APPLICATION OF ICP-MS TECHNOLOGY FOR TRACE METALS ANALYSIS

Transcription

1 MR. TELLIARD: Our next speaker is Paula Hogg. Paula is currently a lab manager at Hampton Roads Sanitation District s Central Environmental Laboratory. We would like to also thank Hampton Roads for sending most of their lab people. APPLICATION OF ICP-MS TECHNOLOGY FOR TRACE METALS ANALYSIS MS. HOGG: Today, I will be talking about the use of ICP-MS technology for trace metals analysis. HRSD's Central Environmental Laboratory performs a variety of trace metals analysis of environmental samples, primarily in support of wastewater treatment plant operations. The current total number of metals results is approaching 70,000 annually. Sample matrices include treatment process, industrial pretreatment program samples, treatment plant effluent for NPDES monitoring applications, groundwater, surface water, and biosolids. HRSD purchased an ICP-MS over four years, and the laboratory uses this instrumentation for trace metals analysis along with a Graphite Furnace AA(GFAA), a flame AA, and an ICP. A starting point in evaluating ICP-MS is to compare this technique with more traditional methods. Today, I will discuss and compare ICP-MS to the Stabilized Temperature Graphite Furnace AA(STGFAA) method, including methodologies, applications, method performance, and cost effectiveness of these methods. There are several considerations in choosing an appropriate method for trace metal analysis. These include sample concentration levels, data quality objectives, the application of the analytical results for decision-making criteria and costs. There are various levels of analysis, clean techniques, sample concentration levels, methodologies, and applications for trace metals monitoring as shown on this slide. ICP-MS can be widely applied over concentration ranges, but it is most appropriate and suited for low to sub part per billion concentration ranges and this s the primary application of ICP-MS at HRSD. Moving from the bottom level or at high concentrations to the top level of the triangle or at low concentration ranges, the amount of effort required for contamination control and the use of clean techniques, becomes more important, and with that, costs increase as well. HRSD's approach is to use the most cost effective and practical method in meeting data quality objectives. The purpose of clean techniques is to produce data free from bias due to contamination to achieve an adequate level of reliability and accuracy as defined by data quality objectives. So, as sample concentrations and regulatory levels decrease, clean techniques become necessary. For application of ISP-MS, clean techniques become a given for monitoring samples at water quality-based permit levels. In evaluating the distribution of the metals analysis workload at HRSD, nearly half of the work is dedicated to analysis of effluent for NPDES monitoring applications in Virginia and for other water quality monitoring projects. Clean techniques are used for this level of monitoring, coupled with STGFAA and ICP-MS methods. June

2 For NPDES monitoring and other regulatory program requirements, STGFAA is used, because this method is approved under 40 CFR Part 136. The ICP-MS technique is used for nonregulatory water quality studies, process characterization studies, and is an integral part of our clean sampling and analytical program at HRSD. All of the sampling equipment used for clean level monitoring is prepared using clean techniques and equipment blanks are screened using the ICP-MS prior to taking equipment out into the field. All sampling equipment is certified as free from contamination. Currently, the STGFAA workload is at maximum capacity, due to an increase in clean level monitoring. Pending the method approval, this workload can be shifted to ICP-MS. These are typical analytical concentration range capabilities of STGFAA and ICP-MS. These may vary depending on operating and analytical conditions as well as instrument model and manufacturer. ICP-MS can be applied over a wide concentration range, as seen on the next slide. This is due to the wide linear dynamic range offered by the ICP-MS technology, up to ten orders of magnitude for some elements. The next two slides summarize EPA published methods. The EPA 200 series methods, published in 1983, are currently approved in 40 CFR Part 136, and these are used for NPDES monitoring programs. The elements listed are typically required for effluent monitoring. The Ys indicate which elements are included in each method. The Ns indicate elements not listed in the methods. The more recent EPA methods, and 1639 for Graphite Furnace AA are not approved in 40 CFR, Part 136. However, the inter-laboratory validation studies for 1600 series are currently underway. The ICP-MS methods, and 1638, are also not currently approved. For Method 1638, as with 1639, there are some elements not listed as part of the 1600 series, which may be required for effluent or NPDES monitoring. What has changed and what is different about the more recent EPA methods, and and 1600 series methods? First, all of the digestion protocols include sample concentration steps or an alternative for in-bottle digestion, which helps with contamination control. Also, digestions require the addition of HCl, and all elements can be determined using one digestion method, instead of using separate digestions analysis such as arsenic, selenium and silver. In methods and 1639, a hydrogen argon purge is used. The 1600 series methods include both sampling and analytical methods to specifically address the needs for measuring toxic metals at water quality criteria levels. These methods are designed to preclude contamination in nearly all situations. The 1600 series are also performance based methods or, The laboratory is permitted to omit any steps or modify any procedure, provided all performance requirements set forth in the method are met. QC analysis, however, cannot be omitted. In the 1600 series methods, the terms must, may, and shall are used to indicate the relative importance of steps and indicate which procedures are necessary for successful analysis. These methods also include clean sampling techniques which are incorporated into Method 1669, as mentioned earlier. There are particular clean techniques, which HRSD has found important in controlling contamination for the NPDES monitoring level. For both sampling and analysis, sample handling by personnel, and exposure to air is minimized, and these are the two key components of successful clean level monitoring. Equipment and glassware preparation and analysis are performed in HEPA filtered clean areas, not necessarily Class 100 clean rooms in Class 100 clean benches. Traffic is June 1999

