A rapid method for determining recent sunscreen use in field studies

The role of sunscreens in preventing skin cancer and melanoma is the focus of ongoing research. Currently, there is no objective measure which can be used in field studies to determine whether a person has applied sunscreen to their skin, and researchers must use indirect assessments such as questionnaires. We sought to develop a rapid, non-invasive method for identifying sunscreen on the skin for use in epidemiological studies. Our basic method is to swab the skin, elute any residues which have been adsorbed onto the swab by rinsing in ethanol, and submit the eluted washings for spectrophotometric analysis. In a controlled study, we applied 0.1 ml of sunscreen to a 50 cm(2) grid on both forearms of 21 volunteers. Each forearm was allocated one of 10 different sunscreen brands. The skin was swabbed after intervals of 20 min, 1 h, 2 h and 4 h. In a field study conducted among 12 children aged 2-4 years attending a child care centre, sunscreen was applied to the faces of half the children. Swabs were then taken from the face and back of all children without knowledge of sunscreen status. In the controlled study, sunscreen was clearly detectable up to 2 h after application for all brands containing organic sunscreen, and marginally detectable at 4 h. In the field study, this method correctly identified all children with and without sunscreen. We conclude that spectrophotometric analysis of skin swabs can reliably detect the presence of sunscreen on the skin for up to 2 h after application.     

A new fast method for field screening of polychlorinated biphenyls in air

A new fast method for the detection of a sum parameter for polychlorinated biphenyls in air is presented. Air pollutants are sampled on a thermodesorbable silicone-coated glass fibre filter. Analysis is carried out by a mobile GC-MS system with short GC columns. Total time for analysis in the field is about 10 min. A novel data evaluation is used for quantification. To evaluate the GC run, signals of the characteristic ion traces of each degree of chlorination are integrated. Superposition of ion fragments in the low-resolution GC run are eleminated by a special algorithm.     

A method for determining electrophoretic and electroosmotic mobilities using AC and DC electric field particle displacements

We have developed a method for measuring the electrophoretic mobility of submicrometer, fluorescently labeled particles and the electroosmotic mobility of a microchannel. We derive explicit expressions for the unknown electrophoretic and the electroosmotic mobilities as a function of particle displacements resulting from alternating current (AC) and direct current (DC) applied electric fields. Images of particle displacements are captured using an epifluorescent microscope and a CCD camera. A custom image-processing code was developed to determine image streak lengths associated with AC measurements, and a custom particle tracking velocimetry (PTV) code was devised to determine DC particle displacements. Statistical analysis was applied to relate mobility estimates to measured particle displacement distributions.     

A rapid method for determining sulfur in organic compounds

Conclusions A new, rapid method is given for determining sulfur. It is based on high-temperature pyrolysis of the compound.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1646–1648, July, 1968.     

A test method for determining water in organic solvents

A test procedure is developed for determining water in acetone, dioxane, isobutanol, ethanol, petroleum ether, and ethyl acetate in the ranges 0.5–12; 0.5–10; 0.5–8; 0.5–6, and 0.5–4 vol %, respectively. Determination is based on the measurement of the acidity of a solution obtained upon adding citric acid or sodium hydrogen sulfate to organic solvents using an indicator test strip containing Congo red. The relative standard deviation of the results of analysis is 0.05–0.1; the duration of analysis is about 30 min.     

A general method for the reductive dechlorination of 4,4-dichlorocyclobutenones

Exposure of 4,4-dichlorocyclobutenones to the action of zinc dust in ethanol containing 5 equiv each of AcOH and TMEDA results in smooth reductive dechlorination producing simple cyclobutenones.     

A chronoamperometric method for determining total antioxidant activity

A novel version of a chronoamperometric method of antioxidant determination is described. It is based on the use of the oxidation current of ferrocyanide formed in the reaction of antioxidants to be determined with potassium ferricyanide as an analytical signal. So the total concentration of all antioxidants present in the analyzed solution, i.e., total antioxidant capacity, is measured. The results of blood plasma analysis by the newly presented and certified potentiometry method are in good agreement with each other, R ² = 0.9980. The detection limit makes 2 × 10⁻⁶ M for uric and ascorbic acids and 5 × 10⁻⁶ M for cysteine and glutathione.     

