Page 6 - Solutions for Plastic Evaluation

Evaluation of Raw Materials
Molecular Weight Distribution
HPLC

Evaluation of Plastic Materials Example of Recycling Preparative Separation of Polystyrene
HPLC is widely used as a means to purify samples by separation, but the large preparative columns become quite expensive. Any
cost limitations affect column length and quantity to achieve better separation. In such situations, separation can be improved
by recycling the eluent band containing the target components through the column several times to effectively extend the
column length. In this example, a Prominence semi-preparative recycling system was used to separate polystyrene by GPC.

Fig. 1 illustrates the flow line of the Prominence semi- 4PMWFOU *OKFDUPS
Evaluation of Raw Materials autosampler or manual injector, then separated by the EFMJWFSZ QVNQ 3FDZDMF LJU 1SFQBSBUJWF DPMVNO 67 7*4 EFUFDUPS
preparative recycling system. The sample is loaded by
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ʢ41% "ʣ
preparative column and eluted to the detector. Here, the
system uses a recycle valve to divert the eluate either to the
flow line leading to a fraction collector, or to the flow line 3FDZDMF WBMWF
leading back to the pump inlet. By switching the recycle %FHBTTJOH VOJU 'SBDUJPO DPMMFDUPS
ʢ'3$ "ʣ
valve to divert the flow back to the pump inlet when target ʢ%(6 " ʣ
Product Evaluation preparative column as many times as necessary to obtain Fig. 1 Flow Line of Prominence Semi-Preparative
peaks are eluted, the sample can be recycled through the
a separation equivalent to using a longer column. Since
recycling the eluate does not consume any new mobile phase,
Recycling System
it also helps reduce solvent consumption.

Fig. 2 shows an example of a recycle separation of polystyrene molecular weight markers (molecular weight = 781 and
Product Information polydispersity, can be separated into many oligomer peaks. By switching the recycle valve to the flow line leading to the FRC,
polydispersity* < 1.15). Portions indicated by arrows are recycled. This shows how even polystyrene, which has low
target peaks are easily collected.

Fig. 2 Example of Recycling Separation of Polystyrene

Analysis Conditions
Instrument : Prominence semi-preparative recycling system Flowrate : 3.0 mL/min
Analytical Column : Shim-pack GPC-20025C+2002C+2001C Column Temperature : Ambient
(each 300 mmL × 20 mm I.D.) Detection : UV 254 nm
Mobile Phase : Chloroform

* Polydispersity = Weight-Average Molecular Weight / Number-Average Molecular Weight

6 LAAN-D-XX004A