Analytical Letters

doi: 10.1080/00032718908052404pmid: N/A

Abstract This is a scanned image of the original Editorial Board page(s) for this issue.

Chemnitius, Gabriele C.; Schtnid, Rolf D.

doi: 10.1080/00032718908052405pmid: N/A

Abstract A flow injection system for the enzymatic determination of L-malate is described. It is adapted for the analysis of wines and fruit juices by in-line sample dilution. Malate dehydrogenase (MDH) and aspartate aminotransferase (AST) were coimmobilized on controlled pore glass. The NADH generated in the packed bed