Fluorescence detection and identification of eight sulphonamides using capillary electrophoresis on released excipients in lake water

A simple and sensitive capillary electrophoresis method with fluorescence detection was developed for the determination of sulphanilamide, sulphamerazine, sulphacetamide and sulphanilic acid, sulphathiazole, Sulphisomidine, sulphadoxine and sulphadiazine in lake water. The sulphonamides were extracted from lake water, derivatized with fluorescamine and determination of sulphonamide was achieved using 20 mM borate buffer of pH 9.5 at an applied voltage of 25 kV. Detection was performed using UG-11 excitation filter of 405 nm and 495 nm emission filters. A fast, simple and sensitive method with limit of detection in the range 0.89–1.43 n mol L⁻¹ for all the eight sulphonamides with good recoveries of 80–110% is seen. Inter-day and intra-day validation of the separation method shows fairly good results. The detection and quantification limits for this newly developed method are too low to determine drug residues in lake water.     

Investigation of the efficiency of the sample pretreatment stage for the determination of the Rare Earth Elements in rock samples by inductively coupled plasma mass spectrometry technique

Different methods of rock sample digestion for final analysis by ICP-MS technique are investigated. It is shown that only basic rocks can be quantitatively digested in a microwave (MW) field with the mixture of HF and HNO₃ acids at 210 °C for 60 min. The addition of HCl and H₃BO₃ provides complete digestion of andesites and some types of granites. Even at maximal temperature in the used MW oven of 210 °C syenites, granodiorites and albitized granites are not digested. These types of rocks are not digested in a closed Teflon autoclave for 16 h and can be digested only by fusion with lithium metaborate. The reason for such behavior is discussed. To avoid problems with the introduction of heavily acidic solutions after fusion in ICP the solutions were diluted. To compensate the loss of sensitivity due to the dilution step the REEs (Rare Earth Elements) pre-concentration using aminocarboxylic Pol-DETATA (diethyltriaminetetraacetate) sorbent was tested. The developed scheme is validated by the analysis of a wide range of reference rock materials.     

Determination of Pt,Pd and Rh in Brassica Napus using solid sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry

Conventional approaches for the analysis of platinum group elements (PGEs) in plant material suffer from sample digestion which results in sample dilution and therefore requires high sample intakes to maintain the sensitivity. The presented solid-sampling method avoids sample digestion while improving sensitivity when compared to digestion-based inductively coupled plasma optical emission spectrometry (ICP-OES) methods and allows the analysis of sample masses of 5 mg or less. Detection limits of 0.38 μg g^− 1, 0.14 μg g^− 1 and 0.13 μg g^− 1 were obtained for Pt, Pd and Rh, respectively using a sample intake of 5 mg. The reproducibility of the procedure ranged between 4.7% (Pd) relative standard deviation (RSD, n = 7) and 7.1% (Rh) RSD for 25 ng analytes. For quantification, aqueous standards were applied on paper filter strips and dried. Only the dried filters were introduced into the electrothermal vaporization unit. This approach successfully removed memory-effects observed during analysis of platinum which occurred only if liquid standards came into contact with the graphite material of the furnace. The presented method for overcoming the Pt-memory-effects may be of further interest for the analysis of other carbide-forming analytes as it does not require any technical modification of the graphite furnace (e.g., metal inlays, pyrolytic coating). Owing to lack of suitable certified reference materials, the proposed method was compared with conventional ICP-OES analysis of digested samples and a good agreement was obtained. As a result of the low sample consumption, it was possible to determine the spatial distribution of PGEs within a single plant. Significant differences in PGE concentrations were observed between the shoots (stem, leaves) and the roots. Pd was mainly found in the roots, whereas Pt and Rh were also found in higher concentrations in the shoots.     

