3M Empore™ Sample Preparation Made Easy Supelco Seminar Series, June 2011
Transcription
3M Empore™ Sample Preparation Made Easy Supelco Seminar Series, June 2011
3M Purification Inc. 3M Empore™ Sample Preparation Made Easy An Innovative Look at Using Empore™ for Solid Phase Extraction Supelco Seminar Series, June 2011 Jennifer Heitkamp, M.S. 3M Purification Inc. 1 3M Purification Inc. Introduction Empore™ membranes have been around for more than 20 years and used for thousands of applications. A proprietary process that entraps small absorbent particles into a matrix of PTFE fibrils that creates a mechanically stable membrane. Membrane format as disks, cartridges, or 96-well plates The membrane has a high exposed surface area of active particles. This characteristic property makes the membrane extremely useful for many applications that may not be typical in many laboratories. Examples of ways that the Empore™ membrane format has been used to prepare samples of large volumes used in environmental analysis to very small volumes used in drug discovery. 2 3M Purification Inc. Empore™ Products History 1970’s and 1980’s Early 1990’s Polypropylene Extraction Disk Plates Rad Disks 1999 SDB-based sorbents EPA approvals granted Extraction Disk Cartridges for biological extractions Prefilter for disk cartridges 1997 TLC membranes First products were designed for environmental extractions 1992-1996 Started out as an idea to immobilize molecular sieves to dry organic solvents Filter Plate Field Sampling Products 2001 Universal Resin Plate 3 © 3M 2011. All Rights Reserved. 3M Purification Inc. 3M Empore™ Solid Phase Extraction Membranes What is Empore ? SPE Particle-loaded membrane Sorbent particles tightly held together within an inert matrix of polytetrafluoroethylene (PTFE) 90% sorbent, 10% PTFE (by weight) Resin Particles Silica Particles Features of Empore ™ membranes Benefits Sorbent particles tightly enmeshed in PTFE Eliminates particle fines that plug frits Dense particle packing with no void space & uniform particle distribution High separation efficiency Thin membrane, small bed volume Can filter large volumes (typically up to 4 L of sample with 47 mm discs with pre-filtration) 4 © 3M 2011. All Rights Reserved. 3M Purification Inc. How Does Empore™ Membrane Work? Empore membrane is a thin membrane based chromatography. Extraction/separation, purification and concentration of analytes from an aqueous sample. It may look like a filter but filters are only capable of capturing particles. Empore membrane is capable of capturing analytes and releasing them for analysis. 5 © 3M 2011. All Rights Reserved. 3M Purification Inc. EmporeTM Extraction Kinetics Independent of sample flow rate Extraction of dye at 700 mL/minute 6 © 3M 2011. All Rights Reserved. 3M Purification Inc. Traditional SPE Methods for Sample Preparation Disk extraction methods Water (multiple EPA methods for monitoring drinking water) Maple Syrup (quantify lead) Animal Urine (Isolate large quantities of metabolites for future studies) Cartridge extraction methods Small elution volumes reduce the need for solvent evaporation step 96-well plate extraction methods UR plate for clean up of human serum samples for drug and metabolite quantification 7 © 3M 2011. All Rights Reserved. 