Search

Objectives To evaluate the benefits of therapeutic drug monitoring (TDM) in association with genotypic resistance testing and expert advice to optimize therapy in multiexperienced patients infected with HIV-1. Methods Patients with a viral load>1000 HIV-1 RNA copies/mL and an unchanged antiretroviral therapy regimen over the last 3 months were randomized into two groups: a genotypic group (G) and a geno-pharmacological group (GP). Treatment was selected by an expert committee according to genotypic resistance testing (the G and GP groups) and TDM (the GP group) at week 4. Treatment could be modified at each visit according to toxicity, poor virological response and TDM. Results of TDM were withheld from the G group until week 12. The primary endpoint of the study was the percentage of patients with viral load

A fiber optics refractometer has been developed based on a simple low‐volume cell (5–7 μl) which confines the liquid to be measured around a waveguide whose multiple reflections can enhance the contrast at the critical angle. The electromechanical and electrooptical design allows the fiber optics refractometer to measure absolute refractive index with manual or automatic readout, and differential operation with automatic tracking that permits its use as a universal detector for gradient elution chromatography. Present sensitivity is approximately 1×10−5 refractive index units in the static mode and 7×10−5 refractive index units in the scanning beam mode. These sensitivities can probably be improved by a factor of 5 by appropriate system changes.

Electron Spectroscopy for Chemical Analyses (ESCA) has been used to examine surfaces of safety glass specimens. These specimens consisted of tin float glass laminated with plasticized polyvinyl butyral. ESCA was used to characterize the glass surface after the plasticized polyvinyl butyral had been peeled away. The results show clearly that the specimens fail cohesively and a layer of the plasticized polyvinyl butyral is left on the glass surface. The thickness of this layer was measured and was found to be directly proportional to the force of adhesion, measured as 90° peel strength.

A rapid and accurate atomic absorption method for the determination of chromium in faeces samples from pasture experiments using chromic oxide ‘markers’ is described. Of the elements present after ashing and digesting the samples in a phosphoric acid—manganese sulphate—potassium bromate solution silicate, aluminium, calcium and magnesium were found to interfere in the determination. The effects of these interferences were overcome by the addition of calcium to the test solution and by the addition of silicate to the standards, which were prepared in ‘blank’ solutions.The sensitivities of a number of alternate chromium resonance lines relative to that of Cr 3578·7 Å. are given. These lines may be used to increase the concentration range of the analysis.The results of a comparison of the atomic absorption method with a chemical method are given.

Methods are proposed for the determination of cadmium in soils, plants and fertilizers. Soil is first dissolved by treatment with hydrofluoric and hydrochloric acids and plant material is digested with nitric‐perchloric‐sulphuric acids. The cadmium is then extracted from the resulting solutions as the dithizone complex. After destruction of the dithizone the cadmium is dissolved in dilute hydrochloric acid and determined by atomic absorption spectroscopy. Cadmium in phosphatic fertilizers is determined directly by atomic absorption measurement on hydrochloric acid digests of the fertilizer. The proposed methods have precision adequate for the study of cadmium in soil‐plant systems, the limits of detection being: plant material, 0.004 ppm Cd; soils, 0.02 ppm; and phosphatic fertilizers, 1 ppm.

In these methods of analysis the sample is subjected to temperatures at which its constituent compounds are dissociated into free atoms or converted to temperature-stable molecules. In emission methods, use is made of the fact that a small proportion of the free ground-state atoms or molecules present in a flame, arc or spark are excited to energy levels above the ground-state by heat or electrical effects, then dissipate this energy, either directly or stepwise, by emission of light at wave-lengths characteristic of the atomic or molecular species involved; atomic absorption analysis is based on the fact that free ground-state atoms of an element are capable of absorbing light at the same wave-lengths as the light which they would emit if excited to energy levels above the ground-state.

It is claimed that the concentration of strontium in Bowen's standard kale (Analyst, 1967, 92, 124) is 101·13 ± 2·38 p.p.m., on evidence that X-ray fluorescence values obtained subsequently to Bowen's inter-laboratory comparison were in good agreement at 101 p.p.m. with atomic-absorption values obtained in this laboratory by using anion exchange and the addition method, but not reported separately from other atomic-absorption results by Bowen. Methods used in obtaining the neutron-activation results and these other atomic-absorption results implied in the inter-laboratory comparison should be examined for serious interferences.

RECENT work reported by Menzies1 and Robinson2 has suggested that atomic absorption flame methods3,4 are not applicable to the determination of molybdenum and that the limit of strontium determination lies between 2 and 10 p.p.m. in solution.

Earlier published work on the determination of molybdenum with an incandescent air-acetylene flame showed that aluminium could be used effectively to suppress the interferences of such elements as strontium, calcium, manganese and iron, but this has not been confirmed for manganese and iron by other workers. Indications are that this is caused by instrumental characteristics. Ammonium chloride, subsequently shown to be effective in the suppression of manganese and iron interference in metallurgical analysis, was found to suppress the interferences of alkaline earth chlorides, but to have no effect on a severe interference by calcium ion, sulphate and phosphate in combination. As aluminium ion was found to suppress this interference, a mixture of aluminium and ammonium chlorides is suggested for general application.