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These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA.
Method no.: |
ID132SG |
|
Control no.: |
T-ID132SG-PV-01-0305-SP |
|
Target concentration: |
0.1 mg/m3 |
|
Procedure: |
The sample is collected on an MCE filter
(0.8 µm) and analyzed by atomic absorption with a graphite furnace. |
|
Recommended sampling time and
sampling rate: |
1.502 L/min for a total air
volume of 1000L |
|
Reliable quantitation limit: |
0.4 µg/mL |
|
Status of method: |
Partially evaluated method. This method has
been subjected to established evaluation procedures of the Methods
Development Team and is presented for information and trial use. |
|
|
Spectroscopy Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Sandy UT 84070-6406 |
1. Introduction:
1.1 Scope
This method describes the collection and analysis of airborne tellurium. It is applicable for both ceiling (c) and
time- weighted averages (TWA) exposure evaluations.
The analysis is based on the utilization of a graphite furnace.
1.2 Uses
Tellurium is used as a coloring agent in chinaware, porcelains, and glass. It is a reagent in producing a black
finish on silverware. it is used as a rubber improver; in tellurium vapor "daylight" lamps; in cast iron, where
minute amounts stabilize the iron carbide and appreciably increase the depth of the chill. Tellurium is a p-type
semiconductor, and shows greater conductivity in certain directions, depending on alignment of the atoms. Its
conductivity increases slightly with exposure to light. Tellurium is used in ceramics. Bismuth telluride has been
used in thermoelectric devices. One such device, using two Bi-Te semiconductors, is reportedly capable of freezing or
boiling water in seconds with the power from two flashlight batteries. The unit is said to be capable of bringing the
temperature down to -75°C, using only two amperes of current. The gray iron industry uses hundreds of tons annually,
a considerable amount being for hardening the surface of car wheels. It is also used in malleable iron to improve
ductility and in stainless steel for machinability. A fraction of 1 per cent alloyed with lead improves the
corrosion resistance, strength, and hardening properties of the lead. Tellurium is used to increase the machinability
of copper and bronze, and to improve other metals and alloys. It is also used in several chemical processes,
including use as a catalyst.
1.3 Physical and chemical processes
Crystalline tellurium has a silvery white appearance, and, when pure, exhibits a metallic luster. It is brittle and
easily pulverized. Amorphous tellurium, is formed by precipitating tellurium from a solution of telluric or tellurous
acid. Whether this form is truly amorphous or trade of minute crystals is open to question. In air, tellurium burns
with a greenish-blue flame forming the dioxide. See Table 1.
TABLE I
|
|
Form I
|
Form II
|
molecular formula |
Te |
Te |
molecular weight (g/mole) |
127.60 |
127.60 |
color/crystalline form |
brown black |
rhombic silver |
|
amorphous |
white met |
index of refraction |
1.0025 |
1.0025 |
specific gravity |
6.00 |
6.25 |
melting point (°C) |
449.5 |
452 |
boiling point (°C) |
1390 |
339 |
Solubility (g/100 ml)
|
|
|
cold water |
insoluble |
insoluble |
hot water |
insoluble |
insoluble |
H2SO4 |
insoluble |
insoluble |
HNO3 |
soluble |
soluble |
aqua regia |
soluble |
soluble |
KCN |
soluble |
soluble |
KON |
soluble |
soluble |
HC1 |
insoluble |
insoluble |
CS2 |
insoluble |
insoluble |
2. Range and Detection Limit:
A lower analytical limit, 0.4 µg/ml, was selected for routine analysis.
3. Interferences:
None known
4. Sampling Procedure
4.1 The sample is collected on a 0.8 µm AA cellulose membrane filter using a flow rate between 1.5 and 2.0 liters
per minute. Suggested minimum air volume is 100 liters. A sample blank should also be submitted. (If considerable
loose dust is present in the cassette, a clear. filter should be placed over the dust before sealing).
4.2 The sample cassettes are plugged, sealed with OSHA tape, labeled, and sent to the laboratory for analysis.
4.3 No storage problems are normally anticipated. Vibration or jolting of samples should be kept to a minimum to
avoid dislodging of dust from the filter.
5. Analytical Procedure:
5.1 Apparatus
Atomic absorption spectrophotometer equipped with graphite furnace, argon purge system, and deuterium arc background
corrector.
Chart recorder.
Glassware.
2 or 3 piece filter cassettes
AA filters (0.8 µm, cellulose membrane filters 37-mm dia)
Personal sampling pump (capable of sampling between 1.0 and 2.0 L/pm).
