polycyclic aromatic hydrocarbons ( pahs ) are ubiquitous semi - volatile environmental contaminants ( 1 , 2 ) and have been often monitored in water , air , soil and food matrices ( 3 ) . they are principally by - product of incomplete combustion of organic substances and also generated by fossil fuels or plants burning . due to their ubiquitous presence and potential to cause adverse human health effects environmental waters can be contaminated with pahs from diverse sources such as industrial and municipal wastewaters , runoff , atmospheric deposition via wet and dry particle deposition and gross gas absorption , oil spills , rain water and from asphalt abrasion ( 2 , 4 - 6 ) . long - range atmospheric transport of pahs has been well documented in different countries ( 5 ) . after the arrival of pahs to the atmosphere , they are transferred into water by direct surface contact or as a result of precipitation ( 5 ) . occurrence of pahs in water resources , including drinking water have been reported indifferent parts of the world ( 5 ) . who reported that water is a very significant source of pahs , and in drinking water , fluoranthene , phenanthrene , pyrene and anthracene were usually detected in it ( 7 , 8) . among the routes of exposure of the general public such as inhalation of ambient and indoor air , dermal absorption , and/or dietary intake , drinking water is also important ( 9 , 10 ) . the typical concentration range for sum of selected pahs in drinking water vary between 1 ngl and 11 gl ( 7 , 8) . the incidence of these compounds in the environment is of reasonable concern , as these are known to be mutagenic and carcinogenic ( 3 ) . pahs need metabolic activation to exert their carcinogenic effects , and through a three - step sequence resulting in the formation of diol epoxides , which react with dna to create adducts that can cause mutations and begin the carcinogenic process ( 11 , 12 ) . various pahs vary in carcinogenic capability , but even those that are considered as not being carcinogenic , may act in organisms as synergists , increasing the carcinogenicity of other pahs ( 13 ) . according to the international agency for research on cancer classification system , benzo [ a ] pyrene as one of the most known is classified in group 1 and some of them are also categorized as group 2a or 2b carcinogens ( 14 , 15 ) . it was not conceivable to set up a threshold level for pahs below which danger would be unimportant and so a tolerable daily intake could not be set ( 16 ) . therefore , it suggested that exposures to pahs must be as low as reasonably achievable ( 17 ) . pahs are contaminants which undergo the legislative control or are integrated in the monitoring programs of the eu scientific committee on food ( scf ) , world health organization ( who ) , environmental protection agency ( epa ) , and food and drug administration ( fda ) ( 18 ) . for example , who has recommended maximum permissible concentrations of 0.7 gl for benzo [ a ] pyrene ( bap ) in drinking water ( 19 , 20 ) . the international organizations , i.e. who , epa and european community ( ec ) , have recommended the continual detection and quantification of these compounds in drinking waters ( 21 ) and established the maximum residue levels for bap ( 20 ) . the permissible level for bap in drinking water that was proposed by who is the same as that of iranian national drinking water standard ( 22 ) ( 23 ) have reported the measurement of 16 priority polycyclic aromatic hydrocarbons ( pahs ) in six stations in karaj river , which is the main resource of drinking water in tehran . the single pahs concentrations ranged from not detected to 2,327.8 ng l-1 , with a mean value of 31.5 ng l-1 . the total pahs concentrations ranged from 25.6 , in the spring , to 4,040.3 ng l-1 , in the summer . the sample preparation step in an analytical process typically consists of an extraction procedure that results in the separation and enrichment of analytes of interest from a sample matrix . extraction can differ in degree of selectivity , speed and convenience and depends on the approach , conditions and the type of the extraction phase ( 24 , 26 , 35 - 36 ) . liquid extraction ( lle ) is among the oldest of the preconcentration and matrix separation techniques in analytical chemistry ( 24 , 26 ) . solid - phase extraction ( spe ) uses much less solvent than lle , but can be rather expensive ( 24 , 26 ) . dispersive liquid - liquid microextraction ( dllme ) offers several important advantages over trivial solvent extraction methods : faster operation , no need of large amounts of organic extraction solvent , low cost and time and easy application ( 20 , 24 ) . thus , since its introduction , dllme has been frequently used for determination of organic contaminants in liquid samples , including of pahs in water samples ( 20 , 24 ) . the aim of this study was to determine the level of 13 priority pahs in different brands of water for injection as well as tap water samples collected from tehran , iran , in march , 2014 using dllme procedure and gc / ms . standards and reagents 
