Sample Preparation and Results

Results  Mean, Median, Average  Deviation from the mean  Absolute and Relative Measures: Relative = Absolute/Mean Value  Precision  Accuracy

Precision and Accuracy True Value ●●●●●● ● ● ● ● ● ● ● ● ● ● ● ● ● High Precision High Accuracy High Precision Low Accuracy Low Precision Low Accuracy Low Precision High Accuracy X ‾ ‾ X ‾ X ‾ X

Methods Sensitivity – ability to discriminate between small differences in analyte concentration Signal Amount

Methods Detection Limit – minimum concentration or mass of analyte that can be detected at the known confidence level Signal have to be 5 times bigger than background noise

Methods Dynamic Range (D R) DRDR Signal Concentration

Analytical Process Systematic Error Random Error Standards, Blanks

Results Rounding Off (5 round to nearest even digit) Significant digits (Error of measurement)  0.1% x value  Accuracy of measurement steps – defines significant digits

Samples and Results Sampling Representative Representative Homogeneous (Particles Size) Homogeneous (Particles Size) Number of Samples – Error of measurement Number of Samples – Error of measurement

Sample preparation

Solid – Liquid Extraction Matrix, solvent and analyte Matrix, solvent and analyte Solubility of analyte Solubility of analyte Interaction between solvent and analyte Interaction between solvent and analyte

Soxhlet Extractor 1 – solvent flask 2 – extractor 3 – solvent collector 4 - condenser

Extraction Factors affecting extraction: Factors affecting extraction:  Interaction between solvent and analyte  Distribution coefficient: K D = (m i /V) Solvent /(m i /V) Matrix Where: m i – mass of analyte V – volume of solvent and matrix  Volume of solvent vs. multiple extraction

Multiple Extraction (Oilseed) Solvent Volume Amount extracted Extracted (%) Single extraction 100 mL 0.75 g 75 Multiple extraction 20 mL 0.70 g mL 0.26 g mL g mL g mL g 99.85

Extraction Factors affecting extraction:  Interaction between solvent and analyte  Distribution coefficient: K D = (m i /V) Solvent /(m i /V) Matrix Where: m i – mass of analyte and V – volume of solvent  Volume of solvent vs. multiple extraction  Particles size

Liquid-Liquid Extraction

Distillation - extraction

GC – Sample Extraction with Solvents Methylene Chloride Ethyl Ether Carbon Disulfide

SPME – Solid Phase Microextraction SPME - Fused silica fibres (1 to 2 cm long) coated with various polymeric phase Equilibrium forms between the three phases: Fibre coating to sample phase Fibre coating to sample phase Headspace to sample phase Headspace to sample phase Fibre coating to headspace Fibre coating to headspace

SPME – Solid Phase Microextraction

SPME Fibres The commercial polymeric phases available are: Polydimethylsiloxane(PDMS)Polydimethylsiloxane/divinylbenzene(PDMS/DVB) Polyacrylate (PA) Carbowax/divinylbenzene (CW/DVB) Polydimethylsiloxane/carboxen (PDMS/CAR) Polydimethylsiloxane/divinylbenzene/carboxen1006 (PDMS/DVB/CAR) Carbowax/Templated resin (CW/TPR)

SPME Adsorption and Desorption

SPE Solid Phase Extraction - Cartridges

Sample Preparation - SPE

GC – Derivatization with Silyl Reagents

END

Diagram of SPME Extraction Direct sampling SPME Headspace SPME

SPME - Adsorption