I
The Microchemical Laboratory of the American Medical Association J
J. B. PETERSON AND E. W. SCHOEFFEL Chemical Laboratory of the American Medical Association, Chicago, Ill.
I
being allowable. The relative humidity is set a t 55 per cen with an operating variation of * 1.5 per cent. lems of chemistry related to pharmacy ( 2 , 3, 6,8, 22,26, For efficiency in operation, the room is elaborately in27), medicine, and clinical chemistry (19, 21) the American sulated. The floor, ceiling, and walls are covered with 10 Medical Association established a microchemical laboratory, It is the purpose of this paper to describe this laboratory and em. (4 inches) of cork and 5 em. (2 inches) of cement. To prevent the loss of large volumes of conditioned air, the room some of the methods used in its manifold duties to the associais entered through the vestibule already mentioned. The tion and to physicians. single window is fitted with double (Thermopane) glass and The microchemical laboratory is located in a room 3.5 x is covered a t Rill with a venetian-type shade. 3.3 X 6 meters (10.5 X 10 X 18 feet). At one end of the The machinery for maintaining constant temperature and room are the vestibule for entering and leaving the room and humidity includes the air-conditioning system and the controls. the cases for two balances (1, 9). These protection cases are suspended a t the sides only. The balances themselves are The air-conditioning machinery is located on the floor below supported independently of the protection cases; the former the microchemical room. A mixture of air t o be recirculated and fresh air is cooled in a water spray maintained at approximately rest on type-metal slabs that in turn rest on corrugated lead 10" C. (50" F.). In this n'ay the air is washed, cooled, and desheets, which finally are supported bj7 brackets on the back humidified. After leaving the spray the air is humidified suitably wall. Laboratory work tables occupy the rest of the wall with a water-covered steam coil and then heated to the proper space except for a small sink in a corner a t the opposite end. temperature by another steam coil. The air is delivered to the room through a series of holes in a The tables are equipped with gas, water, and electrical outduct, which runs the length of the room near the ceiling. The lets and drains. The depths of the drawers vary and are air is returned t o the conditioner by means of a large duct that relatively smaller than are the drawers in a laboratory for takes the air at the floor from the same side of the room as the macrochemistrv. For convenience, the drawers have been air intake. A smaller return duct opens on the opposite side of the microlaboratory 1.2 fitted with p a . r t i t i o n s of meters 14 feet) above the floor heavy Cellophane, and the and guides a small amount of glassware in the rupboards air past the master controlling is kept separated with strips instruments. This arrangement of the inlet and outlet of balsam wood. ducts causes most of the air t o In order t h a t microcross the room as it enters at chemical determinations of the ceiling and to recross at a all kinds may be carried out lower level as the air approaches the outlet duct. The r e g a r d l e s s of the outside relatively small amount of air weather conditions, the temthat enters the small duct perature and humidity of after crossing the room once tends to make the system t h e r o o m a r e controlled. quick to react to changes in [ T h e t e m p e r a t u r e of temperature and humidity. 22.22" C. (72" F.) and the The system was calculated to 55 per cent relative humiddeliver 14.16 cu. meters (500 ity seem to be the average cubic feet) of air per minute, but something less than this of different l a b o r a t o r i e s volume is usually used. Private c o m m u n i c a t i o n s The controlling i n s t r u with Doctor Hayman of ments are all activated by compressed air. The master Merck & Co., Inc., Rshway, instruments, a t h e r m o s t a t X. J.] The temperature is and a humidostat, are located usually maintained at CASESFOR BALANCEB in the microchemical labora22.22" C. (72" F.), a variat o r y ; t h e y record t h e Protection cases are suspended at the sides only- the balances are suptemperature and the relative tionof * O . 2 S 0 C . (*0.5"F.) ported independently of the lases.
S ORDER to apply microchemistry to the various prob~
.
-
172
173
.iX.lLYTIC.iL EDITIOY
RIARCH 15, 1938
APPARATCS I N hIICROCHEM1CAL
LABORATORY O F AMERICAX
humidity. The other controlling instruments include electrical sxTitches activated by compressed air, steam valves, water valve..., and air dampers. They are mounted on the air-conditioning machinery.
