REPORT FOR ANALYTICAL CHEMISTS itself readily t o automation for analysis of large numbers of sam ples. I t will probably be a routine instrument in the clinical labora tory in the near future. T h e x-ray spectrograph has most of the instru mentation required for x-ray dif fraction. I t is probable t h a t as this instrument comes into general use in the routine laboratory, x-ray diffraction will also find wider a p plication in clinical chemistry for the identification of organic com pounds. I n some laboratories it is being used already to identify ster oids, b a r b i t u r a t e s , alkaloids, a n d other organic compounds (66, 68). Gases such as carbon monoxide, carbon dioxide, oxygen, and volatile organic compounds should lend themselves readily to analysis by gas chromatography. While this technique has been applied in t h e research laboratory t o amino acid and fatty acid analysis, an instru ment designed for the clinical chem istry laboratory has not y e t a p peared. Such an instrument uses minute samples, is rapid, lends it self to sequential analysis of large numbers of samples, and is rela tively inexpensive. I t is conceiv able t h a t when an instrument de signed for the clinical laboratory appears, it will displace the present microgasometers and m a n y dif fusion procedures. In spite of extensive research with the polarograph, and t h e ver satile n a t u r e of its applications (12), t h e polarograph has found only limited use in t h e clinical labo ratory. I t has been used for lead determinations in cases of intoxica tion (5). I n its present form, how ever, it is too slow, lacks a d e q u a t e sensitivity, a n d requires careful handling to give best results. W i t h these disadvantages it has been b y passed by the clinical chemist. A major need in clinical chem istry is methods to estimate various ion concentrations in serum. T h e significance of this problem can be understood if one considers t h a t t h e rate of heart beat and cardiac out put are controlled directly by t h e calcium and potassium ion concen trations in the blood. Levels of these ions in turn are controlled by circulating hormones. Presence of proteins and a host of other sub-
stances in the blood makes these measurements difficult by available means. This problem, recognized for 30 years, still remains unsolved. B y indirect means it is estimated t h a t approximately 40% of the calcium is in ionic form. This varies widely in disease. As total calcium exists in serum to the ex tent of only 2.5 mmoles per liter, ionic calcium is of the order of 1 mmole per liter. Clinically, varia tions in this value of 20% are sig nificant. Here, one is dealing with small variations in a low concentra tion. W i t h potassium, even less is known of the extent of ionization. I t is estimated t h a t not more t h a n 60% of the total potassium is in the ionic state in t h e serum which nor mally contains not more t h a n 5 mmoles per liter. W i t h o u t direct methods for measuring these ionic concentrations, interpretation of phenomena observed in disease can only be guessed at. A method for the direct determination of t h e bi carbonate ion concentration is also a major problem. Here again only indirect evidence is available. Methods of measurement of ionic concentrations, ideally, should not disturb t h e system. One such sys tem which m a y be of value is R a m a n spectra. Present instruments use a small sample in aqueous solu tion. These conditions are highly desirable in clinical chemistry. F u r t h e r , relative sulfate a n d bisul fate ion concentrations can be de termined, under certain conditions, with existing instruments. F u r t h e r development in instrumentation in this field is being closely watched by the clinical chemist. A major need of t h e clinical chemist is specific chemical methods for the determination of certain or ganic compounds which exist in mi nute amounts in the serum but which are of major importance in the diagnosis and t r e a t m e n t of dis ease. I n this class are substances like aldosterone, cortisone, and the estrogens. Although it w a s felt t h a t analysis by infrared was ideal for these substances, instrumentation has not developed to the point where quantities of the order of fractions of micrograms can be readily determined, except b y elab orate sample preparation (48).
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RAPID, SENSITIVE determination of
SULFATE...
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BARIUM CHLORANILATE GOOD NEWS for analysts deter mining micro amounts of sulfate (or of sulfur after conversion to sulfate)! A determination accu rate to 1% in the range 2 to 400 ppm. with a working time less than % hour! MERELY ADD 'Baker Analyzed' Barium Chloranilate to a buffered, ethanolic solution of sulfate. Filter or centrifuge off barium sulfate. Then determine the concentration of the deep purple acid-chloranilate ion by colorimetric measure ment of the broad band at 538 millimicrons. The method is superior to nephel ometric and classical gravimetric methods, and is applicable to such diverse materials as water a n d petroleum products. ORDER B a r i u m C h l o r a n i l a t e 'Baker Analyzed' Reagent from your favorite laboratory supply house. SEE Analytical Chemistry, 2fJ, 281-3 (1Θ57) for details of the method or W R I T E for a free data sheet.
J. T. Baker Chemical Co. J.T.Baker
Phillipsburg, New Jersey
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