all the data stored in the buffer are processed. During the actual d a t a re duction by P O L U T , subroutine E V E N T is called whenever a nonzero value is sensed on the event code channel of the aircraft data. Subrou tine E V E N T is employed to match the recorded event code t o one of the known range values or to output an error message if no match can be lo cated. T h e F I L T R subroutine was originally designed to detect erroneous data and/or apparent instrument range changes. This error algorithm checked for a 50% variance between any two analogous d a t a readings from two consecutive records. If a 50% vari ation was detected, the data values were flagged as probable errors or the result of nonrecorded range changes and the operator was notified. How ever, this F I L T R algorithm did not work successfully for small data values below 25 since normal fluctuations in this range were incorrectly flagged as errors. Therefore, it now appears t h a t some form of error probability analy sis or a more complicated d a t a correla tion technique would be necessary t o achieve the desired check for errone ous data. For this reason the original F I L T R subroutine is not used in the present P O L U T software. Once G E T R C and P O L U T have read and reduced all of the data stored in the buffer memory, the processed d a t a are output to t h e line printer. Unless an end-of-tape has been sensed, the entire procedure starts over again by filling the buffer from the tape reader. This process con tinues until commanded to stop by the operator, or by reaching the end of the tape, or by sensing an end-of-flight (AIR) or an end-of-run (GND) in the respective event code channels. Periodically during the execution of P O L U T , subroutine ABCHK is called to sense if the operator has requested an abort by setting switches 0 and 15 on the minicomputer switch register. When an abort is detected by ABCHK, control is transferred to the beginning of P O L U T . At the comple tion of a tape processing run, subrou tine C P R T Y is used to o u t p u t the number of parity errors detected in the recorded data.
THE LC COLUMN DuPont guarantees LC Column performance. D u Pont now guarantees* the chroma t o g r a p h i c p e r f o r m a n c e of a n a l y t i cal c o l u m n s based on Zorbax , and D u Pont Size Exclusion columns with tight specifications on efficiency (theo retical plates) and peak symmetry. Mini m u m specifications for c o l u m n efficiency are listed below.
T h e capabilities of a minicomputerbased gas chromatographic data sys tem have been expanded through ad ditional hardware and software to in clude the acquisition and processing of supplementary air monitoring data. T h e result is a portable, flexible, and convenient facility for the on-site re duction of pollutant, meteorological, and navigational information t h a t is routinely collected in atmospheric
Each of these columns is quality con trol tested with an exclusive on-line computerized system. This analytical data reduction system, a development of D u Pont corporate research, elimi nates the uncertainty inherent in c o m monly used manual determinations of c o l u m n parameters. Key performance characteristics are quantified with a precision and accuracy unmatched in the industry. T h e system assures receipt of a c o l u m n with the proven high quality and performance needed for today's HPLC analyses. Circle 0000 on the Reader Service Card for more information. *Du Pont warrants every column to perform as specified or it will be replaced.
COLUMN SPECIFICATIONS Minimum Plates per column (25 cm)
Minimum Plates per meter
Zorba™SIL 9,000" Zorba™ODS 8,000 Size Exclusion 5,000 •15 cm also available at comparable efficiencies
SEC Columns characterize polyolefins in less than 12 minutes. Recent laboratory studies have shown that D u P o n t s exclusive high-tempera ture size exclusion system can rapidly c h a r a c t e r i z e p o l y o l e f i n s , s u c h as polyethylene, for molecular weight and molecular weight distribution as shown in the chromatogram below. A knowledge of these two key para meters can provide predictable control
36,000 32,000 20,000
of f u n d a m e n t a l physical p r o p e r t i e s such as strength, hardness, elasticity and flow characteristics. High tempera t u r e ( 1 3 5 ° C ) is necessary b e c a u s e these materials are insoluble at normal r o o m temperatures. D u Ponts high performance SEC col umns and a unique flow feedback sys t e m provide extremely rapid polymer analysis with high precision. A d d i n g the new Du Pont infrared LC detector gives h i g h l y sensitive d e t e c t i o n for polyolefins with unparalleled operating stability. To take advantage of Du Ponts years of technical experience in solving polymer problems, circle 0000 on the Reader Service Card. Or write D u Pont Instru ments, Room 35622, W i l m i n g t o n , DE 19898.
HIGH PERFORMANCE SIZE-EXCLUSION CHROMATOGRAPHY O F LINEAR POLYETHYLENES OPERATING CONDITIONS Sample: Polyethylenes Column: 1000A( 1 ), 500A< 1 ), 100A( D i n series Column Temp: 135°C Detector Du Pont Infrared LC Detector at 3.40 microns
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Conclusions
March/April
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D
Mw
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53.100 84,100 175,000 170,000
18.300 25.200 14,300 36,000
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CIRCLE 50 O N READER SERVICE CARD ANALYTICAL CHEMISTRY, VOL. 4 9 , NO. 3, MARCH 1977 · 3 6 7 A
