As noted previously, the analytical methods employed for inorganic analyses by the environmental chemistry program at CEMRC are based, when applicable, on various standard procedures (EPA, 1983, Methods for Chemical Analysis of Water and Wastes, EPA/600/4-79-020; EPA, 1997, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, EPA/SW-846; American Public Health Association, 1981, Standard Methods for the Examination of Water and Wastewater, 15^th Edition). For some matrix/analyte combinations, appropriate external standard procedures do not exist, and specialized procedures have been developed to meet the needs of the WIPP EM.

Instrumentation

    A DIONEX 500 ion chromatography (IC) system was used to determine the concentrations of a suite of anions, including nitrate, sulfate, chloride, fluoride, bromide, and phosphate in aqueous extracts. Configured differently, the same instrument was used to determine the concentrations of several cations (calcium, magnesium and potassium). The anion analyses were performed with the use of an AS14 anion exchange column and chemical suppression while the cations were determined using a CG12A guard column and a CS12A analytical column.

    Elemental analyses employed an atomic absorption spectrometer (AAS) with a computer-controlled Perkin-Elmer 5100PC atomic absorption unit with Zeeman background correction. Samples are introduced into the AAS by aspiration through an air/acetylene flame, by vaporization in a heated graphite furnace, by flow-injection via a heated quartz cell, or via an unheated quartz cell (for Hg). The third instrument used for inorganic analyses was a Perkin-Elmer 3300 dual-view, inductively-coupled plasma atomic (or optical) emission spectrometer (ICP-ES). The AAS and ICP-ES are complementary; AAS is more sensitive than the ICP-ES, especially for the hydride elements (As, Sb, and Se), but compared with the ICP-ES, the AAS has a narrower linear range, requires more operator effort for calibration and operation, and has a much lower sample throughput.

General Quality Control

    Several analytes are readily determined by more than one of the three instruments used at CEMRC, which facilitates intra-laboratory comparisons as summarized below. Some of these internal QC comparisons are also summarized in the sections of this report that deal with specific media.

    Independent quality assurance samples are obtained and analyzed to verify the performance of the instrumentation and the proficiency of the analyst. Both blind samples (obtained from an outside source, with true value not known at the time of analysis) and reference samples (obtained from an outside source or prepared internally, with true values known at the time of analysis) are used to perform this function. Regular quality control verifications and batch QC provide records of sample performance data. Copies of the analytical data and performance results are maintained in the environmental chemistry instrument laboratory. The laboratory also carried out several informal inter-laboratory comparisons, but has not participated in a formal intercomparison program.

    Calibrations are verified with a standard obtained from a source different from that used in procuring the primary calibration standards. The calibration standards and the verification standards used at CEMRC are, where possible, traceable to NIST. A calibration blank is analyzed at the beginning of each workday when samples will be run, after every ten samples, and at the end of the day. In the calibration verification, blank results must be less than the minimum detectable level or + 3 SD of control limits. Analysis of a blank and a standard are performed at a frequency of 10% during analytical runs, and these are repeated at the close of each analysis to verify continued calibration validity. Batch quality control samples are counted as samples in determining the 10% frequency, but the continuing check samples are not counted as samples in determining the 10% frequency.

    Various types of field blanks, check solutions and laboratory fortified (spiked) samples are analyzed along with the samples as part of the QA/QC procedures. These vary somewhat among matrices and analyses as described in more detail below. In addition, when feasible, duplicate samples are processed to evaluate reproducibility and sample homogeneity. Control charts for each matrix have been established, and + 3 SD limits have been determined for future reference. Control charts are used to track the performance of the instrument and the sample preparation procedures. Similarly, spike recoveries are calculated, tracked, and reported along with the analytical data.

Quality Control for Analyses by IC

    For the IC analyses, QC samples are analyzed with each sample batch as an indicator of the reliability of the data produced. The types, frequencies of analysis, and limits for these QC samples have been established in a set of standard operating procedures.

