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© SPEX CertiPrep, Inc. 2010
Vanaja Sivakumar, Ph.D.Vice President, Inorganic Manufacturing
Clean Laboratory Techniques
Thursday November 18th, 2010
© SPEX CertiPrep, Inc. 2010
Housekeeping
Everyone in attendance will receive a copy of the slide deck
The webinar is being recorded and will be available for everyone to view on demand
– The recording will be posted about one week after the event
Questions will be answered at the end of the presentation
– Type any questions you may have in the question box and we will answer them during the Q & A portion
Stay tuned after the Q&A session – we’re giving away two free gifts!
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Introduction
Modern analytical instrumentation has detection limits down to the PPB and PPT levels– ICP– ICP-MS– GFAA
Lower detection limits introduces increased importance of eliminating trace contaminations
For accurate trace metals analysis at these low levels, eliminate trace impurities present in:– Reference Materials– Samples– Reagents – Environment
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Trace Metal Analysis at PPB and PPT Concentrations
Just how much is a part per billion or trillion?
Unit 1 part per Billion 1 part per Trillion
Time 1 second / 32 years 1 second / 320 centuries
Money 1 cent / $10 million 1 cent / $10 billion
Volume 1 drop vermouth / 500 barrels gin
1 drop vermouth /
500,000 barrels gin
Length 1 inch / 16,000 miles1 inch / 16 million miles
(6” step on trip to the sun)
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Sources of Contamination
Starting materials used in the preparation of reference materials
Sample digestion techniques
Water
Acids
Glassware/ laboratoryware
Storage containers
Laboratory environment
© SPEX CertiPrep, Inc. 2010
Starting Materials
Starting materials have to be tested for trace impurities in addition to assaying for metal content
Impurities present can give rise to overlap of spectra, resulting in incorrect calibration curve and therefore inaccurate results
Chloride, fluoride, oxalate, and sulfate contaminants have to be identified because presence of these ions can precipitate elements such as Ag, Pb, Ba, and the rare-earth elements
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Water
Specifications of Four Types of ASTM Water
The major component of an aqueous standard
The overall quality and accuracy of analysis depends on the quality of water that is used
RequirementASTM Type
I II III IVSpecific Resist.
(megohm/cm) (max)18 1 4 0.2
pH N/A N/A N/A 5 - 8Sodium (max) 1 µg/L 5 µg/L 10 µg/L 50 µg/L
Total Silica (max) 3 µg/L 3 µg/L 500 µg/L highTotal Organic Carbon
(max) 50 µg/L 50 µg/L 200 µg/L N/A
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SPEX CertiPrep ASTM Type I Water System
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Acids
Any part of analytical process must use high purity acids– Dissolution of materials and samples– Digestions– Dilutions
Contaminants present in acids can contribute to erroneous results
Example: An aliquot of 5 mL of acid containing 100 ppb of Ni as contaminant, used for diluting a sample to 100 mL can introduce 5 ppb of Ni into the sample
High purity acid is very costly
© SPEX CertiPrep, Inc. 2010
Acid Purification Still
PTFE Acid Still can produce sub-boiling high purity acids that can be used to prepare ultra pure acids right in the laboratory at a fraction of the cost of purchasing them
The distillation method of surface evaporation without boiling is employed through the use of infrared heaters. Majority of the metals can be reduced below ppb levels in a single distillation
© SPEX CertiPrep, Inc. 2010
Laboratory Glassware
The most common sources of contamination in a laboratory are the pipettes and other laboratory-ware
Pipettes not only have to be calibrated frequently for accuracy but they have to be thoroughly cleaned to remove all the contaminants that are present even at the PPT levels
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How Clean Are Your Pipettes?
