New
Products
Semiautomated bomb calorimeter The Model 1281 semiautomated oxy gen bomb calorimeter is designed for applications in the waste processing, coal and fuels, and food industries. At the beginning of a test, the system au tomatically charges the bomb with oxy gen to the required initial pressure and fills the calorimeter bucket with a precise amount of water. After the test, it releases the residual pressure in the bomb, flushes it with water and deliv ers the washings for chemical analysis, cools it, and drains the calorimeter bucket. The operator simply opens the calo rimeter and the bomb, loads a preweighed sample in the bomb head, re installs the bomb head, and closes the calorimeter. A microprocessor con trols the instrument with a menudriven interface that allows the user to specify operation modes, calibration controls, thermochemical corrections, data entry methods, reporting for mats and procedures, and digital data communications. Sample weights can be keyed in manually or transmitted
INSTRUMENTATION Universal biosensor platforms Two varieties of prefabricated corundum ceramic strips with integrated electrodes are designed as bases for creating custom biosensors. In each, a biochemically ac tive substance such as a redox mediator, an antibody, or an enzyme is placed in a well on the working electrode and the electrodes are connected via cable to a polarograph or other electrochemical ana lyzer. The smaller type of base, at 0.4 g per strip, has a silver conducting path and ref erence electrode as well as platinum work ing and auxiliary electrodes. This base uses a pin-type cable connector. The larger type of base, at 0.7 g per strip, has a tung sten conducting path and rhenium elec 878 A
via a balance with an RS-232C port, which can be connected to the calorim eter directly or through a network link. The instrument performs isoperibol calorimetry with either post-test or con tinuous temperature measurement correction and can operate in either equilibrium or dynamic mode. In dy namic mode, which is designed to cut analysis time, the instrument control ler performs curve matching to com pare the actual rise in temperature with a known thermal curve and predicts a final temperature by extrapolation rather than waiting for complete test results. For homogeneous samples, dy namic mode has an RSD of 0.05-0.1% when compared with the standard equi librium mode. The Model 1281 uses the same type of 340-mL bomb cylinder used in the fully automated Model 1271, which was introduced two years ago, but the bomb is installed with the head up in stead of inverted. It is sealed manually by giving it a quarter turn rather than with the controlled pneumatic system of the 1271. The electrodes are also
trodes that may be covered with silver, gold, or platinum. The electrode outlets are coated in nickel so they can be sol dered to a cable. Krejci Engineering • 401
longer in the bomb for the 1281. The bomb will safely burn samples releas ing up to ~ 32 kj (8000 cal) and can be used at pressures up to 3000 psi. The standard bomb is made of a sulfuric acid-resistant stainless steel; bombs made of a chloride-resistant alloy are also available. Parr • 403
LITERATURE
Chromatography "Separation Times" (Vol. 8, No. 1) con tains articles on analytical methods for leaking underground storage tanks and on Portable alloy analyzer calculating chromatographic efficiency for GC columns. The newsletter is illus The ARC-MET 930, a portable version of trated with diagrams and sample chrothe ARC-MET 900 atomic emission spec trometer, is designed for alloy analysis on matograms and contains a Q&A column the factory floor. Its compact size (12 χ 7 χ for technical problems. J&W Scientific • 404 21 in., 38 lb.) and the photodiode array detector mounted inside the probe allow the user to determine metal alloy types at field sites such as scrap yards and foun For more information, dries. In addition, the spectrometer can de please circle t h e appropriate termine sulfur and phosphorus content numbers on one of our for applications such as distinguishing be Reader Service Cards. tween different grades of steel. Metorex • 402
Analytical Chemistry. Vol. 66. No. 17. September 1. 1994
