Creatinine picrate

Several red compounds have been isolated from the red solution obtained from creatinine, picric acid and alkali. By acidification a red powder was isolated by Greenwald and Gross [65], On boiling with water (Anslow and King [66]) or on heating to 139°C this was transformed into the usual yellow creatinine picrate. 

It was considered originally to be a tautomer of the picrate. More recently, by treating aqueous solutions of creatinine picrate of different compositions with alcohol, several crystalline compounds have been obtained (Bollinger [67]). 

The formula VI was originally suggested for the red tautomer of creatinine picrate... 

Creatinine, the degradation product of creatine, is determined in serum with the picrate electrode, which uses the Jaffe method to potentiometrically monitor creatinine picrate. A prior separation step is required to remove interfering sub-... 

The measurement of creatinine to assess renal function is fraught with technical problems. The reaction described by Jaffe in 1886, and which bears his name, is still widely used for the measurement of creatinine. The Jaffe reaction, however, despite its remarkable longevity, is notoriously nonspecific. The reaction involves the development of a red-colored complex between creatinine and picric acid in alkaline solution. Although the absorbance maximum for the creatinine-picrate... 

In a clinical lab, creatinine is normally determined using a commercial analyzer utilizing an absorption method based on the Jaffe reaction. In the Jaffe reaction, creatinine is reacted with alkaline sodium picrate solution to form an orange creatinine-picrate complex. The absorbance at 510 nm can then be measured after a specified reaction time (endpoint method). There are, however, a variety of modifications to the basic method because of the positive... 

Representative Method Although each chemical kinetic method has its own unique considerations, the determination of creatinine in urine based on the kinetics of its reaction with picrate provides an instructive example of a typical procedure. 

Description of Method. Creatine is an organic acid found in muscle tissue that supplies energy for muscle contractions. One of its metabolic products is creatinine, which is excreted in urine. Because the concentration of creatinine in urine and serum is an important indication of renal function, rapid methods for its analysis are clinically important. In this method the rate of reaction between creatinine and picrate in an alkaline medium is used to determine the concentration of creatinine in urine. Under the conditions of the analysis, the reaction is first-order in picrate, creatinine, and hydroxide. 

Procedure. Prepare a set of external standards containing 0.5 g/L to 3.0 g/L creatinine (in 5 mM H2SO4) using a stock solution of 10.00 g/L creatinine in 5 mM H2SO4. In addition, prepare a solution of 1.00 x 10 M sodium picrate. Pipet 25.00 mL of 0.20 M NaOH, adjusted to an ionic strength of 1.00 M using Na2S04, into a thermostated reaction cell at 25 °C. Add 0.500 mL of the 1.00 x 10 M picrate solution to the reaction cell. Suspend a picrate ion-selective electrode in the solution, and monitor the potential until it stabilizes. When the potential is stable, add 2.00 mL of a... 

This experiment includes instructions for preparing a picrate ion-selective electrode. The application of the electrode in determining the concentration of creatinine in urine (which is further described in Method 13.1) also is outlined. 

Creatinine The most widely used creatinine methods are based on reaction between creatinine and picrate ions formed in an alkaline medium. 

Brydon and Roberts- added hemolyzed blood to unhemolyzed plasma, analyzed the specimens for a variety of constituents and then compared the values with those in the unhemolyzed plasma (B28). The following procedures were considered unaffected by hemolysis (up to 1 g/100 ml hemoglobin) urea (diacetyl monoxime) carbon dioxide content (phe-nolphthalein complex) iron binding capacity cholesterol (ferric chloride) creatinine (alkaline picrate) uric acid (phosphotungstate reduction) alkaline phosphatase (4-nitrophenyl phosphate) 5 -nucleotidase (adenosine monophosphate-nickel) and tartrate-labile acid phosphatase (phenyl phosphate). In Table 2 are shown those assays where increases were observed. The hemolysis used in these studies was equivalent to that produced by the breakdown of about 15 X 10 erythrocytes. In the bromocresol green albumin method it has been reported that for every 100 mg of hemoglobin/100 ml serum, the apparent albumin concentration is increased by 100 mg/100 ml (D12). Hemolysis releases some amino acids, such as histidine, into the plasma (Alb). 

