How to Avoid Contamination When Using ICP-MS Webcast #3 of 4 ¾ How do we reduce contamination? ¾ What level of contamination is acceptable for ICPMS? ¾ What are the sources of contamination? ¾ What is contamination? Presentation Agenda • An unwanted, detectable enhancement of the background signal caused by an agent which may interfere with the measurement of an analyte of interest ¾ Matthew Knopp (Analytical Definition) • To make impure by contact or mixture ¾ Websters Dictionary (Generic Definition) Definition of Contamination Different sources of water Different sources of acids Different samples and sampling vessels Different analysts • Checks cleanliness of laboratory environment and the instrument ¾ Run blanks exposed to laboratory environment over time • • • • ¾ Reporting negative answers for blanks ¾ Run blanks and compare results Do You Have a Contamination Problem? ¾ Sampling Equipment ¾ Sampling Environment ¾ Sample Bottles/Sample Storage ¾ Sample Transport ¾ Sampling Personnel ¾ Preservation Reagents Sources of Contamination (Sampling the Raw Sample) (Post-sampling) ¾ Analytical Containers (flasks, pipettes,..) ¾ Storage Containers ¾ Lab Reagents (including lab pure water) ¾ Lab Environment ¾ Analyst ¾ Instrumentation (carry-over) Sources of Contamination DO NOT USE for storage! DO NOT USE for dilutions! DO NOT USE for Preparing Standards USE A BALANCE TO MAKE STANDARDS AND PERFORM DILUTIONS ¾ NEVER USE FOR DISSOLUTION OR DIGESTION ¾ ¾ ¾ ¾ NEVER USE THEM!! Sources of Contamination - Glass Vessels and Volumetric Flasks ¾ Pour Samples, Standards and Reagents Into Secondary Containers Before Pipetting ¾ Take Care Not to Contaminate the Tips During Use ¾ Use Separate Pipette Tips for Each Solution ¾ Use Pipettors with disposable tips whenever possible NEVER USE GLASS PIPETTES!! Sources of Contamination - Glass Pipettes Conc. PPB 2.33 6.43 2.62 1.07 18.8 2.02 0.91 1.62 2.56 Element AG AL BE BI CA CO CR FE MG 0.016 0.75 0.28 0.004 2.9 0.0006 0.007 0.13 0.0088 Detection limit ZN TL TI TH SN PB NI NA MN Element 9 1.53 0.56 0.24 0.55 5.4 0.96 19.1 1.72 Conc. PPB 0.4 0.0075 0.003 0.0003 0.0033 0.13 0.18 0.6 0.012 Detection limit 2% Nitric acid run through 5ml pipets and scanned on ICPMS How clean are your pipettes? • Routine analyses (i.e. Environmental) • Clean - low level analyses (i.e. Semiconductor) ¾ Detection limits are limited by contamination • The answer to this question determines the level of acceptable contamination • What level of contamination reduction is necessary to achieve your analytical goals ¾ What do you want to get from your ICP-MS? Acceptable Levels of Contamination Water is the major component of aqueous standards and samples. Its contribution to the overall quality of the sample and standard is considerable. Contaminants in water • Dissolved, ionic solids eg. sodium chloride and calcium carbonate present as minerals in water • Dissolved non-ionic solids or pyrogens from organic matter formed as a result of exposure to biologicals • Particulate matter : Dirt, rust, sand, dust etc. • Microbials : Bacteria, viruses, etc Laboratory Pure Water POLISHING SYSTEM RO SYSTEM Laboratory Pure Water •Ultraviolet Exposure (ASTM Type I) •Ultrafiltration •Organic adsorption •Deionization •Carbon filtration •Meets ASTM Type I or Type II water standards •Reverse osmosis •Carbon filtration •Meets ASTM Type III water standards <0.1 15-18 NA 60 ND 0/ml Specific Resist. (megohm, min) pH Min. color retention time of KMnO4 mins Soluble Silica Bacteria Count I Total matter (mg/L max.) ASTM Type ASTM Water Specifications 0/ml ND 60 NA 1 0.1 II 10/ml 10ug/l 10 6.2-7.5 >1.0 1 III 100/ml high 10 5 -8 0.2 2 IV ¾ This Purifier Trace Metals Work Station is designed specifically for the demands of trace metals analysis of environmental samples included EPA Method 1631 Mercury in Water ¾ Total exhaust vertical clean bench provides a Class 100 particulatefree and metal-free work environment ¾ All components in the HEPA-filtered air stream are non-metallic including the work area, which is PVC and tempered safety glass ¾ Applications involving corrosive chemicals such as acid digestions