3M Purification Inc. EPA Water Extraction Methods C8 Bonded Silica C18 Bonded Silica 8 EPA Method 529 Explosives Residues Anion Exchange EPA Method 515.2 Chlorinated Acids EPA Method 526 Semivolatile Organic Compounds EPA Method 527 Pesticides and Flame Retardants SDB-RPS Polystyrenedivinylbenzene Reverse Phase Sulfonated EPA Method 506 Phthalate & Adipate Esters EPA Method 508.1 Chlorinated Pesticides, Herbicides, & Organohalides EPA Method 525.2 Organic Compounds EPA Method 550.1 Polynuclear Aromatic Hydrocarbons EPA Method 608 ATP 3M0222 Organochlorine Pesticides and PCB’s EPA Method 1613B Dioxins and Furans SDB-XC Polystyrenedivinylbenzene EPA Method 549.1 Diquat and Paraquat EPA Method 548.1 Endothall EPA Method 552.1 Haloacetic Acids and Dalapon Oil & Grease EPA Method 1664 Rev. A n-Hexane Extractable Materials 3M Purification Inc. Cartridge Elution Volume Comparison Traditional 100 mg/1 ml cartridge 4 mm /1 ml EmporeTM Disk Cartridge More concentrated Enhanced sensitivity Time savings 9 © 3M 2011. All Rights Reserved. 3M Purification Inc. LC/MS/MS Quantitation of Parent Drug, Desethyl Metabolite, 3-OH Metabolite, and 4-OH Metabolite in Human Serum Using Empore™ 96-Well Universal Resin (UR) Plate 10 Universal resin is a terpolymer based on styrenedivinylbenzene Designed to provide good retention of a wide range of analytes during solid phase extraction of hydrophilic (acidic or basic) and moderately hydrophobic analytes Designed for processing 96 samples simultaneously Collar around plate tip helps prevent contamination from sample to sample during processing Method development time is saved by eliminating the need to screen a variety of sorbents. Each well contains a proprietary prefilter to enhance sample flow Thin bed mass of the disk allows for minimized solvent and sample volumes High sample throughput Small elution volumes Ability to eliminate the evaporation step Sample processing at maximal flow rates without channeling © 3M 2011. All Rights Reserved. 3M Purification Inc. Method Description Bioanalytical method to quantitate a drug and 3 metabolites in human serum. Sample preparation dilution with buffer addition of internal standard (IS) clean-up using a Universal Resin Empore Extraction Disk Plate Analysis Agilent® HPLC system C18 column Sciex API 4000 triple-quadrupole mass spectrometer operated under positive-ion mode using a Turbo V™ electrospray interface. The linear range for quantitation of drug and metabolites was 0.0500 to 25.0 ng/mL Sample 0.100-mL human serum 11 3M Purification Inc. Sample Preparation Aliquot the samples (0.100 mL) Add 300 µL of 0.1 M TRIS (Base) Add 50.0 µL methanol Add 50.0 µL IS Spiking Solution Cover and vortex for 1 minute 12 3M Purification Inc. SPE Extraction A Speedisk® pressure processor was used with a Universal Resin Empore™ 96-well extraction disk plate Condition with 250 µL of methanol Condition with 250 µL of water Transfer the entire sample to pre-defined wells on the extraction plate Wash with 500 µL of water Wash with 200 µL of 20% methanol in water Elute the samples with 200 µL of 1% formic acid in methanol Remove the solvent with a stream of nitrogen gas at 35 °C Add 200 µL of reconstitution solution to each sample well Cover the 96-well plate with a cap mat and vortex. Analyze by LC\MS\MS. 13 3M Purification Inc. LLOQ Sample Chromatograms of Parent Drug (Top Left), Desethyl Metabolite (Top Right), and IS (Bottom) Int. Type: Retention Time: Area: Height: Start Time: End Time: No 1 15.00 75.00 1 30.0 3.90 0.20 0.01 5.00 4.00 3.00 No 2800 2600 cps cps 2400 sec min 2200 2000 Base To Base 3.88 min 12569 counts 3300. cps 3.79 min 4.01 min Intensity, cps Modified: Bunching Factor: Noise Threshold: Area Threshold: Num. Smooths: RT Window: Expected RT: Sep. Width: Sep. Height: Exp. Peak Ratio: Exp. Adj. Ratio: Exp. Val. Ratio: Use Relative RT: Sample Name: "3 025 9196.93 Validation LLOQ 0.050 1 1" Sample ID: "25" Peak Name: "S28371" Mass(es): "287.0/197.0 amu" Comment: "none" Annotation: "" Sample Index: 25 Sample Type: QC 1370 Concentration: 0.0500 ng/mL Calculated Conc: 0.0515 ng/mL 1300 Acq. Date: 03/03/04 Acq. Time: 08:48:53 PM 1200 Modified: No Bunching Factor: 1 1100 Noise Threshold: 15.00 cps Area Threshold: 75.00 cps 1000 Num. Smooths: 1 RT Window: 30.0 sec Expected RT: 2.81 min 900 Sep. Width: 0.20 Sep. Height: 0.01 Exp. Peak Ratio: 5.00 800 Exp. Adj. Ratio: 4.00 Exp. Val. Ratio: 3.00 700 Use Relative RT: No 1800 1600 Int. Type: Retention Time: Area: Height: Start Time: End Time: 1400 1200 1000 Base To Base 2.80 min 3048 counts 945. cps 2.73 min 2.88 min Intensity, cps Sample Name: "3 031 9196.93 Validation LQC 0.150 1 1" Sample ID: "31" File: "9196-93-Validation-Batch-03.wiff" Peak Name: "R848" Mass(es): "315.0/197.0 amu" Comment: "none" Annotation: "" Sample Index: 31 3.88 Sample Type: QC 3313 Concentration: 0.150 ng/mL 3200 Calculated Conc: 0.157 ng/mL Acq. Date: 03/03/04 3000 Acq. Time: 09:33:16 PM File: "9196-93-Validation-Batch-03.wiff" 600 500 400 800 300 600 200 400 0 100 3.68 3.76 3.7 3.8 Sample Name: "3 031 9196.93 Validation LQC 0.150 1 1" Sample ID: "31" Peak Name: "S-28645" Mass(es): "275.0/203.0 amu" Comment: "none" Annotation: "" Sample Index: 31 Sample Type: QC 3.3e5 Concentration: 1.00 ng/mL 3.2e5 Calculated Conc: N/A Modified: Bunching Factor: Noise Threshold: Area Threshold: Num. Smooths: RT Window: Expected RT: Sep. Width: Sep. Height: Exp. Peak Ratio: Exp. Adj. Ratio: Exp. Val. Ratio: Use Relative RT: 03/03/04 09:33:16 PM No 1 10.00 50.00 1 30.0 3.32 0.20 0.01 5.00 4.00 3.00 No 3.9 4.0 4.1 4.2 4.3 4.4 Time, min File: "9196-93-Validation-Batch-03.wiff" 4.52 4.62 4.71 4.84 4.5 4.6 4.7 4.8 4.89 4.96 0 4.9 3.32 2.8e5 2.6e5 cps cps 2.4e5 sec min Int. Type: Base To Base Retention Time: 3.32 min Area: 839580 counts Height: 333000. cps Start Time: 3.27 min End Time: 3.47 min 2.2e5 2.0e5 1.8e5 1.6e5 Int. Type: Base To Base Retention Time: 3.32 min Area: 858058 counts Height: 346000. cps Start Time: 3.26 min End Time: 3.50 min 1.4e5 1.2e5 1.0e5 14 2.5 3.0 3.5 3.32 1.4e5 1.2e5 1.0e5 8.0e4 6.0e4 6.0e4 4.0e4 4.0e4 2.0e4 1.0 1.5 2.0 Time, min File: "9196-93-Validation-Batch-03.wiff" 1.6e5 8.0e4 0.0 0.5 Sample Name: "3 025 9196.93 Validation LLOQ 0.050 1 1" Sample ID: "25" Peak Name: "S-28645" Mass(es): "275.0/203.0 amu" Comment: "none" Annotation: "" Sample Index: 25 Sample Type: QC 3.4e5 Concentration: 1.00 ng/mL Calculated Conc: N/A 3.2e5 Acq. Date: 03/03/04 Acq. Time: 08:48:53 PM 3.0e5 Modified: No Bunching Factor: 1 2.8e5 Noise Threshold: 10.00 cps Area Threshold: 50.00 cps 2.6e5 Num. Smooths: 1 RT Window: 30.0 sec 2.4e5 Expected RT: 3.32 min Sep. Width: 0.20 2.2e5 Sep. Height: 0.01 Exp. Peak Ratio: 5.00 2.0e5 Exp. Adj. Ratio: 4.00 Exp. Val. Ratio: 3.00 1.8e5 Use Relative RT: No 3.0e5 Intensity, cps Acq. Date: Acq. Time: 4.06 4.13 4.22 4.30 4.39 Intensity, cps 200 2.0e4 0.5 1.0 1.5 2.0 Time, min 2.5 3.0 3.5 0.0 0.5 1.0 1.58 1.5 2.0 Time, min 2.65 2.5 3.07 3.0 3.5 3M Purification Inc. LLOQ Sample Chromatograms of 3-OH Metabolite (Top Left), 4-OH Metabolite (Top Right), and IS (Bottom) Int. Type: Retention Time: Area: Height: Start Time: End Time: Acq. Date: Acq. Time: Yes 1 40.00 100.00 1 10.0 3.89 0.20 0.01 5.00 4.00 3.00 No 550 cps cps 500 sec min 450 Base To Base 3.87 min 1846 counts 495. cps 3.81 min 3.94 min Modified: Bunching