    Method Detection Limits (MDL) were established for each analyte in each sample matrix according to EPA Method 300.0 (Determination of Inorganic Anions by Ion Chromatography) (Table K1). QC samples included Laboratory Reagent Blanks (LRB), with one LRB prepared for each sample batch (normally a set of ten samples). LRB results below MDL are considered acceptable (Table K2). For aerosol filter analyses, some LRB results indicated reagent blank contamination, which was subsequently identified and eliminated. Results for samples analyzed prior to elimination of the contamination were corrected by subtraction of the blank value for each analyte. Laboratory Fortified Matrix (LFM) samples were also used for QC, with one LFM analysis per sample group. Results from analyses of LFMs are used to calculate matrix spike recoveries, with recoveries of 70-130% considered acceptable. As prescribed by EPA Method 300.0, chloride and sulfate values in water samples and chloride, phosphate and sulfate values in sediments were not reported because the concentration of the fortification was less than 25% of the background concentration (Table K3).

    One duplicate analysis was performed for each sample group. When feasible, duplicate aliquots of some field samples were analyzed. In cases where duplicate aliquots from the original sample were not feasible (such as aerosol filters), separate aliquots of the sample extract were analyzed. The relative percent difference (RPD) between the sample and the duplicate was calculated, with a difference of < 20% (or an absolute difference of + MDL for samples less than five times the MDL) considered acceptable. For aerosol filters, differences between the chloride duplicates were not within limits when the observed values were less than or near the MDL (Table K4).

    A Laboratory Fortified Blank (LFB) was prepared and analyzed with each sample batch, using a spiked ultrapure water sample for aerosol filters and water samples, and certified reference materials (CRM) for soils and sediments. Recoveries of 85-115% were considered acceptable for aerosol filters, sediments, and water samples. The CRM was "Anions in Soils" from Environmental Research Associates (ERA) in Arvada, Colorado. The preparation procedure used to certify the standard was found to be slightly different from the procedure employed at CEMRC. ERA provided corrected means for calculations of recoveries based on the CEMRC procedure (Table K5). Because there is no existing standard reference method for extracting solid material for anion analysis by ion chromatography, the results may not be directly comparable.

    Low-volume aerosol filters were also analyzed by IC for five cations with overall acceptable results (Table K6). Acceptance limits for each QC parameter were the same as previously described. In sample batches where the laboratory reagent blanks were above the MDL, blank subtraction was performed for those affected analytes.

Quality Control for Elemental Analyses by ICP-ES and AAS

    For elemental analyses, sets of quality control samples comparable to those previously described for IC analyses were included with each sample batch. Detailed performance results for all QC measures are not presented here due to the number of elements that can be determined by ICP-ES and AAS. For all media (aerosol filters, water, soils, and sediments), ICP-ES and AAS values were reported to the method detection limit as determined by EPA protocols (Table K7). Digestion QC samples were analyzed at a frequency of 10% relative to samples. The digestion QC control parameters used for the evaluation of metals in aerosol filters included LRB filters and vendor-supplied certified reference filters. Due to sample volume limitations, duplicate and post digestion spike analyses could not be performed for ICP-ES analyses of the aerosol samples.

    For water, soils, and sediments, a practical quantitation limit (PQL) was also calculated to evaluate precision based on the analysis of duplicate samples. The PQL is obtained by multiplying the method detection limit (MDL) by five. The digestion quality control parameters used for the evaluation of metals in water, soils, and sediments were based on EPA Contract Laboratory Program (1994, U.S. EPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540/R-94013) and SW846 methods (EPA, 1997, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, EPA/SW-846. No comparable control parameters presently exist for aerosol samples.

    For aerosol samples, unused cellulose ester filters were used as LRB samples. LRB results above the MDL were subtracted from each associated batch of sample results, because the LRB results were greater than the MDL for many of the analytes studied. The sources of this filter contamination have not yet been identified. A cellulose ester CRM ("Trace Metals on Filter Media" from High Purity Standards in Charleston, South Carolina) and a LFB were also used with analyses of aerosol samples. Mean recoveries for all analytes were within 85-115% of control limits, with the exception of Se. The CRM results for Se were 40%, 62%, 43% and 118%, while the LFB recovery for Se was 131%. The source of the inconsistent Se recoveries is not known at this time, and therefore, Se values for aerosol samples should be considered semi-quantitative at best.

