scholarly journals Surface-Enhanced Oxidation and Determination of Isothipendyl Hydrochloride at an Electrochemical Sensing Film Constructed by Multiwalled Carbon Nanotubes

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
S. N. Prashanth ◽  
Shankara S. Kalanur ◽  
Nagappa L. Teradal ◽  
J. Seetharamappa
Keyword(s):  
Limit Of Detection ◽  
Biological Fluids ◽  
Differential Pulse ◽  
Electrochemical Sensing ◽  
Good Precision ◽  
Multiwalled Carbon ◽  
Limit Of Quantification ◽  
Surface Enhanced ◽  
Ph Range

The electrochemical behavior of isothipendyl hydrochloride (IPH) was investigated at bare and multiwalled-carbon-nanotube modified glassy carbon electrode (MWCNT-GCE). IPH (55 μM) showed two oxidation peaks in Britton-Robinson (BR) buffer of pH 7.0. The oxidation process of IPH was observed to be irreversible over the pH range of 2.5–9.0. The influence of pH, scan rate, and concentration of the drug on anodic peak was studied. A differential pulse voltammetric method with good precision and accuracy was developed for the determination of IPH in pure and biological fluids. The peak current was found to be linearly dependent on the concentration of IPH in the range of 1.25–55 μM. The values of limit of detection and limit of quantification were noticed to be 0.284 and 0.949 μM, respectively.

scholarly journals Curcumin and Quercetin-Loaded Nanoemulsions: Physicochemical Compatibility Study and Validation of a Simultaneous Quantification Method

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1650
Author(s):  
Gustavo Richter Vaz ◽  
Adryana Clementino ◽  
Juliana Bidone ◽  
Marcos Antonio Villetti ◽  
Mariana Falkembach ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Biological Fluids ◽  
Thermal Analyses ◽  
Entrapment Efficiency ◽  
Compatibility Study ◽  
Scanning Calorimetry ◽  
Limit Of Quantification ◽  
X Ray ◽  
Simultaneous Quantification

Biphasic oil/water nanoemulsions have been proposed as delivery systems for the intranasal administration of curcumin (CUR) and quercetin (QU), due to their high drug entrapment efficiency, the possibility of simultaneous drug administration and protection of the encapsulated compounds from degradation. To better understand the physicochemical and biological performance of the selected formulation simultaneously co-encapsulating CUR and QU, a stability test of the compound mixture was firstly carried out using X-ray powder diffraction and thermal analyses, such as differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The determination and quantification of the encapsulated active compounds were then carried out being an essential parameter for the development of innovative nanomedicines. Thus, a new HPLC–UV/Vis method for the simultaneous determination of CUR and QU in the nanoemulsions was developed and validated. The X-ray diffraction analyses demonstrated that no interaction between the mixture of active ingredients, if any, is strong enough to take place in the solid state. Moreover, the thermal analysis demonstrated that the CUR and QU are stable in the nanoemulsion production temperature range. The proposed analytical method for the simultaneous quantification of the two actives was selective and linear for both compounds in the range of 0.5–12.5 µg/mL (R2 > 0.9997), precise (RSD below 3%), robust and accurate (recovery 100 ± 5 %). The method was validated in accordance with ICH Q2 R1 “Validation of Analytical Procedures” and CDER-FDA “Validation of chromatographic methods” guideline. Furthermore, the low limit of detection (LOD 0.005 µg/mL for CUR and 0.14 µg/mL for QU) and the low limit of quantification (LOQ 0.017 µg/mL for CUR and 0.48 µg/mL for QU) of the method were suitable for the application to drug release and permeation studies planned for the development of the nanoemulsions. The method was then applied for the determination of nanoemulsions CUR and QU encapsulation efficiencies (> 99%), as well as for the stability studies of the two compounds in simulated biological fluids over time. The proposed method represents, to our knowledge, the only method for the simultaneous quantification of CUR and QU in nanoemulsions.

