sixth commiss direct ec juli relat method analysi check composit cosmet product text eea relev commiss european commun regard treati establish european commun regard council direct eec juli approxim law member state relat cosmet product amend commiss direct ec articl thereof direct eec offici test cosmet product aim ensur condit laid commiss provis composit cosmet product satisfi method analysi laid quickli method adopt commiss direct eec amend direct eec eec amend direct eec eec eec eec identif determin benzoic acid hydroxybenzo acid sorbic acid salicyl acid propion acid cosmet product identif determin hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth cosmet product constitut sixth step measur provid direct accord opinion committe adapt direct eec technic progress adopt direct articl member state step ensur offici test cosmet product identif determin benzoic acid hydroxybenzo acid sorbic acid salicyl acid propion acid identif determin hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth carri accord method annex articl member state bring forc law regul administr provis compli direct septemb forthwith inform commiss thereof member state adopt provis refer direct accompani refer time offici public procedur refer adopt member state member state commun commiss provis nation law adopt field cover direct articl direct enter forc dai public offici journal european commun articl direct address member state brussel juli commiss emma bonino member commiss oj oj oj oj oj oj oj oj oj annex identif determin benzoic acid hydroxybenzo acid sorbic acid salicyl acid propion acid cosmet product scope field applic method applic identif determin benzoic acid hydroxybenzo acid sorbic acid salicyl acid propion acid cosmet product separ procedur describ identif preserv determin propion acid determin hydroxybenzo acid salicyl acid sorbic acid benzoic acid definit amount benzoic acid hydroxybenzo acid salicyl acid sorbic acid propion acid determin method express percentag mass free acid identif principl acid base extract preserv extract analys thin layer chromatographi tlc emploi date derivat depend result identif confirm high perform liquid chromatographi hplc case propion acid ga chromatographi gc reagent gener reagent analyt puriti water distil water water equival puriti aceton diethyl ether acetonitril toluen hexan paraffin liquid hydrochlor acid potassium hydroxid aqueou calcium chlorid cacl lithium carbon li bromo amp prime acetonaphthon hydroxybenzo acid salicyl acid benzoic acid sorbic acid propion acid refer solut prepar solut mg ml preserv diethyl ether derivat reagent solut bromo amp prime acetonaphthon acetonitril mg ml solut prepar weekli store refriger catalyst solut solut lithium carbon water mg ml solut freshli prepar develop solvent toluen aceton liquid paraffin hexan apparatu ordinari laboratori equip water bath capabl maintain temperatur develop tank ultraviolet light sourc nm thin layer plate kieselgel fluoresc indic cm layer thick mm concentr zone cm merck equival microsyring µl microsyring µl oven capabl maintain temperatur ml glass tube screw cap filter paper diamet mm schleicher amp schull weissband equival univers ph indic paper ph ml glass sampl vial rotat film evapor rotavapor equival hot plate procedur sampl prepart weigh approxim sampl ml glass tube screw cap add drop hydrochlor acid ml aceton strongli basic product toilet soap drop hydrochlor acid ad check ph approxim indic paper close tube shake vigor minut facilit extrract preserv aceton phase heat mixtur gentli melt liquid phase cool solut room temperatur filter filter paper conic flask transfer ml filtrat ml conic flask add ml water mix adjust ph mixtur approxim potassium hydroxid indic paper measur ph add calcium chlorid shake vigor filter filter paper ml separ funnel ml diethyl ether shake vigor minut separ draw aqueou layer ml conic flask discard ether layer indic paper adjust ph aqueou solut approxim hydrochlor acid add ml diethyl ether stopper flask shake vigor minut separ transfer ether layer rotat film evapor discard aqueou layer evapor ether layer dryness redissolv residu ml diethyl ether transfer solut sampl vial thin layer chromatographi refer sampl chromatograph appli approxim µl lithium carbon solut syring equal distanc start line concentr zone tlc plate dry stream cold air transfer tlc plate hot plate heat order spot small microsyring appli µl refer solut sampl solut start line plate exact spot lithium carbon solut appli final appli approxim µl derivat reagent bromo amp prime acetonaphthon solut exact spot refer sampl solut lithium carbon solut appli heat tlc plate oven minut cool develop plate tank equilibr minut filter paper line develop solvent toluen aceton solvent front reach distanc cm approxim minut dry plate stream cold air examin spot obtain