Showing papers in "Clinical Chemistry in 1968"
TL;DR: In this article, a new glucose oxidase method employing a polarographic oxygen sensor with a circuit modified to record the rate of oxygen consumption is presented, which provides a direct measure of the glucose level in the sample; results are obtainable within 20 sec. after sample (100 µl.) addition and within 3 min after a blood sample is withdrawn from a patient.
Abstract: Glucose levels in serum, plasma, and urine are determined rapidly and conveniently by a new glucose oxidase method employing a polarographic oxygen sensor with a circuit modified to record the rate of oxygen consumption. The maximum apparent rate of oxygen consumption relative to the rate obtained with a glucose standard provides a direct measure of the glucose level in the sample; results are obtainable within 20 sec. after sample (100 µl.) addition and within 3 min. after a blood sample is withdrawn from a patient. Interferences associated with prior colorimetric glucose oxidase methods are avoided by measuring oxygen consumption instead of hydrogen peroxide formation. The method is described and results are presented showing a standard deviation of less than 1.5% on replicate determinations and a bias of 1% with respect to data obtained on the same samples by the automated ferricyanide method.
830 citations
TL;DR: Total chromogen, true, and AutoAnalyzer methods of measuring serum and urine creatinine by the Jaffe reaction were investigated and their precision, recovery, and sample stability determined.
Abstract: Total chromogen, true, and AutoAnalyzer methods of measuring serum and urine creatinine by the Jaffe reaction were investigated. Some factors influencing this reaction were examined. These included wavelength, blank, linearity, and conditions of color development. Modifications of the three methods were made and their precision, recovery, and sample stability determined. The interference of ketones and glucose were measured. Finally, the values obtained by the three methods on the same samples of serum and urine were compared statistically.
393 citations
TL;DR: The methyl orange dye-binding method tends to give slightly higher results in disease and occasionally larger discrepancies as compared with the electrophoretic and immunoprecipitation methods, but results are little affected, if at all, by the presence of large amounts of paraproteins.
Abstract: Good agreement was obtained between an electrophoretic and an immunoprecipitation method for serum albumin, and it is suggested that these offer a means of determining serum albumin concentration with reasonable accuracy. The methyl orange dye-binding method tends to give slightly higher results in disease and occasionally larger discrepancies as compared with the electrophoretic and immunoprecipitation methods, but results are little affected, if at all, by the presence of large amounts of paraproteins. The dye-binding method appears to be ideal for population surveys.
222 citations
TL;DR: Calculation showed that both methods, P → L and L → P, were essentially equivalent, and this equivalency was verified by a comparative study of the two methods on human serum samples.
Abstract: Optimum reaction conditions at 30° ± 0.5° for two continuous spectrophotometric assay procedures, lactate to pyruvate (L → P) and pyruvate to lactate (P → L), were determined with respect to pH at 30° (pH 30 ) substrate concentration, and coenzyme concentration for the human LDH isoenzymes. For the P → L procedure, broad pH 30 optima were within the range of 7.20-7.40 for all the LDH isoenzymes. The coenzyme optima were identical for all of the isoenzymes tested at a reduced NAD concentration of 1.5 x 10 -4 M. Pyruvate substrate optima ranged from 7.5 x 10 -4 M for LDH 1 to 1.7 x 10 -3 M for LDH 5 at pH 30 7.30. For the L → P procedure, the pH 30 optima were within the range of 8.30-8.88 for the LDH 5 through LDH 1 isoenzymes, respectively. Optimum activity was obtained at a NAD concentration of 6.0 x 10 -3 M and remained constant at least to 1.8 x 10 -2 M for each of the isoenzymes tested. L-Lactate substrate optima ranged from 4.0 x 10 -2 M for LDH 1 to at least 7.2 x 10 -2 M for LDH 5 . From the isoenzyme studies, the degree of variation possibly involved in either method due to variations in isoenzyme distribution was calculated for total LDH samples. These calculations showed that both methods, P → L and L → P, were essentially equivalent. This equivalency was verified by a comparative study of the two methods on human serum samples.
219 citations
TL;DR: A simple method for the determination of plasma and tissue triglycerides is described in this article, which involves extraction and saponification of triglycerides, the oxidation of the glycerol moiety to formaldehyde, and the conversion of formaldehyde to a yellow-colored compound, 3,5 diacetyl-1-4 dihydrolulidine, the intensity of which is determined spectrophotometrically.
