24.11. 2022 Jan Kratzer GENEROVÁNÍ TĚKAVÝCH SLOUČENIN PRO STOPOVOU PRVKOVOU A SPECIAČNÍ ANALÝZU: VÝHODY A OMEZENÍ Oddělení stopové prvkové analýzy Ústav analytické chemie AVČR, v. v. i. GENERATION OF VOLATILE SPECIES • volatile compounds generation (VCG) / volatile species (VSG) • selective conversion of analyte to volatile compound • VSG compatible with all spectrometric techniques • VSG independent of the detector used • most commonly used for hydride forming elements (HG) VSG AAS AFS ICP-OES ICP-MS As Sb Bi Se Te Pb Sn Ge GENERATION OF VOLATILE SPECIES • selective conversion of analyte to volatile species • analyte separation from the matrix (interferences minimized) • high transport efficiency of analyte into the detector → lower LOD • analyte preconcentration in gaseous phase → further LOD improvement • speciation analysis without chromatography feasible APPROACHES TO VSG • Chemical generation (CVG) • analyte reduction by chemical reaction (HCl/NaBH4) • high generation efficiency (~ 100 %) • Electrochemical generation (EcVG) • analyte reduction by current • low generation efficiency • potential to reach low LOD • Photochemical generation (PVG) • analyte reduction by UV radiation • Plasma mediated vapor generation (PMVG) • interaction with plasma - radicals, excited/metastable species, ions PMVG PVG EcVG CVG OUTLINE • VSG of non-hydride forming element – Cd • Novel hydride atomizers for AAS based on DBD plasma • VSG-based speciation analysis (Hg, Te, Ge, As) • VSG of mercury based on PMVG of Hg • VSG of non-hydride forming element – Cd • Novel hydride atomizers for AAS based on DBD plasma • VSG-based speciation analysis • VSG of mercury based on PMVG of Hg L. Sagapova et al., Anal. Chim. Acta 1168 (2021) 338601 conventional approach: HG 2-channel system (HCl/NaBH4) VSG of Cd 4-channel system 0.1 mol L-1 KCN 0.001 mol L-1 Cr3+ • generation efficiency quantified (with additives) • by 115mCd radioactive indicator 66 ± 4 % • by comparison of PN-ICP-MS and VSG-ICP-MS 55 ± 2 % • HCl/NaBH4 without additives < 5% • Cd free atoms (dominant species) + molecular/aerosol-associated • VSG-AAS LOD 60 pg mL-1 Cd • VSG-AFS LOD 0.42 pg mL-1 Cd VSG-AFS of Cd – METHOD VALIDATION CRM certified value (ng mL-1) found value (ng mL-1) NIST 1643 f 5.85 ± 0.13 5.90 ± 0.44 ERM-CA 713 5.00 ± 0.05 5.09 ± 0.20 • VSG of non-hydride forming element – Cd • Novel hydride atomizers for AAS based on DBD plasma • VSG-based speciation analysis • VSG of mercury based on PMVG of Hg B. Baranová et al., Spectrochim. Acta B, accepted. HYDRIDE ATOMIZATION - AAS • externally heated quartz tube atomizers (QTA) • heated to 900 °C • advanced construction (MMQTA) supplied by air/O2 • most common hydride atomizer • dielectric barrier discharge (DBD) plasmas • low temperature, ambient pressure plasmas • AC high voltage • novel atomizer ANALYTICAL FIGURES OF MERIT - SENSITIVITY B. Baranová et al., Spectrochim. Acta B, accepted. • As, Se, Te – sensitivity reached in DBD comparable to (MM)QTA • Pb, Bi, Sn – (MM)QTA performs much better (3-7 times higher sensitivity) • (MM)QTA – sensitivity difference among elements: factor of 2 • DBD - sensitivity difference among elements: factor of 12 L. Juhászová et al., Spectrochim. Acta B 158 (2019), 105630. P. Novák et al., Anal. Chem. 88 (2016), 