Chlorobenzene. Determination in workplace air

2019 ◽  
Vol 35 (1(99)) ◽  
pp. 19-28
Author(s):  
Anna Jeżewska ◽  
Agnieszka Woźnica
Keyword(s):  
Occupational Exposure ◽  
Carbon Disulfide ◽  
Limit Of Detection ◽  
Skin Irritation ◽  
Raw Material ◽  
Good Precision ◽  
Limit Of Quantification ◽  
Selective Determination ◽  
Workplace Air

Chlorobenzene is a colorless, flammable liquid that has an almond-like odor. It is used in industry as a solvent: resins, paints and fats, raw material for the production of plastics, as well as for the production of phenol, aniline and nitrobenzene. Occupational exposure to chlorobenzene vapors can occur through inhalation, absorption through the skin or ingestion. Harmful if inhaled, causes skin irritation. Long-term exposure affects the central nervous system. The aim of this study was an amendment to the PN-Z-04022- 03:2001 withdrawn from the Polish set of standards, and validate method for determination concentrations of chlorobenzene in the workplace air in the range from 1/10 to 2 MAC values, in accordance with the requirements of the standard PN-EN 482. The study was performed using a gas chromatograph (GC) with a flame ionization detector (FID) equipped with a capillary column HP-5 (30 m x 0.32 mm, 0.25 μm). This method is based on the adsorption of chlorobenzene vapors on activated charcoal, desorption with carbon disulfide, and analyzed by GC-FID. Application of HP-5 column allows selective determination of chlorobenzene in a presence of carbon disulfide, aniline, phenol and nitrobenzene. The measurement range was 2.3 ÷ 46 mg/m3 for a 15 l air sample. Limit of detection: 6.75 ng/ml and limit of quantification: 20.25 ng/ml. Analytical method described in this paper enables selective determination of chlorobenzene in workplace atmosphere in presence of other solvents at concentrations from 2.3 mg/m3 (1/10 MAC value). The method is characterized by good precision and accuracy and meets the criteria for the performance of procedures for the measurement of chemical agents, listed in EN 482. The method may be used for the assessment of occupational exposure to chlorobenzene and the associated risk to workers’ health. The developed method of determining chlorobenzene has been recorded as an analytical procedure (see Appendix). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

scholarly journals Micellar Enhanced Spectrofluorimetric Method for the Determination of Ponatinib in Human Plasma and Urine via Cremophor RH 40 as Sensing Agent

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Hany W. Darwish ◽  
Ahmed H. Bakheit ◽  
Ali Saber Abdelhameed ◽  
Amer S. AlKhairallah
Keyword(s):  
Human Plasma ◽  
Fluorescence Intensity ◽  
Limit Of Detection ◽  
Biological Fluids ◽  
Great Success ◽  
Limit Of Quantification ◽  
Human Plasma And Urine ◽  
Spectrofluorimetric Method ◽  
Fluorescence Characteristics

An impressively simple and precise spectrofluorimetric procedure was established and validated for ponatinib (PTB) quantitation in biological fluids such as human plasma and human urine. This method depends on examining the fluorescence characteristics of PTB in a micellar system of Cremophor RH 40 (Cr RH 40). Cr RH 40 enhanced the intrinsic fluorescence of PTB distinctly in aqueous water. The fluorescence spectra of PTB was recorded at 457 nm following its excitation at 305 nm. Maximum fluorescence intensity was attained by addition of 0.7 mL of Cr RH 40 and one mL of phosphate buffer to PTB aliquots and then dilution with distilled water. There is a linear relationship between the fluorescence intensity of PTB and its concentration over the range 5–120 ngmL−1, with limit of detection and limit of quantification equal to 0.905 ngmL−1and 2.742 ngmL−1, respectively. The accuracy and the precisions of the proposed method were checked and gave adequate results. The adopted method was applied with a great success for PTB quantitation in different biological matrices (spiked human plasma and urine) giving high recovery values.