Abstract: A simple method for the determination of plasma and tissue triglycerides is described. This procedure involves the extraction and saponification of triglycerides, the oxidation of the glycerol moiety to formaldehyde, and the conversion of formaldehyde to a yellow-colored compound, 3,5 diacetyl-1-4 dihydrolulidine, the intensity of which is determined spectrophotometrically. The recoveries of triglycerides added to plasma and tissues have been satisfactory. Plasma samples obtained from normal human subjects are found to have triglycerides in the range 83-200 mg./100 ml. From the standpoint of sensitivity, simplicity, and time required, this technic is believed to be an improvement over previously described procedures for triglyceride determination.
197 citations
TL;DR: In this paper, a method for the determination of CO content in blood is described, where carbon monoxide bound to hemoglobin is released by hemolysis and reaction with K3Fe(CN)6 in a closed system.
Abstract: A method for the determination of CO content in blood is described. Carbon monoxide bound to hemoglobin is released by hemolysis and reaction with K3Fe(CN)6 in a closed system. The gases liberated are then swept onto a 5 A molecular sieve column where CO is separated from other blood gases. The CO, after catalytic reduction to methane, is detected by flame ionization. The method is rapid, specific, and sufficiently sensitive to permit analysis of 0.1-ml. samples of normal blood. The accuracy of the method, expressed as the coefficient of variation (S.D. x 100/mean), is 1.8% for normal human blood.
154 citations
TL;DR: The Standards Committee of the AACC presents a discussion of the nature of total serum protein and the problems associated with its determination, and proposes that protein be defined as polypeptide material, and that a reference preparation be promulgated for interlaboratory use.
Abstract: The Standards Committee of the AACC presents a discussion of the nature of total serum protein and the problems associated with its determination. Proposals are made that protein be defined as polypeptide material, and that a reference preparation be promulgated for interlaboratory use. The reference material suggested is bovine serum albumin, produced to rigid specifications and distributed as a stable 7% (w/v) solution, the concentration of which has been established by careful dry weight assay. Comments of readers are invited.
140 citations
TL;DR: A modified method is described for zinc determination in plasma by atomic absorption spectrophotometry using the Boling three-slot burner, with results similar to those obtained with trichloracetic acid filtrates and water standards.
Abstract: A modified method is described for zinc determination in plasma by atomic absorption spectrophotometry using the Boling three-slot burner. Accurate analysis for the element was accomplished after merely diluting the plasma with deionized water (1 part plasma to 1 part water). Sample preparation time was thus greatly decreased. It was found that standards made up in water resulted in an error of 33%. However, standards prepared in 3% dextran solution gave results similar to those obtained with trichloracetic acid filtrates and water standards. Dextran was found not to be contaminated with zinc. The recovery of zinc added to plasma averaged 98.9%. Because of the simplicity of the method, sources of error and possibilities for contamination were reduced.
106 citations
TL;DR: Values from a group of children with sickle cell anemia showed no significant variance with the normal population and the proposed procedure compares favorably with a corresponding ninhydrin technic for plasma amino nitrogen.
Abstract: A simple procedure for the estimation of plasma amino nitrogen based on the reaction of amino groups with 2,4-dinitrofluorobenzene (DNFB) and subsequent measurement of the dinitrophenyl (DNP) amino derivatives at 420 mµ is presented Elevated concentrations of bilirubin, hemoglobin, and the major nonprotein and nonamino acid nitrogen components of plasma do not seriously interfere The proposed procedure compares favorably with a corresponding ninhydrin technic for plasma amino nitrogen The mean plasma amino nitrogen values and range for a group of adults (age 18-50 years) by the proposed method is 556 mg/100 ml (36-70 mg/100 ml) compared to 412 mg/100 ml (36-52 mg/100 ml) for a group of children (age 2-10 years) Values from a group of children with sickle cell anemia showed no significant variance with the normal population Optimum conditions for quantitation of plasma amino nitrogen along with other procedural parameters are presented
99 citations
TL;DR: Three methods for the determination of N-acetyl-p-aminophenol in plasma that differ in principle from the diazotization procedure of Brodie and Axelrod are described and all three methods exhibited satisfactory replication, recovery of added APAP, and comparable plasma levels of the drug.
