Standard Chromatographic Method Research Articles

Electro-generating Cu2+ ions based on electrochemically modified CPE for the determination of malathion pesticide using valid SW-ASV method

This work investigates the validation of the SW-ASV method for the determination of malathion organophosphorus pesticide based on an electrochemically modified (CPE) carbon paste electrode with copper metal. The surface of the modified CPE was constructed by electrodepositing the copper layer at the accumulation step in 1-mM CuSO4.5H2O, PBS at pH 6.6, E accumulation: − 0.8 V, and Taccumulation 240 s. The determining step was performed by adding different concentrations of malathion pesticide and applying the potential toward more positive potential at (− 0.8–+ 1.4 V) to enhance the oxidation of Cu0 metal. It was noticed that the malathion concentration gradient enhances the oxidation peak current of copper at + 0.03 V gradually. SW-ASV method validation was performed at a linearity range confined in (1–10 µM). An analytical curve was constructed and R2 was equal to 0.99995 with good fitted linear relationship. LOD and LOQ were calculated to be 0.0247 and 0.08236 µM, respectively. ANOVA for two sets of measurements using the standard gas chromatographic method and the suggested SW-ASV method was demonstrated via the calculations of F-value and t-value. F and t-values were calculated to be 1.698 and 0.289, respectively, which did not exceed the tabulated F and t-values resulting in the great similarity of results and ensuring the reliability of the suggested test method. This valid SW-ASV method was used to perform the routine analysis of the 95% technical grade and the pesticide formulation 57% emulsion concentrate of the malathion. Valid results were achieved with satisfactory limits of accuracy and precision.Graphical abstract

Bioanalytical RP-HPLC Method for Simultaneous Quantification of Rivaroxaban and Ticagrelor in Spiked Human Plasma: Validation and Stability

For the effective assessment of preclinical, biopharmaceutical and clinical pharmacological investigations, selective and sensitive analytical methods for the quantitative evaluation of drugs and their metabolites (analytes) are essential. Using Rilpivirine as an internal standard (IS), a simple, fast, sensitive, precise and accurate high performance liquid chromatographic method for simultaneous determination of Rivaroxaban and Ticagrelor in human plasma was developed. The analytes were extracted using a direct protein precipitation method with acetonitrile from 500μL aliquots of human plasma. The content of the drugs was assessed using a mobile phase consisting of acetonitrile and 0.1% orthophosphoric acid buffer in a 40:60 v/v ratio and with a flow rate of 1.0ml/min, and an injection volume of 10μL. A Kromasil C18 (250×4.6mm; 5µm) analytical column was used for chromatographic separation and the effluents were monitored at 265nm using a photo diode array (PDA) detector.Rivaroxaban, Ticagrelor and Rilpivirine had retention times of 4.716min, 6.396min and 5.405 min, respectively. Rivaroxaban was shown to be linear at concentrations ranging from 0.018µg/mL - 1.80µg/mL, whereas Ticagrelor was found to be linear between 0.020µg/Ml - 2.00µg/mL. The method was validated according to US-FDA guidelines, and the findings satisfied the acceptance criteria. It was successfully used to determine Rivaroxaban and Ticagrelor in human plasma at the same time and this method is applicable for the pre-clinical and clinical estimation of drugs in biological fluids.

ОПРЕДЕЛЕНИЕ СОДЕРЖАНИЯ АРОМАТИЧЕСКИХ УГЛЕВОДОРОДОВ В МИНЕРАЛЬНЫХ МАСЛАХ МЕТОДОМ ЯМР-РЕЛАКСАЦИИ

Molecular group composition analysis of mineral oils is helpful to predict the performance of a future lubricant and to assess the compatibility of plasticizer oil with rubbers. The method of pulsed low-frequency NMR relaxation was used to determine the molecular group composition of 11 mineral oil samples, and the ratio of aromatic and non-aromatic hydrocarbons in them was calculated. NMR measurements were performed on a Chromatec-Proton 20M NMR analyzer with a 1H resonance frequency of 20 MHz. The method used consists in recording free induction decay signals, reconstructing the total signal amplitude, estimating the relative signal amplitude per unit mass of the sample, and calculating the proportion of aromatic hydrocarbons in the sample. The results were compared with those obtained by the standard chromatographic method. A high degree of correlation (R2 = 0.99) was observed between the results.

Voltammetric Determination of Isopropylmethylphenols in Herbal Spices.

