利用SFC评价提高烷烃和芳烃分离分辨率的温度和压力参数

由于在另一个应用说明中对各种硅柱进行了评估，我们确定较小的孔径导致更好的分辨率，而有趣的是导致烷烃的保留减少。在柱比较中，较高的背压也导致烷烃保留和分辨率的增加。JASCO和 Princeton 30A硅柱证明提供最好的分离烷烃和芳烃。该应用不仅说明了背压的独特参数如何在保留时间中发挥重要作用，还说明了如何在分辨率最小时利用背压来优化分离。烷烃和芳烃在更高的压力下都能被更多地保留，但更高的温度对保留有相反的影响，也导致峰加宽。背压和温度的这些显著影响为用户提供了根据他们希望最大化分辨率的化合物类别来调整分离的能力。Application Note Evaluation of Temperature and Pressure for Increased Resolution for theSeparation of Alkanes and Aromatics Using SFC2/5 JAS.C O Evaluation of Temperature and Pressure for Increased Resolutio n for the S ep aration of Alkanes and Aromatics Using S FC I n tr o d u ct i o n As various silica columns were evaluated in another applicat i on note， it was determ i ned th a t small e r pore s i ze led to better resolution， while interest i ngly producing a decrease in retention of the alkanes.Dur i ng that column comparison higher back pressures a l so led to increased retention and inc r eased resolution of alkanes. The JASCO and Pr i nceton 30A s i lica columns proved to provide the best separation of alkanes and aromatics. In SFC one additional and uniq u e parameter ， back pressure， which is not control l ed in HPLC， can be a d justed in SFC to opt i mi z e a sep a rat i on . As with HPLC the column temperature is controlled in SFC， but this change in temperature alters the density of CO2compared to a change in viscosity i n HPLC producing a different effect on t h e separation i n SFC. To further optimize t he silica separation for t he ASTM D5186 a n d 6550 fuel analysis methods， pressu r e and temperature were evaluated b e low to d e termine their effect on the resolution. Keywords： S F C ， Gaso li n e ， Di e s e l ， S il ic a co lu m n， F I D，Al k a n e s ， A r o m atic s， P res s u re， Te m p e r a t u re ， D e n s i ty AS T M D5186 AS T M D 6550 Ja s co SFC-FID Application Note Exp e r ime nta l Equipment Conditions CO2 Delivery Pump：PU-2080-CO2Co l u m n：JASCO S i lica 4.6x250mm ，5u m Autosam p l er ：XLC-3159AS CO2 Flow r ate：2.0 mL/m in Column Oven ：CO-2060Column temp.：V ari o us FID：DANI Oven-FID Back Pressu r e：V ari o us Back Pressure BP-2080FID Splitte r ：200°℃Regulator ：FID De t ec t or：350 Figure 1. Hexadecane Retention Time Co m pa r ison at 35C and Various Back Pressu r es. Fi g ure 1 and figure 2 s h ow t h at t h e r etention t ime i n creases as t h e bac k pressure is i n creased f or bot h h exadecane and cyclohexane. However t he magnitude of this i ncrease i s d i f ferent fo r each . Hexadecane at 100ba r e l utes a t 1.54 m i nutes a n d has poor peak shape ， whi l e cyclo h exa n e elutes earlie r at 1.46 m i n utes. Th e peak s h ap e s h arpens as t h e back pressure i s in cr e ased f or h exadecane， bu t notic e t h e re t ent i on t i me on l y i n cr e ases to 1.64 m i n u tes at 300 bar compared t o l a t er cycloh e xan e e l u t ion a t 1.70 minu t es. E ff ectively i f t h ese t wo compounds were i n t he same mi xt u re t h ei r el u tio n o r d e r woul d reverse sh o wi n g t h e impor t an c e of t h e b ac k p ress u re. Fi gu r e 2. Cyc l o h exane Re t ention T i me Comparison at 35C and Various Back Pressures . A p plic a t i on L i b ra ry： h tt p ：//www.j a sco i n c.c o m /ap p l i ca t i o n s Figure 3. Toluene Retention Time Comparison at Various Temperat u res and Var i o u s Back Pressures. F i gur e 3 shows t h e r etentio n beh a vior of t oluen e at variou s te m perat u res a n d various te m pe ra t ures. Th e r ete n t i on time does n ot v ar y betwee n 35℃ and 45℃ wi t h the exception a t 100 bar yi elding a sl i g h t l y lo n ge r r ete n tio n .Al t ho ug h t he r ete n tio n times do n ot va ry， t h e peak s h ape is ce r t ai n ly s ha rp er at 35℃. At 55℃ th e p e ak sha p e m imics t ha t b r oad e r p eak sha p e see n at 45℃， bu t t he r ete n tio n t ime dec r eases sl ightl y ， w i t h t h e exce p t io n of 100bar where t he rete n tio n t i me i n c reases. Th i s same data set was r epeated usin g b e n z e ne a s t he samp l e and t h e exact same reten t io n behavior was di spl a y ed . Wit h ben z e n e， the p eak broade n in g wa s a l s o e vid e n t a t 45℃ a n d 55℃ co mp a r ed t o 35℃， b u t was much l ess s ignif ican t . Applicat i on L i brar y ： h ttp：//www.j a s co i n c.co m /appl i c a t i on s Figur e 5. Tol u en e Ret e nt i on Tr e nd s a t Var i ous Temp e r a t u res a n d Pres s ures. T h ese plo t s d ispl a y t he rete n tion t imes f r o m the c hrom a t o gr a m s i n f ig ur e s 3 a nd 4 f o r tolu e ne. Th e re t ent i o n t ime increases as t h e p r essu r e i s i nc reased fr om 150 b ar up to 300 bar wi t h both 100% CO2 and 90% CO2：10% methanol as p l ot t ed i n f ig ure 5 and see n i n fi gu res 3 and 4. The r etention t i me t rend is i dentical for bo th wi t h 10%methanol as exp ecte d produci ng earl i er elu t ion . A t 100 b a r ， h owever， t he r etention t ime does n ot f ol l ow t h e t rend whe n t he mobi l e p h ase is 100% CO2 an d to l ue n e has lo nge r r etention as t he tempe r a t ure is i ncreased from 35℃ to 45℃ to 55℃.T h is s ugg ests t hat t here i s a sig n i f i cant dif f ere n ce i n t he mobile ph ase (100% CO 2) d en s ity a t 100bar for 35℃ and 55℃produc i ng v ery diffe r ent r etention t imes. The p resence of 10% methanol， which is i n t he l iq ui d ph ase， in h i b its t he d e n s ity c ha ng e l ead ing t o r ete ntio n t im e s t hat f ollow t he t ren d s se e n at h i gh er p r essures. Co nclusion This ap p lica t ion has no t on ly i ll u stra te d h ow t h e uni qu e p a r ame t er of b ac k p r e ssure pl ays a sig nifi cant ro le i n retention t i m e ， b ut a l s o how it can b e ut i l i zed to op timize a separation whe n resolut i on i s m i n imal. Bot h a lk an e s and arom a t ics wer e more retai n ed at h ig her p ress u res， b ut h i gher t empera t ures h ad the o ppo site effect on r etention a n d also l ed to p ea k b roade n ing . T hese s ig nif i can t effec t s f rom b ac k p ressure a n d t emperatu r e pr ov i de a user t he ab i li t y t o tu n e a separa t ion d e pen d ing on to which c l ass of com p ounds the y are loo k in g to maxi m ize t h e resolu t ion .