THE N.I.L.
ELECTROLAB®
INSTRUMENTATION
—for Electrochemical Research, Biochemical and Routine Analysis, and Industrial Process Control THE COMPLETE AND COMPACT ELECTROANALYTICAL LABORATORY IN ONE INSTRUMENT 17 Electroanalytical Modes of Operation at Low Cost, with High Accuracy, and Built-in Sequencing
Figure 6. The IKE spectrum of benzene at electric sector voltages greater than the voltage Ε at which the main beam of stable ions is transmitted
The light display on the panel illu minates only those controls associated with a different mode of operation. When the Function Program switch above is turned to one of four posi tions, the corresponding switch setting indicates the analytical mode, the vari able held constant, and the measured variable. FEATURES •
Light display logic illuminates all controls, directs operator for each analytical mode. • Connects to any strip chart recorder with a sensitivity up to 100 millivolts full scale. •
Buffer amplifier (10- 12 ohms) isolation per mits operation of four electrodes in a common solution without drawing common currents.
•
AC operation over a range of 0-10 KHZ at low current (0-5 ma) and 0-1 KHZ at high current (0-1 A).
• All solid state components. For complete description and ordering information send for BULLETIN 4-300
NIL Phone: 933-1144 Area Code: 301
National Instrument Laboratories, INCORPORATED
12300 Parklawn Drive, Rockville, M d . 2 0 8 5 2 In Metropolitan Washington, D. C.
method is quick and accurate and is thought to be of wide application in the analysis of deuterated compounds. OTHER IONIC REACTIONS
All of the ions discussed so far have been truly metastable and undergo fragmentation unimolecularly. Many other ionic reactions can be made to occur by causing the ion beam to inter act with a gas in the field-free region in front of the electric sector. Such a "collision gas" can cause charge ex change between the ion beam and neu tral gas molecules and can also lead to fragmentation of the ions in new ways. The study of all these product ions can be carried out using exactly the same methods as for metastable ions. Consider Figure 6 which shows part of the I K E spectrum of benzene in the presence of nitrogen as a collision gas. All the peaks shown in this partial spectrum are transmitted at electric sector voltages above the voltage Ε at which the main beam of stable ions is transmitted. Peak A, for example, is due to all the species of doubly charged ions in the ion beam which, because of their two charges, have received twice the energy of acceleration of the
Circle No. 37 on Readers' Service Card
102 A ·
ANALYTICAL CHEMISTRY, VOL. 42, NO. 1, JANUARY 1970
singly charged ions. The ions have then lost a single charge by capturing an electron from the collision gas and consequently are transmitted through the electric sector at a voltage 2 E. The mass spectrum of this transmitted peak gives another "fingerprint" for benzene, equally as unique as the normal mass spectrum. Other "finger prints" could be obtained by mass analysis of the other peaks such as Β and C. Peak D is due to the frag ment ion C B H 3 + from C e H 6 2 + which has been discussed above. The measurement of kinetic energy release can be made much more easily in the IKE spectrum where there is no inter ference from stable ions. Thus, the study of metastable ions has become of increasing interest and promises to lead to an improved under standing of fragmentation pathways, the energetics of ion decomposition and the structures and stabilities of positive ions. I t has important applications in analysis, especially of isotopically en riched materials, and the wealth of de tail in the I K E spectra and the various other "fingerprints" may lead to an improved ability to distinguish between structurally similar molecules on the basis of their spectra.