Abstract: Two methods for the determination of N-acetyl-p-aminophenol (APAP) in plasma that differ in principle from the diazotization procedure of Brodie and Axelrod ( 1 ) are described. One method based on the differential absorption peak of APAP at 266 mµ, which corresponds to the isosbestic point of common drugs such as acetylsalicylic and salicylic acids, is simple and most specific for APAP. The other method employs a free-radical dye diphenylpicrylhydrazyl which extracts a hydrogen atom from the APAP molecule and is progressively decolorized. The dye method is the least complex and most sensitive. All three methods exhibited satisfactory replication, recovery of added APAP, and comparable plasma levels of the drug.
93 citations
TL;DR: A biuret method has been developed which provides quantitative measurements of protein in normal urine without interference from drugs or pigments, intended for use in monitoring clinical trials of new drugs—to detect nephrotoxicity.
Abstract: A biuret method has been developed which provides quantitative measurements of protein in normal urine without interference from drugs or pigments. This method is intended for use in monitoring clinical trials of new drugs—to detect nephrotoxicity. Protein is precipitated from duplicate samples of urine by addition of cold ethanolic phosphotungstic acid. The protein precipitates are separated by centrifugation and washed with ethanol. Protein from one of the duplicate samples is dissolvel in biuret reagent. Protein from the second sample is dissolved in an alkaline tartrate reagent which is identical to the biuret reagent, excepting that copper sulfate has been omitted. After 20 min., the differential absorbance of the two samples is measured at 540 mµ. The limit of sensitivity for detection of protein in urine is 0.5 mg./100 ml. The coefficient of variation of replicate analyses of protein in normal urine is 4.2%. The recovery of protein added to urine averages 103 ± 3%. Analyses of urinary protein by the biuret procedure provide close correlation with measurements by an amido black staining method. Systematic search has failed to reveal interference from urinary pigments, compounds, or drugs which are normally or occasionally encountered in hospitalized patients. In 24-hr. collections of urine from 28 healthy adults, the protein concentrations averaged 6.2 mg./100 ml. (range 3.0-12.2), and the protein excretions averaged 77 mg./day (range 40-150).
TL;DR: An improved microprocedure for the determination of tocopherol in blood serum is reported, which is more sensitive than colorimetric methods using 2,2',2''-tripyridine,2,2'-bipyridine ( bipyridyl) or 2,4,6-tripyrsidyl-s-triazine.
Abstract: An improved microprocedure for the determination of tocopherol in blood serum is reported. Tocopherol is oxidized by ferric chloride and the pink complex of ferrous ions with 4,7-diphenyl-10,10-phenanthroline (bathophenanthroline) is determined spectrophotometrically. The test is more sensitive than colorimetric methods using 2,2',2''-tripyridine,2,2'-bipyridine (bipyridyl) or 2,4,6-tripyridyl-s-triazine. The use of phosphoric acid prevents the photochemical reduction of ferric chloride and also reduces interference of carotene to a minimum. The amount of carotene oxidized by ferric chloride in the first 5 min. is negligible in the presence of bathophenanthroline. As its further oxidation is stopped by phosphoric acid, the contribution of carotene to the ferrous-bathophenanonthroline complex is insignificant.
TL;DR: An automatic, high-resolution analytic system for the quantitative determination of the ultraviolet-absorbing molecular constituents of urine and other body fluids is being developed and more than 140 chromatographic peaks have been resolved from a 2-ml urine sample.
Abstract: An automatic, high-resolution analytic system for the quantitative determination of the ultraviolet-absorbing molecular constituents of urine and other body fluids is being developed. This system is comprised of a heated, high-pressure anion-exchange column for the separation step and a continuous-flow ultraviolet spectrophotometer for the detection step. Separation is achieved by elution with an acetate buffer of gradually increasing concentration. The total analysis time is 40 hr. Chromatograms showing the absorbance of the column effluent as a function of time are recorded by a strip-chart recorder and by a data acquisition system containing a digital voltmeter and paper tape punch. The output from the latter is then used as the input to a digital computer for analysis of the chromatogram. More than 140 chromatographic peaks have been resolved from a 2-ml. urine sample. Normal urine samples yield similar chromatograms. A variation in the diurnal cycle has been noted.
TL;DR: A useful technic for the isolation, separation, and identification of biogenic amines as fluores ent dansyl derivatives is described and was applied to the identification of various amines present in mammalian heart.