A rapid method for determining strontium-90 in urine samples

Rapid bioassay methods for ⁹⁰Sr in urine samples are needed to provide an early estimation of possible internal dose resulting from exposure to radiostrontium in the event of a radiological and nuclear emergency. In this work, a fast column separation method followed by liquid scintillation counting for detection of ⁹⁰Sr in urine was developed. Replicate spike and blank samples were analyzed for performance evaluation of the method. Using this method, a detection limit of ~10 Bq L^?1 for ⁹⁰Sr can be achieved with a sample analysis turn-around time of 4 h for a set of 12 samples. The method is adequate to meet the radiobioassay acceptance criteria and is suitable for quick dose assessment of ⁹⁰Sr exposure following a radiation emergency.     

A method for determining the enantiomeric purity of profens

A simple method for determining the enantiomeric purity of profens (based on the carbon skeleton of 2-phenylpropionic acid) is discussed. The enantiomeric purity of a given profen can be determined by stereospecific DCC self-coupling to give a statistical diastereoisomeric mixture of racemic and meso- anhydrides. The relative ratio of diastereoisomers formed can be related to the enantiomeric excess of the original carboxylic acid.     

A new method for determining molecular masses of polyheteroarylenes

It is shown that the nondestructive ablation of polyheteroarylenes induced by submillimeter radiation of a free electron laser may be used to determine the molecular masses of polymers. The experimental procedure is described, and its results are compared with GPC data.     

A flow-injection amperometric method for determining antiviral guanine derivatives

A flow-injection method is proposed for determining antiviral guanine derivatives, acyclovir, valacyclovir, ganciclovir, and famciclovir, based on their amperometric detection on a carbositall electrode with a preactivated surface. The method is characterized by a wide analytical range, relatively low detection limits (0.6–1.2 μg/mL), and high performance (75 h^–1). The results of examination of the accuracy and reproducibility of the analysis of solutions of different pharmaceutical forms containing the test substances are presented. The potentials of the developed flow-injection method in the implementation of the “Dissolution” test in an automated mode are demonstrated.     

A fluorometric method for determining trace quantities of phosphate

Summary A method has been developed for the determination of microgram quantities of phosphate based upon fluorescence quenching by phosphate of the aluminum-morin chelate. A variety of other metal-chelates of aluminium, gallium, and zirconium with morin, 3-hydroxyflavone, and quercetin were examined but none proved as satisfactory as the aluminummorin for the determination of phosphate.

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Zusammenfassung Ein Verfahren zur Bestimmung von Mikrogrammengen Phosphat wurde entwickelt. Es beruht auf der Fluoreszenzlöschung von Aluminmm-Morin-Chelat durch Phosphat. Eine Reihe anderer Chelate des Aluminiums, Galliums und Zirkons mit Morin, 3-Hydroxyflavon und Quercetin erwies sich für diesen Zweck nicht geeignet.

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Résumé On a mis au point une méthode pour le dosage des phosphates en quantités de l'ordre du microgramme; elle repose sur l'extinction de la fluorescence du chélate aluminium-morin par les phosphates. On a examiné divers autres chélates métalliques de l'aluminium, du gallium et du zirconium avec le morin, l'hydroxy-3 flavone et la quercétine, mais aucun d'entre eux ne s'est montré aussi satisfaisant que le système aluminium-morin pour le dosage des phosphates.

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The opinions or assertions contained in this paper are the private ones of the authors and are not to be construed as official or reflecting the views of the Naval Service at large.     

A fluorometric method for determining trace quantities of fluoride

Summary A very selective method has been developed for the determination ofg quantities of fluoride based on the fluorescence quenching by fluoride of the zirconium-flavonol chelate. The fluorescence intensity is read at 460 nm. The reduction in fluorescence intensity caused by the fluoride is a measure of the fluoride concentration present.

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Zusammenfassung Eine sehr selektive Methode zur Bestimmung von Mikrogrammengen Fluorid mittels Fluoreszenzlöschung von Zirkonium-Flavonol-Chelat wurde ausgearbeitet. Die Messung erfolgt bei 460 nm. Die Herabsetzung der Fluoreszenzintensität entspricht der Fluoridkonzentration.

     

A method for the determination of polonium in air

A method for²¹⁰Po determination in air is developed which includes sucking of known volume of air through aerosol filter typ AFA-XA, wet combustion of the filter by a mixture of conc. H₂SO₄ and conc. HNO₃, deposition of²¹⁰Po on nickel plate from hydrochloric acid solution at 90°C. The chemical yield is (90.7±5.4)% and radioisotope purity of the final sample (concerning α-emitters) fully satisfactory. If 3 m³ air is sucked the detection limit is 10⁻¹⁷ Cf²¹⁰Po/1 air.     

An improved method of determining surface area by the adsorption of air

Summary A simple method has been proposed for the rapid approximate determination of specific surfaces by the adsorption of air at a low temperature.