Approaches to analysis of unusual and challenging ...
Transcript of Approaches to analysis of unusual and challenging ...
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Approachestoanalysisofunusualandchallengingformulationsamples
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WhatandWhy
• What makes a sample unusual or challenging?• Matrices? • Sub‐sampling & representative test portions• Chromatography?• Titrations‐ end‐point interference?• Unknowns and new active ingredients
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Typesofchallengingsamples
Matrix Chromatographyor
Analysis
New activesor
Unknown
Unusual samples
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ChallengingMatricesSOLIDS LIQUIDS Mousse or foam Aerosols Collars Shampoos Creams or gels Wipes on a roll Baits (wax or food based) Large tablets Dusts Foggers Non-uniform mixtures
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ApproachestosamplingHowtoobtainarepresentativetestportion
• Always read the product label carefully• Take container size into account• Use tools• Reduce sample size if necessary• Sample the entire product if necessary• Make sure that you have plenty!
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Samplingliquids>2.5gallons• Mix sample for at least 10 minutes
‐Motor driven rod & flange‐Magnetic stir plate & rod‐Rolling techniques
• Remove a sub‐sample while mixing‐tubing & syringe‐center of container
• Transfer to a storage jar with Teflon‐lined lid‐Inspect for floaters‐Is it a uniform sample?
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Samplingliquids<2.5gallons
• Equilibrate to room temperature• Mix by inversion 20 times• Withdraw test portion from center of sample with a disposable pipette
• Use long‐form pipettes for 1 gallon containers• Rinse neck of flask with extraction solvent• For non‐homogeneous samples take at least 3 sample weights
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Samplingaerosols• Read the label
Matrix information on internetClues about propellantSingle‐phase or multi‐phase
• Three units from the same lot number1‐ Off‐the‐Top2‐ Total exhaust3‐ Split sample for registrant
• Determine % propellantTotal exhaust, single‐phase only
• Expect to do more than once!
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Aerosoltesting• 1st can‐‐ Off the top sampling• 2nd can‐‐ Total exhaust sampling• 3rd can– Split to registrant
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Compressedairpropellant
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CarpetSpray
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AerosolSampling
• Remember to read the label!
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Samplingwipesonaroll
• Ask the registrant for their method• Do not include towel weight‐Weigh the sheets wet‐Extract multiple sheets‐Allow sheets to dry‐Subtract weight of dry sheet from sample weight
• Take sheets from various parts of the roll
• Consider active that may be bound to the towel
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Representativesub‐sample?
• Start of roll• Middle of roll• End of roll• Liquid content
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Samplingshampoos,gels&creams• Treat like a solidErlenmeyer, not volumetric flask
• Choose your solvent carefullyTHF is your secret weapon!Mixtures of solvents may be necessary
• Increase extraction timesUse a wrist‐action shakerUse bath or probe sonication to disperse
• Filter before chromatographyGlass fiber, nylon
• Lower the target concentration‐ use a curve
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Shampoo
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Insecticidemousse
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Samplingsolidproducts
• Flowable
1‐Beads2‐Baits3‐Granules4‐Grains5‐Pellets6‐Feeds7‐Fertilizers
• Non‐flowable
1‐Low densityDusts / powders
2‐Baits3‐Bar soap4‐Collars, tags & strips5‐Creams, gels & mousse6‐Tablets
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FOGGER
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FOGGERINSTRUCTIONS
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Subdivisionofsolidflowableproducts• 10lb‐50lb bag sizeCannot be mixedSlotted trier probe10 probes, diagonally across bag = sub‐sample
• <10lb bag & sub‐samples of larger productsSpinning or gated rifflerRandom selection of 3 portionsMix by tumble & roll
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ToolsforSubdivision
• Open golf tubeDusts and powdersSeal with parafilm
• Slotted trierInsert slot side DOWNTurn 180° & removePour into container
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Subdivisionofnon‐flowableproducts
