Linearity Of Calibration Plots Research Articles

Development of a 4‐Nitrophenylhydrazine Sensor Based on MgTi2O4⋅TiO2⋅Zn2TiO4 Nanomaterials

AbstractThe synthesized MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterial was characterized by XRD (X‐Ray diffraction), SEM (Scanning electron microscopy), EDS (Energy dispersive x‐ray spectroscopy), FTIR (Fourier transform infrared spectroscopy) and PL (Photoluminescence) study. Particles size of MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterial was found to be 37.3 nm. PL and PLE (Photoluminescence excitation) spectra are showed several peaks including one red PL at 723 nm, when excited at 320 nm. Nanomaterial was subject to electrochemical sensor study. Thin layer of synthesized MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterials was fabricated onto the glassy carbon electrode (GCE) with conducting binder to result the working electrode of 4‐nitrophenylhydrazine (4‐NPHyd) sensor, which was applied successively to selectively detect the 4‐NPHyd in aqueous phase. The 4‐NPHyd chemical sensor exhibited high sensitivity with lower detection limit, long‐term stability in chemical environment and improved electrochemical responses during sensing performance. The linearity of calibration plot is obtained over the large linear dynamic range (LDR) from 0.1 nM to 0.1 mM of 4‐NPHyd. The sensitivity calculated from the slop of calibration plot (ratio of current to concentration of 4‐NPHyd) is 42.7215 μAmM−1cm−2 with detection limit (DL) of 0.02±0.001 nM at signal to noise ratio of 3(S/N). Therefore, the chemical sensor based on MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterials may be a promising highly sensitive sensor in electrochemical method for the effective detection of hazardous and carcinogenic chemicals in medical as well as biological sectors.

Development of l-glutamic acid biosensor with ternary ZnO/NiO/Al2O3 nanoparticles

Here, on-pot low-dimensional ZnO/NiO/Al2O3 nanoparticles (NPs) were synthesized by simple wet-chemical (co-precipitation) method and followed by the calcination at 500 °C into Muffle furnace. The details characterization of prepared NPs were executed using powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), Energy-dispersive X-ray spectroscopy (EDS), and UV–vis Spectroscopy (UV–vis). Using 5% Nafion adhesive, a layer of thin film of prepared ZnO/NiO/Al2O3 NPs was deposited onto glassy carbon electrode (GCE; surface area = 0.0316 cm2) to result the proposed enzyme-less l-glutamic acid (L-GA) sensor. From the details investigation of enzyme-less L-GA sensor applying electrochemical approach, a calibration curve was plotted from linear relation of current versus concentration of L-GA and the linearity of calibration plot was found in dynamic range (LDR) of 0.1 nM–0.01 mM. The slope of LDR (obtained from linear equation y = 0.915x+35.622) was used to calculate the sensitivity (S = m/A; 28.9557 μAμM−1cm−2), limit of detection (3SD/m; 95.35 ± 4.77 pM), and limit of quantification (10SD/m; 317.83 ± 15.89 pM) of L-GA sensor. The L-GA sensor was exhibited long-term stability in phosphate buffer phase, precious reproducibility, sensitivity, and short response time without any interference effects in presence of common electrolyte in biological samples. These features indicate that this research approach might be future prospective and promising sensor to detect L-GA in biomedical diagnosis.

Calibration graphs for Ti, Ta and Nb in sintered tungsten carbide by infrared laser ablation inductively coupled plasma atomic emission spectrometry.

Infrared laser ablation (IR-LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from +/- 3% to +/- 4% for Ti, Ta, and Nb with internal standardization by tungsten and up to +/- 5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.

Calibration graphs for steels by IR laser ablation inductively coupled plasma atomic emission spectrometry.

Infrared laser ablation (IRLA) was studied as a sample-introduction technique for the analysis of steels by inductively coupled plasma atomic emission spectrometry (ICP-AES). A comparison of two IRLA-ICP-AES systems based on Q-switched nanosecond Nd: YAG lasers was performed. The beam of the LINA-Spark atomizer (LSA Sarl, Cully, Switzerland) based on the Surelite 1-20 laser (Continuum, USA) was moved along a circle. A Perkin-Elmer Optima 3000 DV ICP system was used both with lateral and axial viewing modes. A laboratory-made ablation system based on the Brilliant laser (Quantel) was coupled to a Jobin-Yvon 170 Ultrace ICP (lateral viewing, polychromator part employed). A sample was rotated along a circle during ablation. Linearity of calibration plots was verified at least up to 19% Cr and 12% Ni without internal standardization for both LA-ICP-AES systems. Other elements examined were Mo up to 3%, Mn up 1.5%, Si up to 1.7%, and Cu up to 0.15%. The reproducibility was in the range 5-1 %RSD for a mass percentage 0.5-20% of steel constituents. The relative uncertainty of the centroids of the calibration lines was in the range from +/- 4% to +/- 12% for Cr, Ni, Mn, Mo, and Si, and from +/- 8% to +/- 19% for Cu. The lowest determinable quantities were calculated for calibration dependencies. Performances of both the IR-LA-ICP-AES were comparable.