  naphthalene ( naph . ) , acenaphthene ( ace . ) , fluorene ( fl . ) , phenanthrene ( phen . ) , anthracene ( ant . ) , anthracene - d10 ( ant.d10 ) , pyrene ( pyr . ) , benzo [ a ] anthracene ( b[a]a ) , chrysene ( chy . ) , benzo [ b ] fluoranthene ( b[b]f ) , benzo [ k ] fluoranthene ( b[k]f ) , benzo [ a ] pyrene ( b[a]p ) , dibenz [ a , h ] anthracene ( d[ah]a ) and benzo [ ghi ] perylene ( b[ghi]p ) with purity higher than 98% were purchased from sigma - aldrich / fluka / supelco ( germany ) . hplc grade isooctane , toluene , acetonitrile , dichloromethane , tetrachloroethylene , n - hexane , ethanol , 2-propanol , methanol , acetone and chloroform were obtained from chem - lab belgium . ultrapure water was obtained from a milli - q plus ultra - pure water system ( millipore , molsheim , france ) . tap water and water for injection sampling 
  according to drinking water supply , tehran was divided into six regions . in 2014 , six tap water samples ( each 500 ml ) were collected from each region during two weeks , totally 36 samples and stored in amber glass bottles . the water samples were stored in a cold box while being carried to the laboratory and stored at 4c . water for injection samples commercially available in tehran were purchased from drugstores ( five different brands , six batches each , totally 30 samples ) . calibration standards 
  individual stock standard solutions ( 1 mgml ) of the pahs were prepared in toluene . a mixed intermediate standard solution at a concentration of 100 ngml was prepared via appropriate dilution of the stock solutions in methanol . spiked calibration standards at concentration levels of 0.35 , 0.7 , 1.4 , 2.8 , and 5.6 ngmlwere prepared by addition of 35 l , 70 l , 140 l , 280 l and 560 l of mixed standard stock solution to 10 ml of blank water samples in each case . a stock solution of anthracene - d10 in toluene at concentration of 1 mgml was used as internal standard . an aliquot of 70 l of anthracene - d10 in methanol ( 100 ngml ) was added to the spiked water sample as internal standard . extraction and clean - up by using dllme technique 
  we have already developed a method using dllme technique ( that is environmentally friendly , a very simple and rapid method for extraction and preconcentration of organic compounds from water samples and reduce the cost of analysis by reduction of organic solvents ) and gc / ms analysis for determination of 13 priority pahs in the mineral water samples ( 27 ) . this method was applied for analysis of 13 pahs in tap water as well as water for injection samples as follows : 10 ml ultrapure water was placed in a 10 ml screwed glass tube and 70l of anthracene - d10 ( as internal standard ) at concentration 100ngml was added to the sample . a mixture of 500 l chloroform and 1000 l acetone ( as extraction and disperser solvent , respectively ) was quickly injected into the sample solution with a 500 l hamilton syringe . a cloudy solution was formed after adding the mixture extraction and disperser solvent in the glass tube . the glass tube containing ultrapure water , extraction and disperser solvent was placed in a centrifuge ( hettich zentrifugen universas 320r ) and centrifuged for 3 min at 2500 rpm . the upper layer was discarded and 500 l of the lower phase ( extraction solvent ) was removed by a hamilton syringe and transferred to 1.5 ml amber glass vial . the contents of the vial were dried using a gentle stream of nitrogen at room temperature and re - dissolved with 70 l chloroform . gc  ms instrumentation and conditions 
  the analysis was carried out using gc model agilent 7890a , washington , usa , equipped with a split / splitless injection port , an autosampler model agilent 7693 , electronic ionization and a triple quadrupole mass analyzer model agilent 7000 series . a hp-5ms 5% phenyl methyl silox , agilent 19091s-433 capillary column was used with 30 m  0.25 mm i.d . and 0.25 m film thickness . helium with a purity of 99.99% and a flow rate of 1 mlminwas used as carrier gas . the initial oven temperature was maintained at 60c for 0.5 min , increased to 230c at a ramp rate of 3cmin and kept for 0.5 min , then increased to 290c at 5c min and hold for 10 min at the final temperature . the ion source and triple quadrupole mass analyser temperature were kept at 230c and 280c , respectively . the vial was placed in autosampler and 2 l of the contents was injected into the gas chromatograph for analysis . pahs concentrations were calculated by intrapolating the peak ratio for pah to internal standard on the calibration curve . in order to compensate for losses during sample processing and instrumental analysis , spiked water samples at concentration levels of 0.35 , 0.7 , 1.4 , 2.8 , and 5.6 ngmlwere prepared in triplicates and then treated according to the procedure described previously . method performance characteristics 
