medicine, trace elements, and atomic absorption spectroscopy

MEDICINE, TRACE ELEMENTS, AND ATOMIC ABSORPTION SPECTROSCOPY Gary D. Christian Department of Chemistry University of Kentucky Lexington, Kentucky 4 0 5 0 6

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-L metal analysis and isolation methods for metallo-enzymes have enabled researchers to demonstrate the presence of a large number of elements in plants and mammals. A number of metals have been known for several decades to possess biological activity, but the majority have only fairly recently received interest as possible nutrients. The recent availability of sensitive ana lytical tools has been a major con tributing factor to this interest. Atomic absorption spectroscopy is now at the forefront of these meth ods and its present applications will be discussed here. A consideration of metals in the body and their con centrations will suffice to illustrate the importance of reliable analytical methods. Metals in the Body

Only metals which are ubiquitous (consistently present in biological tissues) and are available can be considered to be essential, since it is impossible for rare metals to be acquired. Because mammals must directly or indirectly obtain their supply of minerals from plants, it 24 A

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ANALYTICAL CHEMISTRY

has been postulated t h a t any ele ment not present in plants is prob ably not essential for man (1). Conversely, any metal found in m a n and not present in plants is prob ably present as a n environmental contaminant and should possess no metabolic function. Metals which are not present a t birth b u t are ac quired and accumulated with age are unlikely to possess any essential biological function. I t is not sur prising t h a t some of the more abun d a n t elements in n a t u r e have evolved as relatively " m a c r o " con stituents in the body and exhibit important biological functions. So dium and chlorine are present in large quantities in the sea where life m a y very well have originated, and are by coincidence major ions in the body. Elements are usually classified as essential or nonessential. Those present in mammals have been di vided between macro and trace ele ments. This latter division is rather a r b i t r a r y and depends on the sensitivity of the analytical meth ods t h a t have been used to detect the elements. One of the most re liable and probably the most useful techniques employed in t h e past

(especially in much pioneering work) is emission spectroscopy. Neutron activation analysis has ex tended the detection limits for m a n y metals to a few nanograms. Anodic stripping voltammetry permits t h e determination of 10~"θΛί concentra tions of certain metals. I n spite of these analytical advances, there are still several cases of disagreement as to the levels of metals present in bi ological tissues. This makes it all the more difficult to assign specific or general roles for these metals. There are two criteria usually used for establishing the essentiality of an element. First, there should be a response in growth or health to dietary supplements of the element ; and second, a deficiency state should develop on diets which are deficient in the element. Schroeder (1) also considers metals which are an integral p a r t of purified enzymes to be essential. According to U n derwood (β), only eight elements meet these criteria for higher ani mals. These are iron, iodine, cop per, manganese, cobalt, molybde num, selenium, and zinc. I t should be emphasized t h a t we cannot nec essarily regard an element which is demonstrated to be essential in ani-

REPORT FOR ANALYTICAL CHEMISTS

Figure 1. Method of standard additions

mais as being essential t o humans, because of the obvious difficulties in performing tests for t h e above cri teria. Underwood classes fluorine, barium, bromine, a n d strontium as being probably essential, based on present knowledge. Of the remain ing trace elements t h a t occur in liv ing tissues, aluminum, silver, lead, gold, bismuth, t i n , titanium, a n d gallium are believed t o be acquired and accumulated as environmental contaminants, while cadminum, chromium, nickel, vanadium, a n d rubidium have suspected functional significance because t h e y are consis tently present {$). Schroeder (1), on the other hand, classifies alumi n u m and in addition, boron, as ubiq uitous a n d cadmium as a contami nant. Based on t h e ubiquitous n a ture a n d availability of t h e ele ments, this worker excludes about V s of t h e elements and leaves 40 for biological interest. Of these, twelve are bulk elements, seven are trace in plants and animals (Β, Μ η , Co, Cu, Zn, M o , I ) , four are nonmetals ( F , Si, Se, B r ) , and seventeen are found in h u m a n tissues with most showing metabolic activity. Those elements which are pres ently considered inert or which are

