Six Channel Respiration System (RS-650)
The RS-650 Respiration System is a complete 6-channel system for measuring cellular respiration or the activity of oxidative enzymes.
The system includes:
- RC-650 respirometer
- 6-Channel 929 meter
- Six 1302 electrodes
- Standard respiration software
- electrode service kit
The RS-650 Respiration System is a complete package offering everything needed to measure respiration on six independent channels.
The system is comprised of an RC-650 six-channel respiration platform, a 929 six-channel meter with software, six 1302 electrodes with polyproplyene membraned jackes, and two electrode service kits for the 1302's. Specific component information is shown below.
The RC-650 includes:
- A sealed water bath that connects to your pumped source of constant temperature water
- Six active cells for use in respiration measurements
- Six parking cells to maintain the oxygen sensors at a stable temperature when not in use
- Six adjustable electrode holders used to set the volume in the active respiration cells from 1-3. ml (user calibrated)
- A 6-position, 12 V magnetic stirrer unit
The RC650 is designed for replicate respiration measurements of cell suspensions, microbial suspensions, mitochondria or enzyme preparations. The chamber body houses a sealed water bath containing both active and parking cells. An intergral magnetic stirrer makes up the base of the assembly.
Active cells are located at the front of the bath and are centered over the coils of the magnetic stirrers below. Each cell is sealed by a neoprene o-ring. The volume of each active cell may be set between 1 and 3 ml by rotating the knurled collar of the electrode holders. The rear of the bath contains the six parking cells used to hold the electrodes at a constant temperature while contents of the active cells are changed. The cells are sealed into the water bath by O-rings to facilitate easy removal and cleaning.
Each electrode holder has an aperture through which the membrane tip of the 1302 oxygen sensor protrudes. The electrode is positioned in the holder by pressure exerted by the cap on three o-rings at the cable-entry end of the electrode. This seals the nose of the electrode against the precision shaped plastic tip of the holder, so that only the membrane-covered cathode protrudes.Each cell also has a slot runs the length of the holder. This slot provides pressure releif as the electrode is inserted into the holder. In addition, respiratory inhibitors or other solutions can be injected directly into the cell via this slot, using an included fine bore needle. Electrode holders are made from black acetal.
Respiring preparations in metabolic studies are often conducted at 37ºC and have a fast time course. For studies of this type, it may be beneficial to use FEP membranes which have a very fast response time (typically 95% of full response within 6-8 secs). The MS-650 comes with standard polypropylene membraned jackets. COntact our offices if FEP based electrodes are desired.
The 928 Six-Channel Oxygen Meter is designed for replicate measurements of dissolved oxygen, together with data recording and analysis by computer, on up to six channels. It is also ideal for multi-chamber repsirometry experiments, using either closed chambers or flow cell respirometry systems.
The main components of the 929 include:
- The 929 meter with electrode inputs and computer interface
- Standard respirometry software
The 929 Oxygen Meter was developed to permit precise replicate experiments, and to monitor and analyze the results by computer. The 929 is particularly valuable in respirometry experiments since the software is written to accommodate the large range of procedures and recording units used by different researchers. The parallel nature of this meter can provide a considerable time saving in both respiration and dissolved oxygen monitoring experiments. All operations are controlled from the computer and output of recordings in chart recorder format to a printer is available.
Logging of data by the 929 is carried out automatically and the complete experiment is conducted on screen. Results can be easily copied to other programs (e.g. spreadsheet) for graphical display or statistical analysis. For those who desire a hard copy output, the facility to print screen traces directly to a printer is also available.
The 929 is sophisticated enough to supply a controllable stable bias voltage to six electrodes, amplify the resulting output currents, convert the analog current signals into digital values, and send these digital values to the computer. The interface is microprocessor-based and incorporates the latest integrated circuits. The input amplifiers are highly sensitive and are high impedance, military specification devices. The the A/D converters are 16/22 bit sigma delta devices which provide integral filtering of noise. The power supply employs a wide input, switched-mode regulator and can run on 110-250 V with no adjustment. To enhance ripple rejection, the interface will only operate on a 50 or 60 Hz supply.
The interface has a single front panel control, the POWER switch, which is disabled while measurements are underway. It has an illuminated text display to inform the user of all operations carried out under control of the computer, including a continuous readout of input oxygen values. The interface provides the bias voltage to the electrodes, amplifies the resulting signal, carries out A/D conversion, provides signal averaging, and communicates with the software resident in the computer.
The software package includes experiment set-up, data recording, and data analysis. When the software is used for monitoring dissolved oxygen, oxygen values at flagged or set points can also be directly transferred to the Results and Reports page. The program has been written to be user-friendly and easy to learn. When used for respirometry experiments, it follows the familiar logical sequences of operations, from electrode calibration to recording and analysis.
The setup screen is used for entering all of the details which the computer needs in order to record in the correct units, and to express the respiration rate, normalised to biomass units if required, in the desired units. All experimental details entered here are transferred through to the final calculated results report page. During setup, the cell volumes (for closed cell) and flow rate, electrode positioning (for flow respirometry), temperature of the experiment, scrolling speed of the traces during recording, and the instruction to print the recording screen to printer (if hard copy is required) are all entered. Many of these will not change from one experiment to the next, and it is only necessary to enter changes.
Clicking the 'Start' button initiates the recording process, and traces the data scroll across the screen. If substrates, inhibitors or other solutions require to be added during the run, the position where this occurs can be recorded with a flag, and the nature of the addition is recorded on a drop down menu. At the termination of the experiment, the data are saved to a data file, and may be analyzed straight away if required.