Thymol and carvacrol—the components of herbal spices—are known for their broad biological activity as antimicrobials and antioxidants. For this reason, it is important to develop new methods for their determination in plant material. A simple, rapid, and sensitive method for determination of total content of these analytes in herbal spices using differential pulse voltammetry (DPV) has been developed. The basis of the research is the oxidation process of isopropylmethylphenols on a platinum microelectrode in glacial acetic acid containing acetonitrile (20%, v/v) and 0.1 mol L−1 sodium perchlorate as the supporting electrolyte. Linear voltammetric responses for thymol and carvacrol were obtained in a wide concentration range from 0.39–1105 and 0.47–640 µg mL−1, with a low detection limit of 0.04 and 0.05 µg mL−1, respectively. The analysis was performed using the multiple standard addition method. The results of the voltammetric determination are in good agreement with the data of the standard chromatographic method. To the best of our knowledge, this is the first presentation of an electrochemical procedure to determine these compounds in these environmental and electrode materials.

Nitrogen-doped carbon dots for dual-wavelength excitation fluorimetric assay for ratiometric determination of phosalone.

N-doped carbon dots (N-CDs) were fabricated in a simple procedure by hydrothermal treatment of cellobiose and urea. When excited at 235 nm or 327 nm, only one emission peak at around 420 nm has been observed. With the addition of phosalone, the excitation band at 235 nm was efficiently quenched within 1 min, while the excitation band at 327 nm showed little change. Accordingly, the fluorescence of the N-CDs-phosalone mixture showed quenching under 254-nm UV light, while nearly no fluorescence quenching could be observed under 365-nm UV light. This phenomenon provides a novel anti-false-positive mechanism for phosalone identification. Therefore, the label-free ratiometric sensor for rapid, naked-eye, and anti-false-positive detection of phosalone was proposed for the first time based on the intrinsic dual-excitation N-CDs. Under the optimum experimental conditions, the linear ranges of the excitation-based ratiometric assay were 0.08~4.0 μg/mL and 4.0~14.0 μg/mL; the limit of detection was 28.5 ng/mL. The as-constructed sensor was applied to detect phosalone residue in actual samples, and results were compared with the standard gas chromatographic (GC) method. The recoveries of the established sensor were between 90.0% and 110.0% with RSD lower than 6.6%, while that for the GC method was between 92.5% and 113.0% with RSD lower than 5.8%. Results reveal that the accuracy (recovery) and precision (RSD) of the as-constructed method are comparable to the standard GC method. In this paper, dual-excitation N-doped carbon dots (N-CDs) were synthesized by a simply one-step hydrothermal method for the first time. The novel dual-excitation ratiometric sensor based on the sole intrinsic N-CDs was constructed for phosalone sensing.

Paper-Based Potentiometric Sensors for Nicotine Determination in Smokers' Sweat.

Herein, we describe for the first time, the design and fabrication of a novel nicotine paper-based sensor, in which a miniaturized paper reference electrode is integrated for potentiometric measurements. The paper-based sensors were designed using printed wax barriers to define the electrochemical cell and the sample zones. The electrodes were based on the use of the ion association complexes of the nicotinium cation (Nic) with either tetraphenylborate (TPB) or 5-nitrobarbiturate (NB) counter anions as sensing materials for nicotine recognition. A poly (3,4 ethylenedioxythiophene)/poly-(styrene sulfonate) (PEDOT/PSS) conducting polymer was used as an ion-to-electron transducer. The performance characteristics of the proposed sensors were evaluated and it revealed a rapid and stable response with a Nernstian slope of 55.2 ± 0.3 and 51.2 ± 0.6 mV/decade over the linear range of 1.0 × 10–5 to 1.0 × 10–2 M and detection limits of 6.0 and 8.0 μM for [Nic/TPB] and [Nic/NB], respectively. The sensors revealed a constant response over the pH range 3.5–6.5. The designed sensors provided a portable, inexpensive, and disposable way of measuring trace levels of nicotine coming from different cigarettes and in the collected human sweat of heavy smokers. All results were compared favorably with those obtained by the standard gas chromatographic method.

Laser engraved microapillary pump paper-based microfluidic device for colorimetric and electrochemical detection of salivary thiocyanate.

