News
EMMA'S determination of LAP A reaction-based chemical analysis method known as electrophoretically mediated microanalysis (EMMA) uses electrophoretic mixing to merge zones containing the analyte and its analytical reagents. The reaction then proceeds with or without an applied potential, and the product is transported under the influence of an applied electric potential to the detector. EMMA allows homogeneous kinetic enzyme assays to be conducted and detected entirely on-column with high TTI3.Ss sensitivity. Fred E. Regnier and colleagues at Purdue University have de-
Determining LDH isoenzymes in normal and leukemia cells In carcinogenesis, gradual cytochemical changes occur and the concentrations of many molecular biomarkers change constantly before morphological changes can be detected. As researchers look for markers to act as indicators for particular types of cancer, they concentrate on the enzymes that control the balance of cytochemicals and participate in the cell proliferation process. Lactate dehydrogenase (LDH) isoenzyme has been pinpointed as such a marker. Using techniques developed for quantifying LDH activity in red blood cells and monitoring the fCHctivity of sintjle enzyme molecules Edward S Yeung and Qifeng Xue did side-by-side analysis of normal lymphocytes and acute lymphoblastic leukemia cells to gain insight into the LDH activity of these cells and the potential use of LDH as a disease indicator They used a Tesla coil to lyse normal cells and B- and T-type acute lymphoblastic leukemia cells, and CE with laser-induced fluorescence detection to study them. They found that LDH isoenzyme activities and the relative ratios between different LDH isoenzymes varied widely among individual cells. They believe that the variation in activity was caused by cell size and age, although the LDH activity for nor-
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scribed the use of leading-edge moving boundary sample introduction as an alternative to zonal injection so that the incubation volume and the sensitivity of kinetic EMMA assays will increase. In leading-edge moving boundary CE, the capillary is filled with running buffer and the analyte is maintained in the inlet buffer reservoir. The application of an electric field causes the sample components to enter the capillary at their characteristic net migration velocities. The resulting electropherogram consists of upward stairsteps, as the leading edge of each succeeding region containing a detectable species reaches the detector. The model system chosen was the kinetic determination of microsomal leucine
mal cells was higher than that for the diseased cells. For normal cells, the variation in ratios was lower than for the diseased cells, but in general, they believe that single-cell measurements are not as good an indicator of cell health as a measurement taken over a cell population. (J. Chromatogr. B 1996, 677, 233-40)
Fast-moving boundary EMMA determination of LAP. (Adapted dith permission from Elsevier Science.)
aminopeptidase (LAP), which was assayed by its hydrolysis of L-leucine//>nitroanilide to form />-nitroaniline and Lleucine. The capillary was filled with the LAP, while the faster-migrating substrate was maintained in the inlet reservoir. The analyte and reagent mixed upon the application of an electric field, and the reaction product p-nitroaniline was transported to the detector. The area, maximum height, and slope of the triangular product profile were each directly proportional to the activity of LAP, and the observed migration times of the product profile features defined the volume and ttme of fhe incubation The moving boundary injection technique offered an order of magnitude increase in concentration sensitivity over zonal injection EMMA The increased sensitivity allowed the use of high electric field strengths and short capillaries resulting in a 24-s kinetic determination of TAP (J Chromatoer A 1A96 72R 193-2041
GOVERNMENT
Trace elements in water program
Single-cell electropherograms of (a) a normal lymphocyte, (b) a T-type lymphoblastic cell, and (c) a B-type lymphoblastic cell. (Adapted with permission from Elsevier Science.)
Analytical Chemistry News s &eatures, June 1, 1996
NIST is looking for industrial, commercial, and government laboratories that do environmental analyses to participate in an interlaboratory study for the determination of trace inorganic elements in water. Participants will be sent samples of natural water for which reference values for 10 elements have been determined by NIST. Each laboratory's results will be coded to ensure confidentiality, but they will be able to compare their data with the reference values and the results of other labs. For information contact Robert Watters, Jr., Deputy Chief, Analytical Chemistry Division, NIST, Gaithersburg MD 20899 (301-975-4122; fax 301-8690413; e-mail robert watters@nist gov)