are well-suited to this enclosure ¾ Provides personnel and product protection from background contamination Routine Trace Metals Analysis - Work Station Common Materials ¾ Glass ¾ Quartz ¾ Ryton 17 z z Spray Chambers Nebulizers Sample Introduction Routine Analysis – Nebulizers and Spray Chambers ¾ Burgener ¾ Meinhard ¾ Cross - flow Routine Analysis – Nebulizers Oils/Organics All acids (HNO3, HCL…) dilute and conc. Up to 10 % TDS ¾ Precision on the order of 1% ¾ Easy to clean, maintain, and very durable • • • ¾ Standard PE nebulizer ¾ Can be used for all sample types 19 Cross Flow Nebulizer Routine Analysis – Cross Flow Nebulizer HI ¾ Can be run without pump (self-aspiration) ¾ Susceptible to clogging • 0.5% Precision • D.L. 40 % lower than crossflow ¾ Cleaner solutions (Usually <1% TDS) ¾ Best Precision and Detection Limits Routine Analysis - Meinhard Nebulizer ¾ Inert and handles over 10 % salts. ¾ Not prone to clogging ¾ Rinse-out is very good ¾ Precision <1 % ¾ Detection limits within 20% of the meinhard concentric ¾ Durable ¾ Can be used with cyclonic or a Scott-Type ( with end cap) Routine Analysis - Burgener Nebulizer ¾ Baffled Cyclonic Spray Chamber ¾ Cyclonic Spray Chamber ¾ Scott - Type Double Pass Chamber Routine Analysis - Spray Chambers ¾ Can run most any solvent ¾ Cleaned with 10-20% warm not boiling HNO3 ¾ 2 - 4% efficient ¾ Durable and inert ¾ Small droplets travel through center tube, large droplet drop out of center tube and into the drain ¾ Separates the small droplets (<10 microns) from the larger droplets 18 Scott Spray Chamber Routine Analysis – Ryton Scott Style Spray Chamber HI 40% higher efficiency than a Scott-Type Cyclonic Spray Chamber ¾ Excellent Rinse-out ¾ Detection limits improve by a factor of 2 over a Scott-Type ¾ Clean with hot mineral acids ¾ Precision worse than a Scott-Type (1%) • ¾ Very efficient 17 Sample Introduction Routine Analysis - Cyclonic Spray Chamber ¾ Allows for the running of volatile solvents ¾ Detection limit comparable with Scott; maybe 10 % lower ¾ Baffle reduces effiency, but increases precision and reduces oxides ¾ Cyclonic spray chamber has fast rinse out will little memory affects Routine Analysis - Baffled Cyclonic Spray Chamber ¾ High Purity Standard http://www.hps.net/toc.html ¾ SPEX http://www.spexcsp.com/crmmain/crm/toc_cl.htm ¾ Cole Parmer http://www.coleparmer.com/ ¾ Fisher Scientific International Inc. http://www.fisherscientific.com/ High purity acids and standard solutions must be used for ICP-MS. AAS grade acids and standard solutions contain impurities. Routine Analysis - Acids and Standard Solutions ¾ Very difficult to determine 20 or more elements at ICP-MS detection limits without contamination ¾ Do as much preparation in plastic or Teflon as possible • Rinse with 1% nitric acid and keep nitric acid in them until used • Use once and discard or rinse with nitric acid (1%) or high purity water and store until used • Use Eppendorf - type pipettes or automatic diluter ¾ Do dissolution in metal-free clean hood if contamination is a problem ¾ Use high purity acids when possible ¾ Best results when dilutions are done on a balance (weight/weight) Routine Analysis – Some Suggestions to Reduce/Avoid Contamination • • • • Glassware: B, Si, Na, and half the periodic table Polyethylene: Sn, Ba Teflon: Fe Polypropylene: best ¾ Containers • Cleanest are NH4OH and HNO3 • Dirtiest are HCl and NaOH ¾ Acids, other reagents ** ASTM Type I for Clean – Ultra low level analyses ¾ Water – ASTM Type II (18 megohm) or better** Routine Analysis – Some Suggestions to Reduce/Avoid Contamination Sample introduction/pump tubing Injector Sampler and skimmer cones ¾ Atmosphere: anything ¾ Laboratory Environment ¾ Argon: Kr, CO, H2O, N2, O2, Xe ¾ Pneumatic tubing: Cl, Sn • • • ¾ Previous samples Routine Analysis – Some Suggestions to Reduce/Avoid Contamination ¾ 99.99% efficient HEPA filter ¾ Class 100 air (ISO Class 5 conditions) ¾ Corrosion-resistant PVC interior, air foil and work surface ¾ Exterior of epoxy-coated steel and aluminum ¾ Designed for ducting to the outside ¾ Tempered safety glass sides and angled pivoting sash ¾ Filter