High Relative Standard Deviation Research Articles

Fumonisins in maize and gluten meal analysed in Argentinean wet milling industrial plants by ELISA compared with HPLC-FLD method

Fumonisins are frequent contaminants of maize. Wet milling industrial plants in Argentina control not only maize, but the fractions of the process. The performance of two ELISA test kits (G and K) from different brands used in six plants to determine fumonisins in maize and gluten meal was evaluated by comparison with HPLC results. ELISA determinations in maize (n = 43) and gluten meal (n = 45) were carried out in the plants and HPLC analysis was done in our laboratory. No significant differences (P > 0.05) were found in most cases when fumonisins concentrations were within the ELISA quantification range. Thus, ELISA tests performed according to validated protocols are useful tools for screening purposes, but levels nearest the settled limits for rejection of lots should be confirmed by HPLC because of the high relative standard deviation of ELISA analyses. The contamination pattern of fumonisins in gluten meal was different from that of maize, with higher levels of FB2 than those of FB1.

Micro-mixing dynamics of active pharmaceutical ingredients in bin-blending

This paper compares the micro-mixing dynamics of three active pharmaceutical ingredients (APIs) varying in particle size, bulk density and cohesion. Chlorpheniramine maleate, acetaminophen and caffeine, in a common blend of excipients, were used in this study. Micro-mixing was studied in a 1-L bin-blender using in-line near infrared chemical imaging (NIR-CI) to monitor the aggregate size distribution of the APIs and excipients. A science-based calibration chemometric method was used to calculate the concentration maps of ingredients in the blends. Chlorpheniramine maleate, smallest in particle size with lowest bulk density, resulted in the highest relative standard deviation (RSD) for all concentrations. The RSDs obtained for acetaminophen and caffeine were similar and dependent on their concentrations. Chlorpheniramine remained in large aggregates throughout the blending process. Overall, other ingredients (e.g. Avicel) required longer blending times to become well dispersed in the presence of chlorpheniramine maleate, as evidenced by the aggregate size measurements. This in-line NIR-CI technique was able to approximate the number of API aggregates and their size during a common blending process. Although further development of this technique is necessary, metrics measured using this technique could potentially be used as a critical quality attributes during pharmaceutical processing.

Evaluation of Inhibition Efficiency for the Detection of Captan, 2,3,7,8-Tetrachlorodibenzodioxin, Pentachlorophenol and Carbosulfan in Water: An Electrochemical Approach.

A novel bio-analytical method has been devised based on the change in catalytic activity of acetylcholinesterase (AChE) enzyme induced by captan, carbosulfan, 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and pentachlorophenol (PCP) for the investigation of inhibition efficiency and sensitivity using Pt/ZnO/AChE/Chitosan bioelectrode. The inhibition curves of captan, carbosulfan, TCDD and PCP were similar to Michaelis-Menten curve. TCDD held the minimum inhibitor Michaelis-Menten constant ([Formula: see text]) value (10.2 nM) in comparison with PCP (10.9 nM), carbosulfan (14.5 nM) and captan (7.9 × 10(3) nM). The maximum inhibition of AChE enzyme by captan was about 100 %, which was much higher than that of TCDD (72.7 %), PCP (68.1 %) and carbosulfan (47.7 %). The calculated theoretical sensitivity was in the order of TCDD > PCP > carbosulfan > captan. Comparing with TCDD (35.3 %), PCP (47.8 %) and carbosulfan (20.9 %), only the inhibition efficiency of captan (55.0 %) was the maximum. The developed bioelectrode exhibited high recovery and low relative standard deviation in local tap water samples.