2% nitric acid run through 5 mL pipettes that were cleaned manually and scanned on ICP-MS
ElementConc. (PPB) Element
Conc. (PPB)
Ag 2.33 Mn 1.72Al 6.43 Na 19.1Be 2.62 Ni 0.96Bi 1.07 Pb 5.4Ca 18.8 Sn 0.55Co 2.02 Th 0.24Cr 0.91 Ti 0.56Fe 1.62 Tl 1.53Mg 2.56 Zn 9
© SPEX CertiPrep, Inc. 2010
Pipette Washer / Dryer
Rows of conical shaped plastic pipette holders are connected to a water line. The water fills each pipette, shoots out of the pipette tip, and rains shower of water over the outside of pipette
Pipette washer/dryer features:
– Holds 23 pipettes
– Accommodates 0.5mL to 200mL pipettes
– Small footprint to fit most spaces
– Dries pipettes using vacuum line
– Wash solutions & surfactants may be used
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Pipettes Cleaned With Washer
2% nitric acid run through 5mL pipettes and scanned on ICP-MS
ElementConc. PPB Element
Conc. PPB
Ag <0.01 Mn <0.01
Al <0.01 Na <0.01
Be <0.01 Ni <0.01
Bi <0.01 Pb <0.01
Ca <0.20 Sn <0.01
Co <0.01 Th <0.01
Cr <0.04 Ti <0.02
Fe <0.20 Tl <0.02
Mg <0.01 Zn <0.01
© SPEX CertiPrep, Inc. 2010
Manual Cleaning Vs. Pipette Washer
Comparison Chart
Element Manual (ppb) Washer (ppb)Al 6.43 <0.01
Ca 18.8 <0.20
Fe 1.62 <0.20
Mg 2.56 <0.01
Na 19.1 <0.01
Zn 9 <0.01
© SPEX CertiPrep, Inc. 2010
Storage Containers
Bottles– Bottles in which purchased
standards were shipped – Bottles laboratory stores its
own dilutions– Various sizes, shapes, and
materials of construction
Contaminants present in the materials of construction can leach into the solution
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Ideal Storage Containers
Best:
– Fluoropolymers
– Quartz – synthetic
– Polyethylene
– Quartz – natural
Worst:
– Borosilicate glass
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Summary of Average Element Content in Storage Containers
MaterialTotal No. of Elements Total PPM Major Impurities
Polystyrene-PS 8 4 Na, Ti, AlTFE* 24 19 Ca, Pb, Fe, CuLow Density PE-LDPE 18 23 Ca, Cl, K, Ti, ZnPolycarbonate-PC 10 85 Cl, Br, AlPolymethyl Pentene-PMP 14 178 Ca, Mg, ZnFEP† 25 241 K, Ca, MgBorosilicate Glass 14 497 Si, B, NaPolypropylene-PP 21 519 Cl, Mg, CaHigh Density PE-HDPE 22 654 Ca, Zn, Si
* TFE-Tetrafluoroethylene † FEP-Fluorinated ethylene propylene
© SPEX CertiPrep, Inc. 2010
Contamination from Bottling Pump Tubing
Material: DI – H2O 5% Nitric
ElementSILICON (leached)
NEOPRENE (leached)
PHARMED (leached)
SILICON (leached)
NEOPRENE (leached)
PHARMED (leached)
Al 1.0 1.0 1.0 10.0 5.0 5.0
Ba 0.02 0.04 0.03 0.15 0.09 0.10
Ca 0.0 0.0 0.0 0.0 0.0 0.0
Cu 0.05 0.01 0.03 0.35 0.20 0.20
Fe 0.0 0.0 0.0 27 5 5
K 2 2 2 2 2 5
Mg 7.0 0.5 0.4 8 2 3
Na 0.0 0.8 0.4 4 4 5
Ni 0.2 0.2 0.2 4 0.1 0.7
Pb 0.1 0.1 0.1 3 2 1
Si 0 0 0 500 0 0
Sn 0.01 0.01 0.18 1 1.9 3.3
Sr 0.04 0.05 0.04 1.1 0.8 0.2
Ti 0.1 0.1 0.1 0.2 0.2 0.2
Zn 1.0 55 25 4 50 27
Zr 0.07 0.07 0.07 0.11 0.07 0.08
(Units in ppb)
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Sample Preparation Method
Traditional open vessel or microwave
Sample to sample cross contamination
Environment in which the samples are prepared
Materials that come in contact with the sample
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Is the Laboratory Clean?
