Zinc bis[O,O-bis(2-ethylhexyl)] bis(dithiophosphate)

Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March, 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was performed according to guideline. The substance was analytically monitored by a substance-specific method. The analytical method was validated with respect to accuracy and precision.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

other: Publication: "Structural determination of zinc dithiophosphates in lubricating oils by gas chromatography-mass spectrometry with electron impact and electron-capture negative ion chemical ionization" Journal of Chromatography A. 905 (2001) 207-222.

Deviations:

not applicable

GLP compliance:

yes

Type of method:

flask method

Test material

Test material information

Constituent 1

Reference substance name:

Zinc bis[O,O-bis(2-ethylhexyl)] bis(dithiophosphate)

EC Number:

224-235-5

EC Name:

Zinc bis[O,O-bis(2-ethylhexyl)] bis(dithiophosphate)

Cas Number:

4259-15-8

Molecular formula:

Too complex

IUPAC Name:

1-Hexanol, 2-ethyl-, O,O-diester with phosphorodithioic acid, zinc salt

Details on test material:

- Substance type: a mixture of coordination compounds in oil consisting of a zinc metal complex bonded to alkyldithiophosphate ligands.

- Stability under test conditions: The substance is predicted to be stable under test conditions. This conclusion is based on a hydrolysis study conducted on a similar ZDDP material (CAS 68909-93-3) in which the alkyldithiohosphate ligands consist of a mixture of C3 and C8 alkyl chains. In a preliminary, Tier 1, hydrolysis study, this ZDDP was found to be hydrolytically stable at pH 4, 7 and 9 and 50 deg. C (stability defined as a < 10% change in the concentration of the alkydithiophosphate ligand).

Results and discussion

Water solubility

Water solubility:

9.1 mg/L

Temp.:

22 °C

pH:

ca. 5

Details on results:

The water solubility of the test substance is 9.1 mg/L at 22 degrees C based on chromatographic data.

The peak eluting at 20.44 min. was identified as the halogenated derivative of 2-ethylhexyl (C8) ZDDP, the primary component in the test substance. This identification was based on a comparison to the chromatogram of the starting material before water extraction (Figure 2A). Peaks eluting earlier than 20.44 min. represent ZDDP pentafluorbenzyl derivatives containing alkyl groups smaller than C8. These early eluting peaks were not conclusively identified by mass spec. because of extensive fragmentation and lack of molecular ions to verify their molecular weights from which their identities could be determined.

The difference in the water solubility results between mixing times of 24 and 48 hours was 7.1% which meets the guideline criterion for an acceptable difference of ≤ 15% between the two longest mixing periods

Any other information on results incl. tables

Results.The mean water solubilities for mixing times of 4, 24 and 48 hours are shown below :

Table 6. Results of Water Solubility Analysis -Mean Water Solubility at Different Shaking Times

Replicate	Shaking time (hours)	TotalAreas	Water Solubility (mg/L)	Mean Water Solubility (mg/L)
1	4	471830	8.6	7.4
2	4	389672	7.1
3	4	367420	6.6
1	24	498150	9.1	8.8
2	24	502076	9.1
3	24	452730	8.2
1	48	576205	10.5	9.4
2	48	514226	9.4
3	48	458559	8.3
*Mean Water Solubility (mg/L)				9.1

* calculated from 24 and 48 hour shaking times

Precision and Accuracy of Method

Three replicate samples at two concentration levels (0.75 and 7µg/mL) were analyzed to determine precision (%RSD) and accuracy (% of nominal) of the method.

 

 Table 7. Precision and Accuracy of GC-MS Method

Nominal (mg/L)	Sum of GC Peak Areas	Concentration (mg/L)	% of Nominal
0.75	358643	0.65	86.7
0.75	342601	0.62	82.7
0.75	304904	0.55	73.3
Mean		0.61	80.9
SD		0.05	6.84
%RSD		8.46
7	4069556	6.73	96.1
7	4139505	6.83	97.6
7	4100776	6.77	96.7
Mean		6.78	96.8
SD		0.05	0.72
%RSD		0.74

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
The water solubility of the substance was determined to be 9.1 mg/L at 22 degrees C.

Executive summary:

The water solubility of the test substance was determined by the shake flask method according to guidelines in OECD 105.

 

Quantitation of the water soluble components in the ZDDP (zinc dialkyldithiophosphate) test material was performed by GC-MS (gas chromatography-mass spectrometry) following derivatization of the water soluble portion to halogenated derivatives with pentafluorobenzyl bromide which can be separated by GC. The derivatization process cleaves the intact ZDDP (zinc dialkyldithiophosphate) molecule in two replacing the zinc atom with two pentafluorobenzyl branches forming two pentafluorobenzyl phosphorodithioic acid molecules, each with two alkyl groups.

 

Results of the study indicate the water solubility of the test material is 9.1 mg/L at 22 degrees C.