A microcapillary grooved paper-based analytical device capable of dual-mode sensing (colorimetric and electrochemical detection) was demonstrated for analysis of viscous samples (e.g., human saliva). Herein, a hollow capillary channel wasconstructed via laser engraved micropatterning functions as a micropump to facilitate viscous fluidic transport, which would otherwise impede analysis on paper devices. Using salivary thiocyanate as a model analyte, the proposed device was found to exhibit a promising sensing ability on paper devices without the need for sample pretreatment or bulky instrumentation, as normally required in conventional methods used for saliva analysis. An extensive linear dynamic range covering detection of salivary thiocyanate for both high and trace level regimes (5 orders of magnitudeworking range) was collectively achieved using the dual-sensing modes. Under optimal conditions, the limit of detection was 6μmolL-1 with a RSD of less than 5%. An excellent stability for the μpumpPAD was also observed for over 30days. Real sample analysis using the proposed device was found to be in line with the standard chromatographic method. Benefitting from simple fabrication and operation, portability, disposability, low sample volume (20μL), and low cost (< 1 USD), the μpumpPAD is an exceptional alternative tool for the detection of various biomarkers in saliva specimens.

A sensitive electrochemical detection of metronidazole in synthetic serum and urine samples using low-cost screen-printed electrodes modified with reduced graphene oxide and C60

Monitoring the concentration of antibiotics in body fluids is essential to optimizing the therapy and minimizing the risk of bacteria resistance, which can be made with electrochemical sensors tailored with appropriate materials. In this paper, we report on sensors made with screen-printed electrodes (SPE) coated with fullerene (C60), reduced graphene oxide (rGO) and Nafion (NF) (C60-rGO-NF/SPE) to determine the antibiotic metronidazole (MTZ). Under optimized conditions, the C60-rGO-NF/SPE sensor exhibited a linear response in square wave voltammetry for MTZ concentrations from 2.5 × 10−7 to 34 × 10−6 mol/L, with a detection limit of 2.1 × 10−7 mol/L. This sensor was also capable of detecting MTZ in serum and urine, with recovery between 94% and 100%, which are similar to those of the standard chromatographic method (HPLC-UV). Because the C60-rGO-NF/SPE sensor is amenable to mass production and allows for MTZ determination with simple principles of detection, it fulfills the requirements of therapeutic drug monitoring programs.

Enzyme and lateral flow monoclonal antibody-based immunoassays to simultaneously determine spirotetramat and spirotetramat-enol in foodstuffs

Spirotetramat is employed worldwide to fight insect pests due to its high efficiency. This chemical is quickly metabolized by plants into spirotetramat-enol, so current regulations establish that both compounds must be determined in foodstuffs for monitoring purposes. Nowadays, immunochemical methods constitute rapid and cost-effective strategies for chemical contaminant analysis at trace levels. However, high-affinity binders and suitable bioconjugates are required. In this study, haptens with opposite functionalisation sites were synthesized in order to generate high-affinity monoclonal antibodies. A direct competitive enzyme-linked immunosorbent assay with an IC50 value for the sum of spirotetramat and spirotetramat-enol of 0.1 μg/L was developed using selected antibodies and a novel heterologous bioconjugate carrying a rationally-designed hapten. Studies with fortified grape, grape juice, and wine samples showed good precision and accuracy values, with limits of quantification well below the maximum residue limits. Excellent correlation of results was observed with a standard reference chromatographic method. As a step forward, a lateral flow immunoassay was developed for onsite screening analysis of spirotetramat in wine. This assay was successfully validated according to Regulation 519/2014/EU for semi-quantitative methods at concentrations in line with the legal levels of spirotetramat and spirotetramat-enol in grapes, with a satisfactory false suspect rate below 2%.

Solid-Contact Potentiometric Sensors Based on Main-Tailored Bio-Mimics for Trace Detection of Harmine Hallucinogen in Urine Specimens.