6064-6070. Sensitivity, s ng-1 Atomizer Pb Bi Sn Se Te As (MM)QTA 0.29 ± 0.01 0.40 ± 0.02 0.33 ± 0.01 0.53 ± 0.03 0.32 ± 0.01 0.48 ± 0.01 DBD 0.09 ± 0.01 0.15 ± 0.01 0.05 ± 0.01 0.60 ± 0.04 0.32 ± 0.01 0.54 ± 0.04 MECHANISTIC STUDIES - LIF Pb: atomization efficiency 23 ± 7% Te: atomization efficiency 100 ± 7% M. Albrecht et al., Spectrochim. Acta B 166 (2020) 105819. K. Bufková et al., Spectrochim. Acta B 171 (2020) 105947. Pb Te Mechanistic studies – DEPOSITED FRACTION Analyte fraction (%) deposited in the atomizer Analyte DBD (MM)QTA Pb 91 ± 5 107 ± 4 This work Bi 94 ± 1 92 ± 3 [27] Se 26 - 43 15 ± 2 [28] Te 62 ± 2 37 ± 2 This work B. Baranová et al., Spectrochim. Acta B, accepted.J. Kratzer et al., Anal. Chem. 88 (2016) 1804-1811. J. Kratzer et al., Anal. Chim. Acta 1028 (2018) 11-21. leaching experiments, ICP-MS detection • fast decay of Pb and Bi free atoms → deposit formation → low sensitivity (DBD) • spatial distribution of deposits differ between DBD and (MM)QTA → DBD – homogeneous distribution even in the discharge area → MMQTA – in the colder atomizer zones J. Kratzer et al., Anal. Chim. Acta 1028 (2018) 11-21. Spatial distribution of 75Se in DBD and MMQTA after atomization of 3 replicates of a 75Se tracer sample solution (exposure time of 68 hours). P. Novák et al., Anal. Chem. 88 (2016), 6064-6070. 1) ANALYTE TRAPPING Ar + O2 2) ANALYTE RELEASE Ar + H2 (blank) No change in DBD HV / power settings PRECONCENTRATION IN-SITU IN DBD IN-SITU PRECONCENTRATION IN DBD P. Novák et al., Anal. Chem. 88 (2016), 6064-6070. 1 ng mL-1 As (2 ng As) IN-SITU PRECONCENTRATION IN DBD element Preconcentration efficiency, % LOD, ng mL-1 As 100 0.01 Se 70 0.01 Sb 100 0.02 Te 51 Bi 60 P. Novák et al., Anal. Chem. 88 (2016), 6064-6070. J. Kratzer et al., J. Anal. Atom. Spectrom. 34 (2019), 193-202 P. Zurynková et al., Anal. Chim. Acta 1010 (2018) 11-29. K. Bufková et al., Spectrochim. Acta B 171 (2020) 105947. J. Kratzer et al., Anal. Chem. 86 (2014), 9620-9625. • VSG of non-hydride forming element – Cd • Novel hydride atomizers for AAS based on DBD plasma • VSG-based speciation analysis (Hg, Te, Ge, As) • VSG of mercury based on PMVG of Hg A) selective VSG VSG → detection Te(IV) and Te(VI) C) Generation of substituted volatile species VSG → separation → detection VSG-CT-ICP/MS B) post-column VSG separation → VSG → detection HPLC-VSG-ICP/MS selective VSG VSG → detection Te(IV) and Te(VI) A. García-Figueroa et al., Anal. Chem. 94 (2022), 13995-14003. ICP-MS/MS LOD: 2.3 pg L-1 VSG-ICP-MS/MS LOD: 0.07 ng L-1 A) selective VSG VSG → detection Te(IV) and Te(VI) C) Generation of substituted volatile species VSG → separation → detection VSG-CT-ICP/MS B) post-column VSG separation → VSG → detection HPLC-VSG-ICP/MS A) selective VSG VSG → detection Te(IV) and Te(VI) C) Generation of substituted volatile species VSG → separation → detection VSG-CT-ICP/MS B) post-column VSG separation → VSG → detection HPLC-VSG-ICP/MS CRYOGENIC SEPARATION • Cryogenic trap (CT) • U-tube immersed in liquid N2 • all species retained @ -196 °C • after heating the U-tube • species separated according to their b.p. trapping release/separation A. García-Figueroa et al., Talanta 225 (2021), 121972. Speciation analysis of Ge – method development • VSG → separation → detection iGe MMGe DMGe Speciation analysis of Ge – applications • VSG → separation → detection M. Filella, T. Matoušek, Appl. Geochem. 