biologically active but for which no function is known, cannot be per manently classified as nonessential. We must remember t h a t less t h a n a half century ago, only iodine and iron were considered unequivocally essential for the nutrition of higher animals. I t is only with the advent of sensitive and selective analytical methods, along with enzymology and other biological disciplines d e veloped in the last two of three de cades, t h a t t h e current knowledge of trace metal physiology h a s been possible. I n line with the arguments above, there is recent evidence t h a t chro mium should now be considered an essential trace element. Mertz and coworkers (3—5) have identified chromium ( I I I ) as the active ingre dient in a dietary agent required for maintenance of normal glucose me tabolism, probably by interaction with sulfur groups of insulin (6). Certain elements in the body in crease with age. While this m a y represent merely an accumulation of contaminants with no resulting ef fect, some of these elements might interact with certain enzymatic (or other) systems b y competition, causing biological changes and dis

ease. On the other hand, chromium decreases with age. This m a y be significant in t h e increased occur rence of diabetes with increased age (see above) and it has been impli cated in heart disease. Some elements cannot be clearly classified as toxic or nontoxic. Large amounts of molybdenum and selenium, for example, have long been known t o be toxic t o animals. However, more recent studies have shown these two elements t o be es sential in t r a c e amounts for proper physiological function in animals. Elements often do n o t act alone in performing their biological func tions. There is sometimes an interelement dependence, a n d t h e effect of one element m a y depend on t h e presence of another and on its con centration. Indeed, such interde pendences with other elements (or with other biological compounds) m a y very well be t h e rule rather t h a n the exception, however subtle. The effect of copper in animals is dependent on the presence of molyb denum as well a s the a m o u n t of in organic sulfate. T h e simultaneous actions of sodium a n d potassium (and other metals such as the alka line earths) in maintaining a b a l VOL. 4 1 , NO. 1 , JANUARY 1969

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25 A

Report for Analytical Chemists

By any other name it's just a paper

S&S "wet-strength" is a fact Calling a paper "wet-strength" does not make it so. Scientists know that when it says S&S it is, in fact, wet strength. "Ash-Free" or "Ash-Low," genuine wetstrength papers come from S&S. "Ash-Free" for Quantitative Analysis: No. 589-1H. Hardened. Extra Rapid. Thin. For filtration of metallic hydroxides. No. 589-BH. Hardened. Rapid. Coarse and gelatinous ppts pressure filtration. No. 589-WH. Hardened. Medium speed and retention. For gravimetric analysis. No. 589 Red. To prevent collodial dis persion during filtration and washing. No. 507 Hardened. Extra dense. Separa tion of finely divided ppts from corrosive solutions. "Ash-Low" for Qualitative Analysis: No. 410 Extremely rapid. Thin. Gelati nous and coarse crystallines. No. 404 Very rapid. Soft. Loose texture. Coarse and gelatinous precipitates. No. 497 Moderately rapid. Retains pre cipitates that are moderately fine. No. 402 Dense. For filtration of very fine precipitates. No. 576 Extra dense. Hardened smooth. Biological products filtration (serum, in jection fluids). Analytical Filter Papers catalog available on request.

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ance in cellular metabolism are well known. These alkali metals also have an ionic strength effect on en zyme systems (which m a y contain other m e t a l s ) . The mode of action of some met als is known, a t least to a certain extent. Probably the most impor t a n t role of trace metals is in the activation (or deactivation) of spe cific enzyme systems. Some are nonenzymatic in function, either in addition to or instead of being en zyme oriented. Examples are vita min, hormone, skeletal, and other controls. Recent evidence has been obtained t h a t trace metals m a y be associated with R N A . M a n y met als show in vitro activity toward enzyme or other systems, but a t present no known in vivo activity or essentiality has been demonstrated. Once the essentiality of an ele ment has been shown, its site of ac tion must be investigated. Suitable isolation and analytical techniques are required for these studies. Those elements for which specific sites of action have already been demonstrated could be found in future investigations to possess ad ditional metabolic functions. While elements are classified as trace or macro, some, notably iron, appear to play the role of both. Iron is present in large amounts, principally in hemoglobin, but traces of iron in tissues function as a component of several enzymatic systems, just as other trace metals in the body. Some elements occur at extremely low concentrations in the body, notably in the blood and, in the author's opinion should be classified as ultratrace elements. These include cobalt, manganese, chromium, nickel, and iodine. This by no means is to imply t h a t these elements should be considered to possess a lesser biological role. Since plants are the basic source of mineral nutrients to both animals and man, their metal content is im p o r t a n t in the maintenance of health. The form in which the met als occur is important, and the min eral content of soils determines the supply and availability to plants. There are over t h i r t y metals and metalloids found in the h u m a n body, most of them in t r a c e quan tities. These are listed in Table I

