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QA/QC in Organic Matter ( Hydrocarbon ) Analysis. Why ?

QA/QC in Organic Matter ( Hydrocarbon ) Analysis. Why ? Millions of individual compounds with a wide range of chemical and physical properties

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QA/QC in Organic Matter ( Hydrocarbon ) Analysis. Why ?

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  1. QA/QC in Organic Matter (Hydrocarbon) Analysis. • Why? • Millions of individual compoundswith a widerangeof chemicalandphysicalproperties • Complexmixturessusceptibletophysicalandchemicalchange, e.g.- evaporation, precipitation, adsorption …- oxidation(O2 …), microbialtransformation, photochemistry … • Standard proceduresand computer-generatedanswersarefine … … but do not forgettouseyourbrainduringanalysisanddataevaluation

  2. Quality Assurance (QA) • (Sampling) • Appropriateanalyticalmethod(s) Sample preparation / Work-upprocedure Analysis • Validity of data Certified standards Round-robintests

  3. Quality Control (QC) • Analytical method(s)Procedural blank Matrix duplicate Instrument calibrationRecovery (usingspikes/internalstandards) Analytical precision / Reproducibility

  4. The Norwegian Industry Guide to Organic Geochemical Analyses The Analysis Guide contains: Minimum requirements Purpose, range of application, terminology Samples to be analyzed Procedural requirements Acceptance criteria and reference samples Reporting requirements Recommendations, information Recommendations and notes Key references Figures The Reporting Guide contains: General guidelines for reporting and digital data transfer. NIGOGA is an industry guide and not an official regulation or norm.

  5. Standard procedures! – Appropriate? – Think! Example: Drill cuttingspilewithlow-toxicitydrilling fluid (offshore) A) Total organic matter (TOM) by Loss-of-Ignitiontechnique: Drying at 50°C toconstantweight, thenburning at 450°C Error sources: Loss of volatile hydrocarbons (50°C) Evaporation of boundwater, carbonatedecomposition (450°C) B) Total hydrocarbons (THC) byextractionand gas chromatography (GC): Wetextraction, GC analysis, datareportednormalizedto dry sediment Error source: Loss of volatile hydrocarbonsduringdrying of sediment 6 - 8% 8 - 33%

  6. Correctassignment of targetcompounds ODP Hole 1018A offshore California Higher plant alkanes Coelution (lycopane) Petroleum alkanes Relative intensity Phytane Pristane Retention time (min)

  7. Coelution • n-C35alkanewithlycopane • Phytanewithcrocetane • Pristanewith C20highlybranchedalkane (HBI) Crocetane

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