  in the present study , the spike calibration curves ( five points ) for all the analytes were constructed by plotting the peak area ratio of each compound to internal standard against the concentration of that pah . the graphs were constructed from triplicate analysis of the ultrapure water spiked at each concentration level ( 0.35 - 5.6 ngml ) . all 12 spiking calibration curves of pahs were linear and the coefficients of determination ( r ) ranged 0.993 - 0.999 . the repeatability and recovery of method for each 12 analytes ranged 4.0 - 16.0% and 71 - 90% respectively . limits of detection ( lod ) and limits of quantification ( loq ) were calculated based on the signal - to - noise ratio of equal to 3 and 10 , respectively . the recoveries and rsds of 12 pahs in quality control samples ( qc ) are summarized in table1 . the recoveries and rsds of 12 pahs in quality control samples ( spiking level : 1.0 ngml ) analyzed using dllme method and gc - ms determination of 13 pahs in tap water and water for injection samples . the optimized and validated method was utilized for extraction and determination of studied pahs in 36 tap water samples and 30 water for injection samples . the results showed that the concentration of 12 pahs in all samples ( tap water and water for injection ) were lower than the loq ( 0.1 - 0.35 ngml ) of the method . regarding naphthalene , the results showed that it was present in all analyzed samples including tap water and water for injection samples , and no analyte - free sample as blank matrix for determining the blank sample baseline and constructing the calibration line was available . therefore , it was not possible to construct the calibration curve for naphthalene , and its concentration in samples was not determined . it is recommended that for accurate determination of naphthalene , an isotope - labeled naphthalene such naphthalene - d8 ( surrogate analyte ) instead of naphthalene is used as calibration standard . by this approach , the true blank matrix , which is not accessible by other methods and is a prerequisite for accurate quantification specially at trace level is provided ( 28 ) . water treatment plants are the hearts and brains of the practice to develop the water quality through chemical mixing , coagulation , flocculation , sedimentation , filtration , post - filtration treatment , including disinfection , ph control , and final storage at the plant ( 30 ) . removal effectiveness of pahs by the mentioned treatment processes are reported to be in the range of 20 - 100% ( 30 ) . in another study , it was shown that the concentration of pahs in mineral water samples collected from tehran were also lower than loq ( 27 ) . there are only few published papers for determination of pah in tap water . in one of these studies , hou et al . the results for tap water showed that it was free of contamination . in another study , maa et al . ( 32 ) evaluated sixteen pahs in three real water samples including tap water , sea water and river water . no pahs were found in the tap water samples . also , zanjani et al . ( 33 ) determined the level of twelve pahs in well water , sea water and tap water , and reported that tap water was free from pahs . ( 30 ) evaluated sixteen pahs standard in the 24 drinking water samples and found contamination including chrysene , benzo[k]fluoranthene and indeno[1 , 2 , 3-cd ] pyrene at concentration levels higher than the european union s drinking water maximum limit . in another study , huixu et al . ( 34 ) found naphthalene and acenaphthene in the tap water samples at 0.059 ngml and 0.399 ngml , respectively . pena et al . ( 20 ) determined eighteen pahs in drinking water samples ( tap , bottled , fountain , well ) . sum of pahs concentration were between 127.8 ng land 413.2 ng l. to the best of our knowledge , this is the first study regarding evaluation of the contamination of water for injection samples with pahs . our results showed that the concentration of pahs in all samples were lower than the loq ( 0.1 - 0.35 ngml ) of the method . considering the few studies regarding pahs contamination in drinking water in iran , to get a clear picture of contamination of drinking water , comprehensive monitoring of pahs in tap water in different provinces and seasons is suggested . in the present study , no contamination of tap water samples and water for injection samples with pahs were found . however , a comprehensive survey for analysis pahs in water is recommended .
polycyclic aromatic hydrocarbons ( pahs ) are classified as persistent and carcinogenic organic pollutants . 
 pahs contamination has been reported in water . 
 many of relevant regulatory bodies such as eu and epa have regulated the limit levels for pahs in drinking water . in this study , 13 priority polycyclic aromatic hydrocarbons ( pahs ) were determined in tap water samples of tehran and water for injection . 
 dispersive liquid - liquid microextraction procedure combined with gas chromatography - mass spectrometry was used for the extraction and determination of pahs in the samples . under the optimized conditions , the range of extraction recoveries and relative standard deviations ( rsds ) of pahs in water using internal standard ( anthracene - d10 ) were in the range of 71 - 90% and 4 - 16% , respectively . 
 limit of detection for different pahs were between 0.03 and 0.1 ngml-1 . 
 the concentration of pahs in all tap water as well as water for injection samples were lower than the limit of quantification of pahs . 
 this is the first study addressing the occurrence of pahs in water for injection samples in iran using dispersive liquid - liquid micro extraction procedure combined with gas chromatography - mass spectrometry .