Spectrophotometric study of a direct determination of serum calcium

A modification of a direct manual procedure for serum calcium has been developed in which a one-piece color reagent is used. When a micro amount of serum is added to the reagent, rapid and stable color formation occurs enabling the procedure to serve either as a manual stat system of in robotized automatic instrumentation. Total color measurement is not attained in such a procedure owing to the described regressive nature of the reagent blank. However, accurate and linear reaction characteristics are effectively achieved. The use of a low dielectric solvent, EG, served well for repressing the ionization of the blank while allowing linear and reproducible calibration characteristics.     

Spectrophotometric study of thiouracil interference in a serum cholesterol determination

A spectrophotometric study of the effect of thiouracil on the determination of cholesterol by FeCl₃ reaction has been described. The depression of the reaction by thiouracil was confirmed and its removal by exchange with the iodate of AgIO₃ studied. It was found that thiouracil appeared to be removed by the exchange, but the iodate that replaced both it, as well as the chloride which is always present, interfered maximally in a FeCl₃-acetic acid protein precipitating system and to a lesser extent in an alcohol-acetone extraction system. One can infer from the results obtained that it would have been more reasonable to use an uncontaminated portion of serum for the determination of cholesterol rather than to carry out an in vitro removal of an in vitro addition of what may have been an unnecessary stabilizing agent.     

Spectrophotometric method for the direct determination of uranium in carbonate solution

Summary A spectrophotometric method for direct determination of uranium in carbonate solution has been developed. No extraction or decomposition steps are necessary. The highly sensitive (4-2-pyridylazo) resorcinol, as well as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, producing very stable uranium(VI) complexes, were used for its spectrophotometric determination.The usefulness of the proposed methods was examined by determination of uranium in real samples from a wet-process phosphoric acid estimation of uranium.     

Spectrophotometric evaluation of interferences in three iron reactions for the determination of serum total cholesterol

A spectrophotometric and chemical evaluation of reported interferences for three iron reactions for the determinations of serum cholesterol has been presented. It has been shown that all three reactions are affected by various interfering substances, such as 2-thiouracil, nitrate, azide, bromide, diethylstilbesterol, and steroids. Spectral differences between the reactions are probably due to solvent and anion effects.The incorporation of uranyl acetate as a precipitating agent into the ferric acetate-uranyl acetate procedure did not make the results obtained comparable with the Abell-type extract of a very icteric serum. Incorporation of ferrous sulfate does not noticeably affect the intensity or stability of color development with standards.As proposed, the ferric acetate-uranyl acetate procedure for the determination of cholesterol represents a modified iron reagent, but the reaction mechanism and the procedure described for it is neither new nor direct. The use of the ferric acetate reagent for serum cholesterol as opposed to ferric chloride, ferric ammonium chloride, or ferric perchlorate appears to have no real advantages as a color reaction. In fact the reaction is less sensitive while reagent preparation is more tedious, time consuming, and expensive than the ferric chloride procedure. Although no quantitative studies were performed, the only effects that chloride had on the reactions were in the region of 400 nm, a wavelength sufficiently far enough away from the 560-nm peak that it did not affect determinations. The concept that the ferric acetate-uranyl acetate reagent contains only acetate and sulfate anions is nullified as soon as one adds serum to the reagents.     

A new method for the titrimetric determination of perchlorate

A new method for the titrimetric determination of perchlorate has been developed, based on its reduction to chloride by iron(II) in a strong sulphuric acid medium at high temperature. The effect of variables, such as the sulphuric acid concentration, the temperature and the period of heating, on the extent of reduction has been studied and the optimal conditions for analytical determination of perehlorate derived.     

A cleanup method for perchlorate determination in urine

There is increasing concern about perchlorate exposure because of perchlorate's potential effects on organisms as a thyroid hormone disruptor, as well as its contamination of the environment being much more widespread than previously thought. Perchlorate is excreted primarily into urine, therefore, evaluating perchlorate residues in urine should be a reasonable approach for determining exposure and if successful could be used as an effective biomarker of perchlorate exposure. Since the presence of ions and other biomolecules in matrices like urine usually confounds accurate determination of perchlorate by ion chromatography, it is necessary to develop efficient methods for perchlorate determination in these matrices. We developed a method that reduces the background signal of urine, which is typically the problem with the analysis of biological fluids and tissues by ion chromatography. Relatively high recovery of perchlorate was shown. In cow urine samples spiked with perchlorate at 2.5, 10, and 100 μg/L, perchlorate recoveries were 67% ± 2.5, 77% ± 3.6, and 81% ± 1.7 (mean ± S.D.), respectively. In addition, the detection limit was as low as 12.6, 12.3, and 18.7 μg/L in cow, vole, and human urine samples, respectively.     

