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Diss Factsheets
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EC number: 201-069-1 | CAS number: 77-92-9
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Partition coefficient
Administrative data
Link to relevant study record(s)
- Endpoint:
- partition coefficient
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Remarks:
- The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.
- Principles of method if other than guideline:
- Liquid-liquid extraction - flow injection analysis using coaxial segmentors to prevent phase separation.
- GLP compliance:
- no
- Type of method:
- other: Liquid-liquid extraction
- Partition coefficient type:
- octanol-water
- Analytical method:
- photometric method
- Key result
- Type:
- log Pow
- Partition coefficient:
- -1.55
- Remarks on result:
- other: Low dispersion, ±0.05
- Key result
- Type:
- log Pow
- Partition coefficient:
- -1.8
- Remarks on result:
- other: Zero dispersion, ±0.07
- Key result
- Type:
- log Pow
- Partition coefficient:
- -1.61
- Remarks on result:
- other: High dispersion (mean of three measurements), ±0.09
- Details on results:
- Although, no further details are available on the pH at which the results are measured; the measured log Kow is used for assessment purposes since the results are very low. Applying any further correction for ionisation will result in log Kow values that are much lower.
- Conclusions:
- Log Kow values of -1.6 to -1.8 were determined in a reliable study conducted according to generally accepted scientific principles.
Reference
Description of key information
Log Kow: -1.6 to -1.8
Key value for chemical safety assessment
- Log Kow (Log Pow):
- -1.6
Additional information
A number of log Kow studies are available which indicate that citric acid has a very low log Kow. A reliable study conducted according to generally accepted scientific principles gave values in the range -1.6 to -1.8 (Kuban 1991). Similarly, in another reliable study conducted according to generally accepted scientific principles, ion-pair octanol water partition coefficients of -0.76±0.10 for H2A- and -0.21±0.11 for H3A were determined for citric acid (Avdeef 1992).
In available secondary sources to which reliability could not be assigned, log Kow values of -1.64 and -1.76 were reported for the substance.
Citric acid is a weak acid with pKa values for the three carboxylic acid groups of 3.13, 4.76 and 6.4 at 25°C. In aqueous solution, in the environmentally relevant pH range, two or three of the carboxylic acid groups will typically be dissociated.
In the Kuban 1991 study, the pH of the solution is not stated and it is not possible to tell which species the result relates to. Therefore, no correction for ionisation is applied to this value.
In the Avdeef 1992 study, the log Kow of unionised citric acid was found to be -0.21. This log Kow for the unionised form was corrected for ionisation using the equation CORR = 1/1 +10A(pH-pKa) [where A = 1 for acids, -1 for bases; pH = pH-value of the environment; pKa = acid/base dissociation constant]. Log Kow values of -0.2 at pH 2, -1.1 at pH 4, -2.1 at pH 5, -4 at pH 7 and -4 at pH 9 were obtained (applying a lower limit of -4 to the estimated values).
An estimated log Kow of -1.7 for the unionised species was predicted using KOWWIN v1.69 [US EPA. [2012]. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.11]. Using the above correction, this corresponds to log Kow values of -1.7 at pH 2, -2.6 at pH 4, -3.5 at pH 5, -4 at pH 7 and -4 at pH 9.
Therefore, estimates for the log Kow of citric acid at pH 7 range from -1.6 to -4. The value of -1.6 is considered to be most conservative in terms of the PBT assessment. Therefore, this value is selected as key. The remaining uncertainty in the log Kow value is not considered critical as the log Kow value is very low.
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