condition indicator ¾ Fluorescent lighting Particle-free Class 100 air (fewer than 100 particles 0.5 µm or larger per cubic foot of air) Clean - Class 100 Work Station • Environment of class 100 (less than 100 particles of 0.5 microns per m3) • Walls, ceilings and floors sealed and dust free • HEPA filters mounted in the ceiling • No exposed metal parts • All work performed under clean hood • Exposure of Samples and Standards to air is limited Clean Laboratory 0.1 35 350 NA NA NA NA 0.2 7.5 75 750 NA NA NA 0.3 3 30 300 NA NA NA 5 NA NA NA 7 70 700 US Federal standard 209E 0.5 1 10 100 1,000 10,000 100,000 5 µm diameter particle in 1 ml solution gives 500 ppt impurity. ULPA (Ultra Low Penetration Air) filter : 99.999% removal of 0.12 µm particles. Polytetrafluoroethylene (PTFE) HEPA (High Efficiency Particle Air) filter : 99.99% removal of 0.3 µm particles. Borosilicate glass Class 1 10 100 1,000 10,000 100,000 Measured Particle Size (micrometers) Definition of Clean Room Resistant to clogging—reliably selfaspirated or pumped. Low, spike-free background for important elements such as Fe and Ca. • • Analyze all sample types with a single introduction system. Direct analysis of volatile and nonvolatile organic solvents. Directly replace any 6 mm (Meinhard) type nebulizer. • • • ¾ Produces a fine aerosol for high transport efficiency and high sensitivity. Chemically resistant—ideal for strong acids, alkalis, organics. • Low flows: 50-400 microliters/minute Ideal for ICPMS - clean Clean Nebulizers – PFA Low Flow Adapts and seals to any 6 mm O.D. nebulizer. Adapters available to interface most ICP and ICPMS systems. • • ¾ High transmission and selectivity - Excellent short and long-term stability - High sensitivity - Fast rinse-out. O-ring-free seal - reduces contamination - easy to clean - low maintenance. • ¾ PFA Teflon construction - low contamination - chemically inert - ideal for dilute-and-shoot analyses Clean Spray Chamber - PFA Double-Pass Scott Style pipette tips have coating to allow better delivery of solution. Can also contaminate solution! ¾Colorless polypropylene tips can be used for sampling of standard solution, but not good for pure chemicals. ¾PFA tip is available from ESI. ¾Pipettors with a stainless steel plunger might be corroded by acid. DON’T USE THEM! Tips ¾Most ¾Pipette A wide mouth PFA bottle is recommended. comes from the cap and mouth. ¾The mouth of volumetric flask is too small. ¾Solution touches the cap while mixing, this is unavoidable. Volumetric Flask ¾Contamination ¾PFA PFA Volumetric Flasks and Pipette Tips 24 25 10 18 21 14 22 14 Teflon-TFE* Teflon-FEP* Polycarbonate-PC Low Density PE-LDPE Polypropylene-PP Polymethyl Pentene-PMP High Density PE-HDPE Borosilicate Glass *TFE-Tetrafluoroethylene *FEP=FluorinatedEthylenePropylene 8 Total No. of Elements Polystyrene-PS Material Impurities in Container Materials 497 654 178 519 23 85 241 19 4 Total PPM Si,B,Na Ca,Zn,Si Ca,Mg,Zn Cl,Mg,Ca Ca,Cl,K Cl,Br,Al K,Ca,Mg Ca,Pb,Fe,Cu Na,Ti, Al Major Impurities PFA bottle was cleaned by the above procedure. pIt was used for preconcentration of HF. pIt still took 14 runs to eliminate the contamination from the bottle. pThis 1. Soak in (1+1) HCl for one week. 2. Soak in (1+1) HNO3 for one week. 3. Heat with the chemical to be used for three hours (under the boiling point of chemical) 4. Heat with UPW for three hours (under the boiling point). Cleaning Procedure http://www.spexcsp.com/crmmain/crm/toc_cl.htm High Purity Standard http://www.hps.net/toc.html SPEX AAS grade single standard solution contain impurities. High purity standard solutions must be used for ICP-MS. Kanto Chemical http://www.kantocorp.com/products-finechem_ultrapur.html Tama Chemical http://www.tama-chem.co.jp/english/reag-line-up.html Two companies guaranty impurity level better than 10 ppt: Clean Acids and Standard Solutions • • • • No jewelry, cosmetics or lotions Wear gloves, but No Powder Cover hair and mouth Protect samples and standards from dust, airborne particles and fibers Clean Techniques – Analyst Procedures RUN A SERIES OF BLANKS!!! How do you determine how clean your lab is? Conclusion