Development of Multiwalled Carbon Nanotube Based Electrochemical Sensor for Reactive Azo Dyes

2013 ◽  
Vol 678 ◽  
pp. 321-325
Author(s):  
Munirathinam Valarmathi ◽  
Anandhan Gomathi ◽  
Paramasivam Manisankar
Keyword(s):  
Carbon Nanotube ◽  
Azo Dyes ◽  
Surface Characterization ◽  
Limit Of Detection ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Multiwalled Carbon Nanotube ◽  
Multiwalled Carbon ◽  
Reactive Azo Dyes

Two reactive azo dyes Reactive yellow 84 (RY84) and Reactive Red 120 (RR120) were investigated voltammetrically using plain glassy carbon electrode (GCE) and multiwalled carbon nanotube modified GCE (MWCNT/GCE). Influence of pH, scan rate and concentration on voltammograms were studied. The irreversible oxidation process observed for both dyes was adsorption controlled. The surface characterization of the modified electrode in the absence and presence of dyes was done using scanning electron microscopy (SEM). A systematic study of the experimental parameters that affects differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived. Under optimized conditions, stripping voltammetry procedure was developed for the determination of reactive dyes. MWCNT/GCE seems to present better responses than plain GCE and the limit of detection (LOD) was 0.6 μg mL-1 for RY84 and 0.3μg mL-1 for RR120 on this modified system. Suitability of the differential pulse stripping voltammetric method using the developed Multiwalled carbon nanotube based sensor, for the trace determination of these textile dyes in real samples was also realized.

scholarly journals Optimization of Kieldahl digestion procedure for determination of mercury in lipstick by Box-Hunter design

2019 ◽  
Vol 16 (3) ◽  
pp. 41
Author(s):  
Nguyen Ngoc Hung ◽  
Huynh Thi Nhan ◽  
Bui Phuoc Hung ◽  
Nguyen Thi Tuyet Nhung ◽  
Phan Thi Hoang Yen
Keyword(s):  
Response Surface ◽  
Limit Of Detection ◽  
Mercury Content ◽  
Good Precision ◽  
Optimal Conditions ◽  
Good Recovery ◽  
Limit Of Quantification ◽  
Optimization Study ◽  
Cold Vapor Atomic Absorption

This article describes the application of response surface methodology to the development of a procedure for mercury determination by cold vapor atomic absorption spectroscopy (CV-AAS) in lipstick samples after digestion by Kieldahl method. A Box-Hunter matrix was used to find optimal conditions for the procedure through a response surface study. Three variables “time, temperature, volume of HNO3 acid” were regarded as factors in the optimization study. In optimized condition, the linearity range was 0.2 ÷ 15 µg/L while the limit of detection (LOD) and limit of quantification (LOQ) were 0.17 and 0.57 ppb, respectively. This method  presented good precision (RSD ≤ 8.2%) and good recovery (81%-109%). This method was applied to determine mercury in seven lipstick samples and the highest mercury content was 0.229 ± 0.016 mg/kg.

Calcium hydroxid. Determination in workplace air

2019 ◽  
Vol 36 (2(100)) ◽  
pp. 61-72
Author(s):  
Jolanta Surgiewicz
Keyword(s):  
Calcium Hydroxide ◽  
Limit Of Detection ◽  
Absorption Spectrometry ◽  
Good Precision ◽  
European Standard ◽  
Limit Of Quantification ◽  
Respirable Fraction ◽  
Air Volume ◽  
Workplace Air

