1. Introduction
1.1 Scope
This method describes the collection and analysis of airborne
triphenyltin hydroxide. It is applicable for time-weighted average exposure
evaluations. The analysis is based on the technique of graphite furnace
atomic absorption.
1.2 Uses
A major use of Triphenyltin Hydroxide is as a Fungicide.
1.3 Physical and Chemical Properties
(C6H5)3 SnOH
mol. wt. |
- 367.02 |
|
white solid |
% Sn |
- 32.34% |
|
density (20) |
m.p. |
- 22°C |
|
|
2. Range and Detection Limit
2.1 The lower analytical limit for TPTH is 0.1 µg/mL.
2.2 This is based on a detection limit of .02 µg/mL for graphite
furnace analysis of Sn as TPTH in ethanol/ammonium hydroxide.
3.
Precision and Accuracy
3.1 Precision |
S = .030 |
|
|
3.2 Coefficient of Variation |
CV=.032 |
|
|
3.3 Recovery |
Average mean recovery = 1.032 |
The above are based on recovery data for eighteen glass fiber
filters,
spiked with TPTH in ethanol/ammonium hydroxide at ½, 1, and 2 times the PEL based on a 200 liter air volume and 0.1 mg/m³ PEL. Six samples were
spiked at each level. Refer to addendum for data on recovery study.
4. Interferences
Other organotins would interfere if they are soluble in ethanol.
5.
Sampling Procedure
The sample is collected on a glass fiber filter (0.8 µm, 37-mm
diameter)
at a flow rate of 1-2 L/min.
The recommended air volume is 200 L.
The sample cassettes are plugged, sealed with OSHA tape, labeled, and sent to
the laboratory for analysis as soon as possible.
6. Analytical
Procedure
6.1 Apparatus
6.1.1 Sample collection
Personal sampling pumps
AA sampling cassettes as needed
6.1.2 Sample analysis
Atomic absorption spectrophotometer
HGA graphite furnace
Electrodeless discharge lamp for Sn
Laboratory glasseware
6.2 Reagents
All reagents should be ACS, analyzed reaged grade or better.
6.2.1 Ethanol
6.2.2 Ammonium hydroxide
6.2.3 Stock triphenyltin hydroxide
6.3 Safety precautions
6.3.1 Use caution when handling ammonia and organotins. TPTH is a
toxic compound. Always wear rubber gloves and work
under a fume hood. Waste organics should be collected in a suitable
marked container and properly disposed of in the organic laboratory.
6.3.2 Avoid using glassware with chips or sharp edges. Never pipette by mouth.
6.3.3 Before using the graphite furnace, the analyst should read the
operator's manual and be familiar with the equipment. Ensure that the
furnace tube is properly seated, the contact rings are clean, and that
cooling water is circulating. Do not exceed an atomization temperature
of 2750 degrees. Heating or cooling problems could cause the tube to
explode on atomization.
Always wear safety glasses and never look at the tube during
atomization. Even during normal firing, the intense light is harmful to the
eyes.
Be aware of the high current supplied to the furnace through the copper
cables; check that the insulating cover is in place over the terminals.
Since toxic substances are vented by the furnace, a fume hood must be
in operation over the furnace.
6.3.4 Observe care with respect to harming the equipment. Do not
operate an EDL below its recommended wattage. Be certain that the purge air
is circulating when using the background corrector. Do not operate any
equipment without first reading its instruction manual.
6.4 Glassware Preparation
Clean the 125 mL conical flasks and the 50 mL volumetric flasks by
refluxing with 1:1 nitric acid. Thoroughly rinse all glassware
with D.I. water, invert, and allow to dry.
6.5 Standard Preparation
6.5.1
The procedure is to analyze the tin in triphenyltin hydroxide. Prepare standards by diluting stock TPTH ethanol/ammonia hydroxide assuming a
theoretical tin content of 32.34%.
6.5.2 Prepare stock solution by weighing 30.92 mg TPTH into a 100 mL
volumetric flask, diluting to volume with 90% ethanol, 10% ammonium
hydroxide and mix well. This is equivalent to 100 ppm Sn.
From this a 10 ppm Sn stock solution is made by one serial 10-fold
dilution.
