REPORT is a measure of inhibitor concentration. An effective method for repetitive analysis is the determination of plno, the negative logio of the concentration of inhibitor necessary to produce 5 0 % inhibition of enzyme activity under specified conditions of t e m p e r a t u r e , enzyme concentration and medium (9). H o w ever, the bimolecular r a t e constant concept (16) is more specific and dependable, especially with u n known material or slower acting inhibitors. One of the biggest problems of in vivo biological assay is t h a t of species variability in the action of a drug when tested in successively higher animals leading t o w a r d man. This problem can be compounded when the in vivo is converted to an in vitro system. However, where species variability in the in vivo system is minimal, the in vitro bioanalytical method is far superior when accuracy and repetitive determinations are required. N u merous examples are available in which highly p o t e n t in vitro a n t i cholinesterases, while potent as insecticides, have little or no a p p a r ent toxicity in higher animals. I n these cases the in vitro method is excellent for the assessment of insecticide residues. T h e converse is true of P a r a t h i o n . I t is a relatively mediocre in vitro inhibitor, but owes its m a m m a l i a n toxicity to metabolic conversion to the strong enzyme inhibitor, Paraoxon. Although biochemical techniques m a y have been somewhat foreign to the analytical chemist in the past, the same might have been said a t an earlier date in relation to organic analysis via functional groups. T h e advantages of biocatalysis for sensitivity a n d possibly specificity offer a broad field for the analytical chemist working in the area of biologically active substances.
Impact of New Analytical Techniques Gas liquid, paper, thin layer, and column c h r o m a t o g r a p h y are excellent aids in the solution of a n a l y t i cal and organic synthesis problems. Prior to the availability of these techniques laborious fractional dis-
N o w you Can Read Chloride Concentration Directly In Milliequivalents .. Buchler v/ith the
DIRECT READER ATTACHMENT
'#
for the COTLOVE CHLORIDOMETER® AUTOMATIC TITRATOR
lw 4R*
If it has an end point, the CHLORIDOMETER w i l l find it more quickly, accurately, automatically . . . in 6 steps and in less than 6 0 seconds!
DIVERSIFIED FOR ALL CHLORIDE TITRATION APPLICATIONS The DIRECT READER speeds output! Automatically subtracts the r e a g e n t blank time a n d p r e sents the net t i t r a t i o n time in milliequivalents per liter on a d i g i t a l register. Does not diminish the r e l i a b i l i t y a n d accuracy o f the o r i g i n a l automatic t i t r a t o r . V a r i a t i o n with 0.1 ml. samples ± 0 . 0 5 % . Easily a t t a c h e d t o A N Y Cotlove automatic chloride t i t r a t o r . Installed f r e e o f c h a r g e a t f a c t o r y , with only shipping costs t o p a y . SEND T O D A Y FOR COMPLETE DESCRIPTION
Direct Reader — Bulletin A 4 - 2 0 5 0
Chloridometer — Bulletin A 4 - 2 0 0 0
LABORATORY APPARATUS
BUCHLER INSTRUMENTS, INC. PRECISION INSTRUMENTS
1 3 2 7 1 6 t h Street, Fort L e e , N e w J e r s e y Phone 2 0 1 - 9 4 5 - 1 1 8 8 or call N.Y.C. direct LO 3 - 7 8 4 4
Circle No. 129 on Readers' Service Card
\oiJuL oJUL weir AND
in a HAWS Emergency Drench Shower. Burning, corrosive, caustic contamination can inflict injuries more dangerous than blazing clothing! Contamination by acids, chemicals, volatile fuels, radioactive elements, etc., must be instantly countered by first aid. Immediate drenching with clear water is the first precaution against permanent injury. HAWS leads in design and production of Emergency D r e n c h Showers! Ask for our complete catalog.
Model 8590 Multiple nozzle shower drenches victim from all angles.
DRENCH
SHOWERS
Since 1909 a product of HAWS DRINKING FAUCET COMPANY
1443 Fourth St., Berkeley 10, Calif.
Circle No. 9 on Readers' Service Card VOL.
35, N O . 6, MAY
1963
•
35
A
