H E R B E R T K . A L B E R A N D J . H A R A N D , B io c h e m ic a l R e s e a r c h F o u n d a ti o n , P h il a d e lp h i a , P a .
T
H E construction and function of a number of microchemical laboratories have recently been described (4, 5, 6, 9, 10). These articles distinctly show the importance of microchemical methods in various fields of research, and in
dicate the necessity for adequate facilities in carrying out such delicate analytical work. Recognizing the value of ap
plied microchemistry for biological research, the Biochemical Research Foundation of the Franklin Institute established a special group for the purpose of carrying out most of the analytical work by means of micromethods.
An extensive report on the construction and function of this microchemical laboratory has been published (S, 7). A condensed review is given here, indicating the principles ac
cording to which the laboratory has been set up.
In planning the laboratory, and selecting the equipment, careful con
sideration was given to the require
ments of the foundation (8), so th a t the microchemical work could be corre
lated to th a t of the various research groups.
The aims and purposes of the micro
chemical departm ent are as follows:
1. All new compounds or other products resulting from the research of the different groups are analyzed by the department, excepting those cases in which the analytical work consti
tutes an integral p art of the research problem. Because most of the prob
lems are related to the fields of organic and biological chemistry, the need for organic analytical procedures was ap
parent. Nevertheless it was decided to include facilities for carrying out the more im portant qualitative and quanti
tative inorganic procedures as well.
The need for microchemical methods arises not only from the frequent scar
city of material (often less than 20 mg.), bu t also from the time saving which can be effected by microanalysis. The latter is especially im portant when the different steps of a given reaction or fractionation m ust be closely followed a t frequent intervals.
2. In addition to carrying out the above analytical work, the microchemical departm ent functions as an advisory group in analytical problems in general.
3. Research in the field of applied microchemistry is also carried out. Frequently the efficiency of standard procedures m ust be controlled, particularly when impure samples of biological origin are being analyzed.
D e s c r ip tio n o f t h e L a b o r a to r y
The microchemical laboratory is located on the fifth floor of an office building. The rooms had not previously been used for chemical work; this was of some advantage, since special equipment could be designed and arranged so as to utilize fully the available space. Proper distribution, ac
M icrochem tcal L a b o r a to r y Floor Plan
Fi g u r e 1
L e g e n d C - g o 5 G C -w a ter-co ld
® - A.C. <2H- w a te r - h o t O - a i« ' • - v a c u u m
5 - s i n k -O — lig h t
403
cessibility, and convenience of laboratory furnishings and special apparatus are of prim ary importance in this type of work. Only in this way can strain to the microanalyst be avoided and high working speed maintained.
Figure 1 shows the floor plan of the laboratory, which is divided into five sections:
Room A is for preparative work, decomposition of samples in
cluding Kjeldahl procedures, and all manipulations which re
quire a hood, so as to avoid corrosion of finer apparatus in the other rooms.
Room B, for qualitative microtechnics and microscopical in
vestigations, serves a t the same time as an office and reference room. All inorganic and organic qualitative and semiquantita- tive analyses, mechanical separations under the microscope, and technics connected with chemical microscopy are carried out here.
Room C is used for drying samples in vacuo, filtration proce
dures in quantitative work, and microtitrations.
Room D is separated from room C by a plywood wall only, and serves as a balance room.
Room E is equipped for quantitative organic elementary micro
analysis and electrolytic procedures, and has ample space for special apparatus which can be set up if needed (benches 2 and 5 in Figure 1).
A few of the furnishings in this laboratory are described below in some detail, as they m ay be of special interest to other microchemists.
W o r k B e n c h f o r Q u a l i t a t i v e M i c r o t e c h n i c s . For all qualitative inorganic and organic microchemical analyses and micropreparative procedures, a unit has been formed consisting of a microscope table and a work bench. This unit, located in room B , is arranged so th a t all necessary equip
ment is conveniently a t hand, and unnecessary movements and distractions can be avoided. This is of particular im
portance in qualitative microanalysis, since otherwise the ad
vantages over the ordinary methods become questionable.
N early all samples submitted for quantitative analysis are subjected to a preliminary qualitative or sem iquantitative organic elementary analysis, so th a t the correct procedure, sample weight, etc., m ay be selected according to the amounts of constituents and impurities present (1).
The microscope table was built by E. H . Sheldon and Co., Muskegon, Mich., according to drawings obtained through the courtesy of the Bell Telephone Laboratories, Inc., New York, N. Y. The work bench for all qualitative technics was spe
cially designed (Figure 2) and is rather unusual.
