REPORT FOR ANALYTICAL CHEMISTS
cology continue to demand atten tion. The most frequently re quested toxicological examination is analysis for ethanol in blood, ex pired breath, or urine. Increased specificity and sensitivity of recent procedures, as in those employing the enzyme alcohol dehydrogenase, permit accurate determination of ethanol in small specimens. On the
other hand, however, chemical in terferences continue to complicate many toxicological examinations, especially those which are made on postmortem tissues and fluids. Such determinations are required with increasing frequency in modern medicolegal investigations of death. The continually increasing number, variety, and complexity of toxic
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Accuracy: ± 1 4 % or 20 microvolts, whichever is greater. Range: standard, 125 mv; additional ranges by use of r a n g e p l u g s , 50, 2 5 , 12.5,5,2.5, 1.25, 1.00 mv. Balancing S p e e d : 1 sec ond full scale. Chart: 250 mm wide with millimeter ruling; length c o n t i n u o u s l y r u l e d in tenths of an inch; 120 feet per roll. Chart D r i v e : s y n c h r o nous, 1 inch per minute standard ; other speeds of 1/60, 1/10,3/10,5/10,3,4, or 12 inches per minute available by purchase of interchangeable motors. nput Resistance Toler ance: 10,000 ohms at 1.25 mv and 1 s e c , increasing with increasing ranges. S-72180 R E C O R D E R S i n g l e - R a n g e , Model S R , Sargent. Complete with one S-72165 chart roll; one each S-72175 ballpoint pens, red, blue ; w r e n c h s e t ; oil b o t t l e ; dust cover. For operation from 115 volt, 60 cycle A.C. circuits. . . . $715.00 For complete information write for Sargent Bulletin SR-B
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2 8 A
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ANALYTICAL CHEMISTRY
agents which are accessible to the public have more than offset instru mental and analytical advances that have been made in the "gen eral unknown" search for unidenti fied poisons which may be present.
Clinical Microchemistry
D e m a n d for clinical microcheniistry arose because of the potential h a r m to infants and small children t h a t could result from removing the large blood samples which were re quired in many older techniques. When one considers that the total blood volume of an infant is less than a pint, it is obvious that pro cedures requiring 15 to 30 ml. of blood are prohibitive for general use. The advantages of a meth odology requiring only micro vol umes of body fluids also apply to adult patients with small veins, those with extensive burns whose veins have become obliterated, and to those in respirators. Biochemical research involving small animals likewise has benefited from develop ments in this field. The terms macro and micro as applied to clinical chemistry are undergoing a slow but continuous change. Sixty years ago, 100 to 500 ml. of blood were required for the analysis of glucose by the best methods available. In 1913, an analytical technique was devised" for 1 ml. of blood. This was con sidered to be a micromethod at t h a t time. T o d a y , the generally ac cepted concept of a clinical micromethod is one requiring less than 200 μ\. of sample, although much smaller volumes can be used in many instances. Clinical microchemistry also implies provision for use of capillary blood (from heel, fingertip, toe, or earlobel. A great many micro procedures have been published during the last two decades, and methods requiring less t h a n 200 μ\. of sample exist for nearly all substances of clinical in terest. Exceptions to this general statement are: a few compounds present in unusually low concentra tions, such as protein-bound iodine,
