Components of the Olis U.S.A. Stopped-Flow

Glossary of Components

DRIVE SYRINGES: The two syringes used to introduce the two reagents into the mixing chamber. The drive syringes are submerged to control reagent temperature and gas exchange. Reagent ratios other than 1:1 are achieved through the use of two different-sized syringes; ratios to 1:10 are confirmed.

EXTRA PORT: A multipurpose opening in the sample chamber through which the new mixture may be observed during absorbance measurements, which houses the sample PMT during fluorescence measurements, and which can be used for a photolyzing flash input.

FILL/FLOW KNOB: There are two fill/flow knobs, one for each drive syringe. These knobs control the valves between the reservoir syringes and the drive syringes. Putting the knobs in "fill" position opens the valve between the reservoir and drive syringes to allow the drive syringes to be filled with reagent and closes the valve between the drive syringes and the mixing chamber to keep the reagents in their respective syringes prior to the firing of the stopped-flow. Putting the knobs is in "flow" position closes the valve between the reservoir syringes and the drive syringes and opens the valve between the drive syringes and the mixing chamber to allow the reagents to flow into the mixing chamber upon firing of the stopped-flow.

FLOW ACTUATOR: The pneumatic cylinder which depresses the drive syringe plungers when the stopped-flow is fired, pushing the reagents from the drive syringes into the mixing chamber.

FLOW/EMPTY/FLUSH KNOB: This knob controls the valve between the mixing chamber and drive syringes and between the stop syringe and purge syringe. Putting the knob in "flow" position opens the valve between the mixing chamber and the stop syringe, allowing the reagents to complete the flow path when the stopped-flow is fired. Putting the knob in "empty" position opens the valve between the stop and purge syringes, allowing the spent reagents to be emptied. Putting the knob in "flush" position opens the valve between the drive and purge syringes, allowing the drive syringes and observation chamber to be flushed between experiments.

SAMPLE CHAMBER: The compartment of the host spectrometer which houses the sample cell. The Olis RSM 1000 sample chamber is shown in the illustrations on this and the previous page. The front view (previous page) shows three ports which can house PMTs and/or provide entry for actinic light.

PMTS: The photomultiplier tubes used as signal detectors, providing single- and dual-beam detection. PMT placement illustrated above is for absorbance measurements; PMT 1 is the sample signal detector and PMT 2 is set at 90º to the sample for reference signal detection. For fluorescence measurements, the sample PMT goes in the position labeled 'extra port' and PMT2 can be placed between the light source and sample chamber to allow monitoring of the excitation light.

PLUNGER BLOCK: The block between the flow actuator and the drive syringes which pushes the drive syringe plungers, thus initiating the mixing process.

PURGE SYRINGE: The syringe into which spent reagents are drained.

RESERVOIR SYRINGES: The two syringes which hold the unmixed reagents before they are introduced into the drive syringes. These syringes can be plastic Hamiltons (as shown), homemade tonometers, or other specialized fluid holders.

STOP SHAFT: The shaft connected to the plunger in the stop syringe which serves as the stopping mechanism at the end of the flow path. The mixed reagents are pushed into the stop syringe, forcing the shaft upwards and activating the sensor on the stop shaft which signals the stop of flow. The system cannot be fired again until the stop syringe is emptied.

STOP SYRINGE: The syringe into which mixed reagents are pushed after they have gone through the sample chamber.

WATER BATH CHAMBER: The floodable well surrounding the drive syringes which is used both for regulating the temperature of the reagents and for gas purging.