Synthesis of Photoluminophors Using a Continuous Solid-phase Technology

Solid phase method of strontium aluminate synthesis (SrAl₂O₄) is based on calcination of the mixture of strontium carbonate (SrCO₃), aluminum oxide (Al₂O₃), oxides of REM (europium, dysprosium) and a mineralizer - borate glass (H₃BO₃) at a temperature of 1200-1400 °C within 4-6 hours. We have proposed a technique of thermal shock – rapid heating and rapid cooling of the sample by means of which the duration of synthesis is reduced to 30 minutes.     

Comparison of two digestion procedures for the determination of lead in lichens by electrothermal atomic absorption spectrometry

The efficiency of two procedures for the digestion of lichen was investigated using a heating block and a microwave oven. In the open vessels, concentrated nitric acid was added to the samples, left for 1 h, and the addition of 30% (v / v) hydrogen peroxide completed the digestion. In the closed system, the complete digestion was performed using concentrated nitric acid and hydrogen peroxide, reducing the amount of chemicals, time and contamination risk. Both digestion methods gave comparable results, and recoveries were statistically not different. For a lichen sample spiked with 10 μg Pb, the recovery was 111% and 110% using microwave and heating block digestion, respectively, while it was 100% and 103% for a 100 μg Pb spike. For the determination by electrothermal atomic absorption spectrometry samples were diluted 20 times with water and a volume of 20 μL was injected into the graphite furnace without chemical modifier. Pyrolysis and atomization temperatures of 700 °C and 1500 °C, respectively, were used. The characteristic mass was 8.4 ± 0.6 pg for aqueous calibration solutions and 8.9 ± 0.8 pg for samples. Calibration was against matrix matched standards. The recovery test showed some contamination problem with the lowest concentrations in both procedures. The detection limits were 4.4 μg L^− 1 with microwave oven and 5.4 μg L^− 1 with the heating block in the undiluted blank.     

Utilization of bromination reactions for the determination of carbamazepine using bromate–bromide mixture as a green brominating agent

One titrimetric and two spectrophotometric procedures have been developed for the assay of carbamazepine (CBZ) in bulk drug, formulations and spiked human urine. The methods are based on the bromination of CBZ by the bromine generated in situ by the action of the acid on the bromate–bromide mixture. The twin advantages of avoiding liquid bromine and analysis in a cost-effective manner are realized. In titrimetry, the drug was treated with a known excess of bromate–bromide mixture in hydrochloric acid medium followed by the determination of unreacted bromine iodometrically. Spectrophotometry involves the addition of a measured excess of bromate–bromide reagent in acid medium to CBZ, and after the reaction is ensured to be complete, the residual bromine was determined by reacting with a fixed amount of either methyl orange and measuring the absorbance at 510 nm (method A) or indigo carmine and measuring the absorbance at 610 nm (method B). Titrimetric procedure is applicable over the range of 1.00–7.50 mg CBZ, and the calculations are based on a 1:1 reaction stoichiometry (CBZ:KBrO₃). In spectrophotometric methods, Beer’s law is valid within concentration ranges of 0.25–1.50 and 0.50–6.00 μg ml⁻¹ CBZ for methods A and B, respectively. The proposed methods were successfully applied to the determination of CBZ in tablets and syrup, in addition to spiked human urine by the spectrophotometric methods, with mean recoveries of 95.50–104.0% and the results were statistically compared with those of an official method by applying Student’s t-test and F-test.     

Utilization of oxidation reactions for the spectrophotometric determination of captopril using brominating agents

