Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 March 2010 - 20 March 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was performed according to guideline under GLP conditions. The test substance was analytically monitored by a substance specific test method. The analytical method was validated with respoect to linearity 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:

Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

EC Number:

270-608-0

EC Name:

Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

Cas Number:

68457-79-4

Molecular formula:

{[(iso-C4H9O)0.64(C5H11O)0.36]PS2}2Zn - neutral, {[(iso-C4H9O)0.64(C5H11O)0.36]PS2}6Zn4O - basic

IUPAC Name:

Phosphorodithioic acid, mixed O,O-bis(iso-Bu and pentyl) esters, zinc salts

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: A preliminary, Tier 1, hydrolysis study was conducted on the substance according to OECD 111, Annex 1, tiered hydrolysis scheme. Results of the study indicated a < 10 change in the concentration of the alkyldithiophosphate ligands which met the guideline criterion for a hydrolytically stable substance.

Results and discussion

Water solubility

Water solubility:

1 658 mg/L

Temp.:

22 °C

pH:

5

Details on results:

The water solubility of the test substance is 1658 mg/L at 22 degrees C based on chromatographic data.

The GC chromatogram of the water solubles (Figure 2B) shows 3 peaks eluting between 11 – 13.3 min. Each can be attributed to the pentafluorobenzyl derivatives of ZDDP (zinc dialkyldithiophosphate) based on the characteristic fragment corresponding to the pentafluorbenzyl ion at m/z 181 and the fragment corresponding to the pentafluorobenzyl-dithiophosphate ions at m/z 311 resulting from the loss of two alkyl groups .

The data show that lower molecular weight ZDDPs are preferentially soluble in water. ZDDPs where all alkyldithiophosphate ligands contained C4 (isobutyl) groups accounted for the bulk of the composition of the water sample (77 % by area). A smaller amount of ZDDPs containing mixed isobutyl/pentyl alkyl dithiophosphates ligands account for the remaining 23 % by area of the water sample. ZDDPs containing all pentyl alkyldithiophosphate ligands were not detected in the water.

The difference in the water solubility results between mixing times of 24 and 48 hours was 1.8% 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)	Sum of GC Peak Areas	Water Solubility (mg/L)	Mean Water Solubility (mg/L)
1	4	35892743	1520	1560
2	4	39227464	1625
3	4	36352353	1535
1	24	49315531	1924	1673
2	24	32855579	1421
3	24	71689969 *	2479 *
1	48	43790817	1764	1643
2	48	35938193	1521
3	48	69020627 *	2421 *
**  Mean Water Solubility (mg/L)				1658

*excluded data; AQL (above quanitation limits)

** calculated from 24 and 48 hour shaking time

Precision and Accuracy of Method

Three replicate samples at two concentration levels (2 and 8 µg/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
2	6187524	1.7	87.0
2	5288538	1.6	79.6
2	6577279	1.8	90.2
Mean		1.7	85.6
SD		0.11	5.4
%RSD		6.3
8	43700065	7.1	88.1
8	45052511	7.2	90.1
8	38705420	6.4	80.5
Mean		6.9	86.2
SD		0.41	5.1
%RSD		5.9

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): soluble (1000-10000 mg/L)
The water solubility of the substance is 1658 mg/L at 22 degrees C. The solubility of the substance is dependent on the carbon chain length of the alkydithiophosphate ligands.

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 CASRN 1765-40-8. Identification of the water soluble components was based on a combination of GC retention times and the interpretation of the fragmentation patterns in the mass spectra obtained for each peak eluted from the GC column.

Results of the study indicate the water solubility of the test material is 1658 mg/L at 22 degrees. The GC data indicate the water solubility of this substance is dependent on the length of carbon chain of the alkyldithiophosphate ligands. The lower molecular weight zinc dialkyldithiophosphates containing C4 (isobutyl) alkyl groups are preferentially soluble over the higher molecular weight zinc dialkyldithiophoshates containing all C5 (pentyl) alkyldithiophosphate ligands.