2638
ANALYTICAL CHEMISTRY, VOL. 54, NO. 14, DECEMBER 1982
Two-Dimensional Convolute Integers for Analytical Instrumentation Thomas R. Edwards (Anal. Chem. 1982,54, 1519-1524). A set of coefficients for Table XI1 were inadvertently omitted. The missing set Table XIIa (given below) is of value in that a smoothing filter is included, and the number of such nontrivial smoothing filters is sparce up to a 7 X 7 mask. TABLE XIIa.
Two-Dimensional 49:POINT
SURFACE ORDER FUNCTION R 7 C -3 -3 -3 -3 -2 -2 -2 -2 -1 -1 -1 -1 0 0 0 0 NORM
-3 -2 -1
0 -3 -2 -1 0 -3 -2
-1 0 -3 -2 -1 0
4 & 5 SMOOTH A (000) 206 -174 -24 89 -174 -279 36 204 -24 36 450 651 89 204 651 863 4851
INDICATES TRANSPOSE
-
c o n v o l u t e Integers
FLLTEa 7 % 7 MASK
5 & 6 4 & 5 5 & 6 PARTIAL PARTIAL PARTIAL A ( 0 1 ) A(lO)'A(O2) A(ZO)'A(03) A ( 3 0 ) l -1484 3176 -2350 0 1116 1701 -4050 0 246 -804 -5880 0 -449 -1909 -6625 0
-823 1407 -69 -1030 -273 1407 -399 -1470 1407 -597 -1734 167 1407 -663 -1822
-60 129 0 -7 -56 133 0
41580
38808
3024
57
_
I
29 -92 97 0 9 -72 117 0 -7
INTERCHANGE R/C
CORRECTION
Gas Chromatography Review Terence H. Risby, Larry R. Field, Frank J. Yang, and Stuart P. Cram (Anal. Chem. 1982,54, 410R-428R). There are unfortunate errors in the references for the Ionization Detectors section on page 415R of the 1982 Reviews issue. The entire section appears below with corrections in bold. Ionization Detectors. Four new ionization detectors have been reported and three, that are patented, are similar in design to the electron capture detector (9L, 17L, 18L). These detectors monitor the ions produced by the collision of solute molecules with electrons or 8-particles and therefore the response is based on the increase in ion current rather than a decrease in standing electron current. The other new detector is based on surface ionization and has been used to selectively detect amines and their derivatives (20L). Sensitivities of 5 x g/s for triethylamine with selectivities as compared to hydrocarbons of los were reported for this latter detector, and the mechanism which explains its response was also discussed. Various studies have been reported on the mode of operation or application of the helium ionization detector. This detector requires high-purity helium in order to reduce the background ionization due to contaminants in the carrier gas. The high ionization potential of helium is sufficient to cause the ionization of most molecules, and as a result of these potential contamination problems this detector has not enjoyed great popularity. A recent study has evaluated helium of varying purities and found that by mixing helium of various purities it was possible to produce the minimum background current (2L).Another means to achieve the same result was found to be the operation of the detector in the saturated region of the applied field (4L). In the mode of operation all compounds were found to give positive responses. The appearances of negative peaks were also shown by another study to occur when ultrapure helium was used and these peaks could be made positive by the addition of a few parts per
million of gaseous additives. However, the introduction of doping gases decreased the magnitude of the signal (3L). The factors that affect the shape and polarity of the signal have been discussed in another report (6L)but no definitive conclusions were drawn. In spite of these difficulties the helium ionization detector has been used successfully to determine various gaseous pollutants in air (5L). The photoionization detector has received the majority of the interest in this area and its development and applications have been reviewed (lOL, 21L). Two patents have been issued for new designs which have claimed improvements to the current state-of-the-art (13L, 16L). Also a laser has also been suggested as a potential excitation source via resonance-enhanced two-photon photoionization. The ability of this detector to monitor polynuclear aromatic compounds and to differentiate spectrally between coeluting anthracene and phenanthrene was demonstrated (14L), and the results have shown good sensitivities. The response of the photoionization detector is dependent upon the carrier gas and a recent study compared seven carrier gases and found the argon produced the optimum response (19L). The molar response of the photoionization detector is dependent upon the ionization potential of the solute and this potential can be explained in terms of the number of ionizable electrons. This approach has been adopted in a recent paper (7L)and has suggested that the number of C-C bonding electrons is a good approximation to the number of ionizable electrons if a 10.2-eV photoionization detector is used. This approach was used to compare the molar response of this detector to a flame ionization detector so that response factors for a series of solutes could be obtained. Other papers have discussed the linearity (IL)and the optimization ( l l L , 12L) of the response of the photoionization detector. The thrusts of the latter papers were to use this detector with capillary columns. The final two papers were concerned with measuring the response factors for series of organic compounds (8L, 15L), and the results confirmed that the signal is based on the ionization potential and the molar concentration of the solute.
