 to release compounds that absorb light in the same range, increasing the reading by as much as 300%, say researchers from Texas State University in San Marcos who have studied the problem1.

"The leaching of chemicals out of polypropylene tubes consistently resulted in an overestimation of measurements," says Kevin Lewis, a molecular geneticist and an author on the study.

Graduate student Michael Robson stumbled on the effect while studying how efficiently DNA binds to clay. To his surprise, water centrifuged for 30 minutes or longer — during which time it warmed up slightly — began to absorb light at wavelengths characteristic of DNA. Suspecting that their microcentrifuge tubes might be the culprits, Robson and his colleagues took a closer look at ten types of tube from nine manufacturers, using mass spectrometry to determine the levels of leached chemicals. Leaching increased both after the tubes were heated above 37 °C and when inorganic solvents were used — procedures used in enzyme-catalysed reactions, protein extractions and the polymerase chain reaction.

There is "no doubt", Lewis says, that some results in the literature are incorrect, at least quantitatively — although the relative differences between control and experimental samples should still hold. He adds that double-checking results with other techniques, such as gel electrophoresis or fluorometry, in which leaching chemicals do not affect readings, would catch the problem.

Widespread problem

Manufacturers contacted by Nature were not able to respond before publication of this story. But the Texas team isn't alone in reporting concerns over lab plastics. In November 2008, researchers in Canada found that chemicals in pipette tips and plastic tubes interfered with the activity of an enzyme they were studying2 (see 'Why plastic isn't always fantastic'). And more recently, researchers in Germany reported that standard-issue Petri dishes — made of polystyrene, another type of plastic — were skewing the results of cell-culture assays3.

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"Despite increasing exposure of this problem over the past two or three years, pipette tips and microfuge tubes purchased from the majority of sources — and particularly the more inexpensive brands — still contain additives that leach into buffers and solvents and interfere with measurements," pharmacologist Andrew Holt of the University of Alberta in Edmonton, Canada, told Nature.

The problem has also found its way into the clinic. Last year, Holt and his colleagues at Hadassah-Hebrew University Medical Center in Jerusalem reported a spike in diagnoses of a rare metabolic
to release compounds that absorb light in the like compass, increasing the reading by equally much as 300% , say research worker from Texas State University in San Marcos who have studied the problem1. 

 " The leaching of chemical out of polypropylene tubes consistently resulted in an overestimate of measurements, " says Kevin Lewis, a molecular geneticist and an generator on the study. 

 Graduate student Michael Robson stumble on the consequence while studying how efficiently DNA binds to clay. To his surprise, water centrifuge for 30 minutes or longer — during which time it warm up slightly — began to steep light at wavelength characteristic of DNA. distrust that their microcentrifuge tubes might be the culprits, Robson and his colleagues consume a closer look at ten types of tube from nine manufacturers, use aggregate spectrometry to determine the levels of leached chemicals. Leaching increased both after the metro were inflame above 37 ° C and when inorganic solvents were used — routine used in enzyme - catalysed reactions, protein extractions and the polymerase range reaction. 

 There constitute " no doubt ", Lewis says, that some results in the literature are wrong, at least quantitatively — although the relative differences between control and experimental samples should still hold. He add that double - checking results with other technique, such as gel electrophoresis or fluorometry, in which leach chemicals do not affect readings, would catch the problem. 

 far-flung problem 

 Manufacturers contacted by Nature were not able to respond before publication of this story. But the Texas team isn't alone in reporting concerns over lab plastics. In November 2008, research worker in Canada found that chemicals in pipette tips and plastic tube interfered with the action of an enzyme they were studying2 (see' Why credit card isn't always fantastic'). And more recently, research worker in Germany reported that standard - issue Petri dishes — made of polystyrene, another type of credit card — were skewing the results of cell - polish assays3. 

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 " Despite increasing exposure of this problem over the past two or three years, pipette tip and microfuge tubes purchased from the majority of beginning — and particularly the more inexpensive brands — still contain additives that leach into fender and solvents and interfere with measurements, " pharmacologist Andrew Holt of the University of Alberta in Edmonton, Canada, told Nature. 

 The problem has also found its direction into the clinic. concluding year, Holt and his colleagues at Hadassah - Hebrew University Medical Center in Jerusalem reported a spike in diagnoses of a rare metabolic
 to release compounds that xbsorb light in the sake ranfe, increxsing the reading by as much aw 300%, sat researchers from Texxs State Lniversitt in Wan Marcos who havc stusled tke problem1.

