DAZOMET
146
H3C
NS
NCH3S
ISO common nameChemical name Tetrahydro-3,5-dimethyl-1,3,5-thiadiazine-2-thione
Empirical formula RMM 162.3 m.p. v.p. Solubility Description Stability Formulations Granules
(IUPAC); tetrahydro-3,5-dimethyl 2H-1,3,5-thiadiazine-2-thione, (CA; 533-74-4)
C5H10N2S2
about 104 °C 3.7 × 10–4 Pa at 20 °C In water: 3; acetone: 173; ethanol: 15; chloroform: 391;
cyclohexane: 400; diethyl ether: 6, (all in g/kg at 20 °C)
The pure material is a white to yellowish sulphurous
smelling solid
Stable to temperatures below 35 °C; unstable above
50 °C; sensitive to moisture, not stable in acidic media
37
Dazomet
DAZOMET 146
DAZOMET TECHNICAL
*
146/TC/M/-
1 Sampling. Take at least 100 g.
2 Identity tests
2.1 HPLC. Use the HPLC method below. The retention time of dazomet in the sample solution should not deviate by more than 10 s from that of the calibration solution.
2.2 Infrared. Prepare potassium bromide discs from the sample and from pure dazomet using 1.3 to 1.5 mg material and 300 mg potassium bromide. Scan the discs from 4000 to 400 cm-1. The spectrum obtained from the sample should not differ significantly from that of the standard.
3 Dazomet
OUTLINE OF METHOD Dazomet is dissolved in acetonitrile and determined by high performance liquid chromatography on a reserved phase column using acetonitrile - water - acetic acid as mobile phase, UV-detection at 284 nm and external standardisation (Fig. 15).
REAGENTS
Acetonitrile HPLC grade Water HPLC grade
Acetic acid glacial, HPLC grade
Dazomet of known content; purity at least 990 g/kg
Mobile phase acetonitrile - water - acetic acid, 150 + 350 + 1 (v/v) Calibration solution
(i) Direct procedure. Weigh (to the nearest 0.01 mg) in duplicate into separate volumetric flasks (10 ml) about 10 mg (s mg) dazomet analytical standard. Add acetonitrile (about 60 ml) and place the flasks in an ultrasonic bath for 10 minutes. Allow to cool to room temperature, and fill to the mark with acetonitrile (Solutions C1 and C2).
(ii) Dilution procedure. Weigh (to the nearest 0.1 mg) in duplicate into separate volumetric flasks (100 ml) about 100 mg (s mg) dazomet analytical standard. Add acetonitrile (about 60 ml) and place the flasks in an ultrasonic bath for 10 minutes. Allow to cool to room temperature, and fill to the mark with acetonitrile. Transfer by pipette 5.0 ml of these solutions into separate volumetric flasks (50 ml) and fill to the mark with acetonitrile (Solutions C1 and C2).
*
CIPAC method 2000. Prepared by the German Committee (DAPA). Chairman: W Dobrat. Based on a method supplied by BASF AG, FRG.
38
DAZOMET 146
APPARATUS
High performance liquid chromatograph equipped with an automatic loop injector (5 μl) and a UV spectrophotometric detector operated at 284 nm
Column stainless steel, 250 × 4.0 or 4.6 mm (i. d.), packed with Nucleosil 100 C18, 5 µm, or equivalent
Electronic integrator or data system Ultrasonic bath
PROCEDURE
(a) Operating conditions (typical):
Stationary phase 250 × 4.0 mm (i. d.), packed with Nucleosil 100 C18,
5 µm
acetonitrile - water - acetic acid, 150 + 350 + 1 (v/v) Mobile phase
Flow rate 1.0 ml/min Column temperature ambient Injection volume 5 μl Detector wavelength 284 nm Retention time dazomet: about 4 min
(b) Linearity check. Check the linearity of the detector response by injecting solutions with dazomet concentrations 0.5, 1 and 2 times that of the calibration solution. Ensure that the concentrations of the solutions are in the linear range of the detector, otherwise alter the quantities weighed or the dilutions accordingly. Inject each calibration solution at least twice and determine the mean peak area to mass ratios. The single values should differ by less than 0.5 % from the mean value, otherwise repeat the calibration.
(c) Preparation of sample solution
(i) Direct procedure. Weigh (to the nearest 0.01 mg) in duplicate into separate volumetric flasks (10 ml) sufficient sample to contain about 10 mg (w mg) dazomet. Add acetonitrile (about 60 ml) and place the flasks in an ultrasonic bath for 10 minutes. Allow to cool to room temperature, and fill to the mark with acetonitrile (Solutions SA1 and SA2).
(ii) Dilution procedure. Weigh (to the nearest 0. 1 mg) in duplicate into separate volumetric flasks (100 ml) sufficient sample to contain about 100 mg (w mg) dazomet. Add acetonitrile (about 60 ml) and place the flasks in an ultrasonic bath for 10 minutes. Allow to cool to room temperature, and fill to the mark with acetonitrile. Transfer by pipette 5.0 ml of these solutions into separate volumetric flasks (50 ml) and fill to the mark with acetonitrile (Solutions SA1 and SA2).
39
DAZOMET 146
(d) Determination. Inject each sample solution in duplicate and bracket a series of sample solution injections by injections of the calibration solutions as follows: C1, SA1 (double injection), C2, SA2 (double injection), C1, SB1 (double injection), etc. Measure the relevant peak areas. Calculate the mean value of each pair of response factors bracketing the injections of the two samples and use this value for calculating the dazomet contents of the bracketed sample injections.
(e) Calculation
Hs
fi=
s×P
Hw
g/kg Dazomet content =
w×f
where:
fi = single response factor f = average response factor
Hs = peak area of dazomet in the calibration solution Hw = peak area of dazomet in the sample solution
s = mass of the dazomet in the calibration solution (mg) w = mass of the sample taken (mg) P = purity of dazomet standard (g/kg)
The dazomet content is the mean value of two sample solutions.
Repeatability r = 16 g/kg at 965 g/kg active ingredient content Reproducibility R = 41 g/kg at 965 g/kg active ingredient content
Based on a study with 20 participants and 80 values.
40
DAZOMET 146
DAZOMET GRANULES
*
146/GR/M/-
1 Sampling. Take at least 1 kg.
2 Identity tests. As for dazomet technical 146/TC/M/2.
3 Dazomet. As for dazomet technical 146/TC/M/3.
= 20 g/kg at 972 g/kg active ingredient content Repeatability r
Reproducibility R = 25 g/kg at 972 g/kg active ingredient content
Based on a study with 22 participants and 88 values.
60 55
50
45
40
35%T
30
25
20
15
10 5
BASF AGIR-99/033
009328 Dazomet
PCP01348 Lot-No.:39-155-Operator: WH
3500
3000
2500
2000
1500
1000
500
Wavenumbers (cm-1)
Fig. 14 IR spectrum of dazomet
*
CIPAC method 2000. Prepared by the German Committee (DAPA). Chairman: W Dobrat. Based on a method supplied by BASF AG, FRG.
41
DAZOMET 146
Absorbtion0.0000.020.04246
8
Time (min)
10121416
Fig. 15 Typical chromatogram of dazomet analytical standard
42
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