    Four standard QC measures were used in association with analyses of water samples. Ultrapure water was used for LRB samples and results were less than the MDLs for all analytes except Al, Ba, Ca, Cd, Fe, Mg and K. For Al and Fe, all sample results were less than the reagent blank, resulting in concentrations reported as <MDL. Cd results in the samples were corrected for the LRB values in each associated batch. For Ba, Ca, K, Mg, and K, all sample measurements were at least 10 times higher than the LRB values, and therefore the contaminant effects for these analytes are considered negligible. A LFB was prepared by adding a known quantity of each analyte of interest to ultrapure water. All analytes were recovered within the 85-115% limits as specified by EPA methods. LFM samples were also used for QC in analyses of water samples, with all recoveries within the 85%-115% acceptance window specified in the EPA methods, with the exception of Pb. Although Pb was recovered at 81%, this level is considered usable according to EPA inorganic usability protocols. A duplicate digestion analysis of water samples was also performed to demonstrate reproducibility, but a slight modification of the EPA CLP program was used for acceptance determination. If the sample result was less than the PQL, a + PQL control limit was used. If the sample result was greater than the PQL, a +20% RPD control limit was used. All duplicate results were within these modified acceptance limits.

    For soils and sediments, LRB samples of ultrapure water were compared to MDLs to determine if contamination was introduced during sample preparation. The LRB results were above the MDLs for Ca, Mg, and Fe. However, the sample measurements were several orders of magnitude higher than the LRB results for these analytes, and therefore the contaminant effects on the measurements were considered negligible. If the LRB result were greater than the MDL, a correction to the sample results was made. Several of the LRB results for Cu, Cd, Ni and Na were at approximately the same level as those measured in the soil samples (within a factor of five), and therefore, results for these analytes may be biased high. These results would be considered "estimated" but would be considered usable according to EPA inorganic data usability protocols (1994, U.S. EPA Contract Laboratory Program National Functional Guidelines for Inorganic Data Review, EPA 540/R-94013.) All other LRB results were within acceptance limits for soils. The elemental concentrations of all analytes in sediment samples were at least ten times higher than LRB results, and therefore the contaminant effects on measurements in sediments are considered negligible.

    A CRM ("Priority Pollutant T/CLP Soil" from ERA) was obtained and prepared with the soil and sediment samples to demonstrate matrix-specific performance of digestion and analysis procedures. All analytes were recovered within the supplier’s specified control limits for all digestions. The average CRM recoveries were within 85%-115% for all analytes, with the exception of Zn at 73% and Sb at 56%. A low bias for Sb was expected, due to use of a standard hotplate digestion procedure that allows loss of Sb as a SbCl precipitate. Additional studies are underway to resolve the low bias for Zn. Duplicate digestions were preformed for soil and sediment using a modification of the EPA CLP program for acceptance determination. If the sample result was less than the PQL, a + PQL control limit was used. If the sample result was greater than the PQL a +20% RPD control limit was used. For soils, the average RPD over the nine digestions performed was within acceptance limits for all analytes. Al, As, Ba, Ca, Cr, Fe, Mg, Ni, K, V, and Zn each had one of the nine digestions outside the acceptance limits. None of the RPDs were outside the limits established in the EPA usability protocols. For sediments, the duplicate precision for Mo in the first digestion was 22%, which is outside the acceptance limit. However, the Mo data are considered usable according to the EPA inorganic usability protocols. All other duplicate results for the sediments were within acceptance limits. A LFM also was prepared for soil, with an average recovery for the nine digestions within 85%-115% windows for all analytes with the exception of Sb at 37%. All individual recoveries were within the 70%-130% acceptance window specified in the EPA methods with the exception of Sb and Se in one sediment digestion. As previously noted a low bias for Sb was expected due to the digestion procedure used. Experiments to resolve the bias for Se are in progress.