143 (2022), 105352. T. Matoušek et al., Anal. Chem. 89 (2017), 9633-9637. Speciation analysis of As – applications • VSG → separation → detection • in whole blood/plasma without extraction • 50-100 µl samples • LOD  pg ml-1 • normal levels of exposure iAs MMAs DMAs Generation of alkyl-/aryl-substituted volatile species • VSG → separation → detection • VSG from HCl and TRIS buffer media • cryogenic trap (CT) used for separation • Hg2+ → Hg0 • MeHg+ → MeHgH • EtHg+ → EtHgH • PhHg+ → PhHgH M. Migašová et al., Anal. Chim. Acta 1119 (2020), 68-76. • decomposition of substituted species during VSG step !!! • more pronounced in HCl than TRIS buffer media quantification of fraction decomposed to Hg0 (%) HCl TRIS MeHgH 41 6 EtHgH 77 28 PhHgH 94 99 M. Migašová et al., Anal. Chim. Acta 1119 (2020), 68-76. A) selective VSG VSG → detection Te(IV) and Te(VI) C) Generation of substituted volatile species VSG → separation → detection VSG-CT-ICP/MS B) post-column VSG separation → VSG → detection HPLC-VSG-ICP/MS Post-column VSG • separation → VSG → detection I. Petry-Podgórska et al., Microchem. J. 170 (2021), 106606. HPLC-ICP/MS HPLC-VSG-ICP/MS HPLC-VSG-ICP/MS mobile phase matrix elimination constant IS response increased ICP/MS sensitivity Post-column VSG: separation → VSG → detection Analytical figures of merit found for HPLC-ICP/MS and HPLC-VSG-ICP/MS HPLC-VSG-ICP/MS Sensitivity increased 30-40 times LOD improved 3-7 times I. Petry-Podgórska et al., Microchem. J. 170 (2021), 106606. VSG-based speciation analysis of Hg M. Migašová et al., Anal. Chim. Acta 1119 (2020), 68-76. I. Petry-Podgórska et al., Microchem. J. 170 (2021), 106606. post-column VSG reliable approach Generation of substituted VS analytical artifacts • VSG of non-hydride forming element – Cd • Novel hydride atomizers for AAS based on DBD plasma • VSG-based speciation analysis • VSG of mercury based on PMVG of Hg G. da Silva Coelho Junior et al., Spectrochim. Acta B, submitted. laboratory made DBD reactor laboratory made power supply source AAS detector QTA atomizer @ ambient temperature 150 mL min-1 He Samples – droplets (2 L) Hg2+ MeHg+ 38 kV, 23 W, 40 kHz, 60% duty cycle • PMVG efficiency quantified • Hg2+ 87 ± 8 % • MeHg+ 91 ± 10 % • both Hg species volatilized and atomized in the DBD reactor • sensitivity of PMVG comparable with CVG • LOD 200 pg Hg CONCLUSIONS • VSG of Cd • promising approach, 60% efficiency • novel DBD hydride atomizers • can compete with QTAs (As, Se, Te) • in-situ preconcentration feasible • VSG for speciation analysis • postcolumn VSG – reliable approach • generation of substituted VS – artifacts due to species decomposition (Hg) – reliable approach for As and Ge • PMVG of Hg • high introduction efficiency • good choice for volume-limited samples Barbora Baranová (Kodríková) Zuzana Kráľová Linda Sagapova Věra Schrenková Michaela Migašová Milan Svoboda Jiří Dědina Gilberto da Silva Coelho Junior Tomáš Matoušek Inga Petry-Podgórska Pavel Dvořák Martina Mrkvičková Jan Voráč Joachim Franzke Sebastian Burhenn Sebastian Brandt ACKNOWLEDGMENTS Institute of Analytical Chemistry of the CAS Department of Trace Element Analysis project 21 – 05285S RVO: 68081715 ACKNOWLEDGMENTS