uv light enhanc fluoresc weak spot tlc plate dip liquid paraffin hexan identif calcul rf spot compar rf behaviour uv radiat obtain sampl obtain refer solut draw preliminari conclus presenc ident preserv present perform hplc section appear propion acid present gc section compar retent time obtain refer solut combin result tlc hplc gc base final identif preserv present sampl combin result determin benzoic acid hydroxybenzo acid sorbic acid salicyl acid principl acidif sampl extract mixtur ethanol water filtrat preserv determin high perform liquid chromatographi hplc reagent reagegnt analyt puriti suitabl hplc water distil water water equival puriti ethanol absolut hydroxybenzo acid salicyl acid benzoic acid sorbic acid sodium acet ch coona acet acid ml acetonitril sulfur acid potassium hydroxid aqueou methoxybenzo acid ethanol water mixtur mix volum ethanol volum water intern standard solut prepar solut approxim methoxybenzo acid ml ethanol water mixtur mobil phase hplc acet buffer water add sodium acet ml acet acid mix prepar mobil phase mix volum acet buffer volum acetonitril preserv stock solut accur weigh approxim hydroxybenzo acid salicyl acid benzoic acid sorbic acid ml volumetr flask make volum ethanol water mixtur store solut refriger solut stabl week standard preserv solut transfer ml stock solut seri ml volumetr flask flask add ml intern standard solut ml sulfur acid make volum ethanol water mixtur solut freshli prepar apparatu usual laboratori equip water bath set high perform liquid chromatograph variabl wavelength uv detector µl inject loop analyt column stainless steel length cm intern diamet mm pack nucleosil equival filter paper diamet mm schleicher schull weissband equival ml glass tube screw cap ml glass sampl vial boil chip carborundum size mm equival procedur sampl prepar sampl prepar addit intern standard weigh sampl ml glass tube screw cap pipett ml sulfur acid ml ethanol water mixtur tube add approxim boil chip close tube shake vigor minut homogen suspens obtain facilit extract preserv ethanol phase place tube minut water bath cool tube immedi stream cold water store extract hour filter extract filter paper transfer approxim ml extract sampl vial store extract perform hplc determin hour prepar sampl prepar includ addit intern standard weigh decim place gram sampl ml glass tube screw cap add pipett ml sulfur acid ml ethanol water mixtur add approxim boil chip ml intern standard solut close tube shake vigor minut homogen suspens obtain facilit extract preserv ethanol phase place tube minut water bath cool tube immedi stream cold water store extract hour filter extract filter paper transfer approxim ml filtrat sampl vial store filtrat perform hplc determin hour prepar high perform liquid chromatographi mobil phase acetonitril acet buffer adjust flow rate mobil phase column ml minut set detector wavelength nm calibr inject µl portion standard preserv solut liquid chromatographi solut determin ratio peak height investig preserv height intern standard peak obtain chromatogram plot graph preserv relat peak height ratio concentr standard solut ascertain linear respons obtain standard solut calibr procedur determin inject µl sampl extract liquid chromatograph record chromatogram inject µl standard preserv solut record chromatogram compar chromatogram obtain chromatogram sampl extract peak appear present approxim retent time methoxybenzo acid recommend intern standard inject µl sampl extract ad intern standard liquid chromatograph record chromatogram interf peak observ chromatogram sampl extract retent time methoxybenzo acid intern standard select preserv investig absent chromatogram preserv intern standard ascertain chromatogram obtain standard solut sampl solut meet requir peak separ worst separ pair definit peak separ figur gt refer film gt figur peak separ oj requir separ achiev effici column mobil phase composit adjust requir met asymmetri factor peak obtain rang definit peak asymmetri factor figur record chromatogram determin asymmetri factor chart speed cm minut recommend gt refer film gt figur peak asymmetri factor steadi baselin obtain calcul ratio height peak investig preserv height methoxybenzo acid intern standard peak calibr graph calcul concentr acid preserv sampl solut calcul benzoic acid hydroxybenzo acid sorbic acid salicyl acid content sampl percentag mass xi formula xi mass test portion concentr µg ml preserv sampl extract obtain calibr graph repeat hydroxybenzo acid content differ result determin parallel carri sampl exce absolut benzoic acid content differ result determin parallel carri sampl exce absolut salicyl acid content differ result determin parallel carri sampl exce absolut sorbic acid content differ result determin parallel carri sampl exce absolut remark result rugged test perform method amount