New analytical approaches in clinical chemistry

Millions of chemical analyses are performed in clinical laboratories every day, and the demand of the medical profession for increasingly accurate and specific assays continues to grow. This has resulted in the development of many new techniques and, just as important, the use of proven analytical systems in novel ways.     

The behaviour of an electrochemical detector used in liquid chromatography and continuous flow voltammetry: Part 2. Evaluation of low-temperature isotropic carbon for use as an electrode material

Unalloyed Pyrolyte, a low-temperature isotropic carbon (LTIC) material is evaluated electrochemically for use as an electrode material in h.p.l.c. thin-layer electrochemical detection cell systems. LTIC is compared to carbon paste electrode material in all systems studied, and to glassy carbon impregnated with ceresin wax in the hexacyanoferrate(II)/(III) redox system. Electrode areas, residual currents, and potential windows are described. Quantitative kinetic studies are reported for the hexacyanoferrate(II)/(III) redox pair in 2.0 M KCl, and rate constants are given. Quantitative rate constant studies are also reported for o-dianisidine in 1.0 M H₂SO₄. Finally, qualitative rate comparisons are made by cyclic voltammetric techniques between carbon paste and LTIC electrode materials for maetanephrine, normetanephrine, adrenaline, noradrenaline, dopamine, 3,4-dihydroxyphenylalanine, 5-hydroxytryptophan, and chlorpromazine in chemical systems reflecting previous applications of h.p.l.c. with electrochemical detection.     

The coulometric titration of tetraphenylborate ion with electrogenerated silver ion and a biamperometric end-point : Application to the determination of potassium and polyethyleneglycols

Microequivalent amounts of TPB in a 40% acetone generating electrolyte were titrated with coulometrically generated silver ions. With a biamperometric endpoint, samples of 0.1–4 μeq of NaTPB were determined with a precision with 1%. The technique was applied to the determination of potassium in potassium chloride alone and in mixtures with other salts.The overall accuracy ranged from -3 to -7% for samples of 4 μeq to 1 μeq of potassium, respectively. Artificial serum samples gave somewhat discordant results, because of difficulty in removing all interfering protein. A method was developed, for the determination of 0.1–1.0 mg of PEG 600 to 4000 with excess TPB in the presence of barium ions. With reasonable care errors may be held to within 5%.     

Studies of intrinsic luminescence in KCl

Measurements have been made of the luminescence intensity, lifetime, emission spectra, and thermoluminescence associated with self-trapped exciton states in KCl, at temperatures of 7°K and above. These results indicate the presence of another exciton-like state in addition to the well-known state that decays by emission at 2.32 eV. Thermoluminescence glow peaks and spectra are correlated with F + V_k and F + H recombination processes.     

Tunable cavity optomechanics with ultracold atoms

We present an atom-chip-based realization of quantum cavity optomechanics with cold atoms localized within a Fabry-Perot cavity. Effective subwavelength positioning of the atomic ensemble allows for tuning the linear and quadratic optomechanical coupling parameters, varying the sensitivity to the displacement and strain of a compressible gaseous medium. We observe effects of such tuning on cavity optical nonlinearity and optomechanical frequency shifts, providing their first characterization in the quadratic-coupling regime.     

Integrating cavity quantum electrodynamics and ultracold-atom chips with on-chip dielectric mirrors and temperature stabilization

We have fabricated an atom chip device which combines the circuitry for magnetic trapping of cold atoms with high-finesse optical resonators suitable for cavity QED in the single-atom strong coupling regime. Fabry–Pérot optical resonators with finesse were formed between a micropatterned on-chip planar mirror with lateral dimension of ≤ 100 μm and a curved mirror suspended above the chip. The strong and rapid thermal coupling between on-chip electrical and optical elements was utilized to stabilize the cavity mirror separation with servo bandwidth exceeding 100 kHz during simulated operation of the atom chip. PACS 42.50.Pq; 03.75.Be; 42.82.Cr