Three simple, accurate and sensitive methods (A–C) for the spectrophotometric assay of captopril (CPL) in bulk drug, in dosage forms and in the presence of its oxidative degradates have been described. The methods are based on the bromination of captopril with a solution of excess brominating mixture in hydrochloric acid medium. After bromination, the excess brominating mixture is followed by the estimation of surplus bromine by three different reaction schemes. In the first method (A), the determination of the residual bromine is based on its ability to bleach the indigo carmine dye and measuring the absorbance at 610 nm. Method B, involves treating the unreacted bromine with a measured excess of iron(II) and the remaining iron(II) is complexed with 1,10-phenanthroline and the increase in absorbance is measured at 510 nm. In method (C), the surplus bromine is treated with excess of iron(II) and the resulting iron(III) is complexed with thiocyanate and the absorbance is measured at 478 nm. In all the methods, the amount of bromine reacted corresponds to the drug content. The different experimental parameters affecting the development and stability of the color are carefully studied and optimized. Beer's law is valid within a concentration range of 0.4–6.0, 0.4–2.8 and 1.2–4.8 μg mL^?1 for methods A, B and C, respectively. The calculated apparent molar absorptivity was found to be 5.16 × 10⁴, 9.95 × 10⁴ and 1.74 × 10⁵ L mol^?1 cm^?1, for methods A, B and C, respectively. Sandell's sensitivity, correlation coefficients, detection and quantification limits are also reported. No interference was observed from common additives found in pharmaceutical preparations. The proposed methods are successfully applied to the determination of CPL in the tablet formulations with mean recoveries of 99.94–100.11% and the results were statistically compared with those of a reference method by applying Student's t- and F-test.     

Comparison of two different isolation methods of benzimidazoles and their metabolites in the bovine liver by solid-phase extraction and liquid chromatography–diode array detection

A new analytical method that uses high performance liquid chromatography–diode array detector (HPLC–DAD) was developed for the analysis of 14 benzimidazoles residues, including metabolites, in bovine liver. Samples were extracted using two different extraction procedures: with phosphate buffer after enzymatic hydrolysis (method A) or using organic solvent, i.e. acetonitrile (method B). Then, samples were purified on a strong cation exchange (SCX) cartridge and analyzed in HPLC/DAD. The recovery percentages, obtained spiking the matrix (liver) at concentrations of 500 and 100 μg kg^?1 with a standard mixture of benzimidazoles, were in the range 6–101% and 80–102% for methods A and B, respectively. The repeatability of the methods was assessed in all cases by the % of correlation value (CV) that was lower than 19%. The limits of quantification (LOQs) in the matrix for methods A and B were in the range 40–60 and 20–50 μg kg^?1, respectively. The best of the two methods, method B, was used for the analysis of 10 bovine liver samples.     

A novel approach for determining total titanium from titanium dioxide nanoparticles suspended in water and biosolids by digestion with ammonium persulfate

Titanium dioxide (i.e. TiO₂) in nano-form is a constituent of many nanomaterials that are used in sunscreens, cosmetics, industrial products and in biomedical applications. Quantification of TiO₂ nanoparticles in various matrixes is a topic of great interest for researchers studying the potential health and environmental impacts of nanoparticles. However, analysis of TiO₂ as Ti⁴⁺ is difficult because current digestion techniques require use of strong acids that may be a health and safety risk in the laboratory. To overcome this problem, we developed a new method to digest TiO₂ nanoparticles using ammonium persulfate as a fusing reagent. The digestion technique requires short times to completion and optimally requires only 1 g of fusing reagent. The fusion method showed >95% recovery of Ti⁴⁺ from 6 μg mL^?1 aqueous suspensions prepared from 10 μg mL^?1 suspension of different forms of TiO_2, including anatase, rutile and mixed nanosized crystals, and amorphous particles. These recoveries were greater than open hot-plate digestion with a tri-acid solution and comparable to microwave digestion with a tri-acid solution. Cations and anions commonly found in natural waters showed no significant interferences when added to samples in amounts of 10 ng to 110 mg, which is a much broader range of these ions than expected in environmental samples. Using ICP-MS for analysis, the method detection limit (MDL) was determined to be 0.06 ng mL^?1, and the limit of quantification (LOQ) was 0.20 ng mL^?1. Analysis of samples of untreated and treated wastewater and biosolids collected from wastewater treatment plants yielded concentrations of TiO₂ of 1.8 and 1.6 ng mL^?1 for the wastewater samples, respectively, and 317.4 ng mg^?1 dry weights for the biosolids. The reactions between persulfate ions and TiO₂ were evaluated using stoichiometric methods and FTIR and XRD analysis. A formula for the fusing reaction is proposed that involves the formation of sulfate radicals.     