On-line coupling of solid-phase extraction and gas chromatography with atomic emission detection for analysis of trace pollutants in aqueous samples

An on-line, solid-phase extraction gas chromatography atomic-emission detection (SPE-GC-AED) system has been set up using an on-column interface to transfer 100 μl of desorbing solvent to the GC part of the system. Analytical characteristics such as recovery, precision and linearity of calibration plots were comparable with those of the off-line combination of SPE-GC-AED using organophosphorus pesticides as test compounds. The fully on-line set-up causes a marked improvement in detection because of the quantitative transfer of the analytes from the SPE module to the GC: detection limits are as low as 5–20 ng l−1 for the analysis of 10 ml raw and spiked surface water samples using the phosphorus channel. Detection levels can be further enhanced by processing up to 100 ml samples. The integrated analytical system is robust. The potential of the on-line set up has been demonstrated for the analysis of surface water and waste water.

Chiral polymeric reagents for off-line and on-line derivatizations of enantiomers in high-performance liquid chromatography with ultraviolet and fluorescence detection: an enantiomer recognition approach.

Optically active and detector-sensitive polymeric reagents have been synthesized, loadings determined, derivatizations/separations/detection optimized, and applications to simple amines and amino alcohols described. Such reagents have been designed to contain different chiral centers, usually amino acids, leashed via an activated ester attachment to an insoluble, structurally rigid, organic polymer backbone. 9-Fluorenylmethyl (FMOC) moieties chemically bonded to the amino acids were used as ultraviolet (UV) and fluorescence (FL) sensitive detector probes to the final diastereomers of enantiomer substrates. Such diastereomers can be readily separated by isocratic or gradient elution normal-phase methods. The kinetics for diastereomer formation have been determined, and final UV/FL responses for known mixtures of enantiomers have been compared to demonstrate overall validity of the method. Minimum detection limits, linearity of calibration plots, dual detector responses, and linear diode array spectra and absorbance ratios have also been demonstrated. In some cases, authentic standards have been prepared to calculate absolute percent derivatizations for specific enantiomer pairs. The overall approach permits, for the very first time, off-line or on-line precolumn derivatization for the formation of diastereomers having unique detector properties. It has been proven that the rates and rate constants for such formations are identical for at least those pairs of enantiomers studied. Separations are base-line or near-base-line, permitting accurate and precise quantitative determinations, by both UV and FL, of enantiomer/optical purity and chemical purity.

Analysis for penicillins and cefoperazone by HPLC—photolysis—electrochemical detection (HPLC—hv—EC)

Continuous, post-column, on-line, real-time photolytic derivatization or degradation can now be used following HPLC separation of various penicillin derivatives prior to conventional thin-layer, amperometric electrochemical detection using oxidative working potentials. Beta-lactam derivatives are separated by conventional reversed-phase HPLC, and each separated penicillin is then photolytically degraded to form, it is presumed, stable anionic species, which are then conveyed to the on-line electrochemical detector for qualitative and quantitative determinations. These methods of trace drug analysis have been applied to four separate penicillins or prodrugs, as well as one typical cephalosporin, viz. cefoperazone. Analytical parameters of the analysis have been determined, including dual electrode response ratios, sensitivity, minimum detection limits, linearity of calibration plots and the range of linear calibration. Finally, the analysis of cefoperazone-spiked saline solutions for i.v. administration has been performed in a single-blind study, as well as the determination of bacampicillin HCl in formulations obtained from a drug manufacturer in the United States. The overall method of analysis for these drugs has been demonstrated as being reproducible, accurate, and precise for at least five beta-lactam analogs. It is suggested that other beta-lactams will be amenable to these newer methods of analysis in a wide variety of sample matrices, including solid or liquid formulations, aqueous infusion solutions, and biological media, such as blood and urine.

Rapid estimation of the molecular weights of protein polypeptide chains using high-pressure liquid chromatography in 6 m guanidine hydrochloride

An attempt was made to perform high-speed gel filtration in 6 m guanidine hydrochloride. A column of silica-based aqueous gels, G 3000 SW or G 4000 SW, in conjunction with a high-pressure liquid chromatograph, gave satisfactory results under conditions where a single run was completed within 50 min. Further increase in speed was possible at some sacrifice of resolution. The reproducibility, resolving power, and sensitivity achieved, together with the linearity of calibration plots, have revealed that this method is exceedingly useful for the rapid estimation of the molecular weights of protein polypeptide chains.