Presentation on theme: "Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC)"— Presentation transcript:
1Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC) Total Carbon (TC) =Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC)CalciteTOC preparation:~0.25 g dry, powdered sampleacidified in baked glass beaker with 1N 60 oC for hoursfiltered with de-ionized water to flush out Cl- onto a baked glass fiber filtertransferred to a crucible boat for drying and elemental analysis
2Trace elements coprecipitated minerals and soil organic matter (SOM) with secondary soilminerals and soil organic matter (SOM)Solid Coprecipitated trace elementsFe and Al oxides B, P, V, Mn, Ni, Cu, Zn, Mo, As, SeMn oxides P, Fe, Co, Ni, Zn, Mo, As, Se, PbCa carbonates P, V, Mn, Fe, Co, CdIllites B, V, Ni, Co, Cr, Cu, Zn, Mo, As, Se, PbSmectites B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, PbVermiculites Ti, Mn, FeOrganic matter Al, V, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, P, N
4X-ray fluorescence (XRF) The technology was developed in the 1950’s.
5X-ray fluorescence (XRF): The emission of characteristic "secondary", or fluorescent, X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays.
6Irradiating an atom with high-energy primary X-ray photons delivers sufficient energy for an electron to be ejected completely out of the atom.An outer shell L electron falls inward to fill the void created in the inner shell, and an X-ray characteristic of the atom's elements is emitted.
7X-ray fluorescence (XRF) spectrometers Schematic arrangement of wavelength dispersive spectrometer.Bragg’s Lawnλ= 2d * sinΘSchematic arrangement of energy dispersive spectrometerThe dispersion and detection are a single operation. Proportional counters or various types of solid state detectors (PIN diode, Si(Li), Ge(Li), Silicon Drift Detector SDD) are used.
8Schematic arrangement of a wavelength-dispersive (WD) X-ray fluorescence (XRF) spectrometer B.
9Various types of detectors most commonly gas flow proportional and scintillation are used to measure the intensity of the emitted beam on bench top models.Gas flow proportional counters are used mainly for detection of longer wavelengths (lighter elements). The gas is usually 90% argon, 10% methane ("P10"). The argon is ionized by incoming X-ray photons, and the electric field multiplies this charge into a measurable pulse. The methane suppresses the formation of fluorescent photons caused by recombination of the argon ions with stray electrons.Scintillation counters consist of a scintillating crystal (typically of sodium iodide doped with thallium) attached to a photomultiplier. The crystal must be protected with a relatively thick aluminum/beryllium foil window, which limits the use of the detector to wavelengths below 0.25 nm. Typically used for heavier elements.Scintillation - a flash of light produced in certain materials when they absorb ionizing radiation.B.A.
10Pressed Powder Disks/Pellets To obtain good XRF results using the pressed powder technique, control of particle size is absolutely critical.Used primarily for trace elements and uniform samples compositions.
11For Major Oxide Analysis Fused Glass DiskFor Major Oxide AnalysisLithium metaborate flux + sample in a 7:1 proportionFusion in Pt crucible> 750 oCFused glass disk fromgold or brass mould
12Resistance to Abrasion Sample PreparationTypical Composition of Grinding UnitsMaterialMajor ElementsMinor ElementsHardness (Mohs)Resistance to AbrasionDurabilityHardened SteelFeCr, Si, Mn, C5.5-6ModerateHighStainless SteelFe, CrNi, Mn, S, Si5-5.5Cr-free SteelC, Mn, Si, MoTungsten CarbideW, C, CoTa, Ti, Nb8.5 +Long-wearing, but brittleAlumina CeramicAlSi, Ca, Mg9Very HighAgateSiAl, Na, Fe, K, Ca, Mg8.5Extremely HighVery long-wearing, but brittleZirconiaZrHf, MgVery long-wearingSilicon NitrideY, Al, Fe, CaPlasticC--1.5LowLow, but disposableAvailable in the Department
13Trace Elements Zr Sr Rb Cr Nb Pb Ni Y Zn Co Major Oxides Cu W Mo Th Detection limit 2 ppm:Zr Sr Rb Cr NbPb Ni Y Zn CoDetection limit 5 ppm:Cu W Mo ThDetection limit 10 ppm:U VDetection limit 50 ppm:BaMajor OxidesDetection limit %:Al2O3 CaOFe2O3 K2OP2O5 Na2OMnO MgOTiO2 SiO2Loss On Ignition (LOI) is carried out at 1000oC. Removes volatiles including carbon, sulfur and nitrogen compounds, and structural and adsorbed water (H2O).Detection limit %:LOI wt.% = (sample weight - residue weight) * 100sample weight
14Laboratory Bench-top Models Field Hand-held Models
15Linear Regressions for Select Trace Elements using Standard Reference Materials (SRMs)