Development of extraction methods for the analysis of perfluorinated compounds in human hair and nail by high performance liquid chromatography tandem mass spectrometry

Perfluorinated compounds (PFCs) are ubiquitous in the environment and are becoming a public health concern. It is desirable to develop sensitive and accurate methods to measure PFCs in non-invasive matrices such as hair and nail for biomonitoring of body burden. Different extraction methods coupled with solid phase extraction were investigated for extraction efficiency. The extracts were separated, identified and quantified by liquid chromatography-tandem mass spectrometry. Extraction with acetonitrile proved to be the most efficient extraction method for human hair sample, while extraction by methanol with alkaline digestion performed best for human nail sample. The matrix recoveries of the optimized methods ranged from 78% to 116% for hair and from 87% to 126% for nail sample. The ranges of the limit of detection (LOD) were 0.026–0.069 ng/g and 0.023–0.094 ng/g for hair and nail, respectively. These methods were validated by evaluating LOD, accuracy and precision and were proven to be useful for measuring paired human hair and nail samples collected from the general population.     

Strontium(II) selective PVC membrane electrode based acetophenone semicarbazone (ACS) as an ionophore

A new PVC membrane based strontium(II) ion-selective electrode has been constructed using acetophenone semicarbazone as a neutral carrier. The sensor exhibits a Nerstian response for strontium(II) ion over a wide concentration range 1.0 × 10⁻²–1.0 × 10⁻⁷ M with the slope of 29.4 mV/per decade. The limit of detection was 2.7 × 10⁻⁸ M. It was relatively fast response time (<10 s for concentration ⩾1.0 × 10⁻³ and <15 s for concentration of ⩾1.0 × 10⁻⁶ M) and can be used for 8 months without any considerable divergence in potentials. The proposed sensor revealed relatively good selectivity and high sensitivity for strontium(II) over a mono, di, trivalent cation and can be used in a pH range of 2.5–10.5. It was also successfully used as an indicator electrode in potentiometer titration and in the analysis of concentration in various real samples.     

In vitro digestibility of soybean β-conglycinin hydrolysates

The in vitro digestibility of alcalase enzymatic hydrolysates ofβ-conglycinin was studied.The results showed that the zeta potentials ofβ-conglycinin hydrolysates decreased and their electronegativity increased when digested with pepsin and trypsin.Furthermore,the content of peptides with molecular weight from 10 kDa to 20 kDa remained stable,while those with higher molecular weight(>20 kDa) decreased,and those with lower molecular weight(<10 kDa) increased.The proportion of highly hydrophobic peptides decreased in the process of the in vitro digestion,but no significant change in the surface hydropliobicity indices of digestion products was observed(P<0.05).These results indicate that theβ-congiycinin hydrolysates were degraded through in vitro digestion,but the degree of degradation was relatively low.Peptides with molecular weight from 10 kDa to 20 kDa in theβ-conglycinin hydrolysates resisted the digestion by pepsin and trypsin and they remained stable during the in vitro digestion processes.     

Influence of sample temperature on the expansion dynamics and the optical emission of laser-induced plasma

We investigate the influence of sample temperature on the dynamics and optical emission of laser induced plasma for various solid materials. Bulk aluminum alloy, silicon wafer, and metallurgical slag samples are heated to temperature T_S ≤ 500 °C and ablated in air by Nd:YAG laser pulses (wavelength 1064 nm, pulse duration approx. 7 ns). The plasma dynamics is investigated by fast time-resolved photography. For laser-induced breakdown spectroscopy (LIBS) the optical emission of plasma is measured by Echelle spectrometers in combination with intensified CCD cameras. For all sample materials the temporal evolution of plume size and broadband plasma emission vary systematically with T_S. The size and brightness of expanding plumes increase at higher T_S while the mean intensity remains independent of temperature. The intensity of emission lines increases with temperature for all samples. Plasma temperature and electron number density do not vary with T_S. We apply the calibration-free LIBS method to determine the concentration of major oxides in slag and find good agreement to reference data up to T_S = 450 °C. The LIBS analysis of multi-component materials at high temperature is of interest for technical applications, e.g. in industrial production processes.     

