Du Pont Instruments solve tough measurement problem New Du Pont 9 1 0 DSC achieves sensitivity of 0 . 0 0 5 mcal/sec/inthe highest available. The polymer is cooled below 0°C and the clustered water is frozen. Upon reheating, the water melts and the associated heat of fusion is quantitatively measured from the DSC endotherm. The total millicalories involved compared to that of pure water (80 mcal/mg) yields the amount of water present. Clustered water levels as low as 10 ppm can be measured. In addition to high sensitivity and stable baseline performance, the 910 DSC provides reliable and reproducibly accurate quantitative heat flow measurements for other analyses such as specific heat and purity. Free Offer: If you have an analysis, characterization or measurement problem that could be solved by DSC or any other form of thermal analysis, we'll be happy to consult with you at no charge. Just write to DuPont Instruments, Room 3 5 7 2 0 , Wilmington, DE 19898. Or call our TA Hot Line at (302)772-5134. Circle reader service number 47
The extremely high sensitivity of the new Du Pont 910 Differential Scanning Calorimeter (DSC) enables you to accurately measure low enthalpy transitions and/or to use small samples. This new DSC system also provides superior resolution and optimal temperature accuracy. For example, it's been shown that dielectric loss in polyethylene
cables is related to the amount of clustered water in the polyethylene. T h e D u P o n t 910 D S C , because of its high sensitivity and excellent baseline stability at subambient temperatures, facilitates the measurement of clustered water in polymers as shown in Figure 1. Figure 1
514 A • ANALYTICAL CHEMISTRY, VOL. 49, NO. 6, MAY 1977
Do analytical and preparative LC with the same instrument. You could use two different instruments to do analytical and preparative liquid chromatography, or you could use just the DuPont 8 4 8 . The DuPont 8 4 8 functions both as an analytical instrument to resolve complex mixtures of chemical compounds and as a preparative instrument to purify or separate gram-size samples. The only change you have to make is to switch columns.
rerun under analytical conditions to show the absence of impurities (Figure 4).
Figure 4
Free Offer: If you have an analysis, characterization or measurement problem that could be solved by any mode of HPLC, we'll be happy to consult with you at no c h a r g e . J u s t write to DuPont Instruments, Room 3 5 7 2 3 , Wilmington, DE 19898. Or call our LC Hot Line (302) 772-5139.
each column. Minimum specifications are listed below. This analytical data reduction system eliminates the uncertainty in commonly used manual determinations of column parameters. Key performance characteristics are quantified with a p r e c i s i o n a n d a c c u r a c y unmatched in the industry. The system assures you will receive a column with the proven high quality and performance needed for any instrument used in today's HPLC analyses.
Circle reader service number 4 8
Figure 2
For example, 5 0 0 micrograms of impure cholesteryl phenylacetate was separated using the DuPont 8 4 8 LC (Figure 2). The impurities represented less than 1 % of the total sample weight.
Figure
Du Pont guarantees your LC Column performance. A computerized data reduction system developed by DuPont measures the high quality perform a n c e of Zorbax™ and Size Exclusion Columns against exacting quantitative specifications. DuPont then warrants each column to perform as specified for 60 days or it will be replaced. You get well-defined test procedures, specified performance parameters and objective data analysis on
The excellent resolution typical of DuPont HPLC Columns is illustrated in Figure 5. This high resolution, coupled with precise feedback flow control used in DuPont liquid chromatographs, permits accurate identification of components of complex mixtures based on retention volumes. Free Offer: If you have an analysis, characterization or other measurement problem that could be solved by any mode of HPLC, we'll be happy to consult with you at no charge. Just write to DuPont Instruments, Room 35726, Wilmington, DE 19898. Or call our LC Hot Line at (302) 772-5139. Circle reader service number 49
Figure 3
One gram of the sample was then purified on the same instrument, simply by substituting a preparative column for the analytical one (Figure 3). The purified cholesteryl phenylacetate obtained was then
C O L U M N SPECIFICATIONS Minimum Plates per Column (25 cm)
Peak Symmetry (Skew)
Zorbax™ SIL 4.6 m m ID
9,000"
1.1 max.
Zorbax™ ODS 4.6 m m ID
8,000*
1.1 max.
Size Exclusion 6.2 m m ID
5,000
1.4 max.
* 1 5 c m also available at comparable efficiencies
DuPont Instruments
DUPONT
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ANALYTICAL CHEMISTRY, VOL. 49, NO. 6, MAY 1977 • 515 A
