Barbiturates analysis

Spectrophotometric methods have traditionally been used for the analysis of barbiturates, but these procedures are time consuming, do not identify the barbiturate in question, and it is difficult to quantify accurately unless this identity is known. For these reasons, the development of thin layer and gas chromatographic methods for barbiturate analysis has been occurring. Jain and Cravey (32) have reviewed all the different types of methods being used for the identification of barbiturates from biological specimens. 

One of the problems of barbiturate analysis is the isolation of the compound from biological material.427,428,437,449,513 Extraction is the most accepted method, but some assays take advantage of omitting the isolation and purification step. Special attention was devoted to separation and assay of particular barbiturate drugs in combination with other compounds. For example, many methods were devised for the determination of phenobarbital and hydantoin used together in anticonvulsive therapy.514 Several procedures were proposed for the determination of barbiturates along with their metabolites in body fluids.437... 

The analysis of clinical samples is often complicated by the complexity of the sample matrix, which may contribute a significant background absorption at the desired wavelength. The determination of serum barbiturates provides one example of how this problem is overcome. The barbiturates are extracted from a sample of serum with CHCI3, and extracted from the CHCI3 into 0.45 M NaOH (pH 13). The absorbance of the aqueous extract is measured at 260 nm and includes contributions from the barbiturates as well as other components extracted from the serum sample. The pH of the sample is then lowered to approximately 10 by adding NH4CI, and the absorbance remeasured. Since the barbiturates do not absorb at this pH, the absorbance at pH 10 is used to correct the absorbance at pH 13 thus... 

Cyanide compounds are classified as either simple or complex. It is usually necessary to decompose complex cyanides by an acid reflux. The cyanide is then distilled into sodium hydroxide to remove compounds that would interfere in analysis. Extreme care should be taken during the distillation as toxic hydrogen cyanide is generated. The cyanide in the alkaline distillate can then be measured potentiometricaHy with an ion-selective electrode. Alternatively, the cyanide can be determined colorimetricaHy. It is converted to cyanogen chloride by reaction with chloramine-T at pH <8. The CNCl then reacts with a pyridine barbituric acid reagent to form a red-blue dye. 

Authors are designed row sensitive and selective test-systems for analysis of heavy metals, active chlorine, phenols, nitrates, nitrites, phosphate etc. for analysis of objects of an environment and for control of ions Ee contents in the technological solutions of KH PO, as well as for testing some of pharmacological psychotropic daigs alkaloids (including opiates), cannabis as well as pharmaceutical preparations of phenothiazines, barbiturates and 1,4-benzodiazepines series too. 

Analysis of alkaloids, barbiturates, and other drugs and poisons in forensic science 97AC123R. 

Figure 11.19 SPME-CE analysis of urine samples (a) blank urine (a) directly injected and extracted for (b) 5 (c) 10 and (d) 30 min (b) Urine spiked with barbiturates, extracted for (e) 30 and (f, g) 5 min. Peak identification is as follows 1, pentobaitibal 2, butabarbital 3, secobarbital 4, amobarbital 5, aprobarbital 6, mephobarbital 7, butalbital 8, thiopental. Concenti ations used are 0.15-1.0 ppm (e, f) and 0.05-0.3 ppm (g). Reprinted from Analytical Chemistry, 69, S. Li and S. G. Weber, Determination of barbiturates by solid-phase microexti action and capillary electrophoresis, pp. 1217-1222, copyright 1997, with permission from the American Chemical Society.

Nestorov lA, Aarons LJ, Rowland M. Physiologically based pharmacokinetic modeling of a homologous series of barbiturates in the rat a sensitivity analysis. / Pharmacokinet Biopharm 1997 25 413-47. 

Fernandez Garcia-Borregon, R, Lores, M., and Cela, R., Analysis of barbiturates by micro-high-performance liquid chromatography with post-column photochemical derivatization, /. Chromatogr. A, 870 (1 2), 39, 2000. 