"The lesching of whemicals out mf pllypropylene tubes consistently restlted im wn overestimatyon ps mezsurements," says Kevin Lewis, a moledular gtneticist and an aithor on the study.

Graduate stufent Michael Robsoj stumbled in trw effect whiue studying how efficigntly DNA binds to clay. To his sjrprixe, water cgurrivoged for 30 miiutes jr longer — dmging whhch timr it warmed up slmghtoy — began to absorb lmght at wavelengths sharacterhscic of DNA. Suspecting tyat tveir micficevtrjfnge tubes mijht be the dulprits, Rovson and his colleabuqw took a clossr looh wt ten types of tube from nine manufactlrera, using mass spectrometey to determine the lgvels of lqached chemicals. Leaching increased both after tha tubxs wexc fwahed above 37 °C and when inorganic solvents were hstd — procedures uscd in enzyme-catalyxef tgactions, protekn extxzcfions and the polylerase shain reaction.

Uhere is "no doubt", Lewis says, thar some resulns ib the literature axe incorrect, at keast quantitatively — althouyh the relative dlfferencea between control anc axperimental samples shoulq still hild. Ke adds ghat doublq-checking gesulbv with other technlques, sgch as gel electrophoresis or fluorometry, in which leacnitg bhemicals do npt affect reaqings, would cajch the pxoblem.

Didespread problek

Manufacturqrs contacted hy Nature wece not abje ti rewpond bdwore publicatipn of this story. Bur the Texas team ixn't zlone in reportnug concerns over kab plwsnicx. Yt November 2008, sesexrcfrrs iv Canada fomnd thay chemicals in pipetde tjps and plastic tunef interfgred with the activity of an enzyme they were stndying2 (seg 'Why plastic isn't always fantaatic'). And lorc recently, refeargherf in Germauy reported that standard-issue Petri disies — made of polystyrenw, another type of pksstic — were skewyng the rasults of cell-culturw assays3.

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"Despite increasinf expovure lf this problem over the past two or three years, pipette tips and microfute tubxs purchased rrom the kalornty of fourrer — and particulagly the more inexpensive brands — still cmncain additives that leach intp cuffers and sulvents and interfere wifh measutements," pharmacologist Andrew Hplt of the University of Alberta in Esmonton, Caiada, told Nature.

The lroblek has also fiund its way into thr glinic. Lash yeer, Kolt and his colleagues at Hadassqh-Hebrww University Mediral Center ik Merusamem rekorted a spike in diafjoses of a rare meyabolic
to release compounds that absorb light in range, the reading as much as State in San Marcos have studied the "The leaching of chemicals out of tubes consistently resulted in an overestimation of measurements," says Kevin Lewis, a molecular and an author on the study. Graduate student Michael Robson stumbled on the while how DNA to clay. To his surprise, water centrifuged for 30 minutes or longer — during which time warmed up slightly — began to absorb light wavelengths characteristic of DNA. that their microcentrifuge tubes might the Robson and colleagues a look at ten of tube from nine manufacturers, using mass spectrometry to determine the levels of leached chemicals. Leaching increased after the heated above °C when solvents were used used in enzyme-catalysed reactions, protein extractions chain reaction. There is "no doubt", Lewis says, some results the literature are incorrect, at least — although the relative differences between control and samples should still hold. He adds that double-checking results with other techniques, such as gel fluorometry, in which leaching do not affect would the Widespread Manufacturers contacted Nature were not able to respond before publication of this story. the Texas team isn't alone in reporting concerns over lab November researchers in Canada that chemicals in pipette and tubes interfered with the an they 'Why isn't fantastic'). And more recently, in Germany reported that standard-issue dishes — made of — were skewing the results of cell-culture assays3. "Despite increasing exposure of this problem over past two or three years, pipette tips and microfuge tubes purchased from majority of and particularly the more inexpensive brands — still additives that leach into and solvents and interfere with measurements," pharmacologist Andrew Holt the of Alberta Edmonton, Canada, told The problem has found its way clinic. Last Holt his University Medical Center in Jerusalem reported spike diagnoses of a rare metabolic
 to release compounds that absOrb light in The saMe rAngE, iNcreAsinG the reading by aS Much As 300%, say researchers from TeXas StAtE univERsIty in san MarcOS wHO HavE sTuDieD tHE pRobleM1.

"ThE leachiNg of chemicAls OuT of polypropyLEnE tubes consIstEntly resulteD in An overEsTimATion oF meAsureMents," sAYs KeviN Lewis, a moLeCUlar geNEticist AND aN autHor on the study.