Factor: Noise Threshold: Area Threshold: Num. Smooths: RT Window: Expected RT: Sep. Width: Sep. Height: Exp. Peak Ratio: Exp. Adj. Ratio: Exp. Val. Ratio: Use Relative RT: 400 350 300 Int. Type: Retention Time: Area: Height: Start Time: End Time: 250 200 500 cps cps 450 sec min Base To Base 4.08 min 2227 counts 574. cps 3.99 min 4.16 min 400 350 300 250 200 100 100 50 50 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 Time, min File: "9196-93-Validation-Batch-03.wiff" 4.6 4.7 4.8 0 4.9 1.6e5 Int. Type: Base To Base Retention Time: 3.32 min Area: 858058 counts Height: 346000. cps Start Time: 3.26 min End Time: 3.50 min 1.4e5 1.2e5 1.0e5 3.8 4.6 4.7 4.8 4.9 3.32 1.4e5 1.2e5 1.0e5 8.0e4 6.0e4 6.0e4 4.0e4 4.0e4 2.0e4 3.9 4.0 4.1 4.2 4.3 4.4 4.5 Time, min File: "9196-93-Validation-Batch-03.wiff" 1.6e5 8.0e4 0.0 3.7 Sample Name: "3 025 9196.93 Validation LLOQ 0.050 1 1" Sample ID: "25" Peak Name: "S-28645" Mass(es): "275.0/203.0 amu" Comment: "none" Annotation: "" Sample Index: 25 Sample Type: QC 3.4e5 Concentration: 1.00 ng/mL Calculated Conc: N/A 3.2e5 Acq. Date: 03/03/04 Acq. Time: 08:48:53 PM 3.0e5 Modified: No Bunching Factor: 1 2.8e5 Noise Threshold: 10.00 cps Area Threshold: 50.00 cps 2.6e5 Num. Smooths: 1 RT Window: 30.0 sec 2.4e5 Expected RT: 3.32 min Sep. Width: 0.20 2.2e5 Sep. Height: 0.01 Exp. Peak Ratio: 5.00 2.0e5 Exp. Adj. Ratio: 4.00 Exp. Val. Ratio: 3.00 1.8e5 Use Relative RT: No 3.32 File: "9196-93-Validation-Batch-03.wiff" 550 150 Sample Name: "3 025 9196.93 Validation LLOQ 0.050 1 1" Sample ID: "25" Peak Name: "S-28645" Mass(es): "275.0/203.0 amu" Comment: "none" Annotation: "" Sample Index: 25 Sample Type: QC 3.4e5 Concentration: 1.00 ng/mL Calculated Conc: N/A 3.2e5 Acq. Date: 03/03/04 Acq. Time: 08:48:53 PM 3.0e5 Modified: No Bunching Factor: 1 2.8e5 Noise Threshold: 10.00 cps Area Threshold: 50.00 cps 2.6e5 Num. Smooths: 1 RT Window: 30.0 sec 2.4e5 Expected RT: 3.32 min Sep. Width: 0.20 2.2e5 Sep. Height: 0.01 Exp. Peak Ratio: 5.00 2.0e5 Exp. Adj. Ratio: 4.00 Exp. Val. Ratio: 3.00 1.8e5 Use Relative RT: No Intensity, cps No 1 20.00 150.00 2 30.0 4.12 0.20 0.01 5.00 4.00 3.00 No 150 0 Int. Type: Base To Base Retention Time: 3.32 min Area: 858058 counts Height: 346000. cps Start Time: 3.26 min End Time: 3.50 min 03/03/04 08:48:53 PM Intensity, cps Modified: Bunching Factor: Noise Threshold: Area Threshold: Num. Smooths: RT Window: Expected RT: Sep. Width: Sep. Height: Exp. Peak Ratio: Exp. Adj. Ratio: Exp. Val. Ratio: Use Relative RT: Sample Name: "3 025 9196.93 Validation LLOQ 0.050 1 1" Sample ID: "25" Peak Name: "S32899" Mass(es): "331.0/213.0 amu,331.0/267.0 amu" Comment: "none" Annotation: "" Sample Index: 25 Sample Type: QC 622 Concentration: 0.0500 ng/mL 600 Calculated Conc: 0.0530 ng/mL 08:48:53 PM Intensity, cps Acq. Time: File: "9196-93-Validation-Batch-03.wiff" Intensity, cps Sample Name: "3 025 9196.93 Validation LLOQ 0.050 1 1" Sample ID: "25" Peak Name: "S32483" Mass(es): "331.0/267.0 amu,331.0/213.0 amu" Comment: "none" Annotation: "" Sample Index: 25 Sample Type: QC 642 Concentration: 0.0500 ng/mL Calculated Conc: 0.0451 ng/mL 600 Acq. Date: 03/03/04 2.0e4 0.23 0.31 15 © 3M 2011. All Rights Reserved. 0.60 0.5 1.03 1.19 1.0 1.58 1.72 2.12 1.5 2.0 Time, min 2.50 2.65 2.97 3.07 2.5 3.0 3.5 0.0 0.23 0.31 0.60 0.5 1.03 1.19 1.0 1.58 1.72 2.12 1.5 2.0 Time, min 2.50 2.65 2.97 3.07 2.5 3.0 3.5 3M Purification Inc. E xamp le Cali brati on Cu rves 2.00 Pa re n t D ru g 1.80 1.60 1.40 De s e th y l 1.20 M e ta b o il te 1.00 4 -O H 3 -O H 0.80 0.60 0.40 0.20 0.00 0. 