A new approach for the determination of sunscreen levels in seawater by ultraviolet absorption spectrophotometry.

Sunscreen is released into the marine environment and is considered toxic for marine life. The current analytical methods for the quantification of sunscreen are mostly specific to individual chemical ingredients and based on complex analytical and instrumental techniques. A simple, selective, rapid, reproducible and low-cost spectrophotometric procedure for the quantification of commercial sunscreen in seawater is described here. The method is based on the inherent properties of these cosmetics to absorb in the wavelength of 300-400 nm. The absorption at 303 nm wavelength correlates with the concentration of most commercial sunscreens. This method allows the determination of sunscreens in the range of 2.5-1500 mg L-1, it requires no sample pretreatment and offers a precision of up to 0.2%. The spectrophotometric method was applied to quantify sunscreen concentrations at an Atlantic Beach with values ranging from 10 to 96.7 mg L-1 in the unfiltered fraction and from the undetectable value to 75.7 mg L-1 in the dissolved fraction. This method is suggested as a tool for sunscreen quantifications in environmental investigations and monitoring programs.

Development and validation of a cost-effective and sensitive bioanalytical HPLC-UV method for determination of lopinavir in rat and human plasma.

A simple, sensitive and cost-effective HPLC-UV bioanalytical method for determination of lopinavir (LPV) in rat and human plasma was developed and validated. The plasma sample preparation procedure includes a combination of protein precipitation using cold acetonitrile and liquid-liquid extraction with n-hexane-ethyl acetate (7:3, v/v). A good chromatographic separation was achieved with a Phenomenex Gemini column (C18 , 150 mm × 2.0 mm, 5 µm) at 40°C with gradient elution, at 211 nm. Calibration curves were linear in the range 10-10,000 ng/mL, with a lower limit of quantification of 10 ng/mL using 100 µL of plasma. The accuracy and precision in all validation experiments were within the criteria range set by the guidelines of the Food and Drug Administration. This method was successfully applied to a preliminary pharmacokinetic study in rats following an intravenous bolus administration of LPV. Moreover, the method was subsequently fully validated for human plasma, allowing its use in therapeutic drug monitoring (TDM). In conclusion, this novel, simple and cost-efficient bioanalytical method for determination of LPV is useful for pharmacokinetic and drug delivery studies in rats, as well as TDM in human patients.

Determination of six benzotriazole ultraviolet filters in water and cosmetic samples by graphene sponge-based solid-phase extraction followed by high-performance liquid chromatography.

An approach for fabrication of graphene sponge (GS)-based solid-phase extraction (SPE) followed by high-performance liquid chromatography (HPLC) with ultraviolet detection (HPLC-UV) is proposed, which was applied to determine the six benzotriazole UV filters in water and cosmetic samples. Several extraction conditions including type of elution solvent, the volume of elution solvent, and salt effect were optimized. Under the optimum conditions, the GS-SPE-HPLC-UV method shows a low limit of detection (LOD, S/N = 3) of 0.02-0.08 µg L-1 for standard solution, limits of quantification (LOQ, S/N = 10) of 0.07-0.26 µg L-1 for standard solution, wide linear ranges from 20.0 to 1000 µg L-1 for all compounds for standard solution, correlation coefficients (r) of more than 0.999, except for 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (UV-P), and acceptable reproducibility (relative standard deviations, RSDs < 6.5% for intra-day, RSDs < 8.1% for inter-day). The satisfactory recoveries were obtained in the range 89-105% with RSDs lower than 9.8% at the three spiked levels of 20, 50, and 100 µg L-1. Every home-made GS-SPE cartridge can be reused for more than 60 cycles. The method is facile, low-cost, rapid, sensitive, and suitable for the determination of UV filters in water and cosmetics samples. Graphical abstract ᅟ.

A Validated Method for Quantification of Dolutegravir Using Ultra Performance Liquid Chromatography Coupled With UV Detection.