Solid-phase extraction of Pb2+ ion from environmental samples onto L-AC-Ag-NP by flame atomic absorption spectrometry (FAAS)

The development of a solid-phase extraction (SPE) procedure for the pre-concentration of trace amounts of Pb2+ ion on 2-furan-2-yl-1-furan-2-ylmethyl-1H-benzoimidazole loaded on activated carbon modified with silver nanoparticles (L-AC-Ag-NP) was presented. The metal ion retained on the sorbent was quantitatively determined via complexation with the ligand. The complexed metal ion was efficiently eluted using 10 mL of 4 mol L−1 sulphuric acid in 10 w/v% acetone. The influences of the analytical parameters, including pH, amounts of the ligand and the solid phase, eluent conditions and sample volume, on the recoveries of the metal ion were optimised. Using the optimised parameters, the linear response of the SPE method for Pb2+ ion were in the ranges of 0.2–160 µg L−1, and the detection limit for Pb2+ ion was 0.034 µg L−1. The proposed method exhibits a pre-concentration factor (PF) of 80 and an enhancement factor of 30 for Pb2+ ion. The presented results demonstrate the successful application of the proposed method for the determination of Pb2+ ion in some real samples with high recoveries (>93%) and reasonable relative standard deviation (RSD < 2%).

Highly Reproducible and Sensitive SERS Substrates with Ag Inter-Nanoparticle Gaps of 5 nm Fabricated by Ultrathin Aluminum Mask Technique.

Applicable surface enhanced Raman scattering (SERS) active substrates require high enhancement factor (EF), excellent spatial reproducibility, and low-cost fabrication method on a large area. Although several SERS substrates with high EF and relative standard deviation (RSD) of signal less than 5% were reported, reliable fabrication for large area SERS substrates with both high sensitivity and high reproducibility via low-cost routes remains a challenge. Here, we report a facile and cost-effective fabrication process for large-scale SERS substrate with Ag inter-nanoparticle (NP) gaps of 5 nm based on ultrathin alumina mask (UTAM) surface pattern technique. Such closely packed Ag NP arrays with high density of electromagnetic field enhancement ("hot spots") on large area exhibit high SERS activity and excellent reproducibility, simultaneously. Rhodamine 6G molecules with concentration of 1 × 10(-7) M are used to determine the SERS performance, and an EF of ∼10(9) is obtained. It should be noted that we obtain RSDs about 2% from 10 random spots on an area of 1 cm(2), which implies the highly reproducible signals. Finite-difference time-domain simulations further suggest that the enhanced electric field originates from the narrow gap, which agrees well with the experimental results. The low value of RSD and the high EF of SERS signals indicate that the as-prepared substrate may be promising for highly sensitive and uniform SERS detection.

DEVELOPMENT AND VALIDATION OF REVERSED PHASE HPLC METHOD FOR ESTIMATION OF CEFTRIAXONE IN PHARMACEUTICAL DOSAGE FORM

A simple, accurate rapid and precise RP-HPLC method has been developed and validated for determination of Ceftriaxone in bulk drug. The RP-HPLC separation was achieved on Promosil C-18, (250 mm, 4.6 mm, 5µm) using mobile phase buffer: methanol ph 6.8 (90: 10 v/v) at flow rate of 1.0 ml/min at ambient temperature. The retention times were 7.111 min. for Ceftriaxone. Calibration plots were linear over the concentration range 1-20µg/ml. Quantification was achieved with photodiode array detection at 260 nm over the concentration range of 1-50 µg/ml. The method was validated statistically and applied successfully for the determination of Ceftriaxone. Validation studies revealed that method is specific, rapid, reliable, and reproducible. The high recovery and low relative standard deviation confirm the suitability of the method for the routine determination of Ceftriaxone in bulk drug. Keywords Ceftriaxone , Water, Buffer, Validation, HPLC.

Screening method for stimulants in urine by UHPLC-MS/MS: identification of isomeric compounds.