sulfur acid ad extract acid sampl critic limit amount sampl work prescrib boundari desir guard column determin propion acid scope field applic method suitabl determin propion acid maximum concentr cosmet product definit concentr propion acid measur method express percentag mass product principl extract propion acid product determin perform mean ga chromatographi methylpropion acid intern standard reagent reagent analyt puriti distil water water equival qualiti ethanol propion acid methylpropion acid orthophosphor acid propion acid solut accur weigh approxim gram propion acid ml volumetr flask make volum ethanol intern standard solut accur weigh approxim gram methylpropion acid ml volumetr flask make volum ethanol apparatu usual laboratori equip ga chromatograph flame ioniz detector glass tube mm screw cap water bath ml glass syring filter membran pore diamet µm procedur sampl prepar sampl prepart intern standard glass tube weigh approxim sampl add ml phosphor acid ml ethanol close tube shake vigor place tube water bath heat minut order complet dissolv lipid phase cool rapidli run water filter part solut membran filter chromatograph filtrat dai sampl prepar intern standard weigh decim place gram sampl glass tube add ml phosphor acid ml intern standard solut ml ethanol close tube shake vigor place tube water bath heat minut order dissolv lipid phase cool rapidli run water filter part solut membran filter chromatograph filtrat dai condit ga chromatographi oper condit recommend column type stainless steel length diamet amp prime pack sptm equival po chromosorb waw mesh temperatur injector column detector carrier ga nitrogen flow rate ml min chromatographi calibr seri ml volumetr flask transfer pipett ml propion acid solut volumetr flask transfer pipett ml intern standard solut make volum ethanol mix solut prepar mg ml methylpropion acid intern standard mg ml mg ml propion acid mg ml inject µl solut obtain calibr curv plot ratio propion acid methylpropion acid mass axi ratio peak area axi make inject solut calcul averag peak area ratio determin inject µl sampl filtrat compar chromatogram standard solut peak approxim retent time methylpropion acid chang intern standard interfer observ inject µl sampl filtrat measur area propion acid peak intern standard peak make inject solut calcul averag peak area ratio calcul calibr curv obtain obtain ratio mass peak area ratio calcul ratio mass obtain calcul propion acid content samp percentag mass formula ratio calcul mass gram intern standard weigh mass gram sampl weigh round result decim place repeat propion acid content differ result determin parallel carri sampl exce ii identif determin hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth cosmet product identif scope field applic method describ detect identif hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth monobenzon cosmet product lighten skin principl hydroquinon ether identifi thin layer chromatographi tlc reagent reagent analyt grade ethanol chloroform diethyl ether develop solvent chloroform diethyl ether ammonia ml ascorb acid hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth monobenzon refer solut refer solut freshli prepar stabl dai weigh hydroquinon ml graduat test tube add ascorb acid ml ethanol add ammonia ph make volum ml ethanol weigh hydroquinon monomethyleth ml graduat test tube add ascorb acid ml ethanol add ammonia ph make volum ml ethanol weigh hydroquinon monoethyleth ml graduat test tube add ascorb acid ml ethanol add ammonia ph make volum ml ethanol weigh hydroquinon monobenzyleth ml graduat test tube add ascorb acid ml ethanol add ammonia ph make volum ml ethanol silver nitrat molybdophosphor acid potassium ferricyanid hexahydr ferric chlorid hexahydr sprai reagent aqueou solut silver nitrat add ammonia precipit form dissolv warn solut explos unstabl stand discard solut molybdophosphor acid ethanol prepar aqueou solut potassium ferricyanid aqueou solut ferric chlorid mix equal part solut apparatu normal laboratori equip usual tlc equip tlc plate readi silica gel ghr uv cm macheri nagel equival layer thick mm ultrason bath centrifug uv lamp nm procedur prepar sampl weigh sampl ml graduat tube add ascorb acid ml ethanol adjust ph solut amonia make volum ml ethanol close tube stopper homogen ultrason bath minut filter filter paper centrifug rpm tlc satur chromatograph tank develop solvent deposit plate µl refer solut µl sampl solut develop dark ambient temperatur solvent front migrat cm start remov plate dry room temperatur detect observ plate uv light nm mark posit spot sprai plate silver nitrat reagent molybdophosphor acid reagent heat approxim potassium ferricyanid solut ferric chlorid solut identif calcul rf spot compar spot obtain sampl solut refer solut respect rf valu colour spot uv radiat colour spot