All-solid-state potentiometric sensors have attracted great attention over other types of potentiometric sensors due to their outstanding properties such as enhanced portability, simplicity of handling, affordability and flexibility. Herein, a novel solid-contact ion-selective electrode (SC-ISE) based on poly(3,4-ethylenedioxythiophene) (PEDOT) as the ion-to-electron transducer was designed and characterized for rapid detection of harmine. The harmine-sensing membrane was based on the use of synthesized imprinted bio-mimics as a selective material for this recognition. The imprinted receptors were synthesized using acrylamide (AA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and cross-linker, respectively. The polymerization process was carried out at 70 °C in the presence of dibenzoyl peroxide (DBO) as an initiator. The sensing membrane in addition to the solid-contact layer was applied to a glassy-carbon disc as an electronic conductor. All performance characteristics of the presented electrode in terms of linearity, detection limit, pH range, response time and selectivity were evaluated. The sensor revealed a wide linearity over the range 2.0 × 10−7–1.0 × 10−2 M, with a detection limit of 0.02 µg/mL and a sensitivity slope of 59.2 ± 0.8 mV/hamine concentration decade. A 40 mM Britton–Robinson (BR) buffer solution at pH of 6 was used for all harmine measurements. The electrode showed good selectivity towards harmine over other common interfering ions, and maintained a stable electrochemical response over two weeks. After applying the validation requirements, the proposed method revealed good performance characteristics. Method precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty were also evaluated. These analytical capabilities support the fast and direct assessment of harmine in different urine specimens. The analytical results were compared with the standard liquid chromatographic method. The results obtained demonstrated that PEDOT/PSS was a promising solid-contact ion-to-electron transducer material in the development of harmine-ISE. The electrodes manifested enhanced stability and low cost, which provides a wide number of potential applications for pharmaceutical and forensic analysis.

Novel Solid-State Potentiometric Sensors Using Polyaniline (PANI) as A Solid-Contact Transducer for Flucarbazone Herbicide Assessment.

Novel potentiometric solid-contact ion-selective electrodes (SC/ISEs) based on molecularly imprinted polymers (MIPs) as sensory carriers (MIP/PANI/ISE) were prepared and characterized as potentiometric sensors for flucarbazone herbicide anion. However, aliquat S 336 was also studied as a charged carrier in the fabrication of Aliquat/PANI/ISEs for flucarbazone monitoring. The polyaniline (PANI) film was inserted between the ion-sensing membrane (ISM) and the electronic conductor glassy carbon substrate (GC). The sensors showed a noticeable response towards flucarbazone anions with slopes of −45.5 ± 1.3 (r2 = 0.9998) and −56.3 ± 1.5 (r2 = 0.9977) mV/decade over the range of 10−2–10−5, 10−2–10−4 M and detection limits of 5.8 × 10−6 and 8.5 × 10−6 M for MIP/PANI/ISE and Aliguat/PANI/ISE, respectively. The selectivity and long-term potential stability of all presented ISEs were investigated. The short-term potential and electrode capacitances were studied and evaluated using chronopotentiometry and electrochemical impedance spectrometry (EIS). The proposed ISEs were introduced for the direct measurement of flucarbazone herbicide in different soil samples sprayed with flucarbazone herbicide. The results agree well with the results obtained using the standard liquid chromatographic method (HPLC).

Development and validation of a quick assay for the total glucosinolate content in horseradish (Armoracia rusticana) using glucose strips and a blood glucose meter.

A quick assay to determine the total glucosinolate content of fresh horseradish roots in less than 10 minutes is described. The method involves the following steps: 1. Maceration of horseradish root with 4% phosphoric acid to avoid enzymatic degradation of endogenous glucosinolates, 2. neutralization of the extract and determination of free glucose using a commercial blood glucose meter, 3. enzymatic hydrolysis of the glucosinolates by exogenous myrosinase, 4. detection of released glucose, again using a blood glucose meter, and 5. calculation of the glucosinolate content on the basis of the difference between the two glucose values determined. The newly developed assay (‘ITC quick test’) was compared with a standard high-performance liquid chromatographic method for glucosinolate analysis.

A Low Cost and Simple Lab-on-a-Chip for Spectrophotometric Determination of Ethanol

A simple lab-on-a-chip system was developed for the rapid determination of ethanol in different sample matrices, including gasohol and various alcoholic beverages. The colorimetric detection of ethanol using a spectrophotometer was based on the reaction between ethanol with 0.12 M ceric ammonium nitrate in acidic medium to produce a red colored product which gave a maximum absorption at 470 nm. A non-lithographic method was used for creating lab-on-a-chip molds to reduce manufacturing cost and preparation steps. The lab-on-a-chip device was fabricated from polydimethylsiloxane which consisted of a simple Y-shaped working channel. Under optimum conditions, a linear calibration graph was obtained in the concentration range of 0.20 - 20 % (v/v) (r2&gt; 0.999). The limit of detection (3 SD) and limit of quantification (10 SD) were 0.039 and 0.13 % (v/v), respectively. The precision reported in terms of relative standard deviation (RSD) values was less than 1.40 % (n = 15). To demonstrate the lab-on-a-chip’s performance, the determination of ethanol in gasohol and various alcoholic beverages was applied. The results obtained from the developed method compared with a standard gas chromatographic method were well correlated using the paired t-test and linear regression test. The results indicate that the proposed method has shown potential to extend the use of this simple lab-on-a-chip analytical device, due to its simplicity, low cost, lower reagent and sample consumption and high analytical performance. Moreover, the method of fabrication would be an additive manufacturing technique featuring a low equipment cost with no need for clean rooms.