Drug/Lab test interactions Methyidopa may interfere with tests for Urinary uric acid by phosphotungstate method serum creatinine by alkaline picrate method AST by colorimetric methods. Because methyidopa causes fluorescence in urine samples at the same wavelengths as catecholamines, falsely high levels of urinary catecholamines may occur and will interfere with the diagnosis of pheochromocytoma. 

Urinary creatinine is determined on a Cobas Bio Analyser using a commercial modification of the Jaffe acid-picrate method (Wako, Neuss, Germany). Urine samples corresponding to 20 pg creatinine are applied directly as a thin streak in a stream of warm air, 1.5 cm from the lower edge of a 20x20 cm pre-coated silica gel TLC plate. Reference standards (10 pg) are used at a concentration of 1 pg/pl. 

Certain cephalosporins (cefoxitin, cefpirome, cefacetrile, cefaloglycin, cefaloridine, cefalotin) react with alkaline picrate solution, forming a chromogen with the same spectrum of absorbance as that formed by creatinine and alkaline picrate, producing falsely high serum... 

El54 Gerard, S. and Khayam-Bashi, H. (1984). Comparison of Ektachem-400 with alkaline picrate methods for the measurement of creatinine in ketotic patients. Clin. Chem. 30, 968, Abstr. 143. 

E200 Gerard, S.K. and Khayam-Bashi, H. (1985). Characterization of creatinine error in ketotic patients. A prospective comparison of alkaline picrate methods with an enzymatic method. Am. J. Clin. Pathol. 84, 659-664. 

Chemical Methods the Jaffe Reaction Most chemical methods for measuring creatinine are primarily based on the reaction with alkaline picrate. In this reaction, first described by Jaffe in 1886, creatinine reacts with picrate ion in an alkaline medium to yield an orange-red complex. Despite considerable literature on the subject, the reaction mechanism and the structure of the product remain unclear. 

Vasitiades J. Reaction of alkaline sodium picrate with creatinine 1. Kinetics and mechanism of formation of the non creatinine picric acid complex. Clin Chem 1976 22 1664-71. 

Weatherburn MW, Trotman RBB, Jackson SH. Specific method for serum creatinine determination based on ion exchange chromatography and an automated alkaline picrate reaction A proposed reference method. Clin Biochem 1978 11 159-66. 

Several methods may be used for the determination of the serum creatinine concentration, most of wWch are based on the nonspecific Jaffe reaction, a colorimetric method based on the reaction of creatinine with alkaline picrate. This nonspecific method also reacts with noncreatinine chromogens in the serum, which may result in a falsely high Jaffe serum creatinine concentration. The noncreatinine chromogens are not present in the urine in sufficient quantities to interfere... 

Creatinine (2-imino-l-methyl-4-oxoimidazolidine) [60-27-5] M 113.1, m 305 (dec), pK] 4.80, pK 9.2. Likely impurities are creatine and ammonium chloride. Dissolve it in dilute HCl, then neutralise with ammonia. RecrystaUise it from H2O by adding excess of Me2CO. The picrate crystallises from 23volumes of boiling H2O and has m 220-22l°(dec). [King J Chem Soc 2377 1930, Beilstein 25 III/IV 2543.]... 

Your laboratory is evaluating the precision of a colorimetric method for creatinine in semm in which the sample is reacted with alkaline picrate to produce a color. Rather than perform one set of analyses, several sets with different samples are performed over several days, in order to get a better estimate of the precision of the method. From the following absorbance data, calculate the pooled standard deviation. 

Creatinine S Spectrophotometric PFF (TCA) reacted with alkaline picrate and absorbance measured at 490 nm... 

Plasma and urinary creatinine are commonly measured by the colorimetric alkaline picrate method of Jaffe or by alternative enzymatic methods. Enzymatic methods use creatinine amidohydrolase or creatinine iminohydrolase and are more specific for creatinine. The measurement of plasma creatinine may be affected by endogenous noncreatinine chromogens (e.g., bilirubin and ketones) this can overestimate plasma creatinine in dogs by up to 45% and to an even greater extent in rats... 

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