Paint samples were prepared from paint chips collected from a variety of sites in North Carolina and Ohio, including a school, a hospital, and a warehouse. The chips were ground to a maximum particle size of 120 micrometers (IJ.m). Soil samples came from drip lines around North Carolina residences. Soil samples were dried and then sterilized by heating the soil to 325Of for a minimum of 2 hours, and finally sieved to a maxi- mum particle size of 150 IJ.m. Dust wipes were prepared from dust collected from households in North Carolina and Milwaukee, Wis. Following sterilization by gamma-irradiation, the household and post-abatement dust was sieved to 150 IJ.m and gravimetrically loaded on a premoistened PaceWipe, which has been shown to meet ASTM E 1792(1) specifications. The loaded wipes were, stored under refrigeration until shipment; as an antimicrobial measure. Also it was recommended that dust wipe samples be refrigerated until the laboratory analyses were performed, as an additional precaution to reduce/prevent the growth of mold. For ELPAT Round 26, a total of 332 laboratories was enrolled with 305 laboratories (92%) submitting results. For Round 27, 328 laboratories enrolled with 307 laboratories (94%) submitted the results. Tables I and II list summary statistics of reference laboratories for each matrix and sample number. Agreement among reference laboratories using a variety of sample preparation techniques and analytical methods is demonstrated by relative standard deviations (RSDs). For Round 26, the ranged from 6.5 to 8% for paint chips, 5.4 to 9.4% for soils, and 6.3 to 9.2% for dust wipes. For Round 27,'the RSDs ranged from 6:1 to 11.9% for paint chips, 5 to 12.1% .for soils, and 7.5 to 9.1% for dust wipes. The RSDs are similar to the findings on previous ELPAT rounds. Tables III and IV show the number of all participating laboratory analyses that were identified as outliers. For Round 26, the percentage of all participating laboratory analyses that were identified as outliers was less than 10.3% (5.8 to 7.1% for paint chips, 5.8 to 11.1% for soils, and 4 to 10.3% for dust wipes). For Round 27, the percentage of outliers was less than 8.8% (5.7 to 7.4% for paint chips, 5.3 to 8.8% for soils, and 6.2 to 7.6% for dust wipes). This is similar to the frequency of outliers reported on the earlier rounds of ELPAT for each matrix. Tables V and VI show a summary of acceptable results for the three lead matrices by sample preparation technique and instrumental method used by participating laboratories. Analytical methods that were not identified by laboratories were omitted from the table. Sample extraction techniques are grouped into hotplate, microwave, and I "other" techniques reported by participants. Hotplate digestion categories are: NIOSH 7082/7105 (a nitric acid/hydrogen peroxide digestion method modified from the NIOSH Manual of Analytical Methods,- Method 7082)(21, EPA SW846-3050A(3) (an., EPA nitric acid/hydrogen peroxide method), American Society for Testing Materials (ASTM) hotplate methods,(4.S) and other hotplate techniques. Microwave digestion categories are: EPA SW846-3051(6) (a nitric acid digestion method), ASTM microwave methods, and other microwave techniques. The "other" category includes non- microwave and nonhotplate techniques, such as X-ray fluorescence sample preparation, leaching techniques, ultrasonic extraction, and Parr bomb. Instrumental methods are categorized into flame atomic absorption (FAA), inductively coupled plasma-atomic emission spectroscopy (ICP-AFS), graphite furnace atomic absorption (GFAA), laboratory X-ray fluorescence (lAB-XRF), anodic stripping voltammetry (ASV), and others, which includes inductively coupled plasma mass spectroscopy (ICP-MS).
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