along with the concentrations found in blood serum, urine, and tissues. The concentrations of several of these are so small t h a t reported lev els v a r y over a wide range depend ing on the analytical method em ployed. These concentrations listed in the table represent a sampling of several values reported believed to to be most reliable. T h e extremely small amounts of some metals dem onstrate the importance of sensi tive analytical techniques. Atomic Absorption Spectroscopy

T h e principles of atomic absorp tion spectroscopy have been amply described elsewhere (7) and will be dealt with here only briefly. Basi cally, the technique involves aspi ration of the sample solution into a flame where the metal ions are con verted into the atomic vapor state. Most of this atomic vapor exists in the ground electronic state and can therefore absorb resonant radiation of an appropriate wavelength. A hollow cathode lamp is used as the source. This is a sharp line source consisting of a cathode made of the particular element in question (or an alloy of it) with a tungsten an ode. T h e lamp is under reduced pressure and is filled with an a p propriate inert gas (e.g., argon, he lium, or neon). When a sufficient voltage is impressed across the elec trodes, the filler gas is positively ionized a t the anode and is acceler ated toward the cathode. As these ions bombard the cathode, they cause the cathode material to "sput t e r " and form atomic vapor which in the process is raised to an excited electronic state. Upon returning to the ground state, the lines charac teristic of the element are emitted. (The line corresponding to the t r a n sition from the ground state to the lowest electronic excited state is known as the resonance line. This is often, but not necessarily, the most strongly absorbed line.) These pass through the flame (along with lines of the filler gas) where certain ones are absorbed. This absorption is measured with an a p propriate monochromator. T h e a b sorption obeys Beer's law. Since, generally, only the test element can absorb this radiation, the method becomes very specific. In addition,


because most of the atomic vapor occurs in the ground state, atomic absorption is sensitive for a large number of elements. This is in con t r a s t to flame photometry where the light emitted from the small amount of excited atomic vapor is measured. Recent improvements have been m a d e in the construction of hollow cathode lamps. The "high inten s i t y " lamps offer greater sensitivity and linearity for elements such as nickel and cobalt in which nearby nonabsorbing lines cannot be re solved from the absorbing line. These, however, require a separate power supply to operate auxiliary electrodes. T h e "shielded" hollow cathode lamps exhibit greater inten sity t h a n conventional lamps and do not require a separate power source. These are commercially available for most elements now.

desired, and a calibration curve straightener. A new P e r k i n - E l m e r model will include these latter fea tures. Jarrell-Ash is developing an instrument with internal s t a n d a r d capabilities. H e w l e t t - P a c k a r d now markets an inexpensive instrument in which a conventional monoehromator is replaced by a series of in terference filters. This allows the rapid determination of six elements just by changing the hollow cathode lamp and pushing a button to change the filter. While this will not be as sensitive as, and will be more subject to interference than, prism or grating instruments, it is quite convenient for routine deter minations. A welcome feature on several new instruments is the in clusion of a number of safety fea tures in the ignition systems, espe cially for nitrous oxide-acetylene flames.