Redistilled nitric acid concentrated in regular and clean labs.
Element Regular Lab Clean Lab Element Regular Lab Clean LabAg 0.006 0.01 Mn 1.1 0.1Al 60 15 Mo 0.8 0.03As 0.17 <0.02 Na TOO HIGH 25Ba 1.95 0.25 Nd 0.14 0.025Ca 150 100 Pb 0.5 0.4Cd 0.3 0.003 Rb 0.03 <0.001Ce 1.5 0.06 Sb 0.04 0.013Co 0.6 0.008 Sm 0.015 0.003Cr 2.5 0.4 Sr 0.6 0.3Cu 1.7 0.23 Th 0.017 0.001Fe 50 9 Ti 1 0.77Ge 0.02 <0.01 V 0.35 <0.3Mg 10 4 Zn 5.5 0.7
(Units in ppb)
© SPEX CertiPrep, Inc. 2010
Clean Laboratory
What is a clean room?
– Filtered Air
– Transports particulate contaminants away from sensitive samples
– Maintains a clean environment with low particle concentrations
Applicable Standards:
– ISO 14644
– US Federal Standard 209E
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Clean Laboratory
Environment of class 100
– No more than 100 particles, >0.5µm in diameter, per cubic foot
Walls, ceilings, and floors are sealed and dust free
HEPA filters mounted in the ceiling
No exposed metal parts
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Common Contaminating Sources
Ceiling tiles, paints, cements, and dry walls
Dust and rusts on shelves, equipment, and furniture
Temperature control systems
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Prep Lab for Trace Analysis
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Packaging Comparison
Comparison of a solution made in clean room environment and packaged in regular lab and clean lab
ElemRegular
Lab Clean Lab ElemRegular
Lab Clean LabAl 5 ppb 0.1 ppb Na 6.0 0.1
As 0.05 <0.01 Ni 0.1 <0.01
Co 0.2 <0.01 Sb 1.0 <0.01
Fe 7.0 <0.7 Sn 2.0 <0.01
Mn 0.08 <0.01 Zn 8.0 <1.0
Mo 0.02 <0.01 Zr 0.1 <0.01
© SPEX CertiPrep, Inc. 2010
Impurities Increase With Time
There was a considerable increase in concentration of impurity for elements such as Al, Ca, Fe, Mg, Na, Si, and Zn
Several probable reasons:
– Dust from the lab environment can contribute to Ca, Na, K, Mg, and Si
– Ti and Zn from LDPE bottles
– Al and Fe from the materials of various fixtures in the laboratory
© SPEX CertiPrep, Inc. 2010
Controlling Contamination
Minimize exposure:
– The apparatus that will contact samples, blanks or standards should be opened in clean room, clean bench, or glove box
– When not in use, the apparatus should be covered well in plastic bag or box
Clean work surfaces:
– Before processing samples, all work surfaces in the hood, clean bench, or glove box should be cleaned with a wipe soaked with reagent water
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Controlling Contamination – cont.
Wear gloves:
– Sampling personnel must wear clean gloves when handling equipment, samples, blanks and standards
– Sweat contains K, Pb, Ca, Mg, SO4, PO4, and NH4 ions, in addition to Na and Cl
Use metal free containers:
– Volumetric flasks, beakers made out of FEP, polycarbonate, and polypropylene should be used
© SPEX CertiPrep, Inc. 2010
Controlling Contamination – cont.
If clean room is not available, all sample preparation should be performed in a class 100 clean bench or glove box with a flow of air or preferably nitrogen
Use adhesive mats at entry points to control dust and dirt from shoes
Change shoes and / or wear shoe coverings to reduce bringing in dirt from the outside
© SPEX CertiPrep, Inc. 2010
Controlling Contamination – cont.