Development and validation of a stability-indicating LC method for simultaneous determination of related compounds of guaifenesin,terbutaline sulfate and ambroxol HCl in cough syrup formulation

A new liquid chromatographic method has been developed and validated for the determination of terbutaline sulfate (TLS), guaifenesin (GFN) and ambroxol HCl (AML), for its potential impurities in drug substances and drug products. Efficient chromatographic separation was achieved on X-Terra RP-18 column with a simple mobile phase combination containing a gradient mixture of solvents A and B at a flow rate of 1.0 mL min⁻¹ and quantitation was carried out using ultraviolet detection at 222 nm with column temperature of 35 °C. The resolution between TLS, GFN and AML, its associated impurities was found to be greater than 1.5. Regression analysis shows an r value (correlation coefficient) greater than 0.998. This method was capable to detect all the process impurities of TLS, GFN and AML, at a level below 0.015% with respect to a test concentration of 0.125, 5.0 and 1.5 mg mL⁻¹, respectively. The % RSD for the inter-day and intra-day precisions for all the impurities of TLS, GFN and AML were found to be less than 3.0. The method has shown good, consistent recoveries. The drugs were subjected to stress conditions of acid, base, water hydrolysis, oxidation, photolysis and thermal degradation, as prescribed by international conference on harmonization (ICH).     

Determination of silicon in plant materials by laser-induced breakdown spectroscopy

In spite of the importance of Si for improving the productivity of many important crops, such as those from the Poaceae family (e.g. sugar cane, maize, wheat, rice), its quantitative determination in plants is seldom carried out and restricted to few laboratories in the world. There is a survey of methods in the literature, but most of them are either laborious or difficult to validate in view of the low availability of reference materials with a certified Si mass fraction. The aim of this study is to propose a method for the direct determination of Si in pellets of plant materials by laser-induced breakdown spectroscopy (LIBS). The experimental setup was designed by using a Q-switched Nd:YAG laser at 1064 nm (5 ns, 10 Hz) and the emission signals were collected by lenses into an optical fiber coupled to an Echelle spectrometer equipped with an intensified charge-coupled device. Experiments were carried out with leaves from 24 sugar cane varieties, with mass fractions varying from ca. 2 to 10 g kg^− 1 Si. Pellets prepared from cryogenically ground leaves were used as test samples for both method development and validation of the calibration model. Best results were obtained when the test samples were interrogated with laser fluence of 50 J cm^− 2 (750 μm spot size) and measurements carried out at Si I 212.412 nm emission line. The results obtained by LIBS were compared with those from inductively coupled plasma optical emission spectrometry after oven-induced alkaline digestion, and no significant differences were observed after applying the Student's t-test at 95% confidence level. The trueness of the proposed LIBS method was also confirmed from the analysis of CRM GBW 07603 (Bush branches and leaves).     

Determination of major and trace elements in six herbal drugs for relieving heat and toxicity by ICP-AES with microwave digestion

ObjectiveTo establish a method to simultaneously determine major and trace element contents of Na, K, Cu, Fe, Zn, Mn, Ca, Mg, Cr, Ni, Pb, Se, As and Cd in six herbal drugs.MethodsMicrowave digestion procedure was applied under optimized conditions for digesting medicinal herbs. Concentrations of elements were determined by ICP-AES.ResultsThe results indicated that the herbal drugs were abundant in major and trace element contents which are healthy for human body. After optimizing the microwave digestion technology, the recovery of the element was 96.79–103.47% and the RSD < 5.0%.ConclusionICP-AES combined with the microwave digestion technology has a lot of merits in terms of saving time and effort, reducing environmental pollution, fast and accurate determination of results in determining major and trace elements.     

