NATIONAL WATER QUALITY LABORATORY TECHNICAL MEMORANDUM 99.04 April 8, 1999 Subject: Inductively Coupled Plasma - Optical Emission Spectrometry to replace Flame Atomic Absorption Spectrometry and Direct Current Plasma - Atomic Emission Spectrometry for the determination of whole-water recoverable trace metals and major ions in digested water samples Effective date of changes: April 1, 1999 Authors: Edward J. Zayhowski, Supervisor, Plasma Unit, Inorganic Chemistry Program, NWQL (303) 236-3180 (ZAYHOWSK) Tedmund M. Struzeski, Chemist, Plasma Unit, Inorganic Chemistry Program, NWQL (303) 236-3191 (STRUZESK) Revision: None Supplemental: None SCOPE Effective April 1, 1999, the National Water Quality Laboratory (NWQL) has replaced the Flame Atomic Absorption Spectrometry (FAAS) and Direct Current Plasma - Atomic Emission Spectrometry (DCP-AES) methods for the determination of whole-water recoverable (WWR) trace metals and major ions in digested water samples with the Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES) technique. The ICP-OES WWR method is described in Open-File Report 98-165. The WWR digestion is described in Open-File Report 96-225. The WWR FAAS and DCP-AES methods being replaced by the ICP-OES method are listed in Table 1. Four additional WWR tests -- molybdenum, silica, silver, and vanadium -- are also being offered by the ICP technique. These additional tests are listed in Table 2. The NWQL has been performing WWR tests for several trace metals and major cations by FAAS for many years. In addition, WWR aluminum and boron have been determined by the DCP-AES technique. A study was undertaken to replace these outdated methods by the ICP-OES technique. Using the current generation of simultaneous, multielement ICP-OES instrumentation allows for improved efficiency, accuracy, and precision in a single sample analysis. Whereas the ICP-OES method can determine up to twenty-one elements simultaneously, the current FAAS and DCP-AES methods can only determine one element per analysis. ICP-OES validation data demonstrate that the accuracy and precision for most trace metal determinations by the ICP-OES method are equivalent to or better than those for the comparable FAAS and DCP-AES techniques. These interim LT-MDLs were based on 30 to 33 replicate analyses performed over two weeks. The instrument was powered-down, restarted, and recalibrated prior to collecting each MDL data set. Table 1. Whole-water recoverable tests being replaced by the inductively coupled plasma - optical emission spectrometry methods. All units are in micrograms/liter. Method being replaced Replacement method ________________________________________________________________________ Trace metal Method Lab MRL New Lab Parameter LT-MDL2 LRL1,2 or major code method code code ion ________________________________________________________________________ Aluminum DCP 1283 1105C 10 ICP 2351 1105D 14 28 Barium FAAS 234 1007A 100 ICP 2352 1007C 0.6 1.2 Beryllium FAAS 230 1012A 10 ICP 2353 1012C 2 4 Boron DCP 1286 1022B 10 ICP 2354 1022C 12 24 Cadmium FAAS 131 1027A 10 ICP 2355 1027G 5 10 Calcium FAAS 324 0916B 100 ICP 2356 916C 5 10 Cobalt FAAS 149 1037A 50 ICP 2391 1037G 8 16 Copper FAAS 156 1042A 10 ICP 2358 1042G 6 12 Iron FAAS 189 1045B 10 ICP 2359 1045C 7 14 Lead FAAS 192 1051A 100 ICP 2360 1051H 65 130 Lithium FAAS 277 1132A 10 ICP 2361 1132B 6 12 Magnesium FAAS 261 0927B 100 ICP 2362 927C 4 8 Manganese FAAS 41 1055A 10 ICP 2363 1055D 1.5 3 Nickel FAAS 198 1067A 100 ICP 2365 1067H 25 50 Sodium FAAS 320 929B 100 ICP 2368 929C 70 140 Strontium FAAS 290 1082A 10 ICP 2369 1082B 0.7 1.4 Zinc FAAS 296 1092A 10 ICP 2371 1092C 20 40 ________________________________________________________________________ The method detection levels (MDLs) for the ICP method have been calculated by using a long-term method detection level (LT-MDL) approach. 1 Laboratory Reporting Levels are equivalent to two times the LT-MDL. Data will be reported as indicated in Open-File Report 99-xxx (in review). 2 Interim values. LTMDLs and LRLs to be established this FY. Table 2. Additional whole-water recoverable tests using the inductively coupled plasma - optical emission spectrometry methods. All units are in micrograms/liter. ________________________________________________________________________ Trace Method Lab code Parameter LT-MDL LRL metal or code major ion ________________________________________________________________________ Molybdenum ICP 2364 1062C 38 76 Silica ICP 2366 956A 60 120 Silver ICP 2367 1077G 4 8 Vanadium ICP 2370 1087A 5 10 ________________________________________________________________________ Requesting ICP WWR Analyses Three different requesting options are offered to provide maximum flexibility in meeting each customer's specialized project objectives. These options include requesting by individual laboratory codes; using schedule 1202 which includes all twenty-one WWR elements that are listed in Table 1 and 2; or using a pre-arranged custom laboratory schedule. Customized schedules can be arranged by contacting Steve Glodt via E-mail (SRGLODT) or at 303-467-8021. Pricing information is available in the NWQL catalog at http://wwwnwql.cr.usgs.gov/USGS/catalog/CatIntro.html. A 250-mL raw acidified (RA) bottle type will still be required for the WWR analyses. However, it will be noted in the Schedules, Parameters, & Network Program (SPN) that a 250-mL raw unacidified (RU) bottle will also be required for any ICP-AES analysis since specific conductance is mandatory prior to this analysis. Summary of Planned Changes The specified WWR metals and major ions at present offered by FAAS and DCP-AES will be offered only by ICP-AES starting on April 1, 1998. All methods being replaced will become invalid lab codes and schedules. Effect on Data Base: None References: Garbarino, J.R., and Struzeski, T.M., Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of elements in whole- water digests using inductively coupled plasma - optical emission spectrometry and inductively coupled plasma - mass spectrometry: U.S. Geological Survey Open- File Report 98-165. Hoffman, G.L., Fishman, M.J., and Garbarino, J.R., Methods of Analysis by the U.S. Geological Survey National Water Quality Laboratory - In-Bottle Acid Digestion of Whole-Water Samples: U.S. Geological Survey Open-File Report 96-225. /Signed/ Robert S. Williams, Jr., Chief National Water Quality Laboratory Branch of Analytical Services Key Words: Direct Current Plasma - Atomic Emission Spectrometry, Inductively Coupled Plasma - Atomic Emission Spectrometry, Spectrometry, Whole-Water Recoverable, Flame Atomic Absorption Spectrometry Supersedes: None Distribution: E and http://wwwnwql.cr.usgs.gov/