0 5.0 10. 0 15.0 N o m i na l C o nc en t r at i o n ( ng / m L ) 16 © 3M 2011. All Rights Reserved. 20.0 25. 0 3M Purification Inc. Method Validation Parameters Accuracy and Precision Response Linearity Specificity and Interference Sample Dilution Analysis Freeze/Thaw Sample Stability Room Temperature Processed Sample Stability 24-Hour Room Temperature Matrix Stability Short and Long Term Matrix Storage Stability (-20 °C) 17 3M Purification Inc. Non-Traditional Uses for Empore Disks Sorbent material for passive sampling device Capture of volatile compounds from air Construction of small-volume protein purification extraction columns (StageTips) Layering of different sorbent phases 18 © 3M 2011. All Rights Reserved. 3M Purification Inc. Passive Sampling Devices - Chemcatcher™ Importance of representative samples Body of holder made of PTFE Constructed to hold an Empore™ disk Permeable membrane covers the Empore disk to prevent fouling of the sorbent material Measures time weighted average (TWA) of pollutants in water Deployment time from days to months depending on the goal of the experiment 19 © 3M 2011. All Rights Reserved. 3M Purification Inc. Researchers using the Chemcatcher™ Passive Sampling Device for Water Contaminants United Kingdom Australia Spain Germany Sweden South Africa Switzerland Slovakia The Netherlands 20 © 3M 2011. All Rights Reserved. 3M Purification Inc. Why Use Passive Sampling? Very low level pollutants can be missed Discrete water samples give a snapshot of concentrations Very low levels require large volumes of water sample Transportation Storage Can miss episodic pollution events Contaminant concentrations in surface water vary over time due to weather events Extractions from organisms to monitor bioaccumulation can be complex Extraction from sediment assumes that the levels in the water and sediment are in equilibrium 21 3M Purification Inc. Considerations Physical Chemical properties of analytes will dictate the absorptive material Organophosphate pesticides Non-polar organic compounds PAH’s Organometallic complexes Metal ions Pharmaceuticals and personal care products Water turbulence Water quality High particulate material Salt content Biofouling potential Permeability reference compounds (QC) Accumulation time frame 22 3M Purification Inc. Passive Sampling Device Development - Milestones inorganic organic Total number of publictions per year 60 1- first passive sampler for organic micro pollutants in water 2- first publication of semi-permeable membrane device 3- detection of compounds in water at pg/L 4- first publication on Chemcatcher™ 50 40 30 20 10 11 23 2 3 4 Vrana, B., Mills, G.A., Allan, I.J., Dominiak, E., Svensson, K., Knutsson, J., Morrison, G., Greenwood, R. Trends Anal. Chem. 2005(24), pp. 845-868 04 20 03 20 02 20 20 01 00 20 99 19 98 19 97 19 96 19 95 19 94 19 93 19 92 19 91 19 90 19 89 19 19 19 87 88 0 3M Purification Inc. Air Sampling with Empore™ Why is air sampling important? Identify and quantify health hazards Correct problems with unhealthy air Compounds Pesticides Volatile and semi-volatile organophosphate esters Explosive residues Chemical warfare agents Why use Empore disks? 