Abstract: A useful technic for the isolation, separation, and identification of biogenic amines as fluores ent dansyl derivatives is described. A thin-layer chromatographic system is presented for the separation of the dansyl derivatives of phenethylamines from their corresponding β-hydroxyl derivatives, of primary amines from their corresponding N-alkylated derivatives, and of the components present in an extract of mammalian heart. Mass spectrums of dansyl derivatives of various amines and amino acids are presented to illustrate parent ion mass determination. This technic was applied to the identification of various amines present in mammalian heart. Identification was based on cochromatography and identity of parent ion mass with authentic compounds. Piperidine, dimethylamine, phenethylamine, methylamine, phenethanolamine, putrescine, spermidine, spermine, and tyramine were identified.
TL;DR: The D2O dilution procedure compares favorably with the tritium dilution technic, with values obtained on 45 out of 46 individuals falling within the ±3 combined S.D. limits for the two methods.
Abstract: A procedure is described for the determination of total body water content of human subjects using 11- to 12-gm. doses of deuterium oxide (D2O), vacuum sublimation of serum samples, and quantitation of the deuterium by infrared spectrophotometry at 2510 cm.-1. The coefficient of variation based on day-to-day procedure reproducibility is less than 2%. D2O added to serum is completely recovered in the sublimation and assay operations. The D2O dilution procedure compares favorably with the tritium dilution technic, with values obtained on 45 out of 46 individuals falling within the ±3 combined S.D. limits for the two methods. The significance of the total body water data is discussed.
TL;DR: A method is described which is potentially capable of closely estimating the normal range from laboratory data using a purposely truncated form of the "normal" distribution.
Abstract: A method is described which is potentially capable of closely estimating the normal range from laboratory data. The estimation is made on probability paper using a purposely truncated form of the "normal" distribution. A fictitious set of data has been used to illustrate the efficiency of estimation of normals. The method has been used to estimate the normal range of blood urea.
TL;DR: The carbohydrate analyzer used in this experimental work should become a useful tool in the clinical laboratory and the lower limit of detectable sugar in physiologic fluids is in the 1-µg range.
Abstract: Automated carbohydrate analysis can be useful clinically in the research laboratory as an aid in understanding the fundamental role of carbohydrates in metabolism, including their pathologic significance. An analytic system being developed at our laboratory utilizes an automated carbohydrate analyzer to chromatograph borated physiologic fluids while using strongly basic anion-exchange resin. The eluted carbohydrates are detected by sulfuric acid-phenol colorimetry. The carbohydrate analyzer used in this experimental work should become a useful tool in the clinical laboratory.
Normal and diabetic human urine and blood serum have been chromatographed and significant differences established. As many as 38 peaks have been observed in the complex urine chromatograms. Using cochromatographic technics, 14 peaks have been tentatively identified as sucrose, raffinose, N-acetylglucosamine, maltose, lactose, ribose, fructose, arabinose, fucose, galactose, xylose, mannoheptulose, glucose, and glucose-1-phosphate. All except fucose have been quantified. Blood serum chromatograms consist of a major glucose peak and several smaller peaks indicating traces of other sugars. Melibiose has been used as an internal standard in chromatograms to determine recovery, resolution, and reproducibility. With the present technic, the lower limit of detectable sugar in physiologic fluids is in the 1-µg. range.
TL;DR: The 8-quinolinol complexes of zinc at pH 8.0 (in universal buffer) are stabilized by gum arabic and demonstrate a marked fluorescence at 517 mµ when excited at 375 m µ.
Abstract: The 8-quinolinol complexes of zinc at pH 8.0 (in universal buffer) are stabilized by gum arabic and demonstrate a marked fluorescence at 517 mµ when excited at 375 mµ. Under these conditions only zinc—not magnesium or calcium at physiologic concentrations—can be determined in plasma and urine. Adult plasma has 94 ± 7 µg. zinc per 100 ml. while the plasma of children contains 108 ± 15g./100 ml.
TL;DR: 2,4,6-trinitrobenzenesulfonic acid (TNBS) was found to be a very simple and sensitive reagent, easier to use than ninhydrin, and has a much lower sensitivity to the imino acid proline than to the amino acids.