3 minimized. Analytically, glassware is washed immediately prior to use. Non-colored labware, powder-free gloves, and high purity reagents are also used. Analysts are dedicated to clean protcols. The use of cosmetics, jewelry, and lotions which sometimes contain low levels of the trace metals are avoided. For dissolved metals determination, capsule filtration is used. In summary, adequate contamination control can be achieved using practical, preventive approaches. This is a picture of the automated enclosed sampling system for unattended collection of composite samples. Tubings, containers, fittings, and all components are metal-free. The sampling equipment is prepared using clean protocols, and is certified as clean using ICP/MS screening prior to each sampling event. The system can be wired to the plant flow measurement system for the unattended collection of composite samples and simultaneous collection of field blanks. Blank data including laboratory reagent blank, field blank, and equipment blank, are used to derive the level of effort needed to control contamination. Another consideration in selection and application of a method is detection and quantitation capabilities. Overall, detection levels for trace metals using ICP-MS technology are significantly lower than that of STGFAA, often by orders of magnitude. For quantification, the minimum level is defined as the lowest level at which the entire analytical system gives a recognizable and reliable signal, an acceptable calibration point, or approximately 3.18 times the method detection limit. Generally, the minimum levels of both STGFAA nd ICP-MS methods are able to measure at water quality criteria levels required by water quality based permitting programs. However, there are exceptions for Graphite Furnace AA. Note that the low ICP-MS quantification levels for arsenic and selenium, are the result of coupling ICP- MS technology with the hydride generation technique. Lead, silver, and thallium are the exceptions for water quality based monitoring for STGFAA, because the minimum levels tend to be slightly above water quality criteria. Based on the experience of HRSD over the last four years, overall method performance, is typically measured by both productivity and quality. Analytically, method performance can be measured by sensitivity, accuracy, and precision. Productivity factors, such as sample through-put or output, are important, because there is a direct effect on laboratory operating costs and data turnaround. With regard to method detection limits for the two methods, the next two slides compare the MDLs listed in Method 1638 and 1639 with HRSD s current MDLs for ICP-MS and STGFAA. These have been determined in reagent water. The MDL for selenium is very low, as a result of coupling ICP-MS with hydride generation technique. For ICP-MS, MDLs are either below or very close to the Method 1638 MDLs. These MDLs have been determined numerous times and these levels can consistently be achieved. For STGFAA, the majority of HRSD current MDLs are slightly higher than those listed in Method In stressing the importance of eliminating unacceptable levels of contamination, laboratory reagent blank data for the two methods can be compared. For most elements, ICP-MS LRBs are an order of magnitude lower than those of STGFAA. These are based on direct instrument readings and therefore may be a result of noise. However, there is a significant difference in the two measurement systems. June

