Methylthiouracil

Particle size distribution (Granulometry)

Administrative data

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 110 (Particle Size Distribution / Fibre Length and Diameter Distributions - Method A: Particle Size Distribution (effective hydrodynamic radius)

Test guideline 2

Qualifier:

according to guideline

Guideline:

ISO 13320 (Particle size analysis - Laser diffraction methods)

GLP compliance:

no

Type of method:

other: Sieving/Laser diffraction both

Type of particle tested:

agglomerate

Type of distribution:

volumetric distribution

Test material

Test material information

Constituent 1

Reference substance name:

Methylthiouracil

EC Number:

200-252-3

EC Name:

Methylthiouracil

Cas Number:

56-04-2

Molecular formula:

C5H6N2OS

IUPAC Name:

methylthiouracil

Test material form:

solid: crystalline

Specific details on test material used for the study:

Test Item: 6-Methyl-2-Thiouracil
Batch No.: 151117
CAS No.: 56-04-2
EINECS No.: 200-252-3
Molecular formula: C5H6N2O2S
Molecular weight: 142.18 g/mol
Purity: Not stated
Appearance: White powder

Results and discussion

Mass median aerodynamic diameter:

> 6 - < 1 065 µm

Geometric standard deviation:

ca. 0.19

Particle size

Key result

Percentile:

D50

Mean:

ca. 6 µm

St. dev.:

0.19

Any other information on results incl. tables

1                      Test Methods

1.1                  Test Principle

The particle size distribution is determined using different sized sieves. The powder is separated into fractions with different ranges of particle size. The fractions are weighed and from the different weighed fractions the particle size distribution is calculated.

In addition the particle size distribution of the fraction < 500 µm is determined using laser diffraction. As measuring device, a Malvern Mastersizer 2000 is used. The powder is brought via a powder dispersing cell Scirocco 2000 into the laser light beam and the diffraction pattern is determined. From the diffraction pattern the particle size distribution is calculated.

1.2                  Equipment

·               Particle Analyser

Malvern Mastersizer 2000

Scirocco 2000

·               Laboratory Equipment

Analytical Balance LP5200P-OCE, Sartorius

4000 µm, S/N 10005727

2000 µm, S/N 10005885

1000 µm, S/N 10004351

500 µm, S/N 10003933

250 µm, S/N 10004222

125 µm, S/N, 10004025

90 µm, S/N, 13039301

·               General Laboratory Equipment

1.3                  Test Procedure

The test was performed according to following SOP and standard:

·               SOP-LO-110Particle size distribution by laser light scattering (OECD 110)

·               CIPAC MT 59: Sieve Analysis

1.4                  Test Description

1.4.1              Particle Size Distribution: Sieving Analysis

The first measurements using laser diffraction resulted in no reproducible values since the test item has a very inhomogeneous particle size distribution with larger and stable agglomerates (seeFigure 1). Due to this result, a sieving analysis with whole amount of test was carried out first.

The sieves were stacked in order of aperture size with the largest at the top and the receiver pan at the bottom. The whole amount of test item was filled into the sieve with the largest size. The tower was than shaken with rocking motions and tapped on a hard surface on left and right sides alternately until the amount of the test item was constant in the top sieve. The top sieve was then removed and the sieving was resumed. Each residue was than weighed.From the measured diffraction pattern the particle size distribution is calculated. From the cumulative distribution the characteristic values

1.   D₁₀: 10 Vol.-% of the particles have a smaller diameter

2.   D₅₀: 50 Vol.-% of the particles have a smaller diameter (Median diameter)

3.   D₉₀: 90 Vol.-% of the particles have a smaller diameter

are derivedvialinear regression.

1.4.2              Particle Size Distribution – Laser Diffraction

In the sieving analysis the test item showed a more homogeneous particles size distribution starting at a particle size of < 500 µm. Due to this, all sieved fractions < 500 µm were combined and representative sample of the combined fraction was fed to the powder dispersing cell Scirocco 2000. The test item was loosened by the vibrator of the dispersing cell (40 %). From the dispersing cell the test item is fed to the measuring cell by pressurized air (2.0 bar_g). The concentration of the test item in the air flow is adjusted by the opening of the cell. An opening of 6 mm was used. The optical concentration in the measuring cell was adjusted to 4 – 5 %. An additional sieve in the powder dispersing cell prevents that agglomerates are fed to the measuring cell.