Spectrophotometric method for the determination of 1,2-propylene glycol

A spectrophotometric method is proposed for the determination of 1,2-propylene glycol. It is based on the ADH/ AlDH catalyzed oxidation of propylene glycol by NAD⁺. The NADH formed is measured at 340 nm. Alcohol dehydrogenase from equine liver was found to be much more effective than that of yeast. No enantiomeric selectivity for s(+) propylene glycol was observed. A linear relation was found in the concentration range from 5 to 50 mg/L. The method achieves a correlation coefficient of r = 0.996 and a relative standard deviation of 1.37%. The limit of quantitation was calculated to 9.6 mg/L. Since the total reaction volume was restricted to 800 μL, only 2.8 units of AlDH and 8 units of ADH were sufficient to develop the final absorption within 30 min. Received: 16 April 1997 / Revised: 19 June 1997 / Accepted: 25 June 1997     

Spectrophotometric method for the determination of 1,2-propylene glycol

A spectrophotometric method is proposed for the determination of 1,2-propylene glycol. It is based on the ADH/ AlDH catalyzed oxidation of propylene glycol by NAD⁺. The NADH formed is measured at 340 nm. Alcohol dehydrogenase from equine liver was found to be much more effective than that of yeast. No enantiomeric selectivity for s(+) propylene glycol was observed. A linear relation was found in the concentration range from 5 to 50 mg/L. The method achieves a correlation coefficient of r = 0.996 and a relative standard deviation of 1.37%. The limit of quantitation was calculated to 9.6 mg/L. Since the total reaction volume was restricted to 800 μL, only 2.8 units of AlDH and 8 units of ADH were sufficient to develop the final absorption within 30 min.     

Spectrophotometric method for quantitative determination of montelukast in bulk,pharmaceutical formulations and human serum

A simple ultraviolet spectrophotometric method for the estimation of montelukast in methanol has been devised and been compared with the existing pharmacopoeial RP-HPLC method for estimation of the drug. The limit of detection of montelukast at 283 nm was 75.2 ng/mL. The calibration was linear in the range of 3–45 μg/mL. Analytical parameters such as stability, selectivity, accuracy and precision have been established for the method in MONAKA® tablets and in human serum and evaluated statistically to assess the application of the method. The method was validated under the ICH and USP guidelines and found to comprise the advantages for simplicity, stability, sensitivity, reproducibility and accuracy for using as an alternate to the existing non-spectrophotometric methods for the routine analysis of the drug in pharmaceutical formulations and in pharmaceutical investigations involving montelukast.     

Spectrophotometric method for the determination of telmisartan with congo red

In pH 2.50 HCl-NaAc buffer solution, the reaction between telmisartan and congo red could form ionassociation complex, which has the maximum absorbance at 593 nm in the spectrophotometric experiment. Under this wavelength, the Beer’s law was obeyed within the concentration range of 1.08 × 10⁻⁶−2.24 × 10⁻⁵ M. The linear regression equation was A = −0.1913 × 10⁵ c + 0.0286 (C: M). The regression coefficient r was 0.9986. The apparent molar coefficient ɛ₅₉₃ was 1.63 × 10⁴ L mol⁻¹ cm⁻¹ and the detection limit was 5.66 × 10⁻⁷ M. The established method having high sensitivity and good selectivity could be applied to the determination of telmisartan in pharmaceutical, urine and blood plasma samples with satisfactory results. The reaction mechanism was also discussed by using density functional theory methods. The result obtained was consilient with experimental data. The article is published in the original.)     

Spectrophotometric method for phosphine residue determination in coriander

Spectrophotometric method for the determination of phosphine (PH₃) residues in coriander has been developed based on the reaction of phosphine with silver nitrate in 2% aqueous isopropanol. The yellow chromophore formed has an absorption maximum at 430 nm and the linear relation between the absorbances at 430 nm and the concentration of PH₃ is obeyed in the range of 0.02 to 0.17 g. The method is sensitive with a detection limit of 0.008 g and can be applied for determination of 0.02 g/g residue in coriander. Recovery of added PH₃ from a closed system ranges from 96 to 101%.     

分光光度法测定盐酸多巴胺的含量

研究了氨水溶液中,FeCl3与盐酸多巴胺反应生成紫红色络合物,其最大吸收波长为507 nm,络合比为1∶2.体系的吸光度与盐酸多巴胺的浓度在20.0～220 mg/L范围内呈良好的线性关系,线性回归方程A=0.00842+0.11844 ρ(mg/L),相关系数r=0.9991,表观摩尔吸光系数ε=2.25×104L·...     

A rapid gel electrophoretic chip for serum cholesterol determination

We present a rapid gel electrophoretic chip, composed of 2.5% (w/v) acrylamide and 1% (w/v) agarose gel, for serum cholesterol determination using a photo lithography technique. After optimizations, we determined the lipoprotein concentration of standard serum using a conventional enzyme method. The serum was diluted, stained and loaded for 15 min onto the chip. After loading, the intensities of low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) bands separated at the chip were estimated using an image analyzer. The intensities of these bands corresponded to concentrations obtained from a standard enzyme-based method. The detected LDL-C and HDL-C concentrations were linear up to 146 mg dL(-1) and 53 mg dL(-1) respectively. Finally, we carried out the cholesterol analysis using real biological samples obtained from nine volunteers using our electrophoretic chip. The LDL-C and HDL-C levels detected using our chip correlated well with the results obtained using the conventional enzyme-based method r(2) = 0.98 and r(2) = 0.86 for LDL-C and HDL-C, respectively. Although our sample size is small and confined only to health volunteers, we have demonstrated that this proof-of-concept gel electrophoretic chip can determine lipoproteins, simultaneously.     

Spectrophotometric method for the determination of europium with 2,2′-biquinoxalyl

A selective and sensitive method for the determination of europium was developed. Other lanthanides and oxidants do not require separation. The method is based on the redox reaction of Eu(III) with 2,2′-biquinoxalyl. It was checked for the range of 0.5 to 10 μg/Eu/mL. Sm(III) does not interfere in 1000-fold excess.