The truth about sample prep

TheXTRUTHaboutsample prep_Jvercammwww.is-x.be

Sample prep plays a vital role in virtually every analytical procedure_

Efficiency & of a measurement method are quality primarily determined by sample preparation_

Duration sample prep is often tedious and time- consuming_ Sampling_ 6% Analysis_ 6% Data analysis_ 27% Sample prep_ 61%

Error sources sample prep is prime contributor_ Contamination_ 4% Integration_ 6% Injection_ 6% Chromatography_ 7% Instrument_ 8% Calibration_ 8% Columns_ 11% Operator_ 19% Sample prep_ 30%

What can wedoabout it…?

Adagium the best prep is no prep_ What you want is what you get_ (Unfortunately) • Dilute-and-shoot_ • Generic methods_ • Less selective methods_

New hardware to address this issue_ Powerful black box mass spectrometers_ • Single quad and ion trap_ • Triple quad_ • Q/TOF, orbitrap_ • TOF/TOF

Reality check sample prep remains mandatory Selective detection does not tackle injection issues_ • GC/MS and inlet contamination_ • LC/MS and ion suppression_

Nobody likes sample prep…

Solutions are ubiquitous_ Scientific literature, discussion forums and application notes from manufacturers. Can you still find your way in this maze…?

Recycling is commonplace in analytical chemistry publications_ Unique and original publications are hard to find in the vast and continuously growing amount of data.

Example ScienceDirect @ Jan 2011_ 180.000 x 10 80.000 12.000 10.000

Be vigilant…vig·i·lant ”vij-uh-luh nt”1. keenly watchful to detect danger; wary2. ever awake and alert; sleeplessly watchful

1Know Classify on, your target compounds_ • Compound volatility_ • Polarity & reactivity_ • Intended concentration level_

Know your target compounds_ Compound volatility, • Permanent gases_ • Volatile compounds_ • Semi-volatile compounds_ • Non-volatile compounds_

Know your target compounds_ Polarity & reactivity, • Apolar • Semi-polar • Polar acidic • Polar basic

Know your target compounds_ Classify on concentration level, • percentage level_ • parts-per-million level_ • parts-per-billion level_ • parts-per-trillion level, 1 s in 32.000 year_

2Know Classify on, your matrix_ • Similarity to targets_ • Overall complexity_ • MW distribution_

Know your matrix_ Unsimilarity is the basis of clean-up, • Exploit orthogonality_ • Use normal phase_ • Ionisable at different pH_

Know your matrix_ Combined complexity & similarity, • Good chromatography_ • Heart-cut GC_ • Backflush_

Know your matrix_ High molecular weight interferences, • Matrix solid phase dispersion_ • Backflush_ • Gel permeation_

3Know Combine information, your techniques_ • Direct injection_ • Preconcentration_ • Extraction_ • Derivatisation_

Know your techniques_ Permanent gases with GC, • High levels, direct injection_ • Trace levels, air server_ • Complex matrix, chromatography_

Know your techniques_ Volatile components with GC, • High levels, static headspace_ • Trace levels, thermal desorption_ ITEX_ • Complex matrix, multiple headspace_ thermal extraction_ pyrolysis_ • Polar compounds, derivatisation_

Know your techniques_ Semi-volatile components with GC, • High levels, LLE, SPE • Trace levels, evaporate solvent_ MEPS_ • Complex matrix, clean-up_ • Polar compounds, derivatisation_ • High boilers, on-column injection_

Know your techniques_ Non-volatile components with LC, • GC is possible, derivatisation_ • High levels direct injection_ • Trace levels, SPE_ • Complex matrix, clean-up_ • Polarity, LC mode_

4Use smart calibration solutions_ Exploit the power of MS, • Isotope dilution analysis_ • Internal standards prior to prep_ • Surrogates prior to injection_ • Standard addition for complex matrices_

5Take your time & evaluate_ Developing a sample prep method is often challenging and quite frustrating. Immediate success is highly uncertain, even for experienced users.. Take your time and carefully assess all possibilities.

But what about sorption…?

Definition of sorptive extraction Family of miniature extraction techniques that use polydimethyl siloxane or polyacrylate as enrichment phase_

Applications of sorptive extraction Sorptive extractions are particularly popular in scientific literature. Applications include, • Headspace extraction_ • Direct extraction_ • In-situ derivatisation_ • Passive sampling_

Typical configurations Several techiques have been introduced, • solid phase microextraction_ • stir bar sorptive extraction_ • solid phase dynamic extraction_ • single drop microextraction_

Advantages of sorptive extraction Applied configurations are simple to use and eliminate extraction solvents. After sampling, trapped components are released by heat, without partial losses (sensitivity)_

Some remarks to take into account Sorptive extraction uses equilibrium extraction, • Takes some time to complete • Non-exhaustive extraction • Equilibrium depends on matrix Preserve for clean matrices !

Comparison fiber versus stir bar Use a mixed mode SPME fiber to attain sensitivities superior to SBSE, • Fully automated_ • In a fraction of time_

Concluding remarks

Don’t forget these things… • Nobody likes sample prep_ • Neglecting sample prep is riskful_ • Be vigilante_ • Know your business_ • Take your time_ Good luck !

Additional information Dr. Joeri Vercammen www.is-x.be j.vercammen@is-x.be

The truth about sample prep

by IS-X on Feb 10, 2011

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The truth about sample prep — Presentation Transcript