@article {4528,
	title = {Elemental analysis with quadrupole mass filters operated in higher stability regions},
	journal = {Journal of Analytical Atomic Spectrometry},
	volume = {14},
	number = {8},
	year = {1999},
	note = {ISI Document Delivery No.: 229LPTimes Cited: 23Cited Reference Count: 47},
	month = {Aug},
	pages = {1111-1119},
	type = {Article},
	abstract = {Operation of quadrupole mass filters in higher zones of stability is described with an emphasis on the potential for elemental mass spectrometry. The higher zones allow a resolution at half height of up to 9000 on atomic ions and make possible unit resolution on ions with kinetic energies up to several thousand electron volts. The theory of quadrupole operation is briefly reviewed. Operation of quadrupoles in the third stability region with Mathieu parameters (a,q)approximate to(3,3) and the second stability region with (a,q)approximate to(0.02, 7.55) is described in detail. Previously unpublished data showing the variation of resolution with ion energy are presented. The variation of transmission with resolution is compared with previous calculations and with new calculations presented here.},
	keywords = {2ND, ANALYZER, ATMOSPHERE, DIAGRAM, HELIUM, HIGH-RESOLUTION, ICP-MS, SEPARATION MODE, SPECTROMETER, ZONE},
	isbn = {0267-9477},
	url = {<Go to ISI>://000082196300002},
	author = {Du, Z. H. and Douglas, D. J. and Konenkov, N.}
}
@article {4246,
	title = {Ion source emittance influence on the transmission of a quadrupole operated in the second stability region},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {9},
	number = {10},
	year = {1998},
	note = {ISI Document Delivery No.: 121NBTimes Cited: 6Cited Reference Count: 19},
	month = {Oct},
	pages = {1074-1080},
	type = {Article},
	abstract = {The variation of transmission (T) with resolution (R) has been calculated for a quadrupole mass filter operated in the second stability region with Mathieu parameters q = 7.547 and a = 0 to 0.02995. The fringing fields at the entrance to the quadrupole, which can be strongly defocusing, and which can dramatically reduce the acceptance, have been included in the calculation. Even in the absence of fringing fields, at a resolution of 10,000 the acceptance in the x and y directions is less than 2 x 10(-4) pi r(0)(4) f(2) which is about 10(-3) of the acceptance in the first stability region at low resolution. Because the source emittance can strongly effect the T(R) behavior, the calculation of ion transmission has been done for two source emittances that correspond to different degrees of focusing of ions into the quadrupole. The T(R) characteristics for two realistic source emittances give behavior markedly different from the decrease in acceptance with increasing resolution which previously has been used as a measure of the quadrupole transmission. Comparisons of the calculated transmission losses with increasing resolution to earlier experimental results obtained with an inductively coupled plasma source show good agreement provided an emittance which corresponds to ions being tightly focused into the quadrupole is used. The calculation demonstrates that up to a resolution at half height of 7000 in the experiment, the transmission losses were a result of the decreasing quadrupole acceptance. At higher resolution the experimental transmission was limited by either the residence time of the ions in the quadrupole or the rod quality. It is also shown that the strong defocusing effects of the fringing fields at the entrance of the quadrupole can be largely overcome by accelerating the ions through these fields and then decelerating the ions in the quadrupole. (C) 1998 American Society for Mass Spectrometry.},
	keywords = {ANALYZER, mass filter, SEPARATION MODE, SPECTROMETER},
	isbn = {1044-0305},
	url = {<Go to ISI>://000076019000011},
	author = {Douglas, D. J. and Konenkov, N. V.}
}
@article {3945,
	title = {Inductively coupled plasma mass spectrometry with a quadrupole mass filter operated in the third stability region},
	journal = {Journal of the American Society for Mass Spectrometry},
	volume = {8},
	number = {12},
	year = {1997},
	note = {ISI Document Delivery No.: YG420Times Cited: 18Cited Reference Count: 31},
	month = {Dec},
	pages = {1230-1236},
	type = {Article},
	abstract = {An inductively coupled plasma mass spectrometer system is described in which the quadrupole mass filter is operated in the third stability region with Mathieu parameters (a, q) approximate to (3, 3). Operation at the upper tip of this region is found to give generally better sensitivity and resolution than operation at the lower tip. A limiting resolution at half height of 4000 at m/z 59 is possible with operation at the upper tip. This resolution is insufficient to separate atomic ions from molecular ions of the same nominal mass except in favorable cases. However, operation at moderate resolution (R-1/2 = 500 to 1000) is found to give very high abundance sensitivity (>10(7)). The results suggest that the third stability region may be advantageous for specialized applications of inductively coupled plasma mass spectrometry. (C) 1997 American Society for Mass Spectrometry.},
	keywords = {ANALYZER, HELIUM, HIGH-RESOLUTION, IMPERFECT FIELDS, INTERFERENCES, ION OPTICAL-PROPERTIES, MODE, SEPARATION},
	isbn = {1044-0305},
	url = {<Go to ISI>://A1997YG42000005},
	author = {Du, Z. H. and Olney, T. N. and Douglas, D. J.}
}