In the measuring cell the test item passes the laser beam. The particles diffract the laser light. The diffraction radius depends on the particle size. Small particles have a wide diffraction radius; big particles have a small one. The diffraction pattern of the laser light is measured by the detector of the particle analyzer.

From the measured diffraction pattern the particle size distribution is calculated. From the cumulative distribution the characteristic values

4.   D₁₀: 10 Vol.-% of the particles have a smaller diameter

5.   D₅₀: 50 Vol.-% of the particles have a smaller diameter (Median diameter)

6.   D₉₀: 90 Vol.-% of the particles have a smaller diameter

1                      Results

1.1                  Particle Size Distribution: Sieving Analysis

The results of the sieving analysis are summarized inTable 1andFigure 2shows the course of the fraction distribution (left y-axis) as well as the cumulative distribution on the (right y-axis).

Table1:Results of the sieving analysis

Sieve size in µm	Weight in g	Mass %	Total %
> 4000	1.76	1.05	100.00
< 4000	24.40	14.56	98.95
< 2000	61.54	36.73	84.39
< 1000	57.86	34.54	47.65
< 500	10.56	6.30	13.12
< 250	9.90	5.91	6.82
< 125	1.48	0.88	0.91
< 90	0.04	0.02	0.2

 

Sieving Analysis (Figure2):

D₁₀:       376 µm

D₅₀:       1065 µm         (Median diameter)

D₉₀:       2771 µm

1.2                  Particle Size Distribution: Laser Diffraction

Two test series of 3 measurements each were performed with the fine fraction < 500 µm of the test item.

Figure3andFigure4show the results of both test series. On the left y-axis the fraction distribution and on the right y-axis the cumulative distribution is shown. The test item < 500 µm shows a bimodal particle size distribution with peaks at approx. 5 µm and 250 µm.

 

Test series 1 (Figure3):

D₁₀:       1.5 µm                                                          Standard deviation: 0.07 µm

D₅₀:       6.2 µm(Median diameter)                           Standard deviation: 0.64 µm

D₉₀:       245.3 µm                                                        Standard deviation: 18.96 µm

 

Test series 2 (Figure4):

D₁₀:       1.4 µm                                                          Standard deviation: 0.05 µm

D₅₀:       5.8 µm(Median diameter)                           Standard deviation: 0.40 µm

D₉₀:       235.45 µm                                                      Standard deviation: 20.48 µm

 

Average

D₁₀:       1.4 µm                                                          Standard deviation: 0.01 µm

D₅₀:       6.0 µm(Median diameter)                           Standard deviation: 0.19 µm

D₉₀:       240.4 µm                                                        Standard deviation: 4.92 µm

1.3                  Final Results

The test item6-Methyl-2-Thiouracilin its delivered state has a median particle size D₅₀ = 1065 µm, which was determined by sieving analysis according to CIPAC MT 59 (2009).

The fine fraction < 500 µm has a median particle size of D₅₀ = 6 µm, which was determined by laser diffraction measurementaccording to OECD Test Guideline 110 (1981) and ISO 13320 (2009).

 

Applicant's summary and conclusion

Conclusions:

The test item 6-Methyl-2-Thiouracil in its delivered state has a median particle size D50 = 1065 µm, which was determined by sieving analysis according to CIPAC MT 59 (2009).
The fine fraction < 500 µm has a median particle size of D50 = 6 µm, which was determined by laser diffraction measurement according to OECD Test Guideline 110 (1981) and ISO 13320 (2009).

Executive summary:

The test item6-Methyl-2-Thiouracilin its delivered state has a median particle size D₅₀ = 1065 µm, which was determined by sieving analysis according to CIPAC MT 59 (2009).

The fine fraction < 500 µm has a median particle size of D₅₀ = 6 µm, which was determined by laser diffraction measurementaccording to OECD Test Guideline 110 (1981) and ISO 13320 (2009).