Abstract: The reaction of 2,4,6-trinitrobenzenesulfonic acid (TNBS) with amino acids was investigated by a static system to develop optimum conditions for application to automated amino acid chromatography. TNBS was found to be a very simple and sensitive reagent, easier to use than ninhydrin. The reaction occurs quite rapidly at room temperature, eliminating the requirement of a heating bath. The major disadvantage is a much lower sensitivity to the imino acid proline than to the amino acids.
TL;DR: Four plant starches were used to study human amylase activity in normal serum and urine, "pancreatitis" serum, duodenal fluid (secretin stimulated), saliva, and pancreatic extract, and it was shown that the rate of digestion of starch by each of the fluids tested depends on the plant starch selected as substrate.
Abstract: Four plant starches were used to study human amylase activity in normal serum and urine, "pancreatitis" serum, duodenal fluid (secretin stimulated), saliva, and pancreatic extract. The starches were derived from waxy maize, high amylose corn, potato, and corn (pearl), and were lintnerized. It was shown that the rate of digestion of starch by each of the fluids tested depends on the plant starch selected as substrate. Digestion of waxy maize was most rapid. The advantages of using waxy maize as a substrate are indicated as a means of markedly enhancing the sensitivity of serum amylase determination. It was also found that normal serum, urine, and saliva digested potato starch at a greater rate than corn starch with few exceptions, while pancreatitis serum, secretin-stimulated duodenal fluid, and pancreatic extract digested corn starch at a greater rate than potato. These findings suggest that organ-specific amylases exist, and that plant starches might be used to distinguish them.
TL;DR: A new method is described for the determination of serum lipase using olive oil as substrate, and photometric, copper soap analysis for the measurement of fatty acids formed.
Abstract: A new method is described for the determination of serum lipase using olive oil as substrate, and photometric, copper soap analysis for the measurement of fatty acids formed. The great sensitivity of this technic for measurement of the fatty acids permits a 30-min. incubation time and the use of 0.1 ml. serum. The reaction is zero order for this time period. Other aspects of the enzyme kinetics were studied and the normal values determined.
TL;DR: High-pressure, anion exchange chromatography of urine has resolved more than 100 UV-absorbing urinary constituents, using three methods to identify these constituents.
Abstract: High-pressure, anion exchange chromatography of urine has resolved more than 100 UV-absorbing urinary constituents. Three methods have been used to identify these constituents: (1) chromatographic properties of standards, (2) spectrometric analysis of isolated urinary constituents, and (3) chemical testing of the isolated urinary constituents.
TL;DR: A simplified procedure utilizing ferrous ammonium sulfate-thiourea as the reductant for the determination of inorganic phosphate in serum and urine by the AutoAnalyzer is described, resulting in an improved S.D. of ± 0.25 and troubleshooting during any apparatus malfunction.
Abstract: A simplified procedure utilizing ferrous ammonium sulfate-thiourea as the reductant for the determination of inorganic phosphate in serum and urine by the AutoAnalyzer is described. Elimination of the heating bath usually required for many phosphorus methods for color development yields an improved S.D. of ± 0.25 and facilitates troubleshooting during any apparatus malfunction. Comparison of results between the proposed method and that of Fiske and SubbaRow ( 1 ) is presented. Recoveries of added phosphorous in serum or urine are quantitative.
TL;DR: Comparison of the activities with the corresponding concentrations shows that the two most important parameters influencing the molar activity coefficients of these ions are the water content of serum and the binding between albumin and chloride.
Abstract: Ionic activities of sodium, potassium, and chloride in serums of 26 hospitalized patients were determined with ion-specific electrodes. Comparison of the activities with the corresponding concentrations shows that the two most important parameters influencing the molar activity coefficients of these ions are the water content of serum and the binding between albumin and chloride. Quantitative expressions for activity-concentration conversion factors are given. Calculations show that the conversion factors vary significantly in disease states due to changes in protein.
TL;DR: A scheme for detection of metabolic disorders utilizing commercial dip tests, spot plate tests, and paper chromatographic tests is presented and examples of specific and generalized aminoacidurias are given.
Abstract: A scheme for detection of metabolic disorders utilizing commercial dip tests, spot plate tests, and paper chromatographic tests is presented. Specific details are given for preparation and development of chromatograms for routine screening of urine specimens for disorders of amino acid and carbohydrate metabolism. Specialized tests for confirming positive findings in the screening procedures are described. The results are interpreted with regard to the variations encountered in testing normal infants and children, children hospitalized with a variety of diseases, and mentally retarded children. Examples of specific and generalized aminoacidurias are given.
