Palm Sens User Guide Chapter 1

Chapter 1 - Introduction PalmSens is a hand-held battery powered instrument for use with electrochemical sensors or electrochemical cells. The instrument contains a microprocessor and a low noise and low-current potentiostat/galvanostat which controls the potential or current applied to the sensor and measures the current or potential response. In general the instrument is used with electrochemical sensors or electrochemical cells with three electrodes: working electrode, reference electrode and auxiliary or counter electrode. In the so-called two-electrode configuration the counter and reference electrodes can be combined to a single electrode. In that case the counter and reference connectors are tied together. This manual describes the use of PalmSens connected to a Pocket PC, which is used to specify the parameters of the measurement, to display the measured curves and calculate the results of the measurements. Fig. 1.1 – PalmSens connected to a Pocket PC Chapter 2 - Getting started: Installation and Setup Requirements: - Pocket PC with a cradle connected to the PC with which it is synchronized. - PalmSens installation CD-ROM - PalmSens instrument - Serial cable to connect Pocket PC to PalmSens or a Bluetooth dongle (as optional accessory) - Sensor cable with testsensor - Adapter (6 V - 1500 mA or higher) Sensor connector colour codes: Red - working electrode (WE) Black - counter electrode (CE) Blue - reference electrode (RE, can be connected to CE if sensors or cells with two electrodes are used) Green - ground Ch. 2.1 Installation of the software on the Pocket PC In order to be able to synchronise the Pocket PC with a PC, the Pocket PC must be installed according to the standard procedure described in its manual. If PalmSens is delivered together with a Pocket PC, the software has been installed and the instrument is ready for use. In case the Pocket PC is delivered separately from PalmSens without installed software, this has to be installed. Refer to Appendix ‘Installing and updating Pocket PC software’. After the installation the list of programs on the Pocket PC shown after tapping ‘Start’ → ‘Programs’ includes new programs: PalmScan: program for voltammetric detection PalmTime: program for amperometric detection PSConfig: used to specify mains frequency and optional modules for PalmSens Ch. 2.2 Configuration of PalmSens The PSConfig program is used to configure the mains frequency and optional modules for the PalmSens instrument. The settings are used by both programs PalmScan and PalmTime. Fig. 2.1 – The PSConfig window 1. 2. 3. Mains Frequency; set this to the mains frequency that is used in your region. CH8 Multiplexer; check this option if you are using a PalmSens CH8 Multiplexer Wireless (Bluetooth) dongle; check this option if PalmSens is equipped with a Bluetooth dongle for wireless control. The program also allows updating the PalmSens firmware. This is only relevant when the software is an upgrade of an earlier version. Ch. 2.3 Switching on PalmSens Before PalmSens is used without the adapter, the batteries must be charged. Open the lid at the left-hand side of PalmSens by pressing the hinge upwards and then turning the lid. 2 Turn Lid 1 Push Up Fig. 2.2 – Opening the lid Connect the adapter to the miniDIN-connector or dc-in connector. Switch on PalmSens by pressing the power key until the display shows: ‘Selftest’. During the self test the voltage range of the instrument is tested and shown. The normal range is from approx. –2.035 V to +2.047 V. After the test the display will show: > PalmSens Vs. x.x E= x.xxx V FsChg Fig. 2.3 – Display of PalmSens after being switched on. As long as the display shows the text FsChg, the batteries are being charged. As soon as the display shows PwrOK, the batteries are full and the adapter can be disconnected. The batteries have to be recharged as soon as LowBat is shown and the corresponding beep is heard. PalmSens can be used with the adapter connected and the batteries charged. The adapter however increases the noise level (see Ch. 4. Instrumental considerations). The backlight of the LCD is switched on and off by using the key ▲. Please note that the backlight will reduce the battery-lifetime of PalmSens from approx. 8 hours to not more than 6 hours. PalmSens is switched off by pressing the power key until the display shows ‘Shutting down’. Ch. 2.4 Connecting PalmSens to the Pocket PC with the serial cable The serial cable is used to connect the Pocket PC to PalmSens. Switch on the Pocket PC and tap ‘Start’ → ‘Programs’. Tap ‘PalmScan’. Plug in the sensorcable to PalmSens and connect the testsensor. If the Pocket PC is not able to communicate with PalmSens, the Pocket PC shows PalmSens NOT connected. As soon as PalmSens is found, the Pocket PC display shows the readings of the potential and if applicable also the current. Refer to appendix ‘Troubleshooting’ if PalmSens remains not connected. Fig. 2.4 – Pocket PC display with the ‘Method window’ displaying the readings of E and I, or showing ‘PalmSens NOT connected yet’. Ch. 2.5 Connecting PalmSens to the Pocket PC with Bluetooth PalmSens can be controlled by means of Bluetooth communication. PalmSens must have the Bluetooth dongle placed on the serial connector and the PalmSens instrument must have been adapted for use with Bluetooth. To enable wireless connection the checkbox ‘Wireless (Bluetooth) dongle’ in PSConfig must be checked (see ch. 2.2). You also must have turned Bluetooth ON your Pocket