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 |
|
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