that when the gasoline-range calibration curves were used, low aromatics values were generally obtained. Also, it was observed that these samples of higher boiling range produced two colored zones, rather than a single green zone. The upper zone was brown, and the lower zone was the usual green. Tests with pure compounds indicated that benzene and naphthalene derivatives produced green colors while phenanthrene,
anthracene, and higher aromatics produced brown colors. This suggest the possibility of differentiating aromatics with three or more condensed rings from aromatics with one or two rings. RECEIVED for review August 17, 1967. Accepted October 6, 1967.
Perfluorokerosene: A Useful Internal Reference for Negative Ion Mass Spectrometry R. S . Gohlke and L, H. Thompson Spectroscopy Laboratory, Analytical Department, Dow Corning Corp., Midland, Mich. 48640 WE WISH TO REPORT that perfluorokerosene (PFK) provides a negative ion spectrum rich in ions of useful abundance over a mass range extending from m/e 19 t o at least mje 940. Because the ions occur at m/e values which are not commonly found in nonperfluorinated compounds, the PFK is used as an internal m/e reference by admitting it t o the mass spectrometer with the compound under investigation. As can be ~~
~~
~~~~
~~~
seen from Table I, in the m/e range 220 to 800, any unknown ion peak is always bracketed by a pair of PFK peaks, one of which is never more remote than 6 mass units. Two fractions of PFK are available from Columbia Organic Chemicals Co., Inc., Columbia, S. C.-high boiling and low boiling. We find the former more useful because of its wider mass range.
~~
~
Table I. Positive and Negative Ion Mass Spectra of Perfluorokerosene m/e 19 31 38 39 43 50 59 62 69 70 72 74 81 85 93
Intensity Neg. 100.0
1.7 0.9 2.1 0.5
0.2 0.2 0.2 5.4 0.4 0.2 0.4 0.6 0.3 2.7
94
100 101 105 112 117 119 120 124 131 132 143 144 150 155 162 167 169 170 174 181 182 186 193
1004
Pos.
0.4 3.1 1.1 0.4 0.3 7.2 0.3 1.3 1.1
ANALYTICAL CHEMISTRY
0.7 100.0 1.1
2.2 0.2 4.5 1.0 0.2 0.8 18.0 0.6 0.7 15.4 0.9 1.5 0.3 1.2 1.4 1.9 0.3 10.3 0.5 0.4 10.1 0.6 0.7 1.8
m/e 219 220 224 229 231 232 236 241 243 244 250 255 256 262 267 269 270 274 28 1 282 286 29 1 293 294 300
305 312 313 317 319 320 321 324 329 331 332 336 343 344
Intensity Neg. 8.6
11.4 0.6 3.7 0.2 0.7 1.1 2.2 0.4 8.5 0.7 26.8 1.8 10.2 0.8 0.9 1.5 4.9 0.4 0.7 4.7 0.3 1.5 0.3 30.9 0.6 0.4 9.8 0.9
Pos. 4.5 0.3 0.4 0.2 5.0 0.4 0.7 0.2 2.6 0.3
1.4 0.2 0.3 0.8 2.1 0.2 0.3 3.3 0.3 0.4 0.2 2.2 0.3 0.9 0.5 1.3 0.1 0.2 0.2 2.2 0.2 1.8 0.2