A fast screening method for the detection of more than 60 stimulants in urine was developed. The method consisted of a dilution of the urine (1:5 v/v) and analysis by ultra high performance liquid chromatography coupled to tandem mass spectrometry, using a C18 column (1.7 µm particle size), a mobile phase containing deionized water and acetonitrile with formic acid, and gradient elution. The chromatographic run time was 5 min. The detection was performed in positive mode electrospray ionization, monitoring one or two specific ion transitions for each analyte. Appropriate repeatability was obtained, with relative standard deviation (RSD) values below 25% for most of the analytes. Regarding intermediate precision, estimated during routine work, higher RSDs were obtained, probably due to between-day differences in the status of the mass spectrometer and in the chromatographic system. Matrix effect ranged from 60 to 255% with RSD lower than 35% for the majority of compounds. Despite the matrix effect observed, the signal/noise ratio of the analytes spiked at 50 ng/mL was greater than three in all tested samples, allowing a correct detection of all substances at the minimum required performance levels required by the World Anti-Doping Agency and demonstrating the suitability of the method. The method was tested in administration study samples and satisfactorily in operation for more than one year with routine doping samples. The presence of isomeric stimulants with closely similar chromatographic and/or mass spectrometric properties did not allow the unequivocal identification of these compounds after the first analysis. Different possibilities for separation and identification of isomeric compounds are presented.

Effect of material properties and design parameters on the final blend uniformity using experimental and simulation results

One of the most important operations in the food, chemical, and pharmaceutical industries is powder mixing. In the pharmaceutical industry this operation is currently performed mainly in batch mode. However, the Food and Drug Administration (FDA), using the Process Analytical Technology (PAT) initiative, has been working on the promotion of the application of continuous processes in the pharmaceutical industry. The main goal of this study was to understand the powder phenomena inside the mixer and monitor mixing uniformity using experiments and simulations by Discrete Elements Methods (DEM). The experimental results showed highest relative standard deviation (RSD) using the lowest active pharmaceutical ingredient (API) concentration (2.5%), and after using image analysis part of this effect was attributed to the position of the feed inlet. The two experiments with the highest RSD (50 and 70 RPM) were replicated using a new feeding position (25°). The RSD values for the new feeding position demonstrated an improvement in mixing uniformity. The new feed position was studied in more detail using DEM by performing a simulations set that included simulations at two mixer speeds (50 and 70 RPM), three concentrations (2.5%, 10.5%, and 50%), and two different material properties (with and without cohesion). Values of hold-up, velocity profile, mean residence time (MRT), and mixing uniformity were compared for both feed positions. Also the blend uniformities inside the tumble, at each tumble exit, and at the final exit of the system were compared. The results show a positive effect of the angle in the uniformity inside the mixer, in the exit points, and at the exit of the system. Additionally, a relationship between RSD and concentration was found.

A validated stability indicating RP-HPLC method for simultaneous estimation of Clinidipine and Valsartan in bulk and combined tablet dosage forms

The simple, accurate and precise, isocratic RP-HPLC method has been developed and validated for simultaneous estimation of Clinidipine and Valsartan in bulk and tablets dosage forms. The chromatographic separation was achieved on an Waters symmetry C 18 (150x4.6 Id, 3.5μ) with a composition of Acetonitrile : phosphate buffer pH 3.5 adjusted with orthophosphoric acid (70:30, v/v) as mobile phase; at a flow rate of 1.0 ml/min. PDA detection of separtion was performed at 254 nm. The retention times were 2.33 and 3.55 minutes. for Clinidipine and Valsartan respectively. Calibration curves were linear (r 2 >0.998) over the concentration range 1.2-6.0 μg/ml for Clinidipine and 10-50μg/ml Valsartan. The method was validated for accuracy, precision, specificity, linearity, and sensitivity. The proposed method was successfully used for quantitative analysis of tablets. No interference from any component of pharmaceutical dosage form was observed. Validation studies revealed that method is specific, rapid, reliable, and reproducible. The high recovery and low relative standard deviation confirm the suitability of the method for routine determination of Clinidipine and Valsartan in bulk drug and tablet dosage form.

