US2981092A - Chromatographic sampling valve - Google Patents

Description

April 25, 1961 M. MARKS CHROMATOGRAPHIC SAMPLING VALVE 4 Sheets-Sheet 1 Filed Nov. 25, 1957 IL I INVENTOR. MOA/Tf L. MAR/(J %,%#1

lmxlrlllp April 1961 M. L. MARKS 2,981,092

CHROMATOGRAPHIC SAMPLING VALVE Filed. Nov. 25, 1957 4 Sheets-Sheet 3 FIG. 4

LLSIMIILE loop y 1 INVENTOR. MU/VT/f L. MAR/(d ATTORNEYJ 042mm? [/v SAM/ L: /v

JAMPL: Our 4 COLUMN Our A ril 25, 1961 Filed NOV. 25, 1957 M. L. MARKS 2,981,092

CHROMATOGRAPHIC SAMPLING VALVE 4 Sheets-Sheet 4 INVENTOR. MO/VTf L. M/MKS fm iww U ited States P n 2,981,092 CHROMATOGRAPHIC SAMPLING VALVE Monte L. Marks, Pasadena, Calif'., assignor, 'by mesne assignments, to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of Cahforma Filed Nov. 25, 1957, Ser. No. 698,775 2 Claims. (Cl. 73--23) This invention relates to sampling methods and apparatus for chromatographic analysis. 7

In a typical chromatographic analysis, a mixture of a carrier fluid and a sample fluid are passed through a chromatographic column of absorbent which separates the sample into its pure components.

It is frequently necessary in chromatographic analysis to analyze mixtures containing high and low boiling components covering a wide range of boiling point temperatures. If all components of such a sample are flushed through the column of a conventional analyzer, all .components are separated by the column, requiring anexcessive total analysis time because the high boiling components pass through the column more slowly than the low boiling components. In many cases only the low boiling components in a sample are of analytical interest, and the separation of the higher boiling components in the sample ties up the equipment for an unproductive period. This invention overcomes this disadvantage by providing methods and apparatus for chromatographic analysis 'inwhich the high boiling components are grossly separated from the low boiling components in a short column of relatively poor resolution. At least one group of components is then passed to. a separate column where the components of the group are further separately resolved in' a. specifically designed column at greater eificiency and shorter total analysis time. 1

In termsof method, the invention contemplates chromatographic analysis of a sample, which includes a first group of components having relatively long retention times and a second group of components having shorter retention times, by-passing the sample into a preliminary chromatographic column to effect a gross separation of the first group of components from the second group. Thereafter, a chromatographic separation is effected on the components in at least one of the groups in a secondary chromatographic column.

before-any appreciable portionof'the components of the second group have emerged from the column, and the ing the 'samplechamber to either of the fluidstreams,

and'one of the bodies has spaced passages in it for selectively flowing the: carrier stream through a preliminary chromatographic column in either of two directions. Means are provided for sliding one body with respect to the other to, a first position to fill-the sample chamber with a known volume of sample fromthe sample stream,

Preferably, the flow of a .'sample'through the preliminary column is stopped after substantially all .thecomponents of the first group, and

and also to flow the carrier stream through the preliminary column in one direction. Means are also provided for sliding one of the bodies with respect to the other to a second position to introduce the sample into the carrier stream, and also to flow the mixture of sample and carrier through the preliminary column in the opposite direction.

In. the preferred form of the apparatus, a secondary chromatographic column is adapted to be connected in series with the preliminary column when the mixture of sample and carrier is passing through the preliminary column, and the secondary column is adapted to be flushed with pure carrier fluid when the sample chamber is being filled with sample.

These and other aspects of the invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in 1 tion.

Referring to Fig. 1, a rotary sampling valve 10 includes a lower fixed and upright cylindrical body 12 and an upper rotatable and upright cylindrical body 14 with its bottom surface disposed to slide on the top surface of the fixed body. A vertical rotatable shaft 16 is journalled through a bore 18 in the center of the fixed body. The upper portion of the shaft passes through a bore 20 in the center of the rotatable body and is secured by a longitudinal key 22 to the rotatable body. An annular recess 24 in the top surface of the rotatable body around bore 20 receives the' lower end of a compression spring 26 'coaxially disposed around the upper end of the shaft. A spring retainer cap 27 is secured by a screw 28 to the upper end of the shaft and holds the spring in compression so that the bottom surface of the rotatable body bears against the top surface of the fixed body.