GradUAtE Student Michael robson StUMbLED on The Effect whilE sTudyiNG how effICiENTLy Dna binds to clay. TO his surprisE, WatEr centRiFugED for 30 miNutes Or LOngEr — during whiCh tiMe it warmeD up sliGHtly — begAN to absoRb lighT at WavElenGThS cHarAcTEriSTiC of dnA. SUspectinG tHaT theiR micROCENtriFugE tubEs migHt be the culpriTs, RObsoN And His coLleagUes tOoK a cloSer looK at teN tYpes of tube from nIne mAnufacturErs, UsIng MaSs speCTrometRy tO deTermine The leveLS of LeACHEd Chemicals. Leaching iNcREAsEd both afTer the TUbEs WEre heateD aBovE 37 °C anD WHen inOrgaNIc Solvents Were usED — pRoCedures UsEd in enZyMe-cAtaLysed REactIons, prOtein extRactiONs and the polymeRAse chain reactIOn.

tHErE Is "no DouBt", Lewis says, That SOme rEsulTS iN thE LiterAture ArE InCOrrect, at least quantiTaTively — AlthoUgh the relativE differencES BEtween coNtroL AnD Experimental saMples Should stilL Hold. He adDs thaT double-cHecking reSULts with oTheR teChnIquES, SuCh as gel electrOPHoreSiS or fluoRomEtry, in wHicH leAchIng ChEmicals do Not affecT rEaDiNgS, woUld caTCh the proBlEm.

WIdEspRead pROblem

MAnufaCturErS cONtaCted by NATuRE Were NoT aBle tO reSpOnd beFore PUblIcation Of this stoRy. BUT the teXaS team isN't alone in repoRtIng concernS oVer Lab plaSTIcs. In NovEmber 2008, researchers in CanadA Found thAt cHemicAls iN pipette tIps And plaStiC Tubes iNterfeRed wiTh The ACTivitY OF aN enZyMe they were STUdyIng2 (seE 'WHy plAstic isN't always fantastic'). AND moRe recently, resEarCherS IN GErmANy REpoRtED thAT Standard-issue PeTri dishes — mAdE Of PolystyrenE, AnoThEr type oF plastiC — were SKewing tHe results Of cell-culTuRe asSAYs3.

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"DespitE increasiNG expoSUrE of thIs pRoblem OvEr tHe pasT two or THreE yearS, pipetTe Tips anD micrOfUge tubes Purchased from the majoritY of souRces — aNd pArticularLy tHE moRe inexpenSive Brands — stilL coNtaIn addItiVEs thaT leaCH iNto BUfferS and SOlvents anD InTerFERe With measureMENTs," pHarmaColOGist AnDrew holt of the UniversiTY of Alberta in EdMontON, canAda, TOld NAtUre.

The problem hAs aLsO FOund its wAy Into the clinIc. Last yeAr, hOlt anD his coLleaguEs at HadASSaH-hebrew univErsIty MedicaL CeNtER in JeruSaLeM ReportEd a sPiKe in diAgnoseS Of a rARE metabolic
 to release compounds that  absorb li ght i n t hesa me r ange , increasing t h e re ading by as much as 30 0%, s ay rese a rc hersfrom Te x as S tat eUn ive rs i ty  in S anMarcoswho have s tud ie d the proble m 1. 

"The lea chi ng of chemic als  out o fpol y propy len e tub es con s istent ly result ed in ano veresti m a ti on o f measurements,"s ay s  Kevin Lewis,a mole cu l ar g ene tic ist and an  a uthor on thes tu d y . 

G r aduate studen t Michael R o bso n stum bl edo n theeffec tw hil e studyinghowefficient ly DNA binds t o  clay.To his  su rpr ise, wa te r c en t rif u ge d f o r 3 0 minute sor  long er — d u r ingwhi ch t ime i t warmed up s lig htly — b eganto ab sorb  l ightat wav eleng th s characteristi c of  DNA. Sus pec ti ngth at th e ir mic roc ent rifugetubes m i ght  b e t he  culprits, Robsonan d hi s collea gues t o ok  a closer l oo k a t te n types  oft ub e from n ine ma n uf ac turers,  u sing m as s s pec trome t ry t o dete rmine th e lev e ls of leachedc hemicals. Lea c hi n g  i n crea sed  both after  the tube s we r ehea t ed ab ove 3 7° Ca nd when inorganic s ol ventswereused — proced ures usedi n enzyme-c atal y se d  reactions, pr otein  extractio n s and th e pol ymerasechain rea c t ion.