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I n principle, very little or even no sample preparation is required for biological fluids prior to anal ysis by atomic absorption spectros copy. The amount and n a t u r e of preparation needed will depend on the type of sample, the element to be analyzed, its concentration, and precision and accuracy needed. No one general procedure can therefore be described for all or even several analyses. Some metals can be de termined directly in urine or blood, but others do not have such favor able absorption characteristics or are present in such small concentra tions t h a t matrix effects become in tolerable. In a large number of cases, some method of sample de struction is required. This is true, of course, for all nonliquid samples such as tissues. M e t a l s can often be extracted (dissolved) from ground plant or soil samples. After destruction of organic matter, some metals can be determined directly in the solution of the ash or digest without interference from matrix residues, provided the metal is of sufficient concentration to be de tected. Often, however, a preconcentration or separation step is nec essary in order to eliminate inter ferences a n d / o r to render the de sired element in a concentration high enough to be determined.

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VOL.

4 1 , NO. 1, JANUARY 1969

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27 A


TABLE I

Elemental Content in the Human Body Ele ment Li Na Κ Rb Be Mg Ca Sr Ba

Urine

Serum (ppm) 0.01 3200 120-214

36-58 (ave 43) 90-110

1000-5000 m g / d a y

60-120 m g / d a y 96-800 m g / d a y 0.4 m g / d a y

Ti V

0.005 ± 0.008

Cr

0.03

Mo Mn Fe

Ni

0.01-0.16 d 0.01-0.02 0.80-1.6 (ave 1.25)— men 0.65-1.3 (ave 0.90)— women 0.00007-0.017 ( w h o l e blood) 0.025 (range 0.001-0.08)

Cu

1.05-1.10

Co

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Zn Cd

1.2 0.0033 ± 0 . 0 0 2 4

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0.001-0.007 p p m

Sn Pb As Bi Se a. b. c. d. e.

0.13-0.17 3-17

0.3-0.4 0.04-0.2 0.02 0.14

0.07 g . / g . Ν 20-200 (dry)b 0.00012 (liver) 300-500 60-90 0.1-0.5 ( d r y ) 0.02-0.10 (dry) (1.0 in lung) 0.3-0.6 ( d r y ) (10 i n lung)

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wavelength. If absorption does occur, this is subtracted from all readings a t the analytical wavelength to obtain correct results. As with all analytical methods, a blank should always be run with the method of standard additions. If significant impurities occur in the blank, the actual concentration of these should be determined by the method of s t a n d a r d additions, by adding the standard to a duplicate blank, as with the sample. This is because the flow rate of the sample is often less t h a n t h a t of the aqueous blank solution since it will have a high matrix concentration. When serum or urine samples are simply diluted with water, often no blank correction is necessary if the water is of sufficient purity. If, however, the water does contain significant amounts of the test element, this is an example in which the concentration should be determined as mentioned above since the serum viscosity is greater t h a n t h a t of water. Reporting of Results

A variable found in reporting results for nonfluid samples such as tissues and plants is the form in which the sample is weighed. Some investigators report values based on the fresh (wet) sample weight. Others prefer the dry basis in which the sample is dried by heating a t about 110 °C or is freeze dried, air dried or dried by other means before weighing. Still others report results based on the weight of ash of a sample. These conventions m a k e it very difficult to compare results of different investigators. Reporting concentrations on a fresh basis has more meaning since they can easily be converted to total content of the element in a given sample, organ, plant, etc. and since they represent the concentration in the real sample. Analysis based on fresh weight will be more subject to fluctuations because of differences in water content, water evaporated or water absorbed by handling before weighing the sample. However, these fluctuations m a y be within t h e experimental error of the analysis for some trace elements, and n a t u r a l biological fluctuations of the elemental concentration m a y be as great as or greater t h a n the

uncertainties in weighing. I n addition, it is certainly more convenient simply to weigh the fresh samples t h a n to dry them. T h e weight of dried samples is probably more reproducible t h a n the fresh weight, and for this reason results m a y a p pear to be more reproducible, especially for repeated analysis on a given sample. T h e same is true of the ash content of samples, although this would probably be more variable t h a n the dried sample weight. If samples are dried before weighing, danger of loss of certain volatile elements exists. Because of the above arguments, the author prefers to report concentration on a fresh basis and would like to appeal to other investigators to adopt this as a uniform basis for reporting future results. Or, it would be a simple m a t t e r to weigh samples fresh before drying, and then to report values on both the wet and dry basis for comparison. I n general most tissues or organs contain approximately 70 to 80 per cent water. As an approximation, the ash content of tissues comprises in the neighborhood of 10 per cent of the weight of dried tissue. Determination of Metals in Biological Fluids

