Hollow Fiber Liquid Phase Microextraction-gas Chromatography Method For The Determination Of N-alkanes In Complex Samples

Liquid phase microextraction (LPME) as a new sample pretreatment technology, has the advantages of less solvent, sample purification function outstanding, low cost, easily with a variety of analytical instrument with other extraction technology, operation mode diversification,which can not be replaced by other extraction technology.LPME extraction pattern is rich, it can choose different extraction models according to different sample matrix and the object, and has good enrichment and purification for the object.So far, liquid phase microextraction technique has become a sample pretreatment technology that has a bright prospect in the field of the analysis, has been widely used in the food analysis, pharmaceutical and biological samples analysis, environmental analysis.This subject adopts hollow fiber liquid-phase microextraction mode, study on two extraction methods of the headspace extraction and immersion extraction, for the pretreatment effect of n-alkane in gasoline, diesel, adhesive samples, use gas chromatography to determin the analytes content, and to evaluate the effectiveness of the method, the specific work is as follows:1. Hollow fiber Headspace Liquid Phase Microextraction study on the enrichment method of n-hexane in adhesive samples.Optimal control experiments by extractant species, temperature, time, stirring rate, salt effect parameters in the extraction process, establishes the pretreatment method of the hollow fiber headspace liquid phase microextraction that is applied to enrichment of n-hexane in adhesives sample, and determined by gas chromatography method to evaluate the precision and accuracy. The results show that: n-hexane has good linear relation within0.01384-6.92g/L, correlation coefficient is0.9990, the detection limit is1.02mg/L, the precision is3.5%(n=5). When n-hexane initial concentration at0.0138g/L, the enrichment factor achieve15.6times.2. Hollow fiber Headspace Liquid Phase Microextraction study on the enrichment m et h od o f n-o ct an e in ga s o l i n e sa m p le s. O p ti m al co nt r o l ex pe r im en ts b y ex t r ac t a n t sp ec i es, te m p er a t u r e, ti m e, st i rr i ng ra t e, sa l t ef f ec t p ar am et e r s in th e ex tr ac t i o n pr o ce s s, es t a b li sh es th e p re t re a t m en t m et h o d of th e ho ll o w f ib er h ea d s p ac e li q u i d ph as e m ic r o ex t ra c ti o n th at is ap p li ed to en ri ch m en t of n-o c t an e in ga s o lin e sa m p le s, an d d et er m in ed by g as ch ro m at o gr a p h y m et h o d to ev al u a te th e p re c is i on an d ac c u ra cy. T h e re s u l ts sh o w th at:n-o ct an e h as g oo d li ne ar re l at i on w it h i n0.014-7.0g/L, co rr el a t io n co e f f i ci e nt is0.9991, th ed et e ct i on li m it is6.7m g/L, th e pr e c is i on is2.6%(n=5). W he n n-o c t a n e i n i t ia l co nc e nt r a ti o nat0.014g/L, th e en ri ch m en t f ac t o r ac h ie v e14.6ti m es. T hi s m et h o d u se d in g as o li n esa m p le s, th e st a n d a rd ad di t i o n re c o v ery ra t e re a c h ab o ut94.0%-97.5%, th e p re c i si o n ar e3.2%-3.9%(n=3).3. H o ll o w f ib er im m er s i o n li q ui d p ha s e m ic r o ex t ra c ti o n s tu d y o n t h e en r i ch m en tm et h o d o f he x ad e ca n e i n d ie s e l f u el sa m p le s. Usi n g h ol l o w f ib er f ix ed ex tr ac t a nt, in im mer s i o n m ic r o e x tr a ct i o n, ex t r ac t i on ag en t ca n b ea r la r ge r in cr ea s e o f st i rr i ng sp ee d,in cr ea s e ex tr ac t io n ef f i c i e n cy. O p ti m al co n tr o l ex p er im en ts b y ex t r ac t i o nm et h od s,e x t r ac t a n t sp e ci es, te m pe r a t u r e, ti m e, st i rr in g ra t e, sa l t ef f ec t p ar a m et e r s in th eex t r ac t io n p ro ce s s, es t ab li s h es t h e pr e t re a t m en t m et h od o f th e ho l l o w f i b er im mer s i o nli q u id p h as e m ic r o ex t ra c ti o n th a t i s ap p li ed to en ri ch men t o f h e xa d ec an e in di e s e l f u el sa m pl e s, an d d et e r m in ed by g a s ch ro m at o gr a p h y m et h o d t o ev a l ua t e th e p re c is i on an dac c u ra c y. Th e re s u l t s sh ow th a t: he x a d e c a n e h as go o d li n ea r re l at i o n w i t hi n0.0155-7.75g/L, th e co r r el a t io n co ef fi c i e nt is0.9990, th e de t e c ti o n li m it i s0.83m g/L, t h e p re c i si o n is3.56%(n=5). W h en h ex ad e c an e in it ia l co n ce nt r at i o n at0.0155g/L, th e en r i ch men t f ac t o rac h iev e13.5ti m es. T hi s m e t h o d u se d in di e s e l fue l sa m p le s, t h e st a nd a rd ad d it io n re c o v ery ra t e re a ch ab o u t94.4%, th e p re ci si o n ar e4.1%(n=3).