Simultaneous quantitative detection of multiple tumor markers with a rapid and sensitive multicolor quantum dots based immunochromatographic test strip

A novel multicolor quantum dots (QDs) based immunochromatographic test strip (ICTS) was developed for simultaneous quantitative detection of multiple tumor markers, by utilizing alpha fetoprotein (AFP) and carcinoembryonic antigen (CEA) as models. The immunosensor could realize simultaneous quantitative detection of tumor markers with only one test line and one control line on the nitrocellulose membrane (NC membrane) due to the introduction of multicolor QDs. In this method, a mixture of mouse anti-AFP McAb and mouse anti-CEA McAb was coated on NC membrane as test line and goat anti-mouse IgG antibody was coated as control line. Anti-AFP McAb-QDs546 conjugates and anti-CEA McAb-QDs620 conjugates were mixed and applied to the conjugate pad. Simultaneous quantitative detection of multiple tumor markers was achieved by detecting the fluorescence intensity of captured QDs labels on test line and control line using a test strip reader. Under the optimum conditions, AFP and CEA could be detected as low as 3ng/mL and 2ng/mL in 15min with a sample volume of 80μL, and no obvious cross-reactivity was observed. The immunosensor was validated with 130 clinical samples and in which it exhibited high sensitivity (93% for AFP and 87% for CEA) and specificity (94% for AFP and 97% for CEA). The immunosensor also demonstrated high recoveries (87.5–113% for AFP and 90–97.3% for CEA) and low relative standard deviations (RSDs) (2.8–6.2% for AFP and 4.9–9.6% for CEA) when testing spiked human serum. This novel multicolor QDs based ICTS provides an easy and rapid, simultaneous quantitative detecting strategy for point-of-care testing of tumor markers.

Determination of Iron Element in Comb Mushroom by ICP-AES

Iron is indispensable to make hemoglobin and other iron material elements, is also necessary to exchange and oxygen in the blood of an element, many organisms in REDOX system cannot leave it. Most of the iron distribution in special cells in the body. Using the high pressure nitrifying pot method and wet method and treatment of samples were determined in Comb Mushroom samples Fe element content, the determination results are shown in table 2. High pressure nitrifying pot method relative standard deviation of Fe element is 3.689%; Wet method to determine the relative standard deviation of Fe elementt is 5.473%. Visible high pressure nitrifying pot method and treatment of samples of precision of the measuring precision and wet processing samples are relatively good, the measuring precision of the former better. By comparison, high pressure nitrifying pot method specific humidity method to deal with the sample good measuring precision, higher accuracy, and the measurement process to save time.

Determination Content of Zinc Element in Natural Huazi Mushroom by ICP-AES

Zinc is an essential trace element, zinc content in human body is 1.4~2.3g, is widely distributed in various tissues, including skeletal and skin are more, the nutritional status of zinc content in hair Znn reflect the long-term supply of dietary zinc level and human zinc. Using the high pressure nitrifying pot method and wet method and treatment of samples were determined in natural Huazi Mushroom samples Zn element content. High pressure nitrifying pot method relative standard deviation of Zn element is 5.82%; Wet method to determine the relative standard deviation of Zn elementt is 4.81%. Visible high pressure nitrifying pot method and treatment of samples of precision of the measuring precision and wet processing samples are relatively low. By comparison, high pressure nitrifying pot method specific humidity method to deal with the sample good measuring precision, higher accuracy, and the measurement process to save time.