BACKGROUND: Dolutegravir (DTG) is an integrase strand transfer inhibitor, which is a newly approved antiretroviral drug used for the treatment of HIV-infected naive and experienced individuals. Many aspects of DTG pharmacology remain to be studied. Our aim was to develop and fully validate a robust analytical method for the quantification of DTG in plasma using liquid chromatography coupled with UV detection. METHODS: A simple and rapid protein precipitation method was used for analyte extraction from 100 µL plasma. The separation was achieved on a C8 reverse-phase analytical column using a gradient elution with 50 mmol/L formic acid and 50 mmol/L ammonium acetate in water (mobile phase A), and 100% acetonitrile (mobile phase B) and at a flow rate of 0.3 mL/min and a total run time of 10 minutes. The detector wavelength was set at 258 nm. RESULTS: The linearity of the calibration curve (r > 0.9999, n = 6) was validated over a concentration range of 0.25-10 mcg/mL. Intra-assay variability ranged from 3.3% to 6.1% and inter-assay variability ranged from 4.5% to 5.7%. The overall accuracy ranged from 90.7% to 97.7% for the 3 different concentrations of quality control samples. Recovery efficiency of extraction ranged from 94.3%-100%. This method is highly selective with no interferences from commonly concomitant antiretroviral drugs or endogenous metabolites. CONCLUSIONS: The described method is simple, robust, selective, accurate, precise, and cost-effective. Thus, this assay can be readily transferred and implemented in clinical settings and used for pharmacokinetic studies and therapeutic drug monitoring programs.

Effect of genetic algorithm as a variable selection method on different chemometric models applied for the analysis of binary mixture of amoxicillin and flucloxacillin: A comparative study.

Different chemometric models were applied for the quantitative analysis of amoxicillin (AMX), and flucloxacillin (FLX) in their binary mixtures, namely, partial least squares (PLS), spectral residual augmented classical least squares (SRACLS), concentration residual augmented classical least squares (CRACLS) and artificial neural networks (ANNs). All methods were applied with and without variable selection procedure (genetic algorithm GA). The methods were used for the quantitative analysis of the drugs in laboratory prepared mixtures and real market sample via handling the UV spectral data. Robust and simpler models were obtained by applying GA. The proposed methods were found to be rapid, simple and required no preliminary separation steps.

An UV-vis spectroelectrochemical approach for rapid detection of phenazines and exploration of their redox characteristics.

Phenazines are widely distributed in the environment and play an important role in various biological processes to facilitate microbial metabolism and electron transfer. In this work, an efficient and reliable spectroelectrochemical method is developed to quantitatively detect 1-hydroxyphenazine (1-OHPZ), a representative phenazine, and explore its redox characteristics. This approach is based on the sensitive absorption change of 1-OHPZ in response to its changes under redox state in rapid electrochemical reduction. The redox reaction of 1-OHPZ in aqueous solution is a proton-coupled electron transfer process, with a reversible one-step 2e(-)/2H(+) transfer reaction. This spectroelectrochemical approach exhibits good linear response covering two magnitudes to 1-OHPZ with a detection limit of 0.48µM, and is successfully applied to detect 1-OHPZ from a mixture of phenazines produced by Pseudomonas aeruginosa cultures. This method might also be applicable in exploring the abundance and redox processes of a wide range of other redox-active molecules in natural and engineered environments.

The contribution of Raman spectroscopy to the analytical quality control of cytotoxic drugs in a hospital environment: eliminating the exposure risks for staff members and their work environment.

The purpose of the study was to perform a comparative analysis of the technical performance, respective costs and environmental effect of two invasive analytical methods (HPLC and UV/visible-FTIR) as compared to a new non-invasive analytical technique (Raman spectroscopy). Three pharmacotherapeutic models were used to compare the analytical performances of the three analytical techniques. Statistical inter-method correlation analysis was performed using non-parametric correlation rank tests. The study's economic component combined calculations relative to the depreciation of the equipment and the estimated cost of an AQC unit of work. In any case, analytical validation parameters of the three techniques were satisfactory, and strong correlations between the two spectroscopic techniques vs. HPLC were found. In addition, Raman spectroscopy was found to be superior as compared to the other techniques for numerous key criteria including a complete safety for operators and their occupational environment, a non-invasive procedure, no need for consumables, and a low operating cost. Finally, Raman spectroscopy appears superior for technical, economic and environmental objectives, as compared with the other invasive analytical methods.

Label-free silver nanoparticles for the naked eye detection of entecavir.