4 For accuracy, a summary of recent laboratory-fortified blank data for both methods is shown. In a pure reagent water matrix, accuracy is excellent for both methods. However, for laboratoryfortified effluent samples, recoveries change. Typically, method acceptance limits can be met. However, for silver and selenium analysis by STGFAA, often the method of standard additions must be employed to overcome sample matrix interferences. As a result, productivity decreases and costs increase due to increased analytical time requirements. For trace metals analysis by ICP-MS, there are fewer matrix interferences for effluent samples and spike recoveries are improved, with the exception of copper. Low copper recoveries may be a result of sulfate levels in effluent. In comparing precision of the two methods, both methods are very good. ICP-MS has slightly improved precision over GFAA. One exception is with selenium, which is 8% for GFAA and 11% for ICP-MS. When productivity of the two methods is compared, there is a significant difference. This is due to the capability of simultaneous, multi-element analysis by the ICP-MS. Although the sample injection time is the same for both, up to 21 elements can be determined simultaneously with ICP- MS. In addition, elemental isotopes can be monitored. On a good day, using overnight operation, up to three elements per day can be determined using STGFAA, compared to less than one day for ICP- MS. Currently, there are STGFAA instruments available on the market that can determine up to six elements simultaneously. This has the potential to improve productivity but not to the level of ICP- MS technology. Higher productivity leads to improved data turnaround and cost effectiveness. Costs can be broken those down into three areas- initial investment costs, ongoing operating costs, and a resulting cost per test. Initial cost for instrumentation, training, and method development are outlined on this slide. These costs are current and may vary, depending on the manufacturer and model. For initial costs, ICP-MS instrumentation is typically twice as costly as that of STGFAA instrumentation. Usually, training and installation are provided with purchase of a new instrument, so these training and development costs are for laboratory hours or labor required to implement the methods. For operating costs, there are several components, including all expenses associated with the ongoing analysis. Operating costs include all labor costs calculated from time requirements, salaries and fringe benefits, material and supply costs, and operational overhead calculated from utility and other facility operating costs. The evaluation for annual operating costs is based on 10,000 results per year. This will vary, depending on the workload. Based on 10,000 results per year, the operating costs of the ICP-MS method is approximately one-third less than that of GFAA. The higher service contract, maintenance and material and supply costs are outweighed by the productivity of ICP-MS. When these two components are combined and evaluated over the long term, approximately $50,000 per year can be saved with a workload of 10,000 results per year, after the first year, using ICP-MS for trace metal analysis. Therefore, initial investment costs can be recovered in a three to five-year period, depending on workload. In summary, application of ICP-MS for trace metal analysis has many advantages, including a lower cost per test, improved data turnaround, and increased reliability, all which are important to the data user and customer. For the laboratory, the enhanced method performance of ICP-MS, low June 1999

5 detection capabilities, and a wide linear concentration range, this technology offers reliability, flexibility, increased control over matrix interferences, and a long-term cost savings. The disadvantages of ICP-MS are few. Initial investment and ongoing maintenance costs are higher. These disadvantages are quickly outweighed by high productivity. Because method approval is pending, currently ICP-MS cannot be utilized to its full potential. In addition, coupling ICP-MS with the hydride technique for arsenic and selenium analysis can provide additional benefits. Based on HRSD s experience, ICP-MS is overall superior, and we look forward to method promulgation in the near future. Thank you. Finally, I would like to acknowledge HRSD s dedicated analysts. QUESTION AND ANSWER SESSION MR. TELLIARD: Any questions? MR. CIARLEGLIO: Peter Ciarleglio from Dames & Moore. I was wondering if...i don't know how variable the waters that you are measuring in there are, but if you did have samples that were extremely high in metals or anything like that, what experience do you have? Can it shut the ICP-MS down for a while because of carryover and you have to restart analyses after cleaning up or any experiences in that regard? MS. HOGG: For contamination control, high concentration level samples are separated from low level sample analysis. At this point, high level samples are not analyzed using ICP-MS due to the large workload associated with NPDES monitoring. The ICP method is used for analysis of higher concentration samples. MR. CIARLEGLIO: So, you pre-screen your samples? MS. HOGG: No, higher level concentration samples are primarily associated with pretreatment program monitoring. ICP method will meet regulatory limits for this program and is more appropriate based on the historical database. MR. CIARLEGLIO: Okay. In a commercial lab, you don't always know which samples are going to be high ahead of time. MS. HOGG: Yes.. MR. CIARLEGLIO: Then, I did have a second question. In studies that I had read before in papers dealing with, well, particularly, lead and zinc, even when they claimed to use clean room techniques and stuff like that, they gave average zinc blank levels that were like 2 and 3 ug/l, and I notice there you had them down around 0.1 or 0.2. Do you think you have got your zinc contamination under control that well, or does it flare up sometimes? June

