Overview
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Key numbers
The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:
- between 1798 and 4217 𝜇g/g for Co and 1472−1672 𝜇g/g Mo a useful and cost-effective qualitative technique suitable for
- sidered a qualitative indicator of the presence of CNTs, not a cation 100% extraction efficiency is not required, the goal
- 26). A variety of sample pretreatments have been employed 40–60 wt% carbon content and 30–35% metal content. This
- and finally dissolution and dilution in 1% HNO3 . Grinberg USA) is a bituminous coal fly ash sieved through a nominal
- reagent addition several times (i.e., three to six heating and Suprapur 30% aqueous solution of hydrogen peroxide
- prepare the calibration standards (Delta Scientific Laboratory with radial optical system (163 to 782 nm range) was used
- prepared in 1% HNO3 to match the matrix of the samples. elements of interest. The instrument was operated at 1400 W
- (10 𝜇g/mL). Individual high-purity standards solutions of Ge, solution of 10 mg/L Mn (2% HNO3 ).
- In, and Re (1000 mg/L) were used to prepare the internal
- effect of GW on extraction efficiency. The present study used sample). Spiked samples (20 and 250 ppb level) and spiked
- a 3.5 cm diameter circular disk of GhostWipes material as procedural blanks (4 and 25 ppm level) were analyzed along
- control was used for all microwave digestions. DigiPrep 30% hydrogen peroxide (5 mL, 45 min), and evaporated to
- samples, a NexION 300s Dual-Channel Universal Cell ICP- 0.5 mL 30% hydrogen peroxide. The microwave digestion step
- nebulizer, cyclonic spray chamber with a PC3x chiller (2∘ C), residues were dissolved in 1% nitric acid, vortexed, and
- acid, 0.1 mL hydrofluoric acid, and 1.9 mL ultrapure water and Table 1: Metal concentrations (>0.5%) of NIST 2483, Test-CNT,
- by ICP-MS after appropriate dilution with 1% HNO3 . The Nickel 184801 ± 4090 132745 ± 12664
- after appropriate dilution. The final digestion solutions were Table 2: Metal concentrations (ppm range) of NIST 2483-CNT
- Gd, 208 Pb, and 238 U were monitored. Internal standard Certificate value Mean ± STDEV (𝜇g/g)
- the experiment for analytes in the mass ranges 87, 95–138, Boron 74.7 32.2 ± 5.71 46 ± 2.88
- and 207–238, respectively. Analytical errors up to 10% for Aluminum 723 ± 19 552 ± 116 621 ± 51.9
- 47%; Al spike not recovered) and 86–107% with UD method Arsenic 12.5 12.5 ± 1.02 7.98 ± 0.57
- (except Mo 122%) in the presence of GW (spiked procedural Barium 119 ± 3.4 95.2 ± 5.92 99.5 ± 7.55
- of detection (LOD) are reported in Table 3. The LODs NIST 2483-CNT Standard Reference Material (SRM), Test-
- for Inductively Coupled Plasma Mass Spectrometry using 3 efficiency for the residual catalysts (>0.5%). NIST 2483-
- digestion (MD) and ultrasonic digestion (UD), are compared for the other metals (B, As, and Cu) as shown in Tables 2
- in Table 1 and for CNT impurities present in lower concen- methods are compared using aliquots of NIST 2483-CNT
- Table 3: Metal concentrations of NIST 2483-CNT with microwave digestion (MD) and ultrasonic digestion (UD) methods in the presence
- CNT Samples. Table 1 presents the high metal concentra- residual catalyst metals are incorporated in the graphitic
- tions (>0.5%) in NIST 2483, Test-CNT, and Aldrich-CNTs structure (7, 22). Even though in case of ultrasonic digestion
- shown in Table 1 for all investigated CNTs, the MD method CNTs.
- no significant difference (𝑝 = 0.128), for all other residual CNTs due to improved extraction (Table 1) yielding high
- NIST 2483-CNT (Table 1) for which 2–5 times lower Mo structure (30–34). Overall, the MD extraction method takes
- than with MD method resulting in recoveries of 74 ± 2.0% steps plus evaporation and 4 h for microwave digestion and
- Co and 82 ± 2.5% Mo with MD method and just 16 ± evaporation/filtration). In contrast, the UD method has a
- 1.7% Co and 39 ± 2.0% Mo with UD method. Although shorter sample-reagent contact time (2 h ultrasonication)
- ranges were similar (i.e., Test-CNT Co: 17487 𝜇g/g MD versus extraction efficiency for high concentration metallic impuri-
- concentrations of Al, V, Mn, and Ba were extracted with (see Table S1 in the Supplementary Material available online
- the differences were not significant (𝑝 > 0.05). In contrast, 91% were obtained with the UD method for most elements
- the MD method extracted significantly higher (𝑝 < 0.001) in NIST 1633b (with the exception of As, Zn, and Gd; Table
- amounts of As, but significantly lower (𝑝 < 0.05) amounts of S1) which were better than recoveries of 29–69% achieved
- (>0.5%) and low concentration (ppm range) metals in NIST concentration metals in NIST 2483-CNT (i.e., Al, V, Cu, Ba,
- elements (27). Generally the recoveries for low concentration in Table 1 with better extraction efficiency for Test-CNT
Methods (brief)
- Sampled Using Surface Wipes
- carbon in environmental samples. A practical and cost-effective analytical approach is needed to support routine surface monitoring
- presence of CNTs, not a quantitative exposure metric. In this study, two digestion approaches (microwave-assisted nitric acid/H2 O2
- digestion and ultrasonic nitric/HF acid digestion) in conjunction with Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
- were used to compare the performance of the digestion methods. The microwave digestion method accommodated the bulky wipe
- sample and also eliminated potential ICP-MS signal interferences related to incomplete digestion. Although quantitative recoveries
- requiring lengthy multistep digestion protocols may be necessary in other applications, the near-total recoveries achieved in the
- Produced by various processes (i.e., cold vapor deposition, between CNT and non-CNT sources of elemental carbon
- carbon nanotubes (CNTs) contain metal impurities (e.g., Fe, metal impurities in environmental samples provides a means
- example, an ICP-MS study of commercially important CNTs sampling methods have been suggested as possible strategies
- showed that impurity concentrations in three multiwall CNTs to collect samples for workplace monitoring of metal impuri-
- (and potential exposures), evaluate housekeeping or clean- identified by comparing ICP-MS and ICP-OES results for the
- NIOSH (18) and OECD (17) provided guidance on ate digestion approach for ICP-MS determination of metal
- collecting surface wipe samples in nanotechnology applica- impurities in CNTs collected using wipe samples. Two
- included an analytical methodology for determining CNTs in the extractions: a microwave-assisted digestion method and
- wipe samples. Wipe sampling for CNT metal tracers is con- an ultrasonic digestion method. Although for this appli-
- with background particle concentrations. Even though wipe the digestion approach must be able to accommodate wipe
- sampling may be considered qualitative, an analytical method samples which are quite bulky. The possibility that wipes may
Implications
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Update history
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