TL;DR: The present method has shown excellent reproducibility in replicate analyses of normal and pathologic serums, and has shown nearly quantitative isolation of human serum albumin in a rapid manner.
Abstract: A rapid method for nearly quantitative isolation of human serum albumin is described. The present technic ( 1 ) is a modification of the Schwert method ( 2 ). In the present method 4 ml. of serum is precipitated with trichloroacetic acid in a final concentration of 5% (w/v). The precipitate is washed with TCA, and after aqueous suspension, ethanol is added to a final concentration of 80%. The undissolved globulin is washed with ethanol and the solubilized albumin used for quantification, characterization, and isotope counting.
Recovery of added human serum albumin was approximately 98%; recovery of added 131I albumin was 90%.
Cellulose acetate electrophoresis showed a single band, and agar diffusion produced one precipitate line. Immunoelectrophoresis with anti-human serum revealed one or two very faint arcs in the α-, or α- and β-globulin regions, in addition to the major arc of albumin.
The method has shown excellent reproducibility in replicate analyses of normal and pathologic serums.
TL;DR: It was concluded that all or most of the remaining difference was due to weighting of the inpatient data by low values of pathologic significance; the proportion of these low values was too great to allow a normal range to be extracted from the data by statistical methods.
Abstract: The serum sodium concentrations of three groups of patients selected from laboratory records and of one group of outpatients selected for a prospective study were examined. The mean serum sodium concentration of inpatients with normal serum urea concentrations was 8.5 mEq./ L. lower than that of a group of healthy normal subjects. Part of this difference (2.6 mEq./L.) could be attributed to a nonspecific effect of illness. It was not possible to demonstrate any effect due to the hospital environment, but the results do not exclude the possibility of such an effect. It was concluded that all or most of the remaining difference was due to weighting of the inpatient data by low values of pathologic significance; the proportion of these low values was too great to allow a normal range to be extracted from the data by statistical methods.
The concept of the normal range is discussed. It is suggested that two ranges are required for serum sodium, a normal range (137-147 mEq./L. in this laboratory) to make assertions about alterations in specific diseases, and a range derived from patients likely to have no manifest disturbances of salt and water metabolism (135-144 mEq./ L.) to detect such disturbances.
TL;DR: The commercial reduced-NAD preparations most rapidly oxidized by LDH were white, free-flowing substances with 260 nm:340 nm absorbance (A260:A340) ratios below 2.45.
Abstract: The physical and chemical properties of several commercial sources of reduced NAD were examined. Properties compared included physical appearance, sodium and phosphorus content, ultraviolet light absorption at 260 and 340 nm, and relative rates of oxidation with two human LDH isoenzymes. Major differences between individual preparations were noted with respect to physical and chemical properties, as well as in the activity measurements. The commercial reduced-NAD preparations most rapidly oxidized by LDH were white, free-flowing substances with 260 nm:340 nm absorbance (A260:A340) ratios below 2.45. Detectable amounts of an LDH inhibitor were found in all preparations examined. A strong LDH inhibitor, which had the same properties as the inhibitor present in commercial reduced NAD, was isolated by column chromatography. This LDH inhibitor was found to produce the same degree of inhibition toward four LDH isoenzymes.
TL;DR: The atomic absorption spectrophotometric method for the measurement of lithium in biologic samples is evaluated and the preparation of standards for measurement of serum and urinary lithium concentrations is provided.
Abstract: The atomic absorption spectrophotometric method for the measurement of lithium in biologic samples is evaluated. The preparation of standards for measurement of serum and urinary lithium concentrations is provided with discussion of some interfering substances.
TL;DR: Bio-Gel filtration is introduced as a rapid and reproducible method for purifying HGH-131I which has been obtained by a modification of the method of Greenwood et al. ( 1 ).
Abstract: Detailed methods for: (1) 131I iodination of human growth hormone (HGH); (2) purification of labeled HGH (HGH-131I; and (3) radioimmunoassay of HGH are given. Bio-Gel filtration is introduced as a rapid and reproducible method for purifying HGH-131I which has been obtained by a modification of the method of Greenwood et al. ( 1 ). Highly purified HGH-131I with a bindability of 96% or more is usually achieved.