PC. This can easily be done in the Today screen. Tap the small Bluetooth logo in the bottom-line at the right of your screen and tap ‘Turn Bluetooth ON’ or ‘Turn Radio ON’. If PalmScan or PalmTime is opened, the program will ask if you want to connect using Bluetooth Wireless Connection. After tapping ‘Yes’ the Pocket PC will search all Bluetooth devices within range. All found Bluetooth devices are shown. The PalmSens you want to connect to is identified by its serial number. Tap once on this icon. If you can’t see the PalmSens device in the list, make sure the Bluetooth dongle is properly connected to the PalmSens and within the range of maximum 10 meters. Tap the round refresh icon at the bottom of the screen to search again. With Bluetooth enabled in PSConfig, you can still connect to PalmSens using a serial cable. In that case PalmScan and PalmTime will skip the ‘Connect to PalmSens - Yes/No/Exit’-window and automatically connect using the serial cable. The Pocket PC displays the same information as shown in Fig. 2.3. This chapter applies to Pocket PC types that come with PalmSens. For support of other Pocket PC types, please contact Palm Instruments. Chapter 3 - First measurements using the testsensor In order to get acquainted with the instrument, a testsensor is supplied which is used to perform easily reproducible measurements. Before measurements are performed connect the testsensor to the PalmSens device. Please note that this testsensor is a standard accessory which is NOT used to measure nice curves but to test the instrument. This means that some curves may look too noisy, however this does NOT mean that the instrument performs badly. The curves must be noisy in order to see whether the noise level is too high or not. Ch. 3.1 Recording a differential pulse voltammogram Run the program PalmScan. Select ‘File’ → ‘Load method’ → ‘PSDiffPulse’. This means: tap ‘File’ followed by ‘Load method’ followed by selection of ‘PSDiffPulse’ from the list. Fig. 3.1 shows the display of the Pocket PC with the relevant parameters of this method. The measurement starts when ‘Sample’ is selected from the ‘Measure’ menu. Recorded points are shown during the scan. After the measurement the curve is shown on the screen and the measured peak height is marked. The scaling of the plot can be changed manually by selecting either ‘Manual scaling’ or ‘Mark new scaling’. Manual scaling requires specification of y-top and y-bottom. This can be done by clicking on the keyboard icon in the lower right corner. When ‘Mark new scaling’ is selected, the stylus is used to mark the lower left and upper right points of the new curve. In case the curve disappears select ‘Automatic scaling’. Fig. 3.1 – Method used to record a differential pulse voltammogram and the measured voltammogram using the testsensor. Measure the same curve again after changing the ‘Smooth window’ available in the ‘Settings’ window under ‘Instrument’. Ch. 3.2 Measuring the noise level of the instrument Select ‘File’ → ‘Load method’ → ‘ PSNoiseTest’ from the list given. Tap ‘Measure’ → ‘Sample’. If necessary, select ‘Plot’ → ‘Automatic scaling’. A typical measured curve is shown in Fig. 3.2. Repeat the measurement but with a scan rate of 0.0500 V/s. Note that the noise level is lower, due to the fact that the current measurement time is longer now, which decreases the measured noise level. The instrument is controlled manually when ‘Control’ from the ‘Instrument’ menu is selected. Tap ‘Cell on’. Change the applied potential from E= 0.000 V to E= 0.500 V by manipulating the horizontal scrollbar. There are three options to change the value. Clicking on one of the two arrows, clicking between the arrows and the scrollbar and moving the scrollbar. Select the current range 10 nA. The measured values of the potential and current as well as the noise are shown. Please note that the noise level has the same units as the given current value. Fig. 3.2 – Typical noise levels as measured with the method PSNoiseTest and using the testsensor. The left plot is a measurement without using a faraday cage. The right plot is a measurement in a metal box which is connected to the green GND connector of the sensorcable. In case the measured noise levels are much higher then shown in fig. 3.2 please refer to Chapter 4. Ch. 3.3 Recording an amperometric detection curve Close the program PalmScan and run the program PalmTime. Load the method ‘PSTime’ (‘File’ → ‘Load Method’). Check the parameters shown in Fig. 3.3. Start the measurement by tapping ‘Start’ from the ‘Measure’ menu. The measured current is constant with a normal value of approx. 1-3 nA. During the measurement the plot can be re-scaled by selecting ‘Plot’ → ‘Automatic scaling’. Fig. 3.3 – Parameters for the measurement specified in the method called PSTime and the measured curve using the testsensor. Ch. 3.4 Simulating a voltammetric determination Switch off PalmSens and run the program PalmScan. Select the method ‘PSSimulation’ from the list shown after tapping ‘Load Method’ from the ‘File’ menu. Check the method parameters. Tap ‘Sample’ in the ‘Measure’ menu. The program shows the message that curves will be simulated. Next tap also ‘Standard 1’ and later ‘Standard 2’ and rescale the plot. The measured curves are shown in Fig. 3.4. The calculation of the concentration in the sample is carried out when one of the buttons with the name of the analytes is tapped. Fig. 3.4 – A simulated determination of heavy metals by means of square wave voltammetry.