HPLC METHOD DEVELOPMENT FOR DETERMINATION OF GLYOXAL CONTENT IN ONDANSETRON HCL DRUG SUBSTANCES BY DERIVATIZATION WITH 2,4 DNPH

A simple, sensitive, and reproducible stability-indicating high-performance liquid chromatography method was developed for the analysis of glyoxal content in ondansetron HCl by derivatization technique. Chromatographic separation was achieved on symmetry shield RP18 (250 mm length, 4.6 mm inner diameter with 5 µm with a mobile phase consisting of a mixture of monobasic potassium phosphate and acetonitrile and pH adjusted to 3.0 with orthophosphoric acid (95:5 v/v) as mobile phase A, and acetonitrile, methanol, and water (85:5:10 v/v/v) as mobile phase B. UV detection was performed at 385 nm, the flow rate was 1.0 mL/min, and the column oven temperature was maintained at 30 °C. The high correlation coefficient (r 2 > 0.999) values indicated clear correlations between the investigated compound concentrations and their peak areas within the test ranges. The repeatability and intermediate precision, expressed by the RSD, were less than 2.0%. The accuracy of the method was further ascertained by performing recovery studies via a spike method. The high recovery and low relative standard deviation confirm the suitability of the method for routine quantification of glyoxal content in ondansetron HCl. The method was validated according to the present ICH guidelines for, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness, and robustness.

Quantitative Determination of Acetic Acid in Gefitinib by Reverse Phase HPLC

A improved, simple and economic reverse phase high performance liquid chromatography (RP-HPLC) method has been developed and validated as per ICH guidelines for the quantification of acetic acid present in Gefitinib as an solvent impurity. Validation studies demonstrated that the proposed RP-HPLC method is simple, specific, rapid, reliable and reproducible. The high recovery and low relative standard deviation confirm the suitability of the proposed method for the routine quality control analysis for the quantification of acetic acid in Gefitinib.

RP-HPLC METHOD DEVELOPMENT FOR THE ASSAY OF AMPHOTERICIN B

A sensitive and precise HPLC procedure has been developed for the assay of amphotericin B in bulk samples and pharmaceutical formulations by using a C18 column [Kromosil, C18, (5 µm, 4.6mm x 250 mm; Make. Waters)], and mobile phase combination is 1% formic acid in water and acetonitrile in ratio of 45:55 V/V. The procedure has been validated as per the ICH guidelines. The λmax of detection was fixed at 407 nm, so that there was less interference from mobile phase with highest sensitivity according to UV analysis. Calibration plots were linear in the range of 10-100 µg/mL and the LOD and LOQ were 0.02 µg/mL and 0.06 µg/mL respectively. The high recovery and low relative standard deviation confirm the suitability of the method for routine quality control determination of amphotericin B in different formulations.

Validation of assay for bulk clopidogrel and for some tablet forms by reverse-phase high-performance liquid chromatography

A novel, simple, economical reverse-phase high-performance liquid chromatography (RP-HPLC) method was developed for quantifying clopidogrel in bulk and tablet form with greater precision and accuracy. Separation was achieved on a Develosil ODS HG-5 RP C18 (15cm×4.6mm, i.d. 5μm) column in isocratic mode with a mobile phase consisting of acetonitrile:phosphate (65:35) buffer (pH 2.85) with a flow rate of 1mL/min. Detection was carried out at 225nm. The retention time of clopidogrel was 7.48min. The method was validated as per the guidelines of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). Linearity was established for clopidogrel in the range 10–60μg/mL, with an r2 value of 0.999. The recovery of clopidogrel was 99.71–100.03%. The high recovery and low relative standard deviation confirm the suitability of the proposed method for estimating the concentrations of the drug in bulk and tablet dosage forms. Validation studies demonstrated that the proposed RP-HPLC method is simple, specific, rapid, reliable and reproducible for the determination of clopidogrel for quality control.