visual sprai reagent perform hplc section compar retent time obtain sampl peak refer solut combin result tlc hplc identifi presenc hydroquinon ether remark condit rf valu observ hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth determin scope field applic method specifi procedur determin hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth cosmet product lighten skin principl sampl extract water methanol mixtur gentl heat melt lipid materi determin analyt result solut perform revers phase liquid chromatographi uv detect reagent reagent analyt qualiti water distil water water equival puriti methanol hydroquinon hydroquinon monomethyleth hydroquinon monethyleth hydroquinon monobenzyleth monobenzon tetrahydrofuran hplc grade water methanol mixtur mix volum water volum methanol mobil phase tetrahydrofuran water mixtur mix volum tetrahydrofuran volum water refer solut weigh hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth ml volumetr flask dissolv make volum methanol prepar refer solut dilut ml solut ml water methanol mixtur solut freshli prepar apparatu normal laboratori equip water bath capabl maintain temperatur high perform liquid chromatograph variabl wavelength uv detector µl inject loop analyt column stainless steel chromatograph column length mm intern diamet mm pack zorbax phenyl chemic bond phenethylsilan zorbax sil end cap trimethylchlorosilan particl size µm equival guard column phenyl guard equival filter paper diamet mm schleicher schull weissband equival procedur sampl prepar weigh decim place gram sampl ml volumetr flask dispers sampl ml water methanol mixtur close flask shake vigor homogen suspens obtain shake minut place flask water bath enhanc extract cool flask make volum water methanol filter extract filter paper perform hplc determin hour prepar extract high perform liquid chromatographi adjust flow rate mobil phase ml min set detector wavelength nm inject µl sampl solut obtain section record chromatogram measur peak area perform calibr compar chromatogram obtain sampl standard solut peak aera respons factor rf calcul calcul concentr analyt sampl solut calibr inject µl refer solut record chromatogram inject time constant peak area obtain determin respons factor rfi rfi pi ci pi peak area hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth ci concentr ml refer solut hydroquinon hydroquinon monomethyleth hydroquinon monoethyleth hydroquinon monobenzyleth ascertain chromatogram obtain standard solut sampl solut meet requir peak separ worst separ pair definit peak separ figur gt refer film gt figur peak separ requir separ achiev effici column mobil phase composit adjust requir met asymmetri factor peak obtain rang definit peak asymmetri factor figur record chromatogram determin asymmetri factor chart speed cm min recommend gt refer film gt figur peak asymmetri factor steadi baselin obtain calcul area analyt peak calcul concentr analyt sampl calcul analyt concentr sampl percentag mass xi formula xi bi rfi mass sampl gram bi peak area analyt sampl repeat hydroquinon content differ result determin carri parallel sampl exce absolut hydroquinon monomethyleth content differ result determin carri parallel sampl exce absolut hydroquinon monoethyleth content differ result determin carri parallel sampl exce absolut hydroquinon monobenzyleth content differ result determin carri parallel sampl exce absolut reproduc hydroquinon content differ result determin carri sampl condit laboratori oper apparatu time exce absolut hydroquinon monomethyleth content differ result determin carri sampl condit laboratori oper apparatu time exce absolut hydroquinon monoethyleth content differ result determin carri sampl condit laboratori oper apparatu time exce absolut hydroquinon monobenzyleth content differ result determin carri sampl condit laboratori oper apparatu time exce absolut remark hydroquinon content consider higher found accur estim content requir sampl extract dilut similar concentr obtain sampl hydroquinon determin repeat instrument absorb linear rang detector high hydroquinon concentr interfer method determin hydroquinon ether singl isocrat run phenyl column assur suffici retent hydroquinon guarante column mobil phase method prone interfer number paraben case determin repeat emploi mobil phase stationari phase system suitabl method found refer column zorbax od mm mm equival temperaur flow ml min mobil phase hydroquinon methanol water hydroquinon monomethyleth methanol water hydroquinon monobenzyleth methanol water column spherisorb od equival mobil phase water methanol flow ml min condit suitabl hydroquinon iso iso iso herpol borreman mass identif dosag de hydroquinon de se éther méthyliqu benzyliqu dan le produit cosmétiqu pour blanchir la peau int cosmet sci firth rix determin hydroquinon skin tone cream analyst