The data file and recorded traces, and event marker flags are recalled to the screen. If the recording has exceeded one screen width, it can be contracted to fit the screen, if required. Alternatively it is possible to scroll along long recording traces. Selector lines may be dragged to enclose specific parts of the trace. Thus if the traces show both control respiration and changed respiration after adding a solution, the selector lines would be dragged to the control rate first and then to the changed rates.
In each case respiration rates (normalized if so designated) are calculated automatically by clicking the Calculate button. The calculated rates are tabulated, together with the experimental details entered during Setup, on the report page. The results may be exported to a spreadsheet, word processing or statistics package. The Analysis screen and the Report page may be printed, if required.
When the software is used for dissolved oxygen monitoring, the Analysis screen displays the recorded traces and the oxygen values at flagged points or at set times can be transferred to the Results and report page. The program requires a computer with a minimum specification of: Pentium processor, 1 free serial port, 128 MB RAM, Windows 95 or later and 4 MB hard disk space. A comprehensive Instruction Manual is also supplied.
The 1302 Oxygen Electrode is a precision electrode with a very small diameter. Its rate of oxygen consumption is extremely low so that when used with the relatively low permeability polypropylene membranes, most of the resulting oxygen gradient is confined to the distance between the outside of the membrane and the cathode surface. Consequently there is no requirement for physical movement of the solution to replenish the oxygen at the outer surface of the membrane.
The relaxation of a stirring requirement for the 1302 results in a small stirring artifact (2-3%) when the electrode has been calibrated in stirred solution and is then used in an unstirred environment (and vice versa). In general, electrodes using the fast-responding, highly permeable FEP membranes have a large O2 flux through the membrane. This causes the electrode to behave as a macrocathode making it necessary to stir.
Unfortunately, it is not possible to build a fast electrode with no stirring requirement, and it is important to note that most Clark-type electrodes require stirring. Only in a microcathode electrode such as the 1302, fitted with a low permeability membrane, is stirring not required.
Stirred Clark-type electrodes
Clark-type oxygen electrodes consist of a probe with an exposed tip containing a gold or platinum cathode and a silver or silver/silver chloride anode. When the anode and cathode are polarized so that the cathode is held at a voltage of -0.6 to -0.8 volts relative to the anode, the following reaction will occur at the anode when placed into a solution of electrolyte such as KCl:
4Ag -> 4Ag + + 4e, and 4Ag + + 4Cl- -> 4AgCl
Simultaneously, at the cathode, any oxygen which is present is reduced:
O2 + 2H2O + 4e -> 4OH-
Thus for each oxygen molecule reduced, 4 electrons of current flow in the circuit. Oxygen is therefore continually consumed as it is reduced to OH at the cathode. In practice, the anode and cathode are covered by an oxygen permeable membrane to exclude other species which would interfere. The KCl electrolyte is buffered to remove the OH produced in the cathode reaction. As oxygen is removed at the cathode, a pO2 gradient is set up which extends outwards into the surrounding medium. In unstirred water, oxygen therefore diffuses inwards along the pO2 gradient. Because of the pO2 gradient, the outside of the electrode membrane is effectively sensing a lower pO2 than that in the surrounding water. For this reason, most Clark electrodes require the surrounding sample to be stirred. The size of the signal generated by the electrode is proportional to the flux of oxygen molecules to the cathode.
Last Revision 6.28.12
|Resolution with 1302 Oxygen Sensor||0.1% of air-saturated water|
|Polarizing Voltage||400-900 mV (anode connected to ground)|
|Power Requirements||100 to 250 VAC, 50/60 Hz|
|Dimensions||275 x 258 x 117 mm (11 x 11 x 4.5 in)|
|Diameter of Cells||16 mm|
|Volume of Cells||1 to 3 mL (adjustable)|
|Cell||Precision bore glass|
|Electrode Holder||Black acetal, with peek tip|
|Bath||Clear and black acrylic|
|Magnetic Stirrer||6-position; 12 VDC
from external plugtop power supply,
100-230 V, 47-63 Hz.
This is a Clark-type polarographic electrode, with a 22 micron diameter platinum cathode and silver/silver chloride anode, connected by a buffered potassium chloride electrolyte solution.
In the normal configuration the cathode is covered with a relatively low permeability polypropylene membrane, in order for the electrode to be used in unstirred solutions or where minimal stirring is required. With these membranes, there is a relatively slow response time. For fast response, as required for rapidly respiring enzyme preparations, a thin FEP membrane (used with a special electrode jacket) is used. Rapid stirring of the medium is then necessary. The electrodes are not temperature compensated and require to be used at controlled temperatures (within + or -0.05°C). They should always be used in the electrode holder, so that only the tip of the electrode is exposed to the medium.
|Response time at 37°C:|
|Polypropylene membranes||18 sec. for 90% change|
|FEP membranes||6 sec. for 90% change|
|Oxygen consumption (polypropylene membranes)||0.5 to 3x10-10mg O2/min|
|Temperature coefficient||2% per °C|
|Resolution of 928 and 782 meter||0.1% with 1302 electrode*|
*The display resolution of the 982 and 782 meter is 0.1%. The A/D converter is capable of at least 0.01%, so you can work on an expanded scale. However, the limit is normally set to about 0.1% by the noise level of the 1302 electrode.