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1.1 Scope

This method describes the collection and analysis of airborne dibutyltin oxide (DBTO). It is applicable for time-weighted average exposure evaluations. The analysis is based on the technique of L'vov platform graphite furnace atomic absorption.

1.2 History

1.3 Uses

Dibutyltin oxide is used as an intermediate for preparation of, other organotins and as a condensation catalyst.

1.4 Physical and chemical proprieties:
 

(C4H9)2 Sn0		White Powder
Molecular Weight    248.92		Density   1.58 g/mL
% Sn   47.68 %		M.P.   > 300°C

2.1 The lower limit for DBTO is 1-2 µg.

2.2 This is based on a detection limit of 0.05 µg/mL for graphite furnace analysis of DBTO as Sn in 10% acetic acid in toluene.

5.1 The samples are collected on a glass fiber filter with a backup pad and an XAD-2 tube in series at a flow rate of 1-2 L/min, using an MSA Model G sampling pump, or equivalent.

5.2 The recommended air volume is.100-250 L.

5.3 The sample cassettes and tubes are plugged, sealed with OSHA Form 21, and then sent to the laboratory for analysis as soon as possible.

6.1 Apparatus

6.1.1 Sample Collection

Personal sampling pumps, glass fiber filters with backup pads, and sampling cassettes.

6.1.2 Sample Analysis Laboratory glassware including volumetric flasks, 125-mL Erlenmeyer flasks, and assorted pipettes. An atomic absorption spectrophotometer with graphite furnace and a Sn electrodeless discharge lamp (EDL). In this study, a L'vov platform was used in the graphite tube.

6.2 Reagents: ACS analyzed reagent grade or better

6.2.1 Acetic acid, Glacial; Baker Analyzed Reagent, or equivalent

6.2.2. Stock Dibutyltin Oxide, 98%; Aldrich, or equivalent.

6.3 Safety Precautions

6.3.1 Use caution when handling acids, solvents, and organotins. Dibutyltin oxide is a toxic material. Always wear rubber gloves and work in a fume hood. Waste organics should be collected in a suitable, marked container and be properly disposed of as a hazardous waste.

6.3.2 Never pipette by mouth; an assortment of pipetting bulbs is available. Avoid using glassware with chips or sharp edges.

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 and aligned, the contact rings are cleaned, that cooling water is circulating, and the argon cylinder has been turned on. Do not exceed an atomization temperature of 2650 degrees.

6.3.4 Always wear safety glasses and never look at the furnace tube during atomization. Even during normal firing, the intense light may be harmful to the eyes.

6.3.5 Be careful to not damage the equipment. Do not operate an EDL below its recommended wattage. Be certain that the purge air is circulating when using the background corrector. Don't operate any equipment without first reading its instruction manual.

6.4 Glassware Preparation

6.4.1 Volumetric flasks should be rinsed with either acetic acid toluene or 10% nitric acid and deionized water.

6.4.2 Clean the conical beakers with 1:1 nitric acid. Then thoroughly rinse with deionized water, invert, and allow to dry.

6.5 Standard Preparation

6.5.1 Prepare a 1000 µg/ml stock standard of DBTO (as Sn) by weighing 0.20978 g DBTO into a 100 ml volumetric flask and diluting to volume with 10% acetic acid in toluene. DBTO is 47.68% Sn.

6.5.2 Prepare a 100 ppm stock Sn standard by volumetrically pipetting 5 ml of the 1000 ppm stock standard into a 50 ml volumetric flask and diluting to volume with 10% acetic acid in toluene.

6.5.3 Prepare a 10 ppm stock Sn standard by volumetrically pipetting 5 ml of the 100 ppm stock standard into a 50 mL volumetric flask and diluting to volume with solvent.

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

 

Prepared Std		Std Soln Used		Aloquot		Dil Vol
1.0 ppm		10.0 ppm		5 mL		50 mL
0.5 ppm		1.0 ppm		25 mL		50 mL
0.2 ppm		1.0 ppm		10 mL		50 mL
0.1 ppm		1.0 ppm		5 mL		50 mL
0.05 ppm		0.5 ppm		5 mL		50 mL
0.02 ppm		0.2 ppm		5 mL		50 mL
0.01 ppm		0.1 ppm		5 mL		50 mL

6.6 Sample Preparation

6.6.1 Transfer the glass fiber filter to a clean 125-mL conical beaker. Add 10 mL 10% acetic acid toluene to each beaker and swirl for 5 minutes.

6.6.2 Repeat step 6.6.1 with a second 10 mL aliquot.

6.6.3 In a 25 ml volumetric flask, dilute to volume with 10% acetic acid in toluene and invert several times to ensure thorough mixing.

6.6.4 Transfer the A and B portions of the XAD-2 tubes to two separate 125-mL conical beakers, add 10 mL 10% acetic acid in toluene to each beaker and swirl or sonicate for 5 minutes. Dilute to volume in a 25 mL volumetric flask with 10% acetic acid in toluene and invert several times to ensure complete mixing.

6.6.5 If subsequent dilutions are necessary, make them in the 10% acetic acid toluene. Include aliquots for reagent blank and filter blank.

6.7 Analysis

6.7.1 This analysis is done by graphite furnace atomic absorption with a L'vov platform. It is very important that a pyrocoated tube is used. The instrument parameters for determining this organotin are as follows:

Sn Wavelength	286.3 nm
Injection Volumes(s)	10 µL for the sample 5 µL for the matrix modifier
Slit Width	0.7 Low

Graphite Furnace
 

Step	Dry		Char		Atomize		Burnout		Cooldown
Temp	110		800		2500		2650		20
Ramp	40		30		0		1		1
Hold	10		10		8		5		10
Int. Flow	300		300		0		300		300

6.7.2 The entire series of standards is run at the beginning and end of the analysis; a standard is also run after every fifth or sixth sample during the analysis.

6.8 Calculations

6.8.1 Blank corrected peak area and the standard concentrations are used for the calculations.

6.8.2 Results are reported as mg/m³ Sn based on the total micrograms of DBTO (as Sn) and the air volume in liters.

7.1 Condensed Chemical Dictionary, G.G. Hawley, 10th Edition, 1981.

7.2 "Determination of Butyl Organotin Compounds in Air Samples by AAS-Graphite Furnace," Standard Test Methods, Method Number AA-62 M&T Chemicals, Inc. June 6, 1984.