Humidity:
– Keep lab humidity around 45% to minimize electrostatic charge
Surface charges can be eliminated:
– By use of commercial static eliminators
– By wetting a lint free cloth with high purity ethanol or high purity water and letting it evaporate
© SPEX CertiPrep, Inc. 2010
Controlling Contamination – cont.
Separate labware into “low level” & “high level”:
– “Low level” labware is used only for solutions that have metals at below 1 ppm concentration
– “High level” labware for solutions with above 1 ppm concentration of metals
Reason:
– Labware tends to exhibit “memory effects” from previous solutions
© SPEX CertiPrep, Inc. 2010
Controlling Contamination – cont.
Segregate labware for specific metals
Metals such as Pb and Cr are highly absorbed by glass but not by plastics
For B and Si analysis, avoid borosilicate glass. Use plastic, TFE or quartz labware
Samples containing low levels of Hg (PPB levels) should be stored in glass, polypropylene, or fluoropolymer because Hg vapors diffuse through polyethylene bottles
Avoid lint-producing paper products
© SPEX CertiPrep, Inc. 2010
Controlling Contamination – cont.
Use membrane filters instead of ashless filter paper
– Ashless filter paper contains 20 trace elements at >1 ppm level
Use “NOCHROMIX” instead of Chromic Acid to clean labware
No jewelry, cosmetics, or lotions
– Cosmetics and lotions can introduce the contaminants Al, Be, Ca, Cu, Cr, K, Fe, Mn, Ni, Ti, and Zn into the samples
– Some hair dyes contain lead acetate
– Calamine lotion used for skin irritations contains ZnO
– Se is an active ingredient in some anti-dandruff shampoos
Wash lab coats regularly
© SPEX CertiPrep, Inc. 2010
Controlling Contamination – cont.
No powder gloves
– Powder in the gloves contains high conc. of Zn
Replace gloves and shoe covers regularly
Use ultra clean sample introduction system
How do you determine if you have a clean lab?
– By running blanks! “THINK BLANK”
– Blanks have to be clean to avoid false positive and false negative results
– Carry blanks through all steps of an analytical procedure
“Anything that touches the sample must be absolutely clean!”
© SPEX CertiPrep, Inc. 2010
Helpful Hints
Test personnel, equipment, and methods with QC samples
Observe clean lab procedures and techniques
Use reference materials that have not expired
Make up and use only freshly prepared calibration standards
Rerun samples using a different dilution factor
Spike appropriate QC samples with expected levels of analytes or use standard additions
© SPEX CertiPrep, Inc. 2010
Helpful Hints – cont.
Prepare the dilution in plastic or FEP (as much as possible)
Rinse volumetric flasks with 1% nitric acid and keep in nitric acid until used
Do dissolutions in metal free clean hood
Use high pure reagents and acids:
– Ammonium hydroxide and nitric acid are relatively clean
– HCl has high impurities
Rinse pump tubing with high pure acids (about 2%) used in the matrix
© SPEX CertiPrep, Inc. 2010
Helpful Hints – cont.
New Product: OdorEroder
Effectively neutralizes offensive odors and fumes in the lab
Absorbs & chemically transforms chemical odors into harmless compounds that remain trapped within the product
Highly effective at neutralizing volatile compounds
Non-toxic and environmentally safe
Non contaminating
© SPEX CertiPrep, Inc. 2010
References
Guidance in Establishing Trace Metal Clean Rooms in Existing Facilities: USEPA 821-B-95-001
Accuracy in Trace Analysis: NBS Special Edition 422
Guide to Environment Analytical Methods: Roy-Keith Smith
Clean Manufacturing: A2C2, April 2003
Water Environment Laboratory Solutions: April/May 2003
Sampling of sea and fresh water for the analysis of trace Metals: E. Helmers 1997
“New Solutions for Trace Metals Analysis,” Agilent Technologies, 2005
Nalgene Labware – Technical Data
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Thank You!
Patric Blackett Born 18 November, 1897 Nobel Prize winner 1948
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