XThe

TRUTHabout sample 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_

Sampling_ 6%

Analysis_ 6%

Data analysis_ 27%

Sample prep_ 61%

Duration sample prep is often tedious and

time-consuming_

61%

6%

6%

27%

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%

30%

8%

8%

6%

7%

6%

4%11%

19%

What can we

do about 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.

SPE SPME SDME SBSE

Num

ber

of

pu

blic

ati

on

s

0.0

100,000.0

200,000.0

Example ScienceDirect @ Jan 2011_

x 10

180.000

80.000

12.000 10.000

Be vigilant…

vig·i·lant   ”vij-uh-luh nt”

1. keenly watchful to detect danger; wary 2. ever awake and alert; sleeplessly watchful

Classify on,

• Compound volatility_

• Polarity & reactivity_

• Intended concentration level_

1Know 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_

Know your target compounds_

2Know your matrix_

Classify on,

• 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 your techniques_

Combine information,

• 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