Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry Chapter 4 Chromatography-Atomic Spectroscopy: Hyphenated Techniques Courtesy O.F.X. Donard

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/25/2006Chapter 4 Chromatography-Atomic Spectrometry Courtesy W. Cullen

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/25/2006Chapter 4 Chromatography-Atomic Spectrometry Speciation Analysis Determination of the concentrations of the individual physico-chemical forms of an element in a sample that together, constitute its total concentration

Speciation Analysis of Trace Elements in Environmental & Biological Systems Oxidation States e.g. As(III), As(V); Se(IV), Se(VI) Metal-Carbon Covalent Forms e.g. CH 3 Hg +, (CH 3 ) 3 AsCH 2 Coo - CH 3 AsO 3 H 2, and (CH 3 ) 2 AsO 2 H Speciation Analysis Physical Speciation e.g. particulate, colloidal and dissolved phases Complex Forces or Ionic Bonds e.g. Hg(OH) 2, HgCl 4 2- ; Others e.g. differentiation based on binding strength

Chemical cycling of organotin compounds in coastal and estuarine environments air-water interface water-sediment interface Bu p SnX 4-p Me n SnX 4-n Bu p SnMe 4-p Bu p SnX 4-p Bu p SnMe 4-p Me n SnX 4-n Me n SnH 4-n Bu p SnH 4-p tri- butyltin leaching Bu = butyl Me = methyl X = OH -, Cl -, R-S -, R-COO - n = 0,1,2,3,4 p = 0,1,2,3 inorgani c tin inputs Bu p SnH 4-p Me n SnH 4-n AIR WATER COLUMN SEDIMENT ? ? ? ? Courtesy O.F.X. Donard

MSMAAsO 4 3- DMA Degradation Methylation Degradation AdsorptionLeaching AsO 3 3- Reduction Adsorption Leaching Methylation ??? Soil Percolate water Note: Arrow size proportional to Importance of interaction A conceptual model showing arsenic transformation and transport after MSMA application in a Golf Green ® Y. CAI

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry Speciation? Why  Bioavailability and Toxicity  Biogeochemical cycling  Decontamination

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry Speciation? How Speciation of environmentally and biomedically important elements is a very challenging task: Two techniques are necessary:  One should provides efficient separation  The Other should provides adequate detection  The combination of these two parts is desirable  Generally, this is done by coupling either chromatography with a number of atomic spectrometry

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry

1GC-AS (atomic spectrometry) 1.1General considerations of GC-AS design  Sample transport  Atom cell design maximum sensitivity lowest possible detection limit High efficiency of the atomization Long residence time The graphite and more often the various type of quartz furnace have been used as atomizer in GC-AS system.

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry 1.2.Direct GC/AS 1.2.1Sample preparation  Volatile species (e.g. tetraalkyllead) Direct analysis  Ionic species Derivatization required

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry 1.2.2GC-quartz furnace AAS (QFAAS) detector

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry The sensitivity was enhanced about three orders of magnitude over that achieved with conventional flame AAS.

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry 1.3Purge and trap-GC/AS (PT-GC/AS) 1.3.1Design of the PT-GC/AS system Example 1 In situ derivatization Purge-trap-GC-AAS for Organotin and Organomercury speciation

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2004Chapter 4 Chromatography-Atomic Spectrometry Example 1 Derivatization Purge-trap-GC-AFS for organomercury speciation Step-1

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry Example 1 Derivatization Purge-trap-GC-AFS for organomercury speciation Step 2

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry Basic stages for Purge-Trap AS:  On-line (in situ) aqueous derivatization  Pre-concentration by cryofocusing or a trap  Chromatographic separation  Detection by AS

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry 1.4Derivatization methods (Cai, Elsevier Book chapter) 1.4.1Hydride generation with NaBH 4 Hydride generation has also proved to very efficient for the quantitative conversion of the organiometallic forms of Ge, Se, Sb, As, Sn, Pb(?), and Hg(?). RxSn (4-x)+ + NaBH RxSnH (4-x) + H 2 (n=1-3) MeHg + + NaBH MeHgH + 3H 2 + H 3 BO 3 + Na +

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry 1.4.2Ethylation with NaBEt 4 An important breakthrough in organometallic speciation was the use of Sodium tetraethylborate NaBEt 4. This reagent was first synthesized by Honeycutt et al. in 1961, and was introduced to speciation analysis by Rapsomanikis et al in MeHg + + NaBEt MeHgE t + BH 3 + Na + Hg NaBEt HgEt 2 + 2BH3 + 2Na + RxSn (4-x)+ + NaBEt RxSnEt (4-x) R: butyl, methyl X: 0, 1, 2, 3

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry

2.GC or LC-ICPMS GC and LC-ICPMS coupling techniques (especially the later one) are currently one of the most important analytical method for trace element speciation in environmental and bioinorganic chemistry.

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2006Chapter 4 Chromatography-Atomic Spectrometry GC-ICPMS:  Multi-element detection in a single run  Isotopic information  Solvent venting to prevent plasma instability is unnecessary  Coupling GC to ICP-MS is easily  Makeup gas is needed

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/25/2006Chapter 4 Chromatography-Atomic Spectrometry GC-ICPMS chromatogram of a 10 ppm as S standard for sulfur compounds normally found in gasoline. This work was modeled after that done by S.M. Wilbur and E. Soffey (Agilent Application Note) as well as B. Bouyssiere, et al. (JAAS 2004, ). The ICPMS is set to monitor the 32 and 34 isotopes of sulfur. Nitrogen is used as the optional gas to enhance sensitivity in the plasma. The Agilent 7500ce collision cell is used with helium to reduce the background.

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/25/2006Chapter 4 Chromatography-Atomic Spectrometry LC-ICPMS:

Advanced Analytical Chemistry – CHM 6157® Y. CAIFlorida International University Updated on 9/26/2004Chapter 4 Chromatography-Atomic Spectrometry