1.1 Scope

This method describes the collection and analysis of airborne dibutyltin maleate (DBTM). It is applicable for time-weighted average exposure evaluations. The analysis is based on the technique of graphite furnace atomic absorption.

1.2 History

This method is developed as a 'stop-gap' for sample analysis.

1.3 Uses

Stabilizer for polyvinyl chloride resins; condensation catalyst.

1.4 Physical and Chemical Properties

(C4H9)2Sn(OOCCH)2
Mol. wt.	-	346.98		White amorphous powder
% Sn	-	34.20		m.p. - 110 °C
flash pt.	-	204 °C		combustible

2.1 The analytical limit for DBTM is 2.5 µg as Sn. This is based on an analytical detection, limit of 0.05 µg/mL for graphite furnace analysis of DBTM as Sn using the standards and- parameters listed within.

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 glassware

6.2 Reagents

All reagents should be ACS analyzed reagent grade or better.

6.2.1 Sulfuric acid

6.2.2 Hydrogen perozide, 30%

6.2.3 Hydrochloric acid

6.2.4 Stock dibutyltin maleate or 1000 µg/mL Sn standard.

6.3 Safety precautions

6.3.1 Use caution when handling concentrated acids and organotins. Dibutyltin Maleate 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 furnaces a fume blood 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

6.4.1 Clean the laboratory glassware used 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 Using standard stock 1000 µg/mL Sn (Fisher, S.P., or equivalent), prepare a 10 ppm Sn stock solution by making two serial 10-fold dilutions with 10% HCl.

6.5.2 Working standards are prepared from the 10 ppm Sn stock as follows:

Prepared std.		Std. soln. used		Aliquot		Dil. Vol.
2.0 ppm		10.0 ppm		20 mL		100mL
1.0 ppm		10.0 ppm		10 mL		100 mL
0.5 ppm		10.0 ppm		5 mL		100 mL
0.2 ppm		1.0 ppm		20 mL		100 mL
0.1 ppm		1.0 ppm		10 mL		100 mL
0.05 ppm		1.0 ppm		5 mL		100 mL

6.6 Sample Preparation

6.6.1 Prepare several 'carry-through' samples for a recovery check by weighing known amounts of DBTM onto AA filters and ashing them with the samples. A theoretical tin content of 34.2% is expected based on the molecular weight of tin in DBTM.

6.6.2 Transfer the AA filter to a clean 125 mL Phillips beaker. Add 2 mL concentrated sulfuric acid and heat. When solution darkens, add (dropwise) 30% hydrogen peroxide until clear. Cool and dilute to volume (50 mL) with 10% HCl and invert several times to ensure thorough mixing.

6.7 Analysis

The analysis is done by graphite furnace/AA. The instrumental parameters for determining Sn in DBTM are as follows:

Atomic absorption unit:
Sn wavelength	286.4 nm
integ. time	10 sec.
slit width	0.7 low
signal	Pk. Ht.
mode	Abs.
BGC	on

Furnace parameters:
step	temperature	ramp time		hold time		internal flow
dry	120 °C	50 s		40 s		300 mL/min
char	800 °C	50 s		20 s		300 mL/min
atomize	2500 °C	0 s		8 s		100 mL/min
(with HGA 500, program -10 chart and 0 read in atomization step)
Chart = 5 mv scale, 20 mm/min
Injection = 20 µL

6.7.2 Parameters are adjusted so that the 2.0 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 Colorimetric program is used for the calculations.

6.8.2 Results are reported as mg/m³ Sn.

1. 2 mL concentrated H₂SO₄
2. When solution darkens, add (dropwise) 30% H₂0₂ until clear.
3. Cool and dilute to volume (100 mL) with 10% HCl.

	DBTM weighed		theor. Sn	found Sn	% recovery
Recovery Sutdy 1 -	70		23.90	25.30	1.059
Recovery Sutdy 2 -	400		136.8	135.5	0.990
Recovery Sutdy 3 -	6000		2052	2007	0.978
				average    =	1.009

1. Ethyl Acetate
2. Methl Ethyl Ketone
3. Methyl Isobutyl Ketone
4. Acetone
5. Ethyl Alcohol
6. Isopropyl Alcohol
7. Ethyl Acetate + 10%

1. Nitric acid
2. Hydrochloric acid
3. Nitric + Hydrochloric Acid (Aqua Regia)
4. Hydrochloric Acid + Hydrogen Peroxide (30%)
5. Ammonium Hydroxide