On its right side a hand centrifuge with a special head for micro centrifuge cones and capillaries is fixed to the table, the top of which is covered with gray linoleum. The centrifuge is sur
rounded with a protecting shield and cover; its projecting handle is set into a small quadrant, thus eliminating accidental knock
ing. Two “music room” bulbs are mounted on the under side of the lowest shelf for reagent bottles, etc., providing uniform illumination without shadows from the fingers and body of the analyst. On the left side a special reagent block with 5 tiers of holes serves for vials filled with various reagents for qualitative organic analysis.
The drawers of the table on the left side are arranged for in
coming samples, for all small apparatus in the spot test technic, and for working tools. Over the kneehole is a wide drawer for slides, cover glasses, forceps, etc. On the right side are 7 narrow compartments containing the liquid reagents for the qualitative organic elementary analysis, capillaries, pipets, glass rods, plati
num loops, wires, and spatulas, etc. In the section of the bench below the centrifuge are drawers, one of which is provided with a special rack for the various micro centrifuge cones; the other
Fi g u r e 2 . Wo r k Be n c h f o r Qu a l i t a t i v e Mi c r o t e c h n i c s
JULY 15, 1938 ANALYTICAL EDITION 405 drawers contain separatory funnels, specific gravity pipets, and
microapparatus for extraction, sublimation, and distillation, all of which are thus kept dust-free and ready for immediate use.
W o r k B e n c h f o r S u c t i o n , F i l t r a t i o n , a n d V a c u u m D r y i n g . A suction plate similar to the one described by Clarke and Ilermance (5) is inserted in the linoleum-covered table top of this bench in room C (Figure 3).
In the vacuum line leading to this plate lie two outlets to which are connected the different filter devices and the filter tubes in their drying blocks as used in quantitative microana- lytical work; a few of these arrangements are shown in the center of Figure 3. Six needle valves allow the independent use of each of these suction areas. The high-vacuum pump is located in the right cupboard of the bench on a wooden case, which rests on
6 rubber stoppers to reduce the otherwise very annoying vibra
tions through the floor.
A few permanent pieces of equipment are placed on this table, one of which is the Abderhalden dryer on the extreme right side.
It is provided with a special metal rack designed by Alber (2) for opening and closing charging tubes with ground caps without bringing the sample into contact with moist air. Another dry
ing apparatus for use with high vacuum, described by Unter- zaucher (11), is supported by one of the Kewaunee buret rods with standard taper, which are successfully used on the other tables. In this laboratory it is very important to dry the samples under carefully controlled conditions, since many of the bio
chemical products are extremely hygroscopic; only by prevent
ing any access of (moist) air can accurate results in the various determinations be obtained. The big shelf carries, in special metal holders, the micro wash bottles, the flasks with inter
changeable ground joints which contain liquids of constant boil
ing point for use with the Abderhalden dryer, etc.
T i t r a t i o n T a b l e . For microtitrations a special table has been designed for use under widely varying conditions. This equipment offers the possibility of changing the illumination
according to the type of titration, and provides for the future use of ultraviolet light necessary with fluorescent indicators.
Figure 4 illustrates this table.
Inserted in the top are two removable glass plates which are illuminated from underneath. The two bulbs on each side are connected to one sliding resistance, which allows dimming the light gradually. Colored light filters of Pyrex glass are inter
posed in the slits below the top by means of wooden holders. The color effects help considerably in observing weak end points by producing sharper color contrasts. The heat from the bulbs is carried off by means of slits in the side walls of the table. Ac
curate readings of the meniscus of the standard solutions in the microburets is made easier through two uniformly illuminated glass plates which are mounted in the back of the burets. Be
sides the standard microburets, other micro- or macroburets can be supported by clamps from the three metal racks, which also serve as supports for covers—e. g., when work in ultra
violet light is to be done.
B a l a n c e R o o m . This room should be air-conditioned, with a constant hum idity of about 50 per cent, a constant tempera
ture of about 24° C., completely dust-free, and free from vibrations, in order to provide ideal surroundings for such delicate weighings (6, 9, 10). I t was impossible to provide all these features in the laboratory a t the present time, the only precaution taken being the installation of a filtering de
vice (Air-Pilot) in room B for the removal of excessive dust from the city air. For the microbalances a space centered in the laboratory was selected and protected as far as possible from the influence of sudden tem perature fluctuations by separating it from the other room with a plywood wall and a gliding door. The vibrations which, for instance, come from the motor for compressed air on the floor ju st above the bal
ance room are eliminated by the special construction of the balance table.
