The Cerex 48 Positive Pressure SPE Manifold provides a means to batch process solid phase extraction columns in the 48-position format. Using positive pressure to push liquid samples through spe columns is a more efficient process than using vacuum. Positive pressure provides more even flow and flow control of liquids going through a spe column.
Each of the 48 holes in the Processor manifold are restricted in order to maintain the manifold pressure even if all of the positions are not filled by columns. In addition there are valves located on top of the manifold that shut off individual rows of 12. With no column in place, there is approximately 0.75 +/- .05 scfh of flow through a hole at 25 psig. The principle of the restrictor manifold design is discussed in the following diagrams.
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The manifold is segmented into 4 rows. Using the 4 toggle switches on the manifold, individual rows of 12 can be turned on or off to save nitrogen. The adjustable flow reading on the rotometer equates to the total flow to the turned on rows.
The CEREX column racks interface to several collection tube racks which are also in the 48-position format. Depending upon the volume of the effluent, the appropriate collection rack can be selected from the ancillary products available with the Pressure Processor.
The processor collection tube racks are optimally designed for 75mm or 125mm high collection tubes. Ancillary collection racks are available to accommodate common collection tube sizes (Auto sampler vial racks, 10x75, 12x75, 13x100, 13 x 125, 16 x 100 and 16x125). Contact customer service for further details and availability of other sizes.
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The waste bin and tube racks are physically keyed to the platform by three elevated pins on the platform that recess into the bottom of the rack. When installed appropriately, the racks should sit level on the platform.
Cerex 48 column racks are keyed to the collection racks so that sample position is preserved throughout the SPE sequence. The column rack is then positioned directly on top of the waste bin or collection tray. Note that when appropriately placed, the stack should sit level on the platform. For each extraction step, slide the platform toward the back until it stops on the guides.
All collection racks are compatible with the system 48 sample concentrator, allowing for samples to be placed in the concentrator without the timely transfer of samples from rack to rack.
- Column Compression & Decompression
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The Processor is designed to accept up to 48 columns installed in the column rack. Because of the unique manifold design, each column will be pressurized to the same level even if columns are omitted. Refer to "Manifold Operation" in the following section.
Assemble the appropriate collection rack and SPE column rack and position the assembly on the System 48 Pressure Processor slide platform. Slide the platform to the rear of the processor until it reaches the stop locating it under the manifold.
The two blue push buttons used to activate the compression mechanism are located on opposite sides of the front panel. Both push buttons must be pressed at the exact same time to open or close the compression mechanism. Activate the column compression mechanism by depressing the push buttons until the manifold has stopped moving (2 to 3 seconds). If you let go too soon the manifold mechanism will automatically open. This is a safety feature designed to keep your hands clear of moving parts during the compression and decompression cycle.
Decompression of the rack assembly is activated similarly. Both push buttons must be depressed simultaneously until the manifold has stopped moving. Slide the rack assembly forward until it reaches the stop and proceed with the next step of the SPE method.
The compression speed is pre-set and is not adjustable. The pressure applied to the compression system is pre-set and is not adjustable.
- Extraction Flow Adjustment
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The System 48 Pressure Processor has a two-level gas delivery system used to pressurize the SPE columns.
One part of the system is controlled by the rotameter located on the left side of the instrument panel. By switching the "SPE FLOW RATE" selector to the left, "ADJUST FLOW" setting, the gas is delivered to the SPE Column Manifold through the ADJ FLOW regulator and then through the rotameter which is controlled by the needle valve located at its base. The rotameter route provides a very precise slow flow through the SPE columns by limiting the gas flow to the manifold from 0 to 2.5 SCFH.
NOTE: The rotometer needle valve is for adjustment only and is NEVER to be used as an on / off valve. Use the selector valve to turn off the nitrogen flow.
The second part of the gas delivery system provides for rapid gas flow to the manifold which is controlled by adjusting the regulator located below the pressure gauge labeled "MAX FLOW." The pressure range is 0-80 psig and is used to maximize flow through the SPE columns for processing viscous or high particulate samples or to dry the columns in situ. By switching the "SPE FLOW RATE" selector to "MAX FLOW", gas is introduced to the manifold at the pressure set on the "MANIFOLD PRESSURE" regulator as indicated by the gauge located directly above it.
By turning the "SPE FLOW RATE" selector to off, no gas will flow to the manifold; it should be in the off position when decompressing the columns between the various SPE method operations.
Note that the regulator is of the "locking" type. The regulator can be adjusted by pulling out on the regulator knob. Once the desired pressure is set, it can be "locked in" by pushing in on the knob.
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