A simple, rapid, field-portable colorimetric method for the detection of entecavir was proposed based on the color change caused by the aggregation of silver nanoparticles. Neutralization of the electrostatic repulsion from each silver nanoparticle resulted in the aggregation of AgNPs and a consequent color change of AgNPs from yellow to wine-red, which provided a platform for rapid and field-portable colorimetric detection of entecavir. The concentration of entecavir could be determined with naked eye or UV-vis spectrometer. The proposed method can be used to detect entecavir in human urine with a detection limit of 1.51µg mL(-1), within 25min by naked eye observation without the aid of any advanced instrument or complex pretreatment. Results from UV-vis spectra showed that the absorption ratio was linear with the concentration of entecavir in the range of 5.04-25.2µg mL(-1) and 1.01-5.04µg mL(-1) with linear coefficients of 0.9907 and 0.9955, respectively. The selectivity of AgNPs detection system for entecavir is excellent comparing with other ions and analytes. Due to its rapid, visible color changes, and excellent selectivity, the AgNPs synthesized in this study are suitable to be applied to on-site screening of entecavir in human urine.

Image-based detection of oligonucleotides--a low cost alternative to spectrophotometric or fluorometric methods.

Herein, we report a sensitive and low cost image-based (photocolorimetric) method for the detection of oligonucleotides on an activated polypropylene microtest plate (APPµTP). The assay was developed on the APPµTP by covalently immobilising 20-mer amino-modified oligonucleotides. Biotin-tagged complementary target sequences were then hybridised with the immobilised oligonucleotides. Colour was developed by streptavidin-HRP conjugate and the image of the coloured assay solution was taken by a desktop scanner and analysed using colour saturation. The developed method was analysed for its detection limit, accuracy, sensitivity and interference. The linearity range was found to be 1.7-170 ng mL(-1) while the lower limit of detection and limit of quantification were 1.7 and 5.6 ng mL(-1) respectively. The method showed comparable sensitivity to fluorometric methods, and was found to be correlated to fluorescence (R(2) = 0.8081, p-value < 0.0001) and absorbance (R(2) = 0.9394, p-value < 0.0001)-based quantification. It discriminates mismatched base sequences from perfectly matched sequences efficiently. Validation of the method was carried out by detecting por A DNA of Neisseria meningitidis in bacterial meningitis samples. The por A-specific probe having a 6-carbon spacer at its 5'-NH2 terminus was immobilised covalently to the APPµTP and hybridised with different samples of biotinylated single-stranded por A DNA.

External surface area determination of lipid vesicles using trinitrobenzene sulfonate and ultraviolet/visible spectrophotometry.

The lamellarity of liposomes is an important parameter to be controlled in liposomal delivery-release applications. A practical estimate of the degree of liposome lamellarity can be obtained by measuring the relative external surface area of the liposomes using a chemical assay. All such assays are based on a signal change caused by exposed marker lipids on reaction with a specific externally added reagent. However, a quantitative determination is often distorted by background reactions and contributions of internal lipid labeling. In the so-called TNBS assay, the marker lipid is phosphatidylethanolamine (PE) and the externally added reagent is TNBS (2,4,6-trinotrobenzene sulfonate). Mechanistic aspects of the TNBS assay were considered for improving the assay. Internal lipid labeling via PE flip-flop and/or TNBS permeation was minimal not only in cholesterol-containing liposomes but also in cholesterol-free liposomes if in the latter case membrane fluidity was decreased by slightly increasing the PE content. Compared with earlier versions of the TNBS assay, the amount of marker lipid and the time for analysis could be reduced considerably. The elaborated protocol was also applied to liposomes prepared from lipidic egg yolk isolates, offering a simple and inexpensive method for the development and in-process control of new liposome formation technologies.

Determination of oil-in-water using nanoemulsions as solvents and UV visible and total organic carbon detection methods.

The aim of this study was to investigate the application of oil in water (O/W) nanoemulsion as solvent in the extraction step for determination of oil content in oily water, measured using a UV visible spectrophotometer (UV-vis) and a total organic carbon (TOC) analyzer. The optical micrographs and distribution size curves showed that the use of a small amount of nanoemulsion was capable of transforming the oily water in a colloidal dispersion that can be read in the UV-vis and TOC-VCHS devices. The oil content results obtained showed great accuracy between the measurements, with very low average standard deviation (∼5%) for both UV-vis and TOC-VCHS. The new methods suggested in this work are very promising, since they allow simple, quick and accurate analyses, and especially require a lower volume of solvent (less than 1%) compared to those used in conventional analytic methods.

[Raman spectroscopy applied to analytical quality control of injectable drugs: analytical evaluation and comparative economic versus HPLC and UV / visible-FTIR]. / La spectroscopie Raman appliquée au contrôle de qualité analytique des médicaments injectables: évaluation analytique et économique comparative versus CLHP et uv/visible-iRTF.

