||Samples are collected by drawing
a known volume of air through a mixed cellulose ester filter. Samples are
extracted with toluene and analyzed by atomic absorption/graphite furnace.
and sampling rate:
500 min at 1 L/min (500 L)
|Status of method:
method. This method has been subjected to established evaluation procedures of
the Methods Development Team and is presented for information and trial use.
Methods Development Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Salt Lake City UT 84115-1802
2. Range and Detection Limit
This method describes the collection and analysis of airborne dibutyltin
dilaurate (DBTDL). It is applicable for time-weighted average exposure
evaluations. The analysis is based on the technique of graphite furnace atomic
Initially, AA filters were spiked with dibutyltin dilaurate in the range of
1/2× and 1× the PEL and were then analyzed according to the NIOSH method for
non-volatile organatins. However, recovery was low and imprecise, ranging from
20 to 60%. It was suspected that loss occurred due to the harsh ashing
required and DBTDL's volatility at the temperatures used in the ashing. When
the spiked filters were extracted with toluene and the extract run directly on
the graphite furnace, recovery was quantitative.
Dibutyltin dilaurate is used as a catalyst for curing silicones, as a
stabilizer for polyvinyl chloride resins, as a corrosion inhibitor, and in
veterinary use, to treat tapeworms in chickens.
1.4. Physical and Chemical Properties
|mol wt. - 631.55
||clear, yellow liquid
|% Sn - 18.79
||density (20) - 1.4683
|m.p. - 27°C
2.1 The lower analytical limit for DBTDL is 0.1 µg/mL.
3. Precision and Accuracy
2.2 This is based on a detection limit of .02 ug/mlL for graphite furnace
analysis of Sn as DBTDL in benzene.
3.2 Coefficient of Variation
|S = .033
Average mean recovery = 1.08
The above are based on recovery data for eighteen AA
filters, spiked with DBTDL in toluene at 1/2, 1, and 2× the PEL based on a
500 L air volume and 0.1 mg/m3 PEL. Six samples were spiked at each
level. Refer to addendum for data on recovery study.
Other organotins would interfere if they are soluble in toluene.
5. Sampling Procedure
The sample is collected on a cellulose membrane filter (0.8 µm, 37 nm diameter) at a
flow rate of 1-2 L/min.
The recommended air volume is 500 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
6.1.1 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
All reagents should be ACS analyzed reagent grade or better.
6.3 Safety Precautions
6.2.2 Stock dibutyltin dilaurate
6.3.1 Use caution when handling toluene and organotins. Toluene is a
central nervous system depressant and irritant of the respiratory tract and
mucous membranes. Dibutyltin dilaurate 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
6.4 Glassware Preparation
6.3.2 Avoid using glassware with chips or sharp edges. Never pipette by
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
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.
6.4.1 The 250 ml Phillips beakers are cleaned by refluxing with 1:1 nitric
acid. All glassware is thoroughly rinsed with D.I. water, inverted, and
allowed to dry.
6.5 Standard Preparation
6.5.1 The procedure is to analyze the tin in dibutyltin dilaurate. The
standards are prepared by diluting stock DBTDL in toluene and assuming a
theoretical tin content of 18.8%.
6.6 Sample Preparation
6.5.2 Prepare a stock solution by weighing 1.064 g DBTDL into a 100 mL
volumetric flask, diluting to volume with toluene, and mixing well. This is
equivalent to 2,000 ppm Sn.
From this a 5 ppm Sn stock solution is made by two serial 20-fold
6.5.3 Working standards are prepared from the 5 ppm Sn stock as follows:
||Std. soln. used
6.6.1 Transfer the AA filter to a clean 125 mL conical
beaker. Wash the
filter with several 5 ml portions of toluene and quantitatively transfer
into a 25 mL volumetric flask. Dilute to volume with toluene.
6.7.1 The analysis is done by graphite furnace/AA. The instrumental
parameters for determining Sn in toluene are as follow:
|Atomic absorption unit:
||.2 low (3 on P.E. 306)
||Pk.Ht. (TCI an P.E. 306)
|| 0 s
|| 9 s
||(with HGA 500, program -10 chart and 0
read in atomization step)
Chart = 10 mV scale, 20mm/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.
6.8.1 The OSHA Auto Colorimetric program is used for the calculations.
6.8.2 Results are reported as mg/m³ Sn.
A recovery study of DBTDL from AA filters by desorption in toluene was done.
5.319g DBTDL was weighed into a 500 ml volumetric, diluted to volume with
toluene, and mixed. Assuming the DBTDL is 18.8% Sn, this is 2,000 ppm Sn as
DBTDL. From this, 50 ml was diluted to 100 ml for a 1,000 ppm Sn standard.
Six AA filters were spiked at each level = 1/2, 1, and 2X the PEL based on a
500 L air volume and 0.1 mg/m³ PEL. The spikes were made as follows:
The filters were then desorbed in toluene, 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 =
The mean recoveries were then pooled =
Average Mean Recovery = 1.08
Standard Deviation = .033
Coefficient of variation .030