Quantitative image analysis of polyhydroxyalkanoates inclusions from microbial mixed cultures under different SBR operation strategies

Polyhydroxyalkanoates (PHAs) produced from mixed microbial cultures (MMC), regarded as potential substitutes of petrochemical plastics, can be found as intracellular granules in various microorganisms under limited nutrient conditions and excess of carbon source. PHA is traditionally quantified by laborious and time-consuming chromatography analysis, and a simpler and faster method to assess PHA contents from MMC, such as quantitative image analysis (QIA), is of great interest. The main purpose of the present work was to upgrade a previously developed QIA methodology (as reported by Mesquita et al. (Anal Chim Acta 770:36-44, 2013a, Anal Chim Acta 865:8-15, 2015)) for MMC intracellular PHA contents quantification, increase the studied intracellular PHA concentration range, and extend to different sequencing batch reactor (SBR) operation strategies. Therefore, the operation of a new aerobic dynamic feeding (ADF) SBR allowed further extending the studied operating conditions, dataset, and range of the MMC intracellular PHA contents from the previously reported anaerobic/aerobic cycle SBR. Nile Blue A (NBA) staining was employed for epifluorescence microscope visualization and image acquisition, further fed to a custom developed QIA. Data from each of the feast and famine cycles of both SBR were individually processed using chemometrics analysis, obtaining the correspondent partial least squares (PLS) models. The PHA concentrations determined from PLS models were further plotted against the results obtained in the standard chromatographic method. For both SBR, the predicted ability was higher at the end of the feast stage than for the famine stage. Indeed, an independent feast and famine QIA data treatment was found to be fundamental to obtain the best prediction abilities. Furthermore, a promising overall correlation (R 2 of 0.83) could be found combining the overall QIA data regarding the PHA prediction up to a concentration of 1785.1mgL-1 (37.3wt%). Thus, the results confirm that the presented QIA methodology can be seen as promising for estimating higher intracellular PHA concentrations for a larger reactors operation systems and further extending the prediction range of previous studies.

Quantification of pepsin in rennet using a monoclonal antibody-based inhibition ELISA

Pepsin and chymosin are milk-clotting enzymes found in rennets. They differ in their pH and temperature sensitivities and their milk-clotting activity (MCA)/proteolytic activity ratio which impact cheese technology. Therefore, characterization of rennet should not be limited to its total MCA, but also its enzymatic composition. Monoclonal antibodies against pepsin, obtained from mice immunized with purified pepsin, were characterized. A specific inhibition enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of pepsin in rennets. The limit of quantification was 143 ng pepsin/mL. The precision within runs ranged from 7.0 to 9.4%, for rennets with low and high pepsin concentrations, respectively. The precision among runs also ranged from 8.8 to 11.4%. Satisfying recovery, from 84.7 to 100.3%, was found with spiked samples. The applicability of the developed inhibition ELISA for pepsin quantification was assessed by analyzing commercial rennets, and compared to the standard chromatographic method 110A of International Dairy Federation. The relation and agreement between methods were evaluated using Deming regression analysis and Bland-Altman plot. A good agreement was found with a fixed bias. By means of bias subtraction, inhibition ELISA could be a reliable alternative for rapid and sensitive determination of pepsin in rennet.

Comparison of a new microbiological assay with a standard high-performance liquid chromatographic method for determination of vitamin B6 in serum.