Elements which have been determined in urine and blood serum by atomic absorption spectroscopy are summarized in Table I I I . Unless specific limits of determination are given, the described procedures are applicable to determination of physiological levels of the elements as listed in Table I. The specified concentration limits in the Table refer to concentration in the sample. The atomic absorption characteristics of these elements are listed in Table IV. T h e sensitivity is defined as t h a t concentration in ppm (aqueous solution) which gives rise to 1 per cent absorption under the defined conditions. Limits of detection m a y be lower t h a n this and sensitivities are usually improved with organic solvents. The alkali metals can be determined in serum by simple dilution of the sample with water. I n the case of lithium and potassium, the other alkali metal(s) present in serum should be added to standards

Report for Analytical C h e m i s t s

TABLEIII

Elements Determined in Blood and Urine by Atomic Absorption Spectroscopy Element Li Na Κ Mg Ca Cr

Mo Fe

Ni

Cu Zn Cd

Hg

Tl Pb

Bi

so 2 p03-

ci-

Serum

Urine

Dilute 1:10 with H 2 0. Stds. contain Na + K. (0.3 ppm Li) Dilute 1:50 with H20 (3302 Â doublet) Dilute 1:50 with H 2 0. Stds. contain Na Dil 1:20 with H20 Dilute 1:20 with 1 % Na2EDTA or SrCU Dilute 1:20 with H20 or 10,000 ppm Dil 1:10 with 1 % SrCI2 or LaCU Na2EDTA. Add Na and Κ to Stds. Digest > 3 ml with HN0 3 -H 2 S0 4 HCIO4 (or dry ash), oxidize with hot KMn0 4 , extract from 3/H HCI into 5 ml. MIBK(cold) Dry ash, take up with H20 (0.2 ppm) Extract bathophenanthroline com Aspirate directly plex into MIBK or aspirate directly and integrate area under absorp tion peak (add albumin to stds.) 1. Aspirate directly (0.5-10 ppm) 2. Extract 50 ml urine with APDC and 1.5 ml MIBK (0.05-0.6 ppm) 3. Digest 50 ml urine with HN0 3 + H2S04, extract into CHCI3 with DMG and back extract into 1 ml 0.5N HCI (normal levels) Extract with APDC and MIBK Dilute with H20 Aspirate directly Dilute 1:10 with H20 Wet digest, extract with NaDEDC Wet digest, extract with NaDEDC and MIBK (0.0025 ppm) or as and MIBK (0.005 ppm) pirate directly Digest, extract with APDC and MIBK Extract with APDC and methyl-namylketone (0.02-0.4 ppm) (0.01 ppm) Ash, extract with APDC and MIBK (0.01 ppm) Ash 10 ml, extract with NaDEDC and Ash, extract with NaDEDC and MIBK (0.005 ppm) MIBK Ppt. proteins with TCA and extract Extract 50 ml with APDC into 1.5 ml methyl-n-amyl ketone (0.04with APDC and MIBK (0.1 ppm) 0.7 ppm) (100-200 ml urine, 0.02 ppm) Extract 200 ml with APDC and 2.5 ml methyl-n-amyl ketone (0.02-0.6 ppm) Ppt. B a S d , dissolve in EDTA and measure Ba Extract molybdophosphoric acid from PFF into 2-octanol and measure Mo Add AgN0 3 , centrifuge, determine Ag+ in filtrate

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in order to compensate for suppression of ionization in the flame. This is true also for calcium. For sodium, the less sensitive 3302 Â doublet is used in order to minimize

the dilution required and hence the danger of contamination. Magnesium can be determined in urine by direct dilution, but in serum, EDTA or strontium chloride must be added Circle No. 152 on Readers' Service Card

