clean laboratory techniques - spex certiprep€¦ · everyone in attendance will receive a copy of...

Vanaja Sivakumar, Ph.D.Vice President, Inorganic Manufacturing

Clean Laboratory Techniques

Thursday November 18th, 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!

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

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)

Sources of Contamination

Starting materials used in the preparation of reference materials

Sample digestion techniques

Glassware/ laboratoryware

Storage containers

Laboratory environment

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

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

SPEX CertiPrep ASTM Type I Water System

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

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

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

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

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

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

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

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

Ideal Storage Containers

– Fluoropolymers

– Quartz – synthetic

– Polyethylene

– Quartz – natural

Worst:

– Borosilicate glass

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

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)

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

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)

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

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

Common Contaminating Sources

Ceiling tiles, paints, cements, and dry walls

Dust and rusts on shelves, equipment, and furniture

Temperature control systems

Prep Lab for Trace Analysis

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

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

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

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

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

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

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

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

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

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!”

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

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

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

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

Thank You!

Patric Blackett Born 18 November, 1897 Nobel Prize winner 1948

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