A high-performance liquid chromatographic (HPLC) assay for vitamin B6 in human serum was compared with a novel microbiological assay (ID-Vit) that uses microtitre plates precoated with a specific microorganism, thus avoiding numerous problems associated with the use of stock cultures utilized by common other microbial assay mit B6. Data obtained using HPLC were compared with 1D-Vit results in 170 healthy individuals and in 68 patients with coronary artery disease (CAD, 37 with acute coronary syndrome [ACS], 31 with stable CAD). Regression and Bland-Altman analysis were performed. Homocysteine in CAD patients was measured by HPLC. The ID-Vit assay correlated well with the HPLC assay (Pearson's r = 0.89 [p < 0.0001] in healthy and 0.82 [p < 0.001] in CAD individuals). Bland-Altman analyses revealed good agreement between the results of both methods in both cohorts, with > or = 95% of all values grouping within the lines of agreement. In CAD patients, mean homocysteine values did not differ between stable CAD and ACS and were normal. Thirty-seven percent of CAD patients had estimated glomerular filtration rates (GFR) below 60 mL/min/1.73m2. GFR correlated inversely with homocysteine levels (r = -0.80, p < 0.001) whereas neither HPLC nor ID-Vit values for B6 did. ID-Vit assay and the HPLC standard are in very good agreement. The new assay can easily be automated and is less laborious than common microbiological assays. The lack of correlation between B6 vitamin and homocysteine can be accounted for by the fact that mean vitamin B6 in our CAD patients was in the normal range and that a relevant percentage of patients had chronic renal disease.

Evaluation of the caseinomacropeptide (CMP) content in raw and uht milk during storage time.

&lt;p&gt;Coolers are used in raw milk storage in order to inhibit the growth of lactic acid producer mesophilic microorganisms. However, refrigerated milk is a favorable environment to psychrotrophic aerobic bacteria growth. These psychrotrophic bacteria promote proteolysis which is of concern to the dairy industry since it may indicate a false positive of fraudulent addition of whey to raw milk. This study evaluated the influence of storage time on the presence of caseinmacropeptide (CMP) in raw milk during storage as well as in ultra-high temperature milk (UHT) throughout its shelf life. Three different determination methods were compared each other, namely the standard chromatographic method and two spectroscopy methods for the quantitative determination of sialic acid. One is based on the determination of ninhydrin acid and the other one is an adapted method using the Ehrlich reagent. An increase of CMP content throughout the storage period for the cooled raw milk and UHT milk was detected despite the fact that none had cheese whey. The spectrophotometric methods showed correlation coefficients greater than 0.97 with the chromatographic method established by Brazilian legislation. The results indicate that the spectrophotometric method using the ninhydrin acid can be used as an alternative method for the determination of CMP in milk samples.&lt;/p&gt;&lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;DOI: http://dx.doi.org/10.14685/rebrapa.v2i2.54&lt;/p&gt;

Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

A colorimetric method for total capsaicinoids in chili pepper (Capsicum) fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and reconstituted in acetonitrile, was treated with Gibbs reagent to produce a beautiful blue product, easily detected by eye. Semiquantitative measurement was made by comparison to a printed color chart. The simple analysis required no electronic equipment or chromatographic separations, so is amenable to classroom demonstration, introductory laboratory, and the field. Accuracy was demonstrated by favorable comparison of results with those from a standard liquid chromatographic method for eight varieties of chili pepper.

Determination of chlorpyriphos in broccoli using a voltammetric acetylcholinesterase sensor based on carbon nanostructure–chitosan composite material

The widespread use of organophosphate pesticides (OPPs) in agriculture leads to residue accumulation in the environment, which is dangerous to human health and disrupts the ecological balance. This study reports results obtained by a standard chromatographic method (high performance liquid chromatography, HPLC) and an amperometric method for chlorpyriphos (CPF) determination in broccoli. Reversed-phase HPLC with UV–VIS detection was used for the separation, and the mobile phase was acetonitrile–water (75:25v/v). The electrochemical experiments were performed in phosphate buffer solutions at pH=7.4, with an incubation time of 10min. The response of the sensor was a linear function of CPF concentration from 10−10 to 10−7M with a corresponding equation: y=0.1467x+1.4472 (R2=0.9959) and a detection limit of 1.58×10−10M. The biosensor methodology was used to analyze CPF directly in broccoli that had been previously spiked with CPF solution.

Avaliação do perfil de dissolução de medicamentos utilizando-se espectroscopia eletrônica multivariada

In this work the evaluation of the dissolution profile of captopril-hydrochlorothiazide and zidovudine-lamivudine associations were carried out by multivariate spectroscopic method. The models were developed by partial least square regression from 20 synthetic mixtures using mean-centered spectral data. The external validation was accomplished with 5 synthetic mixtures shown mean prevision error of about 1%. Good agreement was observed in the analyses of commercial drugs (content uniformity and dissolution profile), considering the results obtained by the standard chromatographic method, with prevision error lower than 10%.