• Cut into pieces, random selection for test portionCollars, tags & strips
• 10 plugs of cork borer, random selection for test portionWax bait, bar soap, soft tablet
• Grind with pestle & mortarSmall tablets, pellets
• Open golf tube for dustsTake multiple sample weights
• Hammer & plastic bag (low tech!)Large tablets
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Particlesizereduction
• Especially useful for non‐uniform mixtures• Do the minimum required‐ analyte stability• Oster food mill• Stein mill• Analytical mill (Retsch ZM1000)5mm pre‐grind, 0.75mm analytical screen
• Freeze samples with high fat or moisture content
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OsterFoodMill
• Good sample cup size• Cups ‐disposable orre‐usable
• Continuous or pulse speed settings
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SteinFoodMill
• Very heavy duty• Metal sample cup• Multiple speed settings
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Samplingofbaits• Variety of matricesGrain & / or grain in waxPeanut butter
• Grain based:‐Individual packets ‐ use random, multiple packetsLoose ‐ split the sampleRequire grinding ‐may be high moisture / high fat
• Grain in wax:‐Blocks or tablets ‐ use random, multiple blocks Require grinding ‐ wax can clog
• Peanut butter:‐Extract whole product in hot solvent & filterGet more than 1 packet from same lot
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Exhaustiveextraction
• Soxtherm automated extraction system• Sample is heated in solvent• Solvent is re‐circulated for optimal extraction• Allows use of larger volumes• Automatic solvent reduction• Great for: Collars, tags & strips (plastic)
Wax baits, gels & creams• Caution: analyte stability may be an issue
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Soxtherm
• Exhaustive extraction• Fully automated• Programmable• Solvent recovery• Solvent reduction• Reproducible• 0‐300°C
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ProblemAnalyses• Incompatible matrix and extraction solvent• Dirty solvent front (GC)• Co‐chromatography• Interference• Concentration effects‐multiple actives
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Quickfixesforpoorchromatography
• Change extraction solvent• Reduce target concentration‐Adjust curve accordingly
• Split injection (narrow bore vs. megabore)• Change columnDB‐225 is a good alternate for a DB‐1 or DB‐5
• Adjust mobile phasePolarity, flow rate, use a gradient
• Adjust inlet or column temperatureUse a gradient
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Shampoo
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Choosingagoodextractionsolvent
• Consult “The Pesticide Manual” for information on solubility
• Consult the method (especially for LC)• Select 4‐5 different solvents Try mixtures of acetone & THF, methanol & H2O
• Set up a series of disposable test tubes• Add several mLs of solvent to each tube• Add several drops of product to each tube
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Problemswithtitrations• Quaternary ammonium compounds by chloride equivalentCoulometric titrations using silver electrodes
• Some products foul the electrodesBlack tarnishing‐Clean electrodes with silver polish & repeat with fresh reagents
• Switch to testing by quaternary nitrogen equivalentTwo‐phase titration with bromophenol‐blue indicator
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End‐pointinterference• Colorimetric titration for quaternary nitrogenUpper phase changes from white to violet
• Quats & HClWe only test for HCl
• Quats & H3PO4Neutralize acid with 1.0N NaOH before titration
• Strong dyes give premature end pointsWe have no way to get around this
• Cream cleansers do not extract wellAbrasive component of matrix needs to be removed
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AbrasivecleanserswithChlorinol
• A.I.=Na dichloro‐s‐trazinetrione• Potentiometric titration of available chlorine
• Sample dissolved in potassium iodide and acidified with sulfuric
• Acid erupt & foamall over the bench top!
• Registrant method: acetic instead of sulfuric and a few mLs of butanol to stop the foaming
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Non‐uniformsolid
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NewActivesorunknowns• Trends in pesticide use• Targeting by pesticide program• Increase capability• Incidents or cases
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Tips…
• Read all product labels carefully• Spend time planning your experiment• Preliminary testing is a good thing• Document preliminary tests• Contact registrants for finished product methods• Ask company tech folks for help• Get to know your investigators/inspectors• Find out about your program