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t o eliminate interference of protein. P r o t e i n m a y suppress or enhance calcium absorption, depending on t h e t y p e of flame used and t h e region of t h e flame where absorption is measured. If a rich air-acetylene flame is used t h e protein in serum nullifies t h e effect of phosphate present a n d t h e sample can be simply diluted with water. I t is safer t o add E D T A or s t r o n t i u m chloride. F o r highly a c c u r a t e measurements, proteins should be precipitated with trichloroacetic acid and strontium chloride added. T h e high phosp h a t e content of urine necessitates adding s t r o n t i u m or l a n t h a n u m salts for calcium determination. C h r o m i u m is t h e only u l t r a t r a c e m e t a l in blood t h a t has been determined a t physiological levels (30 ppb) by atomic absorption spectroscopy. N o r m a l levels of nickel, cadmium, and b i s m u t h have been determined in urine. C a d m i u m det e r m i n a t i o n s b y direct aspiration are somewhat high (0.05 p p m instead of 0.02 p p m ) due t o uncorrected light scattering by salts in t h e urine. T h i s technique is satisfactory for monitoring t h e c a d m i u m in urine of industrial workers exposed to c a d m i u m dust or fumes since t h e levels m a y be as high as 0.6 p p m . B y digesting t h e samples a n d extracting into M I B K , greater sensitivity for c a d m i u m is achieved. Nickel samples m u s t be digested t o determine n o r m a l levels. A s t a n d a r d additions method is used in t h e direct extraction method for bismuth. I r o n can be determined directly in serum diluted with water, b u t results a r e u n s a t i s f a c t o r y a t iron concentrations less t h a n 2.0 p p m due t o sensitivity limits and m a t r i x interferences. W h e n undiluted samples are aspirated, irreproducible results are obtained because of errors due t o v a r i a b l e flow r a t e and sample viscosity. T h i s can be circumvented by integrating t h e area u n der t h e absorption p e a k recorded during t h e aspiration of equal volumes (1 ml) of samples and s t a n dards. T h i s works satisfactorily only when t h e iron concentration is less t h a t 2.5 ppm, and samples with concentrations greater t h a n this are diluted. Absorption is decreased by 38 A

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HOWE & FRENCH NORTH-STRONG SARGENT-WELCH

V A N WATERS & ROGERS WILL

These same dealers supply the seven kinds of precoated EASTMAN CHROMAGRAM Sheet for TLC, sandwich-type CHROMAGRAM Developing Apparatus, and CHROMAGRAM Developing Jar. Acid Titrants Perchloric Acid (70%) (1604) in Acetic Acid (763) Perchloric Acid (70%) (1604) in p-Dioxane (2144) p-Toluenesulfonic Acid (984) in Chloroform (P337) Standards for Acids 1,3-Diphenylguanidine (1270) Phthalic Acid Monopotassium Salt (X538)also known as: potassium acid phthalate potassium biphthalate Base Titrants 2-Amino-2-(hydroxymethyl)-l,3propanediol (4833) in Methanol (467) also known as: tris-(hydroxymethyl)aminomethane Aniline (25) in Acetic Acid (763) Morpholine (P4324) in Acetonitrile (X488) Morpholine (P4324) in Methanol (467) Phthalic Acid Monopotassium Salt (538) in Acetic Acid (763) Phthalic Acid Monopotassium Salt (538) in Acetic Acid (763)/Benzene (777) Sodium Acetate (Anhydrous) (T227) in Acetic Acid (763) Tetrabutylammonium Hydroxide Titrant (25% in Methanol) (7774) Tetrabutylammonium Hydroxide Titrant (10% in Methanol) (P7774) in Benzene (777)/Methanol (467) Tetramethylammonium Hydroxide (10% in water) (1515) Tributylamine (1266), Iodomethane (164), Acetone (297), Ethyl Ether (997) Used to prepare triethylbutylammonium hydroxide which is used in Benzene (777)/Methanol (467) solution. Triethylamine (616) and 1-Iodobutane (56) Used to prepare triethylbutylammonium hydroxide solution which is used in Benzene (777)/Methanol (467). Standard for Bases Benzoic Acid (37) Indicators p-(p-Anilinophenylazo)benzenesulfonic Acid Sodium Salt (823) also known as: Tropaeolin 00 Brilliant Cresyl Blue (C1743) Clayton Yellow (1770) Crystal Violet (C1350) Curcumin (1179) 5-(p-Dimethylaminobenzylidene)rhodanine (2748) also known as: 4'-dimethylaminobenzalrhodanine