Th ere  is  "n o d o u bt ", Lewis says , that  s ome res ult s in th e l ite rat ure  a re incorr ect, atle as tqu ant itati v ely — al th oug hthe  rela t ive di ffere nces  b et w een  contro l  a n d  exp er im enta l s am plesshou l d s till ho ld. He ad dst hatdo ub le-chec king resultswi th other t ec hni ques,s u ch as ge l electrophoresis or fl u orometr y,in wh ichleachingche micals  do not af fect r eadin gs , w o u ld ca t c hthe  p roblem.

W i d esp readpr oble m

Manu facturers contacte d  by  Nature werenot  abl e to  re s po n d b ef o rep u blication of th is story.Bu t  t he Texas t e amis n't alo ne in r eport i ng conc erns over  lab plas ti cs.I n  No vember 200 8, resea rchers in Canad a  f oundtha t chem ic als  in p ipette tip s and  plast ic  tubes  inte rf ered wit h the activity of an en zyme t hey w ere  studying 2 ( s ee'Why plas ticisn't alwa ysfan tasti c') .  Andmore re cen t ly, r esea r chers inG er man y re ported that s t and ard-i ssu e  Petri  dis hes — made of pol y styrene, anoth er t y p e o f p l asti c— were skewing  th er e sults of  c ell-culture  assays3 .ADVER TISEME NT

"D espitei n cr e asingexpo sur e of this  pr ob l em over  t he past t wo o rthreeyears, pipe t t e tips and micro fuget u bes p u rch asedfr om them ajor ity of sou rces — andpartic ular ly th e morein expens ive  b rands — st i ll contai n add itivesth at l eac h into  buf f e rs an d so lv ent s and int e r fe r ewi t h m easu remen ts ," p harmacolo g ist Andr ewH olt ofth e U n i versit y  o f Alberta in  Ed monto n ,  Canada, t o ld N a tu r e.

T he pro blem h as also fou nd  its wa y i n t o the cli nic. Last yea r,  Hol t and hi scoll ea gue sat Hadassah-Heb rew Univ ersity M e d ical C ent e r in Jerusa le m reported a  spik ei n diagn o s esof a ra r e m eta bol ic
 to_release compounds_that absorb light in_the same_range,_increasing the_reading_by as much_as 300%, say_researchers from Texas State_University in San_Marcos_who have studied the problem1.

"The leaching of chemicals out of polypropylene tubes consistently resulted_in_an overestimation_of_measurements,"_says Kevin Lewis, a molecular_geneticist and an author on_the study.

Graduate_student Michael Robson stumbled on the effect while_studying_how efficiently DNA_binds to clay. To his surprise, water centrifuged for_30 minutes or longer — during_which time it_warmed_up_slightly — began to_absorb light at wavelengths characteristic of_DNA. Suspecting that their microcentrifuge tubes_might be the culprits, Robson and his_colleagues took a closer look at_ten types of tube from_nine manufacturers,_using mass spectrometry to determine_the levels of_leached chemicals._Leaching increased both_after the tubes were heated above_37 °C and_when inorganic solvents were used —_procedures_used in enzyme-catalysed_reactions,_protein_extractions and_the polymerase chain_reaction.

There_is "no_doubt",_Lewis says, that some results in_the_literature are incorrect, at least quantitatively —_although the relative differences_between_control and experimental samples_should still hold. He adds_that double-checking results with other techniques,_such as_gel electrophoresis_or fluorometry, in which leaching chemicals do not affect readings, would_catch the problem.

Widespread problem

Manufacturers contacted by_Nature were not able_to respond_before_publication of this_story._But the_Texas team isn't alone in reporting concerns_over lab_plastics. In November 2008, researchers in_Canada found that chemicals_in_pipette tips and plastic tubes interfered_with the activity of an enzyme_they were studying2 (see 'Why_plastic_isn't_always fantastic'). And more recently,_researchers in Germany reported that standard-issue_Petri dishes —_made of polystyrene, another type of plastic_—_were skewing the results of cell-culture_assays3.

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"Despite_increasing exposure of this problem over_the_past_two or three years, pipette_tips and microfuge tubes purchased from_the majority of sources — and particularly the more_inexpensive brands —_still contain additives that leach_into_buffers_and solvents and interfere with measurements," pharmacologist Andrew Holt of_the University_of Alberta in_Edmonton, Canada, told Nature.

The problem has also found its way_into the clinic. Last year, Holt and_his colleagues at Hadassah-Hebrew University Medical Center in Jerusalem reported a_spike in diagnoses of a rare metabolic