6.5.3 Working standards are prepared from the 10 ppm Sn stock as
follows:
Prepared std. |
Std, soln. used |
Aliquot |
Dil. vol. |
(ppm) |
(ppm) |
(mL) |
(mL) |
|
|
1.0 |
10.0 |
|
5 |
|
50 |
|
0.4 |
10.0 |
|
2 |
|
50 |
|
0.2 |
1.0 |
|
10 |
|
50 |
|
0.1 |
1.0 |
|
5 |
|
50 |
|
0.04 |
1.0 |
|
2 |
|
50 |
|
0.02 |
1.0 |
|
1 |
|
50 |
6.6 Sample Preparation
Transfer the glass fiber filter to a clean 125 mL conical
flask. Add 10 mL of 90% ethanol, 10 % ammonium hydroxide to each
beaker and sonicate for 5 minutes. Transfer contents to
50 ml
volumetric flask. Dilute to volume with ethanol/ammonium hydroxide and
invert several times to insure thorough mixing.
6.7 Analysis
6.7.1 The analysis is done by graphite furnace/AA. The instrumental parameters for determining Su in
ethanol/ammonium hydroxide are as follows:
Atomic Absorption Units |
|
Sn wavelength |
224.6 nm |
Integ. time |
7 sec. |
Slit width |
.7 low |
Signal |
Pk. ht. |
Mode |
Abs |
BGC |
On |
Furnace Parameters
Step |
Temperature |
Ramp time |
Hold time |
Interval flow |
|
Dry |
100°C |
20 S |
20 S |
100 mL/min |
Char |
800°C |
20 S |
20 S |
100 mL/min |
Atomize |
2500°C |
0 S |
8 S |
60 mL/min |
(With HGA 500, program -10 chart and 0 read in atomization step) |
Chart = 10 mv scale, 20 mm/min.
6.7.2 Parameters are adjusted so that the 1.0 ppm standard gives a
near full-scale deflection on the chart. The entire
series of standards is run at the beginning and end of the analysis; a
standard is also run after every fourth or fifth sample during the
analysis.
6.8. Calculations
6.8.1 The OSHA Auto AA program is used for the calculations.
6.8.2
Results are reported as mg/m³
Addendum I
A recovery study of TPTH from glass fiber filters by desorption in
ethanol/ammonium hydroxide was done.
30.92 mg of TPTH was weighed into a 100 mL volumetric, diluted to
volume with ethanol/ammonium hydroxide and mixed. Assuming that TFTH is
32-34% Sn, this is 100 ppm Sn as TPTH.
Six glass fiber filters were spiked at each level = ½, 1, and 2 times the PEL based on a 200 liter air volume and 0.1 mg/m³ PEL. The spikes were
made as follows:
Std used |
Spike Vol |
Sn |
PEL |
(ppm Sn) |
(ul) |
(g) |
(multiple) |
|
100 |
100 |
10 |
1/2 × |
100 |
200 |
20 |
1 × |
100 |
400 |
40 |
2 × |
The filters were then
desorbed in ethanol/ammonium
hydroxide, diluted to 50 ml, and run on the graphite furnace as described in
Section 6.7. The mean standard deviation and coefficient of variation
for the recovery at each level using the OSHA "Precision and Accuracy
Data" program =
PEL (multiple) |
Mean Recovery |
Std. Dev. |
CV1 |
|
1/2 × |
0.989 |
.040 |
.040 |
1 × |
1.036 |
.012 |
.011 |
2 × |
1.072 |
.038 |
.036 |
The mean recoveries were then pooled =
Average mean recovery
|
= |
1.032 |
Standard Deviation |
= |
.030 |
Coefficient of variation |
= |
.032 |
Appendum II
A recovery study of the loss of TPTH on glass fiber due to
volatility was done. A 200 µL spike of 100 ppm Sn as TPTH was placed on
six filters and attached to six personnel sampling pumps (calibrated at 2
liters per minute). 200 liters of air (100 minutes) were drawn through each.
The filters were then placed into 50 mL volumetric flasks, diluted to volume
with ethanol/ammonium hydroxide and run on the graphite furnace as described
in Section 6.7. The recoveries are as follows:
Sample |
Found |
Theor. |
Found/Theor. |
|
Test-1 |
20.98 |
20.00 |
1.049 |
Test-2 |
20.94 |
20.00 |
1.047 |
Test-3 |
21.65 |
20.00 |
1.083 |
Test-4 |
22.49 |
20.00 |
1.125 |
Test-5 |
20.76 |
20.00 |
1.038 |
Test-6 |
21.5 |
20.00 |
1.080 |
|