Calcium hydroxide is a white color solid. It is used in construction, chemical industry, water purification and wastewater treatment, flue gas desulphurization. Calcium hydroxide causes serious damage to the eyes, irritates the skin and it can cause after-launch respiratory irritation. Maximum allowable concentration value (MAC) for calcium hydroxide in the work environment in Poland, for the inhalable and respirable fraction is 2 mg/m3 (STEL is 6 mg/m3) and 1 mg/m3 (STEL is 4 mg/m3), respectively. The aim of the study was to develop a method for determining the concentration of calcium hydroxide present in the inhalable and respirable fraction in the workplaces atmosphere, in the range from 1/10 to 2 MAC values in accordance with the requirements of European Standard PN-EN 482. The developed method is based on collecting, stopping calcium hydroxide (contained in the inhalable and the respirable fraction) on membrane filters, mineralizing filters with concentrated nitric acid and determining calcium of the resulted solution by atomic absorption spectrometry with atomization in acetylene-air flame (F-AAS). The described method allows the determination of calcium in workplace air concentrations in the range of 0.50–20.00 µg/ml. The calibration curve characterized by a high value of the correlation coefficient: R2 = 1.0000. The limit of detection (LOD) is 0.1 ng/ml and the limit of quantification (LOQ) is 0.3 ng/ml. The determined coefficient of recovery is 1.00. An analytical method allows the determination of the concentration of the calcium hydroxide present in the workplace air in the inhalable fraction in the concentration range of 0.10–4.11 mg/m3 (sample air volume 720 L) and in the reparable fraction in the concentration range 0.07–2.70 mg/m3 (for a sample air volume of 684 L), which represents 0.05–2.1 MAC value for the inhalable fraction and 0.07–2.7 MAC value for the respirable fraction. The method has good precision and accuracy and meets the requirements of European Standard PN-EN 482 for procedures for determining chemical agents. The method for determining calcium hydroxide has been recorded in the form of an analytical procedure (see Appendix). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

Catalytic Cathodic Stripping Voltammetry of 5-Phenyl-1,3,4-oxadiazole-2-thiol in the Presence of Nickel(II) and Cobalt(II) Ions

2004 ◽  
Vol 69 (8) ◽  
pp. 1600-1609
Author(s):  
Sławomira Skrzypek ◽  
Agata Michałek ◽  
Witold Ciesielski ◽  
Michał Kasprzak
Keyword(s):  
Catalytic Reduction ◽  
Limit Of Detection ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Acetate Buffer ◽  
Limit Of Quantification ◽  
Cathodic Stripping Voltammetry ◽  
Region 10 ◽  
Cathodic Stripping

5-Phenyl-1,3,4-oxadiazole-2-thiol (POT) and the systems Ni(II)-POT-acetate buffer, Co(II)-POT-acetate buffer were investigated by differential-pulse cathodic stripping voltammetry (DPCSV). The results of the voltammetric measurements show that POT gives a DPCSV signal at about -0.2 V vs Ag|AgCl. The presence of both POT and nickel(II) ions gives rise to a new peak at about -0.6 V; in the presence of cobalt(II) ions a new peak appears at -1.1 V. Based on published results obtained for other sulfur compounds in the presence of Ni(II) or Co(II) ions, the peak at -0.6 V is ascribed to catalytic reduction of Ni(II), and the peak at -1.1 V to hydrogen catalytic discharge. Optimum conditions have been found for the determination of POT by DPCSV. A linear dependence has been found only for the catalytic Ni(II) peak in the region 10-8-10-7 M POT. The calculated limit of detection and limit of quantification are 3.4 × 10-9 and 1.1 × 10-8 mol l-1, respectively.

scholarly journals Determination of moxifloxacin hydrochloride in AVELOX pharmacological formulations using modified potentiometer sensors

Polimery ◽  
2021 ◽  
Vol 66 (11-12) ◽  
pp. 589-601
Author(s):  
Sachin Kumar ◽  
Sushil K. Sindhu ◽  
Praveen Kumar ◽  
Amit Sharma ◽  
Suresh Sagadevan
Keyword(s):  
Limit Of Detection ◽  
Modified Electrodes ◽  
Phosphomolybdic Acid ◽  
Official Method ◽  
Carbon Paste ◽  
Limit Of Quantification ◽  
Highly Sensitive ◽  
Electrode Sensor ◽  
Ph Range