N,N-Dimethyl-m-nitroaniline(1208) also known as: m-nitro-N,N-dimethylaniline N,N-Dimethyl-p-phenylazoaniline(338) also known as: p-dimethylaminoa^obenzene 2,4-Dinitroaniline (1843) Ethyl Red (2155) Methyl Violet (1309) p-Naphtholbenzein (924) Neutral Red (C725) Nile Blue (C8679) 2'-Nitroacetanilide (2761) o-Nitroaniline (643) 2-Nitrodiphenylamine (3906) 4-(p-Nitrophenylazo)resorcinol (2484) also known as: azo violet Phenolphthalein (202) Pinacyanol (Chloride) (622) p-Phenylazophenol (417) also known as: p-hydroxyazobenzene 4-Phenylazodiphenylamine (1714) also known as: N-phenyl-p-aminoazobenzene Quinaldine Red (1361) Sudan III (C1754) Sudan IV (C1273) Thymolphthalein (1091) Thymolsulfonephthalein (753) also known as: thymol blue Solvents Acetic Acid (X763) Acetic Anhydride (4) Acetone (297) Acetonitrile « . 0 1 % H 2 0 , for non-aqueous titrations) (X488) 2-Aminoethanol (1597) also known as: ethanolamine (2-hydroxyethyl) amine Aniline (25) Benzene (Thiophene-free) (777) 2-Butanone (383) also known as: methyl ethyl ketone Benzonitrile (Aniline-free) (487) Butyl Alcohol (50) tert. -Butyl Alcohol (820) Butylamine (1261) Carbon Tetrachloride (Sulfur-free) (444) Chlorobenzene (70) Chloroform (Stabilized with Alcohol) (P337) Cyclohexane (702) Dichloromethane (342) Diethylene Glycol (2041) 2,5-Dihydrothiophene-1,1 -dioxide (9345) also known as: 3-sulfolene

Report

Titrimetry Organic Chemicals Solvents (cont'd) N,N-Dimethylformamide (5870) p-Dioxane (2144) 2-Ethoxyethanol (1697) Ethyl Acetate (300) Ethylenediamine (1915) Ethylene Glycol (133) Ethyl Ether (997) Formic Acid (97 + %) (P139) Glycerol (339) Methanol (Acetone-free) (467) Methoxyethanol (2381) 4-Methyl-2-pentanone (416)

Nitrobenzene (387) Nitromethane (P189) Phenol (P201) 1,2-Propanediol (1321) also known as: propylene glycol

Propionic Acid (396) Propionic Anhydride (1291) Propyl Alcohol (848) iso-Propyl Alcohol (212) Pyridine (for Karl Fischer Reagent) (H214) Tetrahydrofuran (Stabilized with 0.025% Butylated Hydroxytoluene) (5308) 1,1,3,3 -Tetramethylguanidine (P8288) Toluene (from Sulfonic Acid) (X325) Toluene (Sulfur-free) (325)

also known as : methyl iso-butyl ketone

Methyl Sulfoxide (P7108) also known as: Morpholine (P4324)

dimethyl sulfoxide

For use with Inorganic acids Salts Alkaloids Amines Amides Amino acids Antihistamines Phenothiazine derivatives Antibiotics

Pyrazolinones Schiff's bases Aldehydes Hydrazides Vitamins Organic acids and phenols Anhydrides of carboxylic acids Sulfonamides

Stilbene and oestrone derivatives Barbiturates and hydantoins Enols and imides Alcohols Aldehydes and ketones Carboxylic acids

