compared with the 3vv- and lzo-um microelectrOQco UocQ lii earner work. 1 ney used the technique to map the current distributions over platinum QISK electrodes. The ac distribution measured in solution was compared with analytical solutions and computer simulations. 1 ne spatial resolution of the probe was defined by varying the height of the probe and the distance between the microelectrodes and was found to be 30-40 um. (J. Electrochem. Soc. 1997,144,1957-65)
Raman for air monitoring Continuous emissions monitoring (CEM) will eventually be required at all coalpowered electric plants. Praveen C. Kumar and Joseph A. Wehrmeyer of the University of Missouri-Columbia have suggested that Raman spectroscopy could be used for simultaneous CEM measurements of CO, NO, and S02. They used a Nd:YAG laser as the excitation source. A liquid-nitrogen-cooled CCD was used to collect the spectra with an integration time of 200 s. The long integration time increased the interference from cosmic rays. The gases were placed in a sample cell that mimicked stack conditions and were maintained at 1 atm. The detection limits were 100 ppm for S02, 250 ppm for CO, and 250 ppm for NO. (Appl. Spectrosc. 1997,51,849-55)
CCC of peptides Because there is no solid support in the separation column, countercurrent chromatography has some advantages over conventional chromatography, such as high sample recovery and minimal denaturation. A variation of the technique called pH-zone refining CCC uses two reagents, one acting as a retainer in the stationary phase and the other as an eluter in the mobile phase. Advantages include increased sampleloading capacity, elution of highly concentrated fractions, and detection and concentration of minor components.
Elution profile of three dipeptides with a broad range of hydrophobicities under four sets of experimental conditions. (Adapted with permission. Copyright 1997 Elsevier Science.)
tial of an adverse effect must receive FDA approval prior to implementation. This rule applies to those products that Biotechnology were previously called "well-characterproduct rule hits the ized" biotechnology products (Anall Chem. 1996,68,674 A-77 A), although street FDA has determined that it is more approThe U.S. Food and Drug Administration (FDA) has issued thefinalrule for making priate to indicate specific products than to use such a broad term. Such products changes to an approved application for include recombinant DNA-derived prospecified biotechnology and biological products (Fed. Regist. 1997, 62, 39890- teins and complexes or conjugates of drugs with monoclonal antibodies. 903). Changes fall into one of three categories based on their potential to have an These changes are part of FDA's onadverse effect on the "identity, strength, going efforts to fulfill the Clinton Adminisquality, purity, or potency of the product, tration's "Reinventing Government" initiaas they may relate to the safety or effective. The rule takes effect Oct. 7. tiveness of the product." Celia Henry Changes that have a minimal effect on the safety and effectiveness can be reported to FDA in an annual report Changes that EPA pushes PBMS have a moderate potential to have aa affect on the safety and efficacy must be reported approach New Text to FDA 30 days before distributton. Changes If all goes as planned, this month each of that are deemed to have a substantial poten- EPA's assistant administrators will submit a GOVERNMENT
Yoichiro Ito and Ying Ma at the National Institutes of Health used this technique to separate underivatized peptides by introducing an ion pair reagent, di-(2-ethylhexyl) phosphoric acid (DEHPA), into the stationary phase. To optimize the separation, they found that the DEHPA concentration and the hydrophobicity of the solvent system needed to be adjusted according to the hydrophobicities of the analytes in question. They separated gram quantities of bacitracin complex and bovine insulin. (J. Chromatosr. A 1997 771 81-88)
plan to the Environmental Monitoring Management Council on how their program office will implement the performancebased monitoring system (PBMS) approach to environmental monitoring. What is signiiicant is that the deadline was imposed by Fred Hansen, the deputy administrator of EPA in a memo circulated in June. Moreover, the memo sets a September e998 9eadline for implementation of PBMS with the warning that any extension will be granted only under exceptional circumstances. PBMS gives analysts greater freedom in selecting a method for an environmental measurement as opposed to prescriptive methods that detail each step in an analytical procedure. Numerous groups have pushed EPA to adopt the PBMS approach, and a program to introduce PBMS methods is already well underway within the agency (Anal. Chem. 1996, 68, 733 A-37 A)) However, ,ome had feared that the effort would fail without high-level support in the agency. Hansen's
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