Solvent-free asymmetric direct aldol reactions organocatalysed by recoverable (Sa)-binam-l-prolinamide

The combination of (S_a)-binam-l-Pro (5 mol %) and benzoic acid (10 mol %) was used as catalysts in the direct aldol reaction between different aliphatic ketones and 4-nitrobenzaldehyde under solvent-free reaction conditions. Three different procedures are assayed: magnetic stirring (method A), magnetic stirring after previous dissolution in THF and evaporation (method B), and ball mill technique (method C), methods A and B being the simplest. These reaction conditions allowed us to reduce the amount of required ketone to 2 equiv to give the aldol product in similar reaction times and regio-, diastero-, and enantioselectivities than in organic or aqueous solvents.     

Assessment of soil quality of arable soils in Hungary using DRIFT spectroscopy and chemometrics

Nowadays, there is a great demand for precise, sensitive and adequate indicators for evaluating the quality of soils. In spite of recent developments in this field, a fast, non-destructive method for soil quality assessment has not yet been evaluated. The objective of this study was to investigate the possibility of using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy to estimate soil quality in the form of soil quality index (SQI). A set of soil samples (n = 89) was scanned and regression was carried out using a combination of DRIFT spectroscopy and partial least-squares (PLS). The reliability of the DRIFT-PLS calibration model (n = 53) was acceptable (coefficient of determination, R² = 0.49; residual prediction deviation, RPD = 1.4) for the estimating of the SQI values. The validation of the calibration model using a validation set (n = 36) of unknown samples also resulted in good acceptability with R² = 0.68 and RPD = 1.85. The DRIFT-PLS based model could provide a rapid, cheap estimate of SQI values and subsequently of soil quality by taking into account the integrated effects of the mineralogical and organic components of the soil. This approach could be useful to monitor soil quality under conditions where the analysis of a large number of soil samples is required.     

Determination of Pb in river water samples by inductively coupled plasma optical emission spectrometry after ultrasound-assisted co-precipitation with manganese dioxide

A simple and efficient procedure for separation and pre-concentration using ultrasound-assisted co-precipitation with manganese dioxide was developed for Pb determination by inductively coupled plasma optical emission spectrometry (ICP OES). The optimization process was carried out using a two-level factorial design and a Doehlert matrix. Three variables (i.e. concentration of oxidizing solution—KMnO₄, concentration of MnSO₄ solution and time of ultrasonic irradiation) were used as factors in the optimization. The recoveries, based on the analysis of spiked samples, were between 90% and 105%, and the precision was ≤ 5%. The detection limit and quantification limit for Pb determination were 3.2 and 10.7 μg L^− 1, respectively. The proposed method was applied for the determination of Pb in water samples from a river heavily polluted by industrial effluents. The recovery measured by analyte addition technique showed that the proposed pre-concentration method had good accuracy.     

Near-infrared diffuse reflectance spectroscopy with sample spots and chemometrics for fast determination of bovine serum albumin in micro-volume samples

Near-infrared diffuse reflectance spectroscopy(NIRDRS) has attracted more and more attention in analyzing the components in samples with complex matrices.However,to apply this technique to micro-analysis,there are still some obstacles to overcome such as the low sensitivity and spectral overlapping associated with this approach.A method for fast determination of bovine serum albumin (BSA) in micro-volume samples was studied using NIRDRS with sample spots and chemometric techniques.10μL of sample spotted on a filter paper substrate was used for the spectral measurements. Quantitative analysis was obtained by partial least squares(PLS) regression with signal processing and variable selection.The results show that the correlation coefficient(R) between the predicted and the reference concentration is 0.9897 and the recoveries are in the range of 87.4%-114.4%for the validation samples in the concentration range of 0.61-8.10 mg/mL.These results suggest that the method has the potential to quickly measure proteins in micro-volume solutions.