In France, central IV admixture of chemotherapy (CT) treatments at the hospital is now required by law. We have previously shown that the shaping of Therapeutic Objects (TOs) could profit from an Analytical Quality Assurance (AQA), closely linked to the batch release, for the three key parameters: identity, purity, and initial concentration of the compound of interest. In the course of recent and diversified works, we showed the technical superiority of non-intrusive Raman Spectroscopy (RS) vs. any other analytical option and, especially for both HPLC and vibrational method using a UV/visible-FTIR coupling. An interconnected qualitative and economic assessment strongly helps to enrich these relevant works. The study compares in operational situation, the performance of three analytical methods used for the AQC of TOs. We used: a) a set of evaluation criteria, b) the depreciation tables of the machinery, c) the cost of disposables, d) the weight of equipment and technical installations, e) the basic accounting unit (unit of work) and its composite costs (Euros), which vary according to the technical options, the weight of both human resources and disposables; finally, different combinations are described. So, the unit of work can take 12 different values between 1 and 5.5 Euros, and we provide various recommendations. A qualitative evaluation grid constantly places the SR technology as superior or equal to the 2 other techniques currently available. Our results demonstrated: a) the major interest of the non-intrusive AQC performed by RS, especially when it is not possible to analyze a TO with existing methods e.g. elastomeric portable pumps, and b) the high potential for this technique to be a strong contributor to the security of the medication circuit, and to fight the iatrogenic effects of drugs especially in the hospital. It also contributes to the protection of all actors in healthcare and of their working environment.

A highly sensitive quantification of phytosterols through an inexpensive derivatization.

A highly sensitive method for quantification of phytosterols based on HPLC has been developed by derivatization with the benzoyl chromophore. Introduction of the chromophore, benzoyl group, to phytosterols via simple and inexpensive derivatization greatly improved the UV response at 254 nm. Quantification of phytosterols was effectively performed by HPLC analysis with methyl benzoate as the internal standard after derivatization. This new method demonstrated outstanding yield of recovery (> 95%) and excellent sensitivity (ng level) and was applicable for sterols from either plant or animal sources. This method is generally useful in phytosterol studies.

Differentiation of tea varieties using UV-Vis spectra and pattern recognition techniques.

Tea, one of the most consumed beverages all over the world, is of great importance in the economies of a number of countries. Several methods have been developed to classify tea varieties or origins based in pattern recognition techniques applied to chemical data, such as metal profile, amino acids, catechins and volatile compounds. Some of these analytical methods become tedious and expensive to be applied in routine works. The use of UV-Vis spectral data as discriminant variables, highly influenced by the chemical composition, can be an alternative to these methods. UV-Vis spectra of methanol-water extracts of tea have been obtained in the interval 250-800 nm. Absorbances have been used as input variables. Principal component analysis was used to reduce the number of variables and several pattern recognition methods, such as linear discriminant analysis, support vector machines and artificial neural networks, have been applied in order to differentiate the most common tea varieties. A successful classification model was built by combining principal component analysis and multilayer perceptron artificial neural networks, allowing the differentiation between tea varieties. This rapid and simple methodology can be applied to solve classification problems in food industry saving economic resources.

Rapid, on-site identification of explosives in nanoliter droplets using a UV reflected fiber optic sensor.

A portable UV (190-400 nm) spectrophotometric based reflected fiber optic sensor system is presented for the on-site detection and identification of explosives. A reflected fiber optic sensor for explosives analysis was developed, with low sample consumption (20-100 nL) and a wide concentration quantification range (1.1-250 mg L(-1)). Seven common explosives [pentaerythritol tetranitrate (PETN), trinitrophenylmethylnitramine (CE), trinitrotoluene (TNT), dinitrotoluene (DNT), picric acid (PA), cyclotetramethylenetetranitramine (HMX), cyclotrimethylenetrinitramine (RDX)] and a PETN-RDX mixture (to simulate the Semtex used in many terrorist bombings) were quantitatively analyzed and identified by the proposed system in less than 3s per test, with limits of detection (LOD) of 0.3 mg L(-1). Due to chemical interference problems in the UV wavelengths range, a novel feature matching algorithm (FMA) was proposed for explosive identification, which was proved to have higher specificity and better anti-interference ability. Real post-blast debris samples were analyzed by the proposed method, and the results were validated against an LC/MS/MS method. The rapid, cost-effective detection with low sample consumption and wide applicability achieved by this system is highly suitable for homeland security on-site applications, such as rapid sample screening in post-blast debris.