Validation of assay indicating method development of meloxicam in bulk and some of its tablet dosage forms by RP-HPLC

A novel, simple and economic reverse phase high performance liquid chromatography (RP-HPLC) method has been developed for the quantification of Meloxicam in bulk and tablet dosage form with greater precision and accuracy. Separation was achieved on Develosil ODS HG-5 RP C18, (15 cm × 4.6 mm i.d. 5 μm) column in isocratic mode with mobile phase consisting of acetonitrile: phosphate buffer(pH 3.4) (60:40) with a flow rate of 1 mL/min. The detection was carried out at 268 nm. The retention time of Meloxicam was found to be 2.09 min. The method was validated as per ICH guidelines. Linearity was established for Meloxicam in the range 20 – 120 μg/ml with R2 value 0.996. The percentage recovery of Meloxicam was found to be in the range 99.99-100.46%. The high recovery and low relative standard deviation confirm the suitability of the proposed method for the estimation of the drug in bulk and tablet dosage forms. Validation studies demonstrated that the proposed RP-HPLC method is simple, specific, rapid, reliable and reproducible for the determination of Meloxicam for Quality Control level.

Challenges and solutions for random sampling of parameters with extremely large uncertainties and analysis of the 232Th resonance covariances

Covariance data in the existing evaluated nuclear data libraries often include large relative uncertainties and mathematical inconsistencies, which arise especially in combination with random sampling. The 232Th evaluation from the ENDF/B-VII.1 library has been taken as an example. Possible solutions for mathematically impossible correlation matrices with negative eigenvalues and too low correlation coefficients between inherently positive parameters with large relative uncertainties are proposed. Convergence of the random sampling for lognormal distribution with extremely high relative standard deviations is slow by nature. Using weighted sampling, single parameters or a limited number of correlated parameters with large uncertainties can be sampled. Efficient sampling of a large number of correlated parameters with extremely large relative uncertainties remains unsolved.

SPME-GC-MS determination of selected aniline pesticides in surface water

An analytical methodology to determine Alachlor, Butralin, and Metolachlor herbicides, and Metalaxyl fungicide, in surface water was developed using Solid Phase Microextraction (SPME) and Gas Chromatography coupled to Mass Spectrometry (GC-MS). The developed method was validated, and the quantification limits were found to be between 0.2 to 1.8 μg.L -1 , depending upon the compound. The precision, as measured by the relative standard deviations (RSD), was in the range 3.5% to 27%. The higher RSD was found for Butralin due to the occurrence of adsorption of this compound in the extraction fiber. After validation the developed methodology was employed to the determination of these four pesticides in water samples that supplies Araraquara and Sao Carlos cities (Sao Paulo - Brazil). Samples from Feijao Creek, Anhumas Creek, Cruzes Creek and Paiol Brook, as well as samples from after-treatment at SAAE (Water and Sewer Supply Service – Sao Carlos, SP, Brazil) and DAAE (Water and Sewer Supply Department – Araraquara, SP, Brazil) were evaluated. Samples from both winter and summer seasons were collected and analysed. The results show that the samples analyzed using the in-house validated methodology were not contaminated with these pesticides within the investigated concentrations.

Quantitation of Acrylamide in Foods by High-Resolution Mass Spectrometry

Acrylamide detection still represents one of the hottest topics in food chemistry. Solid phase cleanup coupled to liquid chromatography separation and tandem mass spectrometry detection along with GC-MS detection are nowadays the gold standard procedure for acrylamide quantitation thanks to high reproducibility, good recovery, and low relative standard deviation. High-resolution mass spectrometry (HRMS) is particularly suitable for the detection of low molecular weight amides, and it can provide some analytical advantages over other MS techniques. In this paper a liquid chromatography (LC) method for acrylamide determination using HRMS detection was developed and compared to LC coupled to tandem mass spectrometry. The procedure applied a simplified extraction, no cleanup steps, and a 4 min chromatography. It proved to be solid and robust with an acrylamide mass accuracy of 0.7 ppm, a limit of detection of 2.65 ppb, and a limit of quantitation of 5 ppb. The method was tested on four acrylamide-containing foods: cookies, French fries, ground coffee, and brewed coffee. Results were perfectly in line with those obtained by LC-MS/MS.