Fi g u r e 3 . Wo r k Be n c h f o r Su c t i o n, Fi l t r a t i o n, a n d Va c u u m- Dr y i n g Pr o c e d u r e s
immediate weighing when needed and are protected from dust.
Fi g u r e 4 . Ti t r a t i o n Ta b l e
This table has an oak top 2 inches thick, which is supported by two triangular iron brackets. These are inserted into the wall and partly insulated from vibrations of the wall by cork plates 1 inch thick. Between the table top and the iron brackets, lead sheets 0.5 inch thick are interposed to break up remaining short.shocks and vibrations coming from the wall; the table top itself has no direct contact with the walls. In order to take care of the long vibrations and short shocks which are not absorbed by the above-mentioned breaking devices, the microchemical balance has further supports: a rubber pad, 1 inch thick, is placed directly on the table, and a heavy marble plate rests upon it. Onto the marble plate are glued, in the position of the feet of the balance, three metal rings filled with
rubber, on top of which are placed round aluminum sheets having no direct contact with the metal rings, the whole serving as a shock-free support. To prevent vibrations which may result from writing directly on the balance table, classroom-type chairs with side arms are used for recording the results at the balances. With these arrangements, no disturbances in weighing at the two Kuhlmann microchemical balances are notice
able.
W o r k B e n c h w i t h D r a w e r s f o r S t o r i n g W e i g h i n g V e s s e l s a n d C o r r e s p o n d i n g T a r e s . A very useful arrangement for keeping the micro weighing vessels and the corresponding counterpoises in place is in
corporated in the work bench in the balance room (Figure 5). I t is a general rule in microanalysis to tare any of the vessels to be weighed on the microchemical balance with an object which has similar shape, the same density, and a weight about I to 2 mg.
less than the vessel. W ith three micro
analysts, the unavoidable accumulation of the numerous tares in the balance cases and around the balances could easily result in mistakes. The drawers of the work
bench in Figure 5 contain wooden blocks F i g u r e 5. with openings corresponding in shape to
E ffic ie n c y o f L a b o r a to r y
In the opinion of the authors, the above construction ful
fills all the requirements for a very useful and efficient micro- chemical laboratory. The various pieces of special equip
m ent are, naturally, not w ithout precedent. The experience leading to this final form of construction was obtained through setting up five other microchemical laboratories for various purposes in different countries and by visits to well-estab
lished microchemical laboratories in this country. I t is hoped th a t this abstract of the original paper (3) will be help
ful to other workers who m ay be concerned with the problem of equipping a microchemical laboratory.
The best proof of its efficiency is the statem ent in a report given by the director of the foundation (7), th a t all incoming problems, which vary considerably because of the wide scope of research done in this foundation, can now be solved w ithout delay.
L ite r a tu r e C ite d
(1) Alber, H . K ., lecture presented a t the Organic Sym posium of th e A m erican Chemical Society, R ichm ond, Va., Decem ber, 1937.
(2) Alber, H . K ., Mikrochemie. in press (1938).
(3) A lber, H . K ., an d H aran d . J., J . F ranklin In st., 224, 729 (1937).
(4) C larke, B. L „ I n d . E n g . Ch em., 23, 1301 (1931).
(5) C larke, B. L., and H erm ance, H . W ., Ibid., Anal. E d., 7, 21S (1935).
(6) K irner, W. R „ Ibid., 5, 363 (1933).
(7) M cD onald, E., J . F ranklin Inst., 225, 164 (1938).
(8) M cD onald, E ., R epts. Biochem. R esearch Foundation, F ra n k lin In st., Vol. I l l , 1934-35.
(9) N iederl, J. B., and N iederl, V., “ M icrom ethods of Q u an titativ e Organic E lem en tary A nalysis,” p. 219, N ew Y ork, John W iley & Sons, 1938.
(10) P eterson, J . B., an d Schoeffel, E . W ., In d. En g. C h e m ., Anal E d., 10, 172 (1938).
(11) U nterzaucher, J., Mikrochemie, 18, 315 (1935).
Re c e i v e d M ay 23, 1938.
Wo r k Be n c h w i t h Dr a w e r s f o r St o r i n g We i g h i n g Ve s s e l s a n d Co r r e s p o n d i n g Ta r e s
406
JULY 15, 1938 ANALYTICAL EDITION
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