5.2 Reagents
HCl, reagent grade
HNO3, reagent grade
A certified aqueous standard such as "SPEX' 1,000 ppm standard
follows:
1,000 ppm Ni solution
Diluting solution:
Twenty AA filters are ashed with 100 mL concentrated HN03 and 100
mL of 1,000 ppm Ni solution to a
volume of 20 - 40 mL, diluted to 500 mL with deionized water and 2 mL HCl.
5.3 Standards Preparation
Standards are prepared to match the matrix of the samples (filter content acid and nickel concentration) as closely
as possible according to the dilution scheme of Table III.
The 0.2. 1, 2, 5. 10 and 20 ppm "stock solutions" are made by serial dilution of the 1,000 ppm stock
(with deionized water) as
5.4 Sample Preparation
Note: All Glassware must be rinsed with 1:1 HNO3 and deionized water prior to use.
Conical beakers used
for the digestion are refluxed with 1:1 nitric acid and rinsed with deionized water before use.
Place filter in 125 mL conical beaker, add 5 ml of 1000 ppm Ni solution and 5 ml concentrated NHO3 and ash to
approximately 1-2 ml volume. After sample has cooled, add 2 drops HCl and swirl contents (no additional heating is
done).
Quantitatively transfer sample to 25 mL volume flask, dilute to volume with deionized water, and mix. Additional
dilutions for samples over 2 ppm As are made with the diluting solution.
TABLE II: STOCK SOLUTIONS
|
STOCK SOL'N
|
SOL'N USED
|
M1 USED
|
M1 FINAL VOL
|
20 ppm |
|
1000 ppm stock |
|
2 |
|
100 |
10 ppm |
|
100 ppm stock |
|
10 |
|
100 |
5 ppm |
|
100 ppm stock |
|
5 |
|
100 |
2 ppm |
|
100 ppm stock |
|
2 |
|
100 |
1 ppm |
|
10 ppm stock |
|
10 |
|
100 |
0.2 ppm |
|
10 ppm stock |
|
2 |
|
100 |
The diluted stock solutions should be prepared just before using them to prepare the working
standards as outlined in Table III.
When preparing the working standards from the stock solutions, all dilutions are made with the diluting solution.
TABLE III: WORKING STANDARDS |
|
|
|
|
Standard
|
Stock
Sol'n used
|
mL stock
|
H1 Final Vol.
|
0.1 ppm |
|
1.0 ppm |
|
5 |
|
50 |
|
0.2 ppm |
|
2.0 ppm |
|
5 |
|
50 |
|
0.5 ppm |
|
5.0 ppm |
|
5 |
|
50 |
|
1.0 ppm |
|
10.0 ppm |
|
10 |
|
100 |
|
|
|
|
|
Wavelength: 214.3 nm |
*Tellurium Conditions
|
Slit 3 |
|
Dry= 90T, 50R, 40H, 150F |
|
|
Char= 500T, 50R, 30H, 100F |
|
|
Atomize= 2000T, Fr. 8H, 15F |
|
|
Chart= Range 10 |
|
|
EDL Power= 9 watts |
|
|
(Stds prepared same as As) |
|
|
*These are guidelines parameters and may differ from your own. |
5.5 Sample Analysis
The analysis for tellurium is performed using a graphite furnace.
Instrumental parameters are as follows:
Atomic absorption unit:
|
Chart recorder:
|
EDL wavelength: 214.3 nm |
10 mV range |
UV mode |
20 mm/min speed |
slit setting 3 |
SERVO function |
Absorbance function |
|
Repeat mode |
|
D2 Background ON |
|
|
|
|
Temperature programs
|
|
Dry: |
90° temp |
|
|
50 sec ramp time |
|
|
40 sec ramp time |
150 ml/min INT flow |
Char: |
500° temp |
|
|
50 sec hold time |
|
|
30 sec hold time |
100ml/min INT flow |
Atomize: |
2000° temp |
|
|
0 sec ramp time |
|
|
8 sec ramp time |
15 mL/min INT flow |
|
|
|
Injection volume: 10 µL
The 1.0 ppm standard should give a near full scale deflection using these conditions. The entire series of standards
should be run at the beginning and the end of the analysis. A standard should be run after every fourth or fifth
sample in the sample rings.
5.6 Calculations
A linear regression of standard ppm vs standard peak height is performed using the OSHA Automatic AA program. The
sample results are calculated based on sample peak heights; a function of sample absorption.
mg/m3 = |
(ppm Te*) (sample volume, mL) (Dilution factor)
air volume, liters
|
*blank corrected
|