This section describes the process for dissolution of vanadium from the vanadium sublimation samples collect in § 1065.1117 and any blanks collected in § 1065.1119 as well as the analysis of the digestates to determine the mass of vanadium emitted and the associated sublimation temperature threshold based on the results of all the samples taken during the reactor aging cycle.
(a) Digest the samples using the following procedure, or an equivalent procedure:
(1) Place the recovered alumina, a portion of the ground quartz tube from the reactor, and the quartz wool in a Teflon pressure vessel with a mixture made from 1.5 mL of 16 N HNO3, 0.5 mL of 28 N HF, and 0.2 mL of 12 N HCl. Note that the amount of ground quartz tube from the reactor included in the digestion can influence the vanadium concentration of both the volatilized vanadium from the sample and the method detection limit. You must be consistent with the amount ground quartz tube included in the sample analysis for your testing. You must limit the amount of quartz tube to include only portions of the tube that would be likely to encounter volatilized vanadium.
(2) Program a microwave oven to heat the sample to 180 °C over 9 minutes, followed by a 10-minute hold at that temperature, and 1 hour of ventilation/cooling.
(3) After cooling, dilute the digests to 30 mL with high purity 18MΩ water prior to ICP-MS (or ICP-OES) analysis. Note that this digestion technique requires adequate safety measures when working with HF at high temperature and pressure. To avoid “carry-over” contamination, rigorously clean the vessels between samples as described in “Microwave digestion procedures for environmental matrixes” (Lough, G.C. et al, Analyst. 1998, 123 (7), 103R-133R).
(b) Analyze the digestates for vanadium as follows:
(1) Perform the analysis using ICP-OES (or ICP-MS) using standard plasma conditions (1350 W forward power) and a desolvating microconcentric nebulizer, which will significantly reduce oxide- and chloride-based interferences.
(2) We recommend that you digest and analyze a minimum of three solid vanadium NIST Standard Reference Materials in duplicate with every batch of 25 vanadium alumina capture bed samples that you analyze in this section, as described in “Emissions of metals associated with motor vehicle roadways” (Herner, J.D. et al, Environmental Science and Technology. 2005, 39, 826-836). This will serve as a quality assurance check to help gauge the relative uncertainties in each measurement, specifically if the measurement errors are normally distributed and independent.
(3) Use the 3-sigma approach to determine the analytical method detection limits for vanadium and the 10-sigma approach if you determine the reporting limit. This process involves analyzing at least seven replicates of a reactor blank using the analytical method described in paragraphs (a) and (b)(1) of this section, converting the responses into concentration units, and calculating the standard deviation. Determine the detection limit by multiplying the standard deviation by 3 and adding it to the average. Determine the reporting limit by multiplying the standard deviation by 10 and adding it to the average. Determine the following analytical method detection limits:
(i) Determine the ICP-MS (or ICP-OES) instrumental detection limit (ng/L) by measuring at least seven blank samples made up of the reagents from paragraph (a) of this section.
(ii) Determine the method detection limit (µg/m
3 of flow) by measuring at least seven reactor blank samples taken as described in § 1065.1119(d).
(iii) We recommend that your method detection limit determined under paragraph (b)(3)(ii) of this section is at or below 15 µg/m
3. You must report your detection limits determined in this paragraph (b)(3) and reporting limits (if determined) with your test results.
(4) If you account for vanadium-loaded particles contaminating catalyst-coated monoliths as a result of physical abrasion as allowed in § 1065.1115(f), use the 3-sigma approach to determine the analytical method detection limits for titanium and the 10-sigma approach if you determine the reporting limit. This process involves analyzing at least seven replicates of a blank using the analytical method described in paragraphs (a) and (b)(1) of this section, converting the responses into concentration units, and calculating the standard deviation. Determine the detection limit by multiplying the standard deviation by 3 and subtracting it from the average. Determine the reporting limit by multiplying the standard deviation by 10 and subtracting it from the average.
(i) Determine the ICP-MS (or ICP-OES) instrumental detection limit (ng/L) by measuring at least seven blank samples made up of the reagents from paragraph (a) of this section.
(ii) Determine the method detection limit (µg/m
3 of flow) by measuring at least seven reactor blank samples taken as described in § 1065.1119(d).