Vol 73, No 7 (2018)

New calibration equations are proposed based on the use of intensity ratios of spectral lines and peaks of coherently and incoherently scattered characteristic radiation of an X-ray tube. Prospects for their application to the X-ray fluorescence analysis of samples containing undetectable light elements are shown. The proposed method ensures high precision of determination and performance of analysis in the lack of adequate reference samples. The method was tested on an example of analysis of standard samples of bronze and samples of iron oxide materials.

A method for simultaneous multi-element analysis of fly ash samples by inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (oaTOF-ICP-MS) after closed-vessel microwave extraction with ammonium fluoride was introduced here. Corrosive and/or toxic acids like HF, HCl or HClO₄, as well as HNO₃, which are commonly used during sample preparation of the fly ash samples, are avoided in this method. The spectral effects due to the formation of different Cl, Na, K, Ca, Mg-containing polyatomic species interfering with the determination of a number of elements like As, Se or Ni during the oaTOF-ICP-MS analysis are negligible. Under the optimum experimental extraction conditions evaluated using a fractional factorial design (10 mg of the sample extracted with 5 mL of 140 g/L NH₄F for 10 min at 200°C), analysis of the resulting supernatant with Rh as an internal standard enabled precise and accurate simultaneous determination of 11 elements (Li, Be, Ni, As, Se, Rb, Sb, Cs, W, Tl and U) at trace and ultratrace levels. The accuracy was assessed by analysing two certified reference materials, namely Fine Fly Ash CTA-FFA-1 and Constituent Elements in Coal Fly Ash Standard Reference Material® 1633b. The precision of the reported method was better than 10%.

A possibility of using a digital camera and the subsequent computer processing of chromaticity characteristics of a photo image for the determination of the turbidity of liquids is studied on examples of measurements of the transparency of technical sulfuric acid and the determination of the kaolin turbidity of water. Measurements were performed on a modified Jackson turbidimeter. It was shown that, in the RGB space, the contrast of a photo image of an alignment template is a chromaticity characteristic suitable for measuring turbidity. The interference of the yellow color of suspensions in measurements of turbidity was eliminated in the green channel. A correlation equation was found for the contrast (degree of turbidity) and concentration of the suspension. The equation does not differ from that of the law of light absorption. Performance characteristics of the determination of the kaolin turbidity of water were estimated in comparison with those of conventional turbidimetry. It was shown that, despite the primitiveness of the instrumentation for the proposed method of photographic turbidimetry, its characteristics are not inferior to those of classical turbidimetry.

The aim of this work is to develop cheap, safe, rapid, reliable and reproducible spectrophotometric method for the assay of some antiulcerative drugs namely Omedar, Nadine and Rantag in their pharmaceutical dosages, using methyl red (MR) as a chromogenic reagent. The proposed method is based on the reaction of each of the three drugs with MR at pH 3.0. The optimum analytical variables have been investigated carefully. The maximum absorbance was obtained at 405 nm with absorptivity of 1.35 × 10⁴ L/mol cm. Beer’s law is obeyed in the range of concentration of 0.5–15 μg/mL for ranitidine (active ingredient) content in the studied drugs. The limits of detection and quantification of the drug active ingredient were 0.05 and 0.13 μg/mL, respectively, with a linear regression correlation coefficient of 0.998, and recovery was in the range 99.91–100.48%. Effects of pH, temperature, standing time and MR concentration on the determination of ranitidine hydrochloride of the drugs have been examined. This method is simple and can be used for the determination of ranitidine in the pharmaceutical dosages of antiulcerative drugs.

This work describes the electroanalytical determination of Chlorpyriphos pesticide in natural waters using hanging mercury drop electrode allied to square wave adsorptive cathodic stripping voltammetry. The best responses were obtained in Britton‒Robinson buffer solutions at pH 2.0, using a frequency of 100 s^–1, a scan increment of 5 mV, a square wave amplitude of 25 mV and an accumulation potential of–0.4 V during 60 s. Therefore, voltammetric responses showed the presence of one well-defined and irreversible reduction peak, at–1.08 V vs. Ag/AgCl/KCl 1.0 M, which involves two electrons in the reduction of carbon‒nitrogen bond in the N-heterocyclic system with the participation of protonation equilibrium preceding the electron transfer reaction. Analytical curves were constructed and compared to similar curves performed by gas chromatograph coupled to a selective nitrogen‒phosphorus detector, which demonstrates that the proposed methodology is suitable for determining contamination by Chlorpyriphos in complex samples.

The effect of measurement conditions and the nature of the plasticizer of an ion-selective electrode membrane (ortho-nitrophenyloctyl ether, dinonyl adipate, dibutyl phthalate) on the main performance characteristics of clotrimazole-selective electrodes with polyvinyl chloride ion-exchange membranes containing potassium tetrakis(4-chlorophenyl)borate as an ion exchanger was studied. The introduction of small (up to 20%) ethanol additives into the aqueous solution leads to a significant improvement of the potential stability and expands the working range of the electrodes. All of the studied electrodes have high selectivity to clotrimazole with respect to both inorganic and organic cations, slope of the electrode function close to the theoretical value, and low limits of detection (5.0 × 10^–8–7.5 × 10^–8 M). An electrode with a membrane plasticized with ortho-nitrophenyloctyl ether was the best for the combination of characteristics. It was demonstrated that clotrimazole can be determined in model solutions and various dosage forms (spray, cream, suppositories, tablets) using direct potentiometry and potentiometric titration with sodium tetraphenylborate. The proposed procedures are rapid (10–15 min) and characterized by excellent reproducibility (the relative standard deviation does not exceed 1.2%).

The problems of the application of total indices “phenolic index” and “petroleum products” for water quality assessment are considered. It is demonstrated that these indices do not reflect the actual contamination of aquatic media by phenols and petroleum hydrocarbons. The effect of hydrocarbons of different classes on the error in determining petroleum products was revealed. The presence of phenols and other organic compounds was found to affect the results of the determination of the phenolic index. It is necessary to identify pollutants contained in wastewater to assess the applicability of total indices in the analysis of such waters. Marker components of wastewater must be included in the research program, in addition to total indices.