The Cover: Quadrupole Mass Spectrometry

Possible paths of an ion traversing the mass filter of a quadrupole mass spectrometer are shown on this month's cover. In two papers that begin on page 1042, Henchman and Steel describe the design and operation of a portable instrument that is especially suitable for undergraduate instruction.

They also provide a computer simulation designed to help students understand how a quadrupole mass filter works something that otherwise would be difficult. The cover graphic represents trajectories of the sort generated by the computer simulation. Taken together these two papers enable one to incorporate mass spectrometry throughout the curriculum, from general chemistry through advanced courses.

Precision and Accuracy
of Measurements

Reporting of error and appropriate use of significant figures are a mundane but necessary part of science.

Treptow (page 992*) describes a model experiment involving graduated cylinders that can be used in the classroom to make students aware of the concepts of precision and accuracy. Guy, Ramaley, and Wentzell (page 1028) describe an experiment that is designed to introduce the idea of sampling error as an important component of the uncertainty of an analytical measurement. Caballero and Harris discuss the proper reporting of error ranges and rounding of results of measurements on page 996*. For those who want the definitive word on this subject, Sykes (page 970*) provides a reference to an NBS (now NIST) publication that consists of ten pages of detailed information. Several other letter writers discuss appropriate rules for rounding on pages 970-971*.

Analytical Methods

This issue includes a number of papers that will help those who are interested in incorporating specific analytical methods into the curriculum. Wolfe, Oates, and Hage (page 1025) describe how to use flow injection analysis (FIA) for automated protein assay in an instrumental analysis course. The sampling-error paper by Guy, Ramaley, and Wentzell mentioned above (page 1028) also uses FIA. Minas da Piedade and Berberan-Santos (page 1013) have developed a way to use an optical fiber to guide light from an external source into a UV-visible spectrophotometer, greatly simplifying the study of atomic emission spectra in a physical chemistry course. Dragan and Fitch (page 1018) apply infrared spectroscopy as part of a thematic instrumental lab sequence based on lead analysis of community-derived samples.

Freeman and McCurdy have developed a sample-preparation method that uses a microwave oven. Its advantages are described beginning on page 1033. Heineman et al. (page 1035) suggest that students should experience liquid chromatography with electrochemical detection and for this purpose their students carry out a two-part experiment. Students in laboratories taught by Goscinska (page 1038) prepare their own microscale electrochemical sensors and use them in an adsorptive stripping voltammetry experiment. A media review by Pringle (page 978*) describes multimedia software designed to help students learn the principles of spectrophotometry.

Chemistry, Society, and History

Jensen's three-part series on "Logic, History, and the Chemistry Textbook" concludes this month with a discussion of three chemical revolutions (page 961*). A detailed description of how experiments by Ernest Rutherford on alpha particles and helium can be used to derive the Avogadro constant begins on page 998*. Holmes (page 1004*) applies the concept of limiting reagent to population growth and produces some interesting ways to look at potential limits to continually increasing numbers of humans. Ibanez, Singh, and Szafran (page 1040), in a continuing series on electrochemical remediation of environmental problems, report a student experiment in which color is removed from simulated wastewater by electrocoagulation-electroflotation. The lead-analysis experiment of Dragan and Fitch (page 1018) was mentioned above.

Two of our book reviews deal with chemistry's relationship with society. Rabinovich's review of A Philatelic Ramble through Chemistry on page page 958* gives the flavor of a book that is "bound to become the new 'Bible'" for those who are interested in chemistry and postage stamps. Stocker's review of What Einstein Didn't Know on page 977* describes a book that responds to everyday questions that have a chemistry component and makes chemistry interesting and fun for the uninitiated. This one sounds like fun for all of us!

Boston ACS Meeting

Cohen and Cohen (page 951*) describe scientific attractions of the Boston area. The full program for the meeting, including the high school day program, begins on page 943*. Be sure to visit the Journal poster session and gala celebration, the Journal symposium, and the Journal booth at the Boston meeting. We look forward to seeing you!

*designate articles of special interest to high school teachers.