Details in this "Informational." PLEASE SEND • •

"Informational" on non-aqueous titrimetry EASTMAN Organic Chemicals

List No. 44 •

Its Cumulative Supplement 44-5

NAME Clip, attach to your laboratory's letterhead, and mail without ob ligation to Eastman Kodak Com pany, Eastman Organic Chemicals, Rochester, Ν. Υ. 14650.

even if not in catalog ψ>

LABORATORY ADDRESS

P.S. Entirely aside from the subject of non aqueous titrants, we may be interested in the following in larger-than-laboratory quantities:

Kodak

the protein present and, therefore, 6 g per cent of iron-free albumin is added t o standards. Hemoglobin in blood is determined b y diluting whole blood or toluene homolyzates 100- to 200-fold with water a n d measuring the iron content. Serum iron-binding capacity can also be determined by adding excess iron ( I I I ) t o t h e serum. Iron can be determined in urine b y direct a s piration, b u t results are 1 to 5 per cent high. More accurate results can be obtained if a urine pool is used to prepare iron calibrating solutions. Mercury can be extracted from urine with A P D C , before or after digestion of t h e sample. I n t h e u n digested urine, standard additions is used for calibration. Several meth ods have been described in which the mercury in untreated or digested (cold permanganate) urine is col lected on a cadmium sulfide p a d . I t is then volatilized into a quartzended cell in which t h e absorption of t h e 2536 Â line is measured with an ultraviolet spectrophotometer. This method is extremely sensitive since 0.02 ^g of mercury can be determined in u p t o 500 ml of solution. Another version is to burn t h e urine sample in an atomizer burner t o convert mercury compounds t o mercury vapor. Exhaust gases from t h e combustion chamber are passed through condensors a n d filters to r e move water vapor a n d salts and then t h e mercury content of t h e gas stream is determined with a commercial mercury vapor meter. T h e limit of detection is 1 0 9 g mercury or 1 μ%/1. Lead can be extracted from urine with A P D C . Another method is to coprecipitate t h e lead in freshly voided or partially decomposed urine with added bismuth nitrate. T h e bismuth does not interfere with the absorption. I n cases of lead poisoning, urine can be aspirated directly. Although t h e resonance lines of most non-metals occur in t h e vac u u m ultraviolet region, there are various indirect ways t o measure these by atomic absorption spec troscopy (34). Inorganic sulfate and phosphate have been deter mined indirectly in biological sam ples. T h e determination of nonVOL. 4 1 , NO. 1, JANUARY 1969 ·

39 A


TABLE IV

(1956).

Atomic Absorption Characteristics of Elements Determined in Serum and Urine Element Li Na Κ Mg Ca Cr Mo

Wavelength, Â 6707.8 d o u b l e t 5890 doublet 3302 doublet 7664.9 2852.1 4226.7 3578.7 3132.6

Sensitivity, ppm

Flame air-coal gas, oxidizing air-coal gas, oxidizing air-coal gas, si. reducing air-C 2 H 2 , reducing air-C 2 H 2 , reducing air-C 2 H 2 , reducing . air-C 2 H 2 , reducing N 2 0-C 2 H 2 air-C 2 H 2 , oxidizing air-C 2 H 2 , oxidizing*

Cd Hg

2483.3 2320.0 3524.54 (using 3524.24 A Fe line) 3247.5 2138.6 2280.0 2536.5

air-C 2 H 2 , oxidizing** air-C 2 H 2 , oxidizing** air-C 2 H 2 , oxidizing** air-C 2 H 2 or Οϋ-Η 2 , oxidizing

Tl Pb Bi

3775.7; 2767.8 2170.0 2230.6

air-C 2 H 2 , oxidizing air-C 2 H 2 , oxidizing** air-C 2 H 2 , oxidizing**

Fe Ni

Cu

Zn

0.03 0.03 5 0.03 0.01 0.08 0.05 0.5 0.4 0.1 0.1 0.1 0.1 0.02 0.03 10 (detection l i m i t 0.5) 0.1-1 0.5 0.5-1

more sensitive ** Air-co

medicine, trace elements, and atomic absorption spectroscopy

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