Microchemical Equipment The microchemical laboratory is equipped for organic and inorganic analysis, including a room for spectrographic and other optical and physical work (16). The following microchemical apparatus was found to be essential: carbon and hydrogen (Pregl); nitrogen (Pregl) ; Kjeldahl, all-glass; muffle (Pregl) ; acetyl (Friedrich) ; methoxyl (ViebockSchwappach) ; methylimide (Friedrich) ; and inorganic analysis (the methods of Behrens-Kley, Emich, Pichler, Feigl, and Chamot are used according to the problem). A Iluhlmann microbalance, a semimicrobalance, and a Starke and Kammerer torsion balance constitute the necessary weighing equipment; microextractors and general microglassware, with a set of ground-glass joints, are useful. Most of the heating units are electrified to minimize the heat radiation and the large amounts of water, carbon monoxide, and carbon dioxide, given off by gas flames. A Kofler melting point microapparatus, together with a polarizing microscope, aids in general drug idwtification (12). An ultraviolet lamp properly fitted with filters for fluorescence analysis provides the necessary light for chromatographic adsorption analysis (SO), capillary strip analysis (15,64), and the fluorescence microscope (4, ?a, 76, 7c, 20). The Kofler melting point apparatus is a valuable instrument in identifying minute quantities. A general description of a typical problem will best illustrate its use.
A few drops of a liquid, suspected to contain a certain barbiturate, were evaporated on the Fisher plate of Kofler’s apparatus at low temperature and under vacuum. After the evaporation the dry solid was sublimed a t atmospheric pressure. The first sublimate was resublimed and the melting point recorded. To identify the barbiturate in the liquid, the capillary strip method
i\lEDICAL ASsOCIlTION
was used (IO,1 7 , 25, 2 5 ) . TKOfilter papers, 15 em. long and 1 em. rT-ide, were immersed to a depth of 0.5 em. in microbeakers, one of which contained 3 cc. of the liquid under investigation and the other the same volume of a liquid resembling the original material in aroma and taste but containing a small amount of the suspected barbiturate. After contact for 3 hours the filter papers were examined under ultraviolet light. Both exhibited a fluorescence of the same bluish white shade and intensity. -4nother small portion of the liquids r a s adsorbed on a microcolumn of aluminum oxide (e), and the chromatograms were developed. (The best solvent, developer, eluting agent, and adsorbent for barbiturates have to be determined in each case.) Both chromatograms showed the same color variation under fluorescent light. A quantitative determination of the barbiturate vas achieved by soaking a small filter paper wit’h1 cc. of the liquid, drying it in a stream of warm air, and extracting it in a micro Soxhlet. (A hair dryer with a heating element is a very useful tool in microwork.) The extract was cautiously evaporated and made alkaline, then shaken out with chloroform in a small pipet. The alkaline liquid was acidified and again extracted with chloroform. The chloroform layer was evaporated in a suitable dish itnd the residue weighed. Themelting point (determinedon the microapparatus) of the sublimate from the weighed product and the crystallographic properties of the crystals (11, IS) proved to be that of the barbituric acid in question. This method is also applicable in case6 of identification of barbiturates in biologic liquids like urine and spinal fluid (i4,i8,28, 29).
Summary The American Medical Association microchemical laboratory and its air-conditioning system are described. A list of apparatus and procedures useful in pharmaceutical analysis is given. Literature references for forensic work, especially for identification of barbiturates, are included.
Litkrature Cited (1) Aber, H. K., and Harand, J., J . Franbtin Inat., 224, 729 (1937). (2) Amelink, F., Lsur, and hl., “Schema zur mikrochemischen Identifikation yon Alkaloiden,” Amsterdam, N. V. D. B. Centen’s Uitgerers Maatschappij, 1934.
INDUSTRIAL AND ENGINEERING CHEMISTRY
174
VOL. 10, NO. 3
MAIN A/R
I I I
I
B.
Fresh air damper.
Air pressure to open dampe;
C. Auxiliary fresh air damper. 4ir pressure to open damper D. Solenoid air valve. Air pressure in branch line when coil is energized
Solenoid liquid valve. Open t o flow when coil is energized Adjustable pressure syitch. Contacts open with air pressure Insertion thermostat i n fan discharge duct. Air pressure on branch line on rising temperature H. Insertion thermostat i n mixture of fresh and return air. Pressure in branch line on rising temper.ature I . Immersion thermostat in cold-water pan. Air pressure in branch line o n loa*ering temperature J. Temperature recorder and controller located in conditioned space. Air on branch line on rising temperature K . Humidity recorder and controller located in conditioned space, Air on branch line on lowering relative humidity 1, 2. Automatic water valve and steam valve 3. Automatic steam valve. .4ir pressure to open valve X, I-, Z. Hand valves E. F. G.