24 Higher air flow than cartridges (up to 20 L/min) Small particles give high sample capacity Active sorbent particles retain absorbed compounds during sample collection and store easily High extraction recoveries Higher stability of compounds stored on disks 3M Purification Inc. Empore™ Disk as Sorbent for Air Borne Pyrethroid Insecticides Some affect humans' central nervous system or have endocrinedisrupting effects 18 pyrethroids chosen based on use in Japanese homes as insecticides Samples collected by pumping air through a glass fiber disk and an Empore™ C18FF disk Collection device shielded from light to prevent photodegradation Sample collected for 24 hours at a flow rate of 3.0 L/min. Total volume of air through the absorbents was 4.32 m³ Disks removed form collector and placed together in sealed tube for storage at 4 °C until analysis 25 Yoshida, T. "Simultaneous Determination of 18 Pyrethroids in Indoor Air by Gas Chromatography/Mass Spectrometry." Journal of Chromatography A. 1216 (2009) 5069-5076 3M Purification Inc. Experimental Method Validation Parameters Retention and breakthrough of compounds during sampling tested Retention efficiency >93% Breakthrough <0.2% Efficiency of extraction of pyrethroids tested Desorption efficiencies >91% for spikes at 5 and 0.5 µg/compound Detection limits 0.4 - 1.7 ng/m³ Precision and accuracy RSD <10% Accuracy range of 35 ng/m³ to 1.3 µg/m³ Storage stabilities at 4 °C on disks 26 Up to 1 month storage showed no degradation if kept shielded from light 3M Purification Inc. Airborne Pyrethroid Concentrations Found Formulation Mothproof repellent for clothes Mosquito Repellents used with electrical devices Sample # Compound Concentration (µg/m³) 1 2 Empenthrin Profluthrin 2.3 1.0 3 4 5 6 7 8 9 Prallethrin Furamethrin Allethrin Furamethrin Transflthrin Parallethrin Metofluthrin Daytime Nighttime 34 39 148 5.0 12 69 0.24 17 24 122 4.1 9.3 23 0.15 ACGIH recommended threshold limit (8-hour workday and 40-hour workweek) for Pyrethrum at 5 mg/ m³ 27 3M Purification Inc. Preparation of Single-Disk Stop and Go Extraction Tips (StageTips) Empore™ 47 mm disk for various functionality 28 C18 C8 Cation exchange Anion exchange SDB-XC Self-made tool for customization Ease-of-use Good recovery Reproducible and robust Rappsilber, J., Mann, M., and Ishihama, Y. “Protocol for Micro-purification, Enrichment, Pre-fractionation and Storage of Peptides for Proteomics using StageTips.” Nature Protocols 2, 1896-1906 (2007) Published online: 2 August 2007 3M Purification Inc. StageTips Preparation Small disk is stamped out using a blunt-ended syringe needle (cutter) Particles held together for easy handling Size of disk adjusted by using different gauge needle Place the cutter inside a pipette tip and release the disk using a correct size needle plunger Press the disk gently into place using the plunger Remove cutter Additional disks can be layered to provide multiple functionality 29 3M Purification Inc. Stage Tip Preparation 30 3M Purification Inc. Multiple Layers for Additional Separating Ability C18 allows for desalting of the protein Fractionation done on the cation exchange disk. Can be followed up by another desalting step with C18 Very clean sample for mass spec analysis Ishihama, Y., Rappsilber, J., and Mann, M., “Modular Stop and Go Extraction Tips with Stacked disks for Parallel and Multidimensional Peptide Fractionation in Proteomics.” J. Proteome Res., 2006, 5 (4), pp 988–994 Publication Date (Web): March 07, 2006 (Technical Note) 31 C18 SCX 3M Purification Inc. In Summary PTFE fibrils immobilized particle provide a unique medium for SPE Disk shape allows for mounting in a variety of configurations and sample holders Can be layered to combine functionality Can be cut to fit desired holder Enhanced chemical stability of Empore™-adsorbed compounds during storage Next new idea ? 32