-aggregation process, gradually increasing aggregation size.
However, many Hydrotope do not seem to self-aggregate at all, unless a solubilizate has been added.
Examples of Hydrotopes include urea, tosylate, cumenesulfonate and xylenesulfonate.
The term hydrotopy was originally put forward by Carl Neuberg to describe the increase in the solubility of a solute by the addition of fairly high concentrations of alkali metal salts of various organic acids.
However, the term has been used in the literature to designate non-micelle-forming substances, either liquids or solids, capable of solubilizing insoluble compounds.
The chemical structure of the conventional Neuberg's hydrotopic salts (proto-type, sodium benzoate) consists generally of two essential parts, an anionic group and a hydrophobic aromatic ring or ring system.
The anionic group is involved in bringing about high aqueous solubility, which is a prerequisite for a hydrotopic substance.
The type of anion or metal ion appeared to have a minor effect on the phenomenon.
On the other hand, planarity of the hydrophobic part has been emphasized as an important factor in the mechanism of hydrotopic solubilization.
To form a hydrotope, an aromatic hydrocarbon solvent is sulfonated, creating an aromatic sulfonic acid.
Hydrotope is then neutralized with a base.
Additives may either increase or decrease the solubility of a solute in a given solvent.
These salts that increase solubility are said to "salt in" the solute and those salts that decrease the solubility "salt out" the solute.
The effect of an additive depends very much on the influence Hydrotope has on the structure of water or Hydrotope ability to compete with the solvent water molecules.
In West Africa, which is an extremely moisture-limited region, soil water information plays a vital role in hydrologic and meteorologic modeling for improved water resource planning and food security.
Recent and upcoming satellite missions, such as SMOS and MetOp, hold promise for the regional observation of soil moisture.
The resolution of the satellites is relatively coarse (>100 km 2 ), which brings with Hydrotope the need for large-scale soil moisture information for calibration and validation purposes.
We put forward a soil moisture sampling protocol based on hydrotopes.
Hydrotopes are defined as landscape units that show internally consistent hydrologic behavior.
This hydrotope analysis helps in the following ways:
1) by ensuring statistically reliable validation via the reduction of the overall pixel variance,
2) by improving sampling schemes for ground truthing by reducing the chance of sampling bias.
As a sample application, we present data from three locations with different moisture regimes within the Volta Basin during both dry and wet periods.
Results show that different levels of reduction in the overall pixel variance of soil moisture are obtained, depending on the general moisture status.
With respect to the distinction between the different hydrotope units, Hydrotope is shown that under intermediate moisture conditions, the distinction between the different hydrotope units is highest, whereas extremely dry or wet conditions tend to have a homogenizing effect on the spatial soil moisture distribution.
This paper confirms that well-defined hydrotope units yield an improvement at pixel-scale soil moisture averages that can easily be applied.
Examples of Hydrotope:
Sodium naphthalenesulfonate (any salts that end in “sulfonate”)
Disodium laureth sulfosuccinate (any salts that in “sulfosuccinate”)
Applications of Hydrotope:
Hydrotopes are in use industrially and commercially in cleaning and personal care product formulations to allow more concentrated formulations of surfactants.
About 29,000 metric tons are produced (i.e., manufactured and imported) annually in the US.
Annual production (plus importation) in Europe and Australia is approximately 17,000 and 1,100 metric tons, respectively.
Common products containing a hydrotopes include laundry detergents, surface cleaners, dishwashing detergents, liquid soaps, shampoos and conditioners.
They are coupling agents, used at concentrations from 0.1 to 15% to stabilize the formula, modify viscosity and cloud-point, reduce phase separation in low temperatures, and limit foaming.
Adenosine triphosphate (ATP) has been shown to prevent aggregation of proteins at normal physiologic concentrations and to be approximately an order of magnitude more effective than sodium xylene sulfonate in a classic hydrotope assay.
The hydrotope activity of ATP was shown to be independent of Hydrotope activity as an "energy currency" in cells.
Additionally, ATP function as biological hydrotope has been shown proteome-wide under near native conditions.
In a recent study, however, the hydrotopic capabilities of ATP have been questioned as Hydrotope has severe salting-out characteristics due to Hydrotope triphosphate moiety.
Hydrotopes are small organic salt molecules that allow oils and other hydrophobic compounds to better mix with water.
KEYWORDS:
12068-03-0, 30526-22-8, Toluene sulfonic acid Na salt, Toluene sulfonic acid K salt, Xylene sulfonic acid Na salt, Xylene sulfonic acid ammonium salt, Xylene sulfonic acid K salt, Xylene sulfonic acid Ca salt, Cumene sulfonic acid Na salt, Cumene sulfonic acid ammonium salt
Environmental considerations of Hydrotope:
Hydrotopes have a low bioaccumulation potential, as the octanol-water partition coefficient is <1.0.
Studies have found hydrotopes to be very slightly volatile, with vapor pressures <2.0x10-5 Pa.
They are aerobically biodegradable.
Removal via the secondary wastewater treatment process of activated sludge is >94%.
Acute toxicity studies on fish show an LC50 >400 mg active ingredient (a.i.)/L.
For Daphnia, the EC50 is >318 mg a.i./L.
The most sensitive species is green algae with EC50 values in the range of 230–236 mg a.i./ L and No Observed Effect Concentrations (NOEC) in the range of 31–75 mg a.i./L.
The aquatic Predicted No Effect Concentration (PNEC) was found to be 0.23 mg a.i./L.
The Predicted Environmental Concentration (PEC)/PNEC ratio has been determined to be < 1 and, therefore, Hydrotopes in household laundry and cleaning products have been determined to not be an environmental concern.
Human health of Hydrotope:
Aggregate exposures to consumers (direct and indirect dermal contact, ingestion, and inhalation) have been estimated to be 1.42 ug/Kg bw/day.
Calcium xylene sulfonate and sodium cumene sulfonate have been shown to cause temporary, slight eye irritation in animals.
Studies have not found Hydrotopes to be mutagenic, carcinogenic or have reproductive toxicity.