Diphosphoric acid, compd. with piperazine (1:1)

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 to 12 February 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Version / remarks:

January 2001

Deviations:

no

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Radiolabelling:

no

Test temperature:

Column temperature: 25 °C

Details on study design: HPLC method:

CHEMICALS
The following chemicals were used for preparing test solutions and HPLC solvent:
- Water, deionized (MilliQ).
- Methanol, ultrapure (Biosolve, Ltd.), batch 29716
- Formic acid, p.a. (Merck), lot K 27372564 006
- Ammonium formiate, p.a. (Fluka), lot 42071111

EQUIPMENT
The retention time of the diluted samples was determined by HPLC-MS. For details see attachment “T-1063FM – HPLC conditions and reference substances adsorption.pdf”.

MOBILE PHASES
- Type: methanol/water 55/45 v/v% and methanol/0.01 Mol/1 NH4COOH, 55/45 v/v% (pH 5.5)
- Solutes for dissolving test and reference substances: methanol (reference substances), water (test substance)

DETERMINATION OF DEAD TIME
- Determination of the dead time to by inert substance (urea) which is not retained by the column

REFERENCE SUBSTANCES
- Identity: Urea, Acetanilide, Monuron, Aniline, Linuron, Methiocarb, Pyrazophos
For details see attachment “T-1063FM – HPLC conditions and reference substances adsorption.pdf”.
For aniline a very bad shaped peak with a indefinable retention time was obtained in methanol/water 55/45 v/v%. For this system, only 5 reference components were used.

REPRODUCIBILITY
For the two solvent systems used in this study, i.e. methanol/water 55/45 v/v % and methanol/0.01 Mol/l NH4COOH 55/45 v/v % (pH 5.5), correlation coefficients of 0.94 and 0.91, respectively, were obtained for the reference substances.

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 8.8 µg
- Quantity of reference substances: 3.92 µg (urea); 1.46 µg (aniline); 0.39-0.59 µg (rest)

REPEATABILITY
The measurements were all carried out in duplicate. In case peaks were obtained the values of log Koc derived from the individual measurement for the test substance were within a range of 0.25 log unit (for the piperazine ion using methanol/0.01 Mol/l NH4COOH 55/45 v/v% (pH 5.5)).

EVALUATION
- Calculation of capacity factors k': k’ = (tr– t0)/t0
- Determination of the log Koc value: logKoc= a*log k’ + b; in which: a = slope; b = intercept

Key result

Type:

log Koc

Value:

3.1

pH:

5.5

Temp.:

25 °C

Remarks on result:

other: positively charged piperazine ion

Key result

Type:

log Koc

Value:

2.02 - 3.46

pH:

5.5

Temp.:

25 °C

Remarks on result:

other: negatively charged pyrophosphate ion

Remarks:

not reliable due to undefined collection of small peaks

Details on results (HPLC method):

METHANOL/WATER 55/45 v/v %
The test substance was analysed in between the mix of reference substances in the positive and in the negative ionisation mode. The results of duplicate injections are shown in Table 1 and 2 in attachment “T-1063 – results adsorption.pdf”. The test substance consisted of two ions, e.g. piperazine ion and pyrophosphate ion. Piperazine was analyzed in the positive mode with characteristic mass of 87.0 m/z. The chromatogram of piperazine showed no peak as under the applied conditions piperazine was not eluted from the column (retention time >> retention of Pyrazophos and as a result of this the log Koc of piperazine was >> 3.65). Pyrophosphate was analyzed in the negative mode with characteristic mass of 177.1 m/z. The chromatogram of pyrophosphate showed peaks at tr of 2.61 (first analysis) and 2.63 min (second analysis). These retention times are smaller than t0, i.e. the retention time of urea. As a result the log Koc could not be calculated.

METHANOL/0.01 MOL/L NH4COOH 55/45 v/v % (pH 5.5)
The test substance was analyzed in between the mix of reference substances in the positive and in the negative ionisation mode. The results of duplicate injections are shown in Table 3 and 4 in attachment “T-1063 – results adsorption.pdf”. The chromatogram of positive piperazine-ion showed a peak around tr= 4.1 min. Using the calibration line of the reference substances, the log Koc of the piperazine ion was calculated and the result is shown in Table 4. The chromatogram of the negative pyrophosphate -ion showed an undefined collection of small peaks around tr= 3.69 - 4.30 min. As a result, no distinct log Koc could be calculated for pyrophosphate. For that reason the results based on tr= 3.69 - 4.30 min, and shown in Table 4, are in italic.

Validity criteria fulfilled:

yes

Conclusions:

For methanol/water 55/45 v/v % the log Koc of the positive ion of the test substance could not be determined as this component was not eluted from the column under the applied conditions. Its retention time was much greater than the retention time of Pyrazophos (with a log Koc of 3.65). The negatively charged pyrophosphate showed a peak in the chromatogram with retention time lower than to. Hence, the Koc could not be calculated. For methanol/0.01 Mol/l NH4COOH 55/45 v/v% (pH 5.5), the log Koc of the positively charged piperazine ion was 3.10. For the negatively charged pyrophosphate ion, an undefined collection of small peaks was observed in the chromatogram with a log Koc of 2.02- 3.46.

Executive summary:

Log K_oc value of piperazin ion (3.10) was used for PNEC determination. 

Description of key information

Log K_oc at 25 °C (column temparature):

positively charged piperazine ion = 3.10

negatively charged pyrophosphat ion = 2.02 - 3.46 (undefined collection of small peaks)

(HPLC method; OECD guideline 121)

Additional information

Log K_oc at 25 °C (column temparature):

positively charged piperazine ion = 3.10

negatively charged pyrophosphat ion = 2.02 - 3.46 (undefined collection of small peaks)

 

Log K_oc value of piperazin ion was used for PNEC determination.