(3) Bernhauer, K., “Einfiihrung in die organische ohemische Laboratoriumstechnik,” Berlin, J. Springer, 1934. (4) Dankwort, P. W.,“Lumineszence analyse,” 3rd ed., Leipzig. Akademische Verlagsgesellschaft, 1934. (5) Ekkert, L., “Erkennung organischer Verbindungen, in besonderen von hraneimittel,” Stuttgart, F. Enke, 1933. (6) Ernst, P., and Weiner, G., Scientia Pharm., 8, 45 (1937). (7a) Garner, W.,“Industrial Microscopy,” London, I. Pitman & Sons, 1932. (7b) Garratt, D. C., “Drugs and Galenicals,” London, Chapman and Hall, 1937. (7c) Haitinger, M . , “Die Fluoreszenzanalyse in der ;Llikrochemic%.” Vienna, Emil Haim, 1937. (8) Kirk, P. L., Ann. Rev. Biochem., 6 , 73 (1937). (9) Kirner, W. R., IKD.ENO.CHEM.,Anal. Ed., 9, 300 (1937). (IO) Kofler, A,, and Fischer, R., Arch. Pharm., 273, 483 (1935). (11) Kofler, L., Mikrochemie, 22, !41 (1937). (12) Kofler, L., and Kofler, B . , Mikroskopische hlethoden in der Mikrochemie,” Vienna, E. Haim, 1936. (13) Kofler, L., and Muller, F. A,, Xikrochemie, 22, 43 (1937). (14) Krautwald, A,, and Oettel, H . , Arcb. Ezptl. Path. Pharmakol.. 186, 498, 512 (1937). (An excellent biography on barbiturate determinations.) (15) Kunz-Krause, H . , Pharm. Zentralhalle, 76, 173 (1935). (16) Leonhardt, H., Merck’s Jahresber., 50, 141 (1936). (17) Neugebauer, H., “Die Kapillar-Luminescenaanalyse im pharmazeutischen Laboratorium,” Leipzig, W.Schwabe, 1933.
118) Papavassiliou, RI. J., and Libbrato, S. X., J. pharm. chim., 25. 586 (1937). (19) Pinkussen, L., “Mikromethodik,” Vienna, F. Deutike, 1937. (20) Radley, J. A , and Grant, J., “Fluorescence Analysis in Ultraviolet Light,” Kew York, D. Van Nostrand Co., 1935. (21) Rappaport, F., “Mikrochemie des Blutes,” Vienna, Einil Hairn, 1935. 122) Rojahn, C. A , “ReitrRge zur pharmazeutischen Analyse.” Akademische Verlag, Halle, 1936. (A most useful.g$ries of analytical procedures in pharmaceutical aqiysis.) b2B) Rojahn, C. A , , Pharm. Ztg., 77, 866 (1932). (The series of Pharmazeutische Analyse is indispensable for pharmaceutical laboratories.) 124) Rojahn, C. A , , Pharm. Zentralhalle, 78, 81 (1937). ( 2 5 ) Rojahn, C. A., and Dinkelmann, B., Apoth. Ztg., 45, 756 ff. (1930). 126) Rosenthaler, L., Mikrochemie, 21, 215 (1937). (27) Rosenthaler, L., “Toxikologische Mikroanalyse,” Berlin, Gebruder Borntriger, 1935. (28) Sack, G., Arch. Exptl. Path. Pharmacol., 183, 71 (19361 (29) Tilly, F., Bull. sci. pharmacol., 43, 587 (1936). (30) Zechmeister, L., and Cholnoky, L. V., “Die chromatographische Adsorptionsmethode,” Vienna, J. Springer, 1937. -_)_
R ~ C E I Y ENovember D 23, 1937. Presented before the Microchemical Section at the 84th Meeting of the American Chemical Society, Rochester, N. Y., September 6 to 10, 1937.