Intensity m/e Neg. 369 5.5 370 0.4 374 1.4 379 0.4 381 21.4 382 1.8 386 0.9 393 9.8 394 1.o 398 0.3 400 0.8 405 5.1 406 0.7 410 0.2 412 3.3 413 0.3 417 1.4 418 0.3 419 4.1 420 0.4 424 1.7 42 5 0.3 0.5 429 431 11.5 432 1.3 436 0.9 441 0.3 443 12.4 444 1.3 448 0.4 450 0.4 455 4.6 456 0.7 462 2.0 467 1.9 468 0.3 469 2.4 470 0.2 474 1.8 (Continued)
Pos. 0.8 0.2 1.9 0.2
1.7 0.2
1.2
0.4
0.4
1.8 0.2 1.6 0.2
1.5 0.2
0.3
0.4
Table I. (Continued) mle 194 200 205 206 212 217 49 3 494 498 500 505 506 510 512 513 517 518 519 524 525 529 530 531 532 536 537 538 541 543 544 548 550 555 556 560 562 563 567 568 569 574 575 579 580 58 1 582 586 587 588 591 59 3 594 598 599 600 605
Intensity Neg. 0.2 0.6 0.3 14.6 1.7 0.5 0.5 4.6 0.7 0.3 2.0 0.2 2.1 0.5 1.4 1.5 0.4 0.9 0.3 5.7 0.7 1.0 0.3 0.4 0.4 12.2 1.5 0.5 0.5 7.3 1.1 0.3 2.2 0.3 2.1 0.4 0.9 1.7 0.3 0.9 0.2 3.9 0.5 1.1 0.3 0.6 0.4 8.5 1.2 0.7 0.2 0.6 9.7
Pos. 0.3 1.2 0.2 1.1 0.7 1.4 0.2 1.0 0.2
0.5
0.6
0.8
0.9
0.5
0.6
0.9
0.6
m/e 350 355 356 362 363 367 606 610 612 613 617 618 619 622 624 625 629 630 631 632 636 637 638 641 643 644 648 649 650 655 656 660 662 663 667 668 669 674 675 679 68 1 682 686 687 688 689 69 1 69 3 694 698 700 705 706 710 712 713
It may be noted from Table I that the negative ion PFK spectrum reaches an intensity maximum at m/e 331 and then decreases monotonically whereas the positive ion spectrum exhibits this behavior above m/e 69 (CF3+). It is tempting to speculate that this mje 331 ion is a cyclic C7F13 ion formed by fluorine rearrangement and simultaneous bond formation between adjacent turns occurring in some kind of helical configuration of the perfluoroalkyl radical existing as a result
Intensity Neg. 0.6 3.3 1.3 5.0 0.4 1.3 1.6 0.3 2.6 0.4
3.0 0.6 0.5 0.2 2.0 0.6 0.8 0.3 2.8 0.4 1.3 0.4 0.9 0.3 5.0 0.9 0.7 0.2 0.8 8.8 1.6 0.4 2.0 0.3 3.5 0.8 0.4 2.8 0.5 0.7 1.7 0.3 1.4 0.4 1.5 0.2 0.2 2.8 0.6 0.7 1.o 5.1 1.0 0.3 2.0 0.3
Pos. 0.8
0.5
0.4
0.4
0.7
0.7
0.3
0.5
0.6
0.5
mle
Intensity Neg.
47 5 479 48 1 482 486 491 717 718 719 724 725 729 731 736 737 738 739 743 744 748 750 755 756 760 762 763 767 768 774 775 779 78 1 786 788 789 793 794 798 800 805 812 813 817 824 831 836 838 839 843 848 850 862 888 900 938
0.3 0.8 8.3 0.9 0.9 0.3 2.8 0.6 0.2 2.1 0.6 0.5 1 .o 1.2 0.3 1.5 0.3 1.6 0.4 0.6 1.0 2.5 0.5 0.2 1.7 0.3 1.1 0.3 1.2 0.3 0.2 0.5 0.7 1.5 0.3 0.8 0.2 0.3 0.8 0.6 0.9 0.2 0.3 0.5 0.2 0.3 1.3 0.2 0.3 0.2 0.7 0.4 0.8 0.2 0.3
of CF3 positive ion formation. be represented as follows: CFa(CF&F
CFs@
Pos. 1.2
0.3
0.4
0.5
0.3
0.1
0.3
0.4
0.2
One possible scheme might
+ *CF?(CF&iF
ie- +
FB=C(CF&
CF,(CF&s
RECEIVED for review February 12, 1968. Accepted March 4, 1968.
VOL. 40,
NO. 6, MAY 1968
1005