Three different carbon paste (CP), silk-screen (SP) and poly (vinyl chloride) (PVC) modified electrodes were obtained to verify the reliability of AVELOX, the generic name of which is Moxifloxacin HCl (AV-MOXH). The sensing membranes were containing AVELOX ion associated complexes with sodium tetraphenylborate (NaTPB), phosphomolybdic acid (PMA), phosphotungstic acid (PTA), and ammonium reineckate (RN) as electroactive materials. All three electrodes gave fast, viable, and near-Nernstian linear responses over a relative wide concentration range that ranged from 1.010-6 to 1.010-2 mol / L AV-MOXH at 25° C with a monovalent cationic decrease. The sensors demonstrated a good discernment of AV-MOXH from numerous inorganic and organic compounds such as glucose, sucrose, Na+, Ca+, etc. Additionally, the isothermal coefficients along with selectivity coefficients were calculated. The modified Screen Printed Electrode sensor appeared to be highly sensitive for the determination of AV-MOXH. The electrode response was observed in pH range 2--6 for ISPE electrodes and IPVC electrodes and 3--7 for ICPE electrodes under various temperature conditions. The short response time, lifetime validity, recovery, and all the methods of validation such as limit of detection and limit of quantification were estimated. The potentiometric method turned out to be suitable for determining AV-MOXH in pharmacological formulations, and the findings obtained are comparable to the “HPLC official method” in terms of the agreement. As a result, the postulated potentiometric approach was verified in accordance with IUPAC guidelines.

scholarly journals An Immunoenzymatic Method for the Determination of Ochratoxin A in Biological Liquids (Colostrum and Cow’s Milk)

Toxins ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 673
Author(s):  
Magdalena Cuciureanu ◽  
Cristina Tuchiluș ◽  
Anca Vartolomei ◽  
Bogdan Ionel Tamba ◽  
Lorena Filip
Keyword(s):  
Detection Limit ◽  
Ochratoxin A ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Biological Fluids ◽  
Cow’S Milk ◽  
Limit Of Quantification ◽  
Cow's Milk ◽  
Low Concentrations

Ochratoxins are mycotoxins that have been extensively studied lately due to the multiple toxic effects such as nephrotoxicity, hepatotoxicity, and carcinogenicity. These toxins contaminate plant and animal foods and after ingestion they reach into body fluids. The method of competitive direct enzyme immunoassay, in the solid phase, was validated through the determination of specific parameters (performance, linearity, recovery percentage, limit of detection, limit of quantification). The validated method was used to determine ochratoxin A in colostrum and cow’s milk. The method applied for the determination of ochratoxin A was linear for the concentration range of 0.0–0.5 ng/mL, the value for the regression coefficient (r) was 0.9838. Ochratoxin A was present in 91.67% of the colostrum and in 93.33% of cow’s milk samples. The linearity of the method, demonstrated for very low concentrations of analyte, the detection limit as well as the limit of quantification recommend the method for the determinations of micro-pollutants from foods, including biological fluids.

Improved Polarographic Method for Determination of Glyphosate Herbicide in Crops, Soil, and Water

1985 ◽  
Vol 68 (1) ◽  
pp. 76-79
Author(s):  
Hakon O Friestad ◽  
Jan O Bronstad
Keyword(s):  
Limit Of Detection ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Good Precision ◽  
Pulse Polarography ◽  
Basic Resin ◽  
Glyphosate Herbicide ◽  
Selection Of ◽  
Better Than

Abstract A prior method for determination of glyphosate in water samples has been modified to accommodate samples of crops and soils. Differential pulse polarography as the determinative step enables analysis in an aqueous medium, which is important during extraction of this compound. Residues are cleaned up and concentrated by ion exchange on a strong basic resin in OH- form. The method is rapid, is applicable to a relatively broad selection of sample types, and gives recoveries consistently better than 60% with good precision. The main shortcoming of the method is that the limit of detection of 0.5-1.0 ppm may sometimes be inadequate. The metabolite, aminomethyl phosphonic acid, is not detected.

Sign in / Sign up

Export Citation Format

Share Document