Exonuclease-assisted cascaded recycling amplification for label-free detection of DNA.

The network consisting of three kinds of unlabeled stem-loop DNA molecular beacons (MBs) is activated by target DNA in the presence of exonuclease-III (Exo-III), achieving the concept of exonuclease-assisted cascaded recycling amplification (Exo-CRA) for DNA detection with a wide dynamic range of 8 orders of magnitude.

Ultra-sensitive determination of cadmium in rice and water by UV-vis spectrophotometry after single drop microextraction.

In this work, a new method based on single drop microextraction (SDME) preconcentration using tetrachloromethane (CCl(4)) as extraction solvent was proposed for the spectrophotometric determination of cadmium in rice and water samples. The influence factors relevant to SDME, such as type and volume of extractant, stirring rate and time, dithizone concentration, pH, drop volume and instrumental conditions were studied systematically. Under the optimal conditions, the limit of detection (LOD) was 0.5 ng L(-1), with sensitivity enhancement factor (EF) of 128. The different maximum absorption wavelength caused by the different extraction acidity compared with some conventional works and the enhancement effect of acetone (dilution solvent) for the spectrophotometric determination were the two key factors of the high EF and sensitivity. The proposed method was applied to the determination of rice and water samples with satisfactory analytical results. The proposed method was simple, rapid, cost-efficient and sensitive.

Development and validation of a high-performance liquid chromatography method for determination of cefquinome concentrations in sheep plasma and its application to pharmacokinetic studies.

Cefquinome has a broad spectrum of antibacterial activity and was developed especially for use in animals. A simple and sensitive high-performance liquid chromatography (HPLC) method with UV-visible detection for quantification of cefquinome concentrations in sheep plasma was developed and validated. Separation of cefquinome from plasma components was achieved on a Phenomenex Gemini C(18) column (250 mm by 4.6 mm; internal diameter [i.d.], 5 µm). The mobile phase consisted of acetonitrile and 0.1% trifluoroacetic acid in water and was delivered at a rate of 0.9 ml/min. A simple and rapid sample preparation involved the addition of methanol to 200 µl of plasma to precipitate plasma proteins followed by direct injection of 50 µl of supernatant into the high-performance liquid chromatography system. The linearity range of the proposed method was 0.02 to 12 µg/ml. The intraday and interday coefficients of variation obtained from cefquinome were less than 5%, and biases ranged from -3.76% to 1.24%. Mean recovery based on low-, medium-, and high-quality control standards ranged between 92.0 and 93.9%. Plasma samples were found to be stable in various storage conditions (freeze-thaw, postpreparative, short-term, and long-term stability). The method described was found to be readily available, practicable, cheap, rapid, sensitive, precise, and accurate. It was successfully applied to the study of the pharmacokinetics of cefquinome in sheep. This method can be very useful and an alternate to performing pharmacokinetic studies in the determination of cefquinome for clinical use.

Automated monitoring of hemodialysis adequacy by dialysis machines: potential benefits to patients and cost savings.

Hemodialysis adequacy can be quantified using ultraviolet absorbance of the spent dialysate, or by analysis of dialysate conductivity at the dialyzer inlet and outlet in response to changes in dialysate electrolyte concentration. These measurements can be made at every dialysis, including initial and acute treatments and can help detect access recirculation. No disposables or reagents are required. Cost may be reduced by reducing the need for blood sampling and laboratory analysis.

A simplified UV spectrometric method for determination of peroxide value in thermally oxidized canola oil.

The aim of present study was to develop a simple method on UV spectrometer for the determination of peroxide value (PV) of the frying oil. The basis of the PV determination was the stoichiometric reaction of triphenylphosphine (TPP) with the hydroperoxides present in frying oil to produce triphenylphosphine oxide (TPPO), which exhibits a readily measurable absorption band at 240 nm by ultraviolet region. The PV ranged between 0.15 and 11.66 meq. of active oxygen per kilogram of oil as the canola oil was heated from 0 to 12h in the fryer at 180 degrees C. The proposed method was correlated with official AOCS titration method and best correlation coefficient (R(2)=0.99525) was achieved, proving that there is no significant difference in the results. Therefore, developed method could serve as an alternative to the titration method, for the determination of PV in frying oils.