Thormartn, W., Meier, R, Marcolli, C., and Binder, F., Analysis of barbiturates in human serum and urine by high-performance capillary electrophoresis-micellar electrokinetic capillary chromatography with on-column multiwavelength detection, /. Chromatogr., 545, 445, 1991. 

Greeley, D.H., New approach to derivatization and gas chromatographic analysis of barbiturates, Clin. Chem., 20,192,1974. 

A collaborative study conducted by Britton et al. (1984) to determine the most reliable method among the three most commonly used methods (two colorimetric methods and the specific ion electrode method) showed that both pyridine-barbituric acid and pyridine-pyrazolone have similar statistical accuracy. The pyridine-barbituric acid method was preferred by Britton et al. (1984) over the pyridine-pyrazolone method for its convenience (quicker analysis time) rather than the statistical accuracy of data. The electrode method had higher data variability. 

Part—VI has been solely devoted to Miscellaneous Assay Methods wherein radioimmunoassay (RIA) (Chapter 32) has been discussed extensively. Various arms of theoretical aspects viz., hapten determinants and purity importance of antigenic determinants and analysis of competitive antibody binding of isotopically labeled compounds. The applications of RIA in pharmaceutical analysis, such as morphine, hydromorphone and hydrocordone in human plasma clonazepam, flurazepam in human plasma chlordiazepoxide in plasma barbiturates, flunisolide in human plasma have been described elaborately. Lastly, the novel applications of RIA-techniques, combined RIA-technique-isotope dilution and stereospecificity have also been included to highlight the importance of RIA in the analytical armamentarium. 

Barbiturates [94, 95] and diazapinones [96-99] are alkylated (e.g. Scheme 5.23) and arylated (see Chapter 2.2) on the amidic nitrogen atom under liquiddiquid phase-transfer catalytic conditions and the procedure has been used as pretreatment of the non-volatile heterocycles for GLC analysis. 

Jones JJ, Kidwell H, Games DE. 2003. Application of atmospheric pressure chemical ionization mass spectrometry in the analysis of barbiturates by high-speed analytical countercurrent chromatography. Rapid Commun Mass Spec-trom 17 1565. 

RPC has found use in the analysis of barbiturates including the determination of drugs taken in an overdose (332). Thiopental was determined using a mobile phase comprised of methanol-0.1% sodium citrate buffer, pH 6.5 (45 55) (333). Hydantoins, along with other species which have anticonvulsant activity, have been determined with barbiturates. These include phenytoin in the presence of phenobarbital and primidone (334,335) and the related anticonvulsants ethosuximide and carbamazepine (336). 

Elemental composition H 3.73%, C 44.44%, N 51.83%. HCN may be analyzed by GC or GC/MS. The aqueous solution may be directly injected onto the GC column and determined by an FID. For GC/MS determination, an alcoholic solution may be injected into the column. The characteristic mass ions are 27 and 26. The cyanide ion in aqueous solution also may be measured by cyanide ion-selective electrode, titrimetry, and by colorimetric methods (APHA, AWWA, WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). For colorimetric analysis, the aqueous solution may be treated with a dilute caustic soda solution, followed by treatment with chloramine-T, and then with pyridine-barbituric acid reagent. A red-blue color develops, the absorbance of which is measured by spectrophotometer at 578 nm. The concentration of CN is determined from a standard cahbration curve using KCN standards. 

Elemental composition Zn 55.68%, C 20.46%, N 23.86%. A small and measured amount is treated with dilute sulfuric acid. Hydrogen cyanide generated is swept with a purging gas and collected in sodium hydroxide solution. The solution is analyzed for cyanide by a colorimetric method using pyridine-barbituric acid reagent or by cyanide ion-specific electrode (See Hydrogen Cyanide, Analysis). The acid solution may be analyzed for zinc to measure its content in the compound. 

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