6 MS. HOGG: Zinc will flare up from time to time. Over the past five years of experience with clean techniques, both zinc and lead can be a problem. The exposure to air and the handling by personnel are the two key components in controlling this problem. When sample handling by personnel is fully minimized the problem can be controlled. MR. CIARLEGLIO: Yeah, you mentioned cosmetics. I think zinc is kind of a component of a lot of cosmetics. MS. HOGG: It is. use? MR. JAGESSAR: Patrick Jagessar, New York City DEP. May I ask what ICP/MS do you MS. HOGG: Fisons Plasmaquad. MR. JAGESSAR: Do you use internal standards in your analysis? MS. HOGG: Yes, we do. That is required by the method. MR. JAGESSAR: Do you do mercury by the ICP/MS? MS. HOGG: No, we don't. We have a mercury analyzer with an atomic fluorescence capability. MR. JAGESSAR: What about marine water? You do marine water, ambient water, marine? MS. HOGG: No, we do not have extensive experience with marine water. We have anlayzed surface water, groundwater, lake water, some river water but this is a very minor part of the workload. MR. JAGESSAR: Thank you. MR. TELLIARD: Thank you, Paula June 1999

7 1999 EPA 22nd Annual Conference on Analysis of Pollutants in the Environment APPLICATION OF ICP-MS TECHNOLOGY FOR TRACE METALS ANALYSIS Paula Hogg, Patty Lee Hampton Roads Sanitation District Virginia Beach, Virginia June

8 TOPICS COMPARISON OF ICP-MS & STGFAA METHODS & APPLICATIONS PERFORMANCE COST June 1999

9 METHODS & APPLICATIONS APPLICATIONS Ambient Monitoring In-Stream Studies WQ Criteria NPDES Regulatory Groundwater ULTRA- CLEAN < 1 ppb CLEAN 1-20 ppb METHODS Pre-Concentration ICP-MS GFAA ICP-MS POTW Process Industrial TRACE METALS > 20 ppb ICP-MS FAA June

10 METALS ANALYSIS WORKLOAD ICP STGFAA FAA PRETREATMENT PRETREATMENT 40% 20% NPDES ICP STGFAA ICP-MS 40% SPECIAL PROGRAMS WQ MONITORING ICP STGFAA ICP-MS FAA June 1999

11 ANALYTICAL CONCENTRATION RANGES Element STGFAA ICP-MS Cd ppb 0.02 ppb ppm Cu ppb 0.08 ppb ppm Cr ppb 0.02 ppb ppm Pb ppb ppb -100 ppm Ni ppb 0.02 ppb ppm Ag ppb 0.02 ppb ppm Zn ppb 0.2 ppb ppm June

12 METHOD DYNAMIC RANGE STGFAA ICP-MS ppt ppb ppm Concentration June 1999

13 EPA METHODS -STGFAA Elements Series Sb Y Y Y Cd Y Y Y Cu Y Y N Cr Y Y Cr 3+ Pb Y Y N Ni Y Y N Ag Y Y N Tl Y Y N Zn Y Y N As Y Y N Se Y Y Y June

14 EPA METHODS -ICP-MS Elements Sb Y Y Cd Y Y Cu Y Y Cr Y N Pb Y Y Ni Y Y Ag Y Y Tl Y Y Zn Y Y As Y N Se Y Y June 1999

15 200.8, AND 1600 METHODS Sample Concentration HCl/HNO 3 Digestion and Hydrogen/Argon Purge 1600 Series Performance Based Clean Techniques-Sampling & Analysis WQ Criteria Levels Additional Quality Control June

16 CLEAN TECHNIQUES Minimize Exposure to Air Enclosed Sampling Equipment Clean Area/ Clean Benches Limit Traffic Clean Techniques Equipment Preparation Glassware Preparation Containers Clean Hands/Dirty Hands Capsule Filtration Reagent Purity June 1999

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18 Se Cr 22 nd Annual Conference METHOD DETECTION LIMITS ug/l Sb Cd Cu Pb Ni Ag Tl Zn As ICP-MS STGFAA June 1999

19 MINIMUM LEVELS (ug/l) Element STGFAA WQ Criteria ICP-MS Sb Cd Cr Cu Pb Ni Ag Tl Zn As-Hydride (As III) 0.05 Se-Hydride June

20 MINIMUM LEVELS ug/l HRSD 1638 WQ Criteria HRSD 1639 Cd Pb Ag Tl June 1999

21 METHOD PERFORMANCE MDL STUDIES ACCURACY Lab Fortified Blanks Lab Fortified Matrix PRECISION PRODUCTIVITY June

22 METHOD 1638 DETECTION LEVELS ug/l EPA Method 1638 HRSD1638 Hydride Sb Cd Cu Pb Ni Se Ag Tl Zn June 1999

23 METHOD 1639 DETECTION LEVELS ug/l EPA 1639 HRSD Sb Cd Cr III Ni Se Zn June

24 LABORATORY REAGENT BLANK DATA ug/l 1 ICP-MS STGFAA Sb Cd Cu Pb Ni Se Ag Zn June 1999

25 ACCURACY- Laboratory Fortified Blanks ELEMENT STGFAA ICP-MS Mean Range Mean Range Ag Cd Cu Pb Se 102% % 107% % 99% % 100% % 97% % 100% % 98% % 106% % 102% % 96% 91-99% (Hydride) June

26 ACCURACY- Laboratory Fortified Matrix ELEMENT STGFAA ICP-MS Mean Range Mean Range Ag Cd Cu Pb Se 81% % 109% % 91% % 101% % 80% % 92% 87-96% 94% 90-97% 81% 73-92% 93% 87-99% 88% % (Hydride) June 1999

27 PRECISION - EFFLUENT RPD - % 15 STGFAA ICP/MS 10 8 % 5 0 Cd Cu Pb Ag Se June

28 PRODUCTIVITY METHOD SAMPLE RESULTS STGFAA 6 Minutes 1 Element ICP-MS 6 Minutes 21 Elements June 1999

29 COSTS INITIAL COSTS ANNUAL OPERATING COSTS COST/TEST June

30 INITIAL COSTS ITEM INSTRUMENT TRAINING DEVELOPMENT MDL IPR TOTAL FURNACE AA $ 70,000 $ 5,000 $ 1,600 $ 1,600 $ 78,200 ICP/MS $ 150,000 $ 5,000 $ 500 $ 500 $ 156, June 1999

31 OPERATING COSTS - COMPONENTS LABOR Analytical Administrative Data Management Fringe MATERIALS & SUPPLIES Service Contract OVERHEAD June

32 ANNUAL OPERATING COSTS 10,000 Results/Year ITEM FURNACE AA ICP-MS SERVICE CONTRACT MATERIALS & SUPPLIES LABOR OVERHEAD TOTAL COST/RESULT $ 10,000 $ 5,000 $ 104,000 $ 28,000 $ 147,000 $ $ 15,000 $ 9,000 $ 56,000 $ 19,000 $ 99,000 $ June 1999

33 LONG TERM OPERATING COSTS $250,000 $200,000 $220,000 GFAA ICP-MS $150,000 $100,000 $50,000 $ YEAR June

34 ICP/MS ADVANTAGES Low Multi-Element Analytical Cost Sensitivity Data Reliability Instrument Stability Data Turnaround Productivity Flexibility June 1999

35 ICP/MS DISADVANTAGES High Initial Cost Increased Instrument Maintenance High Service Contract Costs Method Approval Pending (40 CFR Part 136) ICP/MS-Hydride Methods Needed for As & Se June

36 ACKNOWLEDGEMENTS Cynthia Bato, Chemist Rolando Castro, Specialist HRSD Central Environmental Laboratory P.O. Box 5911 Virginia Beach, VA June 1999