A pair of washers 29 on opposite sides of a ball hearing 30around the shaft are held against. the bottomsurface'of the fixed body -by a C-ring 31 set in an annular retaining groove 32 in the shaft below the lower washer. The shaft is adapted to be turned by any suitablemeans so the rotatable body may be rotated with respect to the fixed body.

The top surface of the fixed body has an annular recess 33 around the shaft to match a similar recess 34 in thebottom surface of the rotatable bodytoprovide a second group is then backwashed from the preliminary sump. for any foreign particles which might find their way into the valve along the shaft.

To facilitate valve operation and insure long life, the valve bodies are preferably made of durable metal and the sliding surfaces preferably are suitably lubricated. For example, in a valve of the type just described, the lower body was made of stainless steel, type 440 C, heat treated to a hardness of 60 Rockwell C, and its upper surface was flame coated with tungsten carbide. The 7 upper body was made from a high nickel steel bearing materialywhich was softer than the lowerbody; The

sliding surfaces were lapped to perfect flatness within a tolerance of 11 m1cro-inches, and were lubricated with v an inert, high temperature (good up to' 400 F.) silicone grease sold by Dow Corning as Heat Stable Silicone Grease.

Referring to Fig. 2, the upper body includes 5 pairs of longitudinal bores 35 which open in the bottom surface of the rotatable body on a'common circumference at vals on a common circumference of the same diameter as the longitudinal bores in the rotatable body. Each of the longitudinal bores in the fixed body terminate in a common plane in an intermediate portion of the lower body. The inner ends of the longitudinal bores 41 and 44 are respectively connected to outlet and inlet ends of asample chamber 48 by radial and outwardly extending lateral bores 50 and 51.

The inner ends of longitudinal bores 37 and 40 in the fixed body are connected by radial and outwardly extending bores 52 and 53, respectively, to opposite ends of a preliminary or short chromatographic column 54. The inner end of longitudinal bore 43 is connected by radial and outwardly extending lateral bore 56 to a sample inlet tube 58, and the inner end of longitudinal bore 42 is connected by a radial and outwardly extending bore 60 to a sample outlet tube 62.

A first carrier inlet tube 64 is connected by a radial bore 66 to the inner end of longitudinal bore 45, and a first carrier outlet tube 68 is similarly connected by a bore 70 to the inner end of longitudinal bore 46. A second carrier inlet tube 72 is connected by a radial and lateral bore 74 to the inner end of longitudinal bore 38, and a second carrier outlet tube 76 is connected by a lateral and radial bore 78 to the inner end of longitudinal bore 39.

As shown most clearly in Fig. 4, which is a schematic flow diagram illustrating the operation of the invention, a stream of carrier fluid, say a gas such as helium, flows in through a line 80, through a pressure regulator 82, into a thermal analysis cell block 84, which may be of conventional type, and then into the fixed body of the valve through the first carrier inlet tube 64. The first carrier outlet tube 68 is connected to the inlet of a secondary or final chromatographic column 86. The outlet of the secondary column flows back through the analysis cell and then exhausts to the atmosphere through a line 87.

One end of a line 88 is connected to the carrier supply line 80 on the high pressure side of the regulator and supplies carrier fluid to the fixed body of the valve through the second carrier inlet tube 72. The second carrier outlet tube 76 is connected by a line 90 to line 87 to exhaust to the atmosphere.

With the rotatable body set so that. the ports in the fixed body are interconnected as shown by the solid lines in Fig. 4, a first stream of carrier fluid flows through the regulator one portion of the analysis block, in the first carrier inlet tube, out the second carrier outlet tube, through the secondary chromatographic column, through a second portion of the analysis cell, and then to the atmosphere. A second stream of carrier fluid flows through line 88 into the second carrier inlet tube 72', through the preliminary or short chromatographic column in a reverse direction, into the fixed body of the valve through bore 53, out the second carrier outlet tube 76, and then through line 90 to exhaust through line 87 to the atmosphere. A sample stream flows through a line 92 into the sample inlet tube, through the sample loop, out the sample outlet tube and exhausts to the atmosphere through line 94.

Thus, in the solid line position shown in .Fig. 4, the sample stream .flows through the. sample loop, one portion of the carrier stream flowsthroughthe secondary chromatographic column, and a second portion of the carrier stream backwashes the preliminary chromatographic column. When it is desired to analyze a sample containing a group of components having a long retention time and a group of components having a short retention time, the valve is rotated 36 in a clockwise direction as shown by the arrow in Fig. 4, so that the radial bores of the fixed body are interconnected by the lateral ports of the rotatable body as indicated by the dotted lines. In this new position, a portion of the carrier stream flows in the first carrier inlet tube 64, out the lateral bore, through the sample chamber, through the short column in a forward direction, through the secondary chromatographic column, through the second portion of the analysis cell, and then to the atmosphere.

As soon as the first group of components with the short retention times have passed through the preliminary column, and before any of the second group of components with the long retention times have left the preliminary column, the valve is rotated 36 in a counterclockwise direction, so that the flow of fluids is as previously indicated. The column is backwashed with a stream of carrier fluid, the sample loop is charged with another sample, and a stream of carrier fluid continues to drive the first group of sample components through the secondary column for complete anaylsis.

The size and con-tents of the preliminary and secondary chromatographic columns can vary widely depending on the type of analysis to be made. For many hydrocarbon samples the short column may be A; to V4 inch in diameter and 4 or 5 inches in length, while the secondary or main analyzer column may be A to inch in diameter and be from 5 to 50 feet long. In both cases, a typical carrier fluid velocity through the columns is 50 cos. per minute.

In analyzing a typical gasoline fraction which had both high and low boiling components, the packing used in the preliminary or short column of the type just described, was alumina, and fire brick coated with dinonylphthalate was used in the secondary column of the type just described. Using conventional techniques, i.e., chromatographic analysis with no preliminary gross separation as provided by this invention, an analysis of the gasoline sample took hour to 45 minutes. Using the preliminary chromatographic column in accordance with this invention, the same analysis was efiected in 10 minutes, resulting in a substantial reduction of analysis time.

It will be appreciated that when the high boiling components backwashed from the preliminary column with the carrier fluid, they can be passed through another chromatographic column and separated into their pure fractions.

Figs. 5 through 9 show schematically an alternate embodiment'of the invention. Fig. 5 is a schematic plan view -of a fixed cylindrical body havingsix longitudinal ports or bores 102, 103, 104, 105, 106, 107, opening in its top surface on a common circumference at 60 intervals. A sample tube is connected at each end to diametrically opposed bores 103, 106 by'lateral and radial bores 112 and 114 respectively. A carrier primary inlet line 116 is connected by lateral bore 118 to' port 104. The inlet of a secondary chromatographic column (not shown) is connected by a line 120 and lateral bore 122 to port 105. .-An exhaust line 124 is connected by a bore 126 to port 107. An alternate supply line 128 is connected by a bore 130 to port 102. A two-way valve 132 is adapted to connect the alternate supply line to either asample inlet line 134 or. an alternate carrier stream line 136.

Fig. 6 is aplan view of a rotatable cylindrical body having a smooth surface'141 adapted to slide on the smooth top surface of the fixed body 100. A set of six ports 142, 143, 144, 145, 146', 147, open into the smooth surface of the rotatable body. Ports 142 and'143 are connected by a lateral bore 148. Ports 144 and 145 are connected bylateral bores 149, 150, respectively, to opposite ends of a preliminary chromatographic column 151. Ports 146 and 147 are connected by lateral bore 152.

Fig. 7 shows schematically the operation of the valve when the rotatable body is mounted on the fixed body to flow sample through the same sample tube and flush the secondary column with carrier fluid which has passed through the preliminary column.

In Fig. 8, the rotatable body is shown turned 60 in a clockwise direction from the position shown in Fig. 7, and simultaneously, the valve 132 is turned to the position shown in Fig. 8 so that carrier gas from the secondary carrier source flushes out line 128, bore 130 in the fixed body, lateral bore 152, and ports 146 and 147 in the rotatable body, port 107 and lateral bore 126 in the fixed body, and exhaust line 124. In the position shown in Fig. 8, carrier gas from the primary inlet 116 flushes sample from the sample tube, through the preliminary chromatographic column in a forward direction, and out line 120 to the secondary or final chromatographic column. After the desired light ends have emerged from the preliminary column and before the unwanted heavy ends have been flushed through, the rotatable body is turned another 60 in the clockwise direction from the position shown in Fig. 8 to the position shown in Fig. 9. In this position, carrier gas continues to force light ends of the sample through the secondary chromatographic column. Carrier gas flowing through the external valve 132 now flushes the sample tube with carrier gas, and backwashes the preliminary chromatographic column either to exhaust the accumulated heavy ends of the sample to atmosphere or to a chromatographic column (not shown) for analysis. The valve may now be returned to its original position shown in Fig. 7 to repeat the cycle for the next analysis.

I claim:

l. A sampling device comprising a first body having a smooth surface'and a plurality of spaced ports each opening at an inner end out of the smooth surface and at an outer end at another part of the first body, a preliminary chromatographic column connected at opposite ends to the outer ends of a first pair of first and second ports in the first body, a source of a fluid carrier stream connected to the outer end of a third port in the first body, a sample chamber. connected at opposite ends to a second pair of fourth andfifth ports in the first body, a

source of a sample stream connected to the outer ends of a pair of sixth and seventh ports and a pair of eighth and ninth ports in the first body, a secondary chromatographic column connected at one end to a tenth port in the first body, a second body having a smooth surfaceheld in sliding contact with the smooth. surface of the first body, the second body having ports in its smooth surface spaced and disposed for selectively connecting the sample chamber to the sample stream and for selectively flowing the carrier stream through the preliminary column in one direction when the second body is in one position with respect to the other, and means for sliding the bodies with respect to each other to a second position to connect the sample chamber in series with the carrier stream, and to flow the sample and carrier through the preliminary column in the opposite direction.

2. Apparatus for chromatographic analysis comprising a source of carrier fluid, fluid outlet means, a preliminary chromatographic column, a secondary chromatographic column, a source of a fluid sample of predetermined volume, a sampling valve interconnecting said chromatographic columns, carrier fluid source, sample fluid source, and fluid outlet means, said valve including first and second bodies, each having a smooth surface, means for holding the smooth surfaces of the valve bodies in slidable contact with each other, a plurality of passages in each of the bodies, a plurality of first passage inlets 'and ber 1956.

outlets in one of said bodies and remote from said smooth surfaces, means connecting the source of carrier fluid, fluid outlet means, preliminary and secondary columns, and source of fluid sample to selected ones of the first passage inlets and outlets, and a plurality of second passage inlets and outlets in said smooth surfaces of said bodies, said inlets and outlets being disposed, when the bodies are slidably disposed in a first relative disposition with respect to each other, to cooperatively form fluid conduits connecting the preliminary column and the secondary column in parallel between the source of carrier fluid and the fluid outlet means so as to cause the parallel flow of carrier fluid therethrough in a pre-selected direction, and said inlets and outlets being disposed, when the bodies are slidably disposed in a second relativedisposition with respect to each other, to cooperatively form a fluid conduit serially connecting the source of fluid sample, the preliminary column, and the secondary column between the source of carrier fluid and the fluid outlet means so as to cause the serial flow of carrier fluid through the source of fluid sample and preliminary and secondary columns and to reverse the direction of fluid flow through the preliminary column while maintaining the direction of fluid flow through the secondary column in the pre-selected direction, and means for selectively disposing said bodies in the first and second relative dispositions.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Publication: Article by Lichtenfels et al., Gas Partition Analysis of Light Ends in Gasolines, published in Analytical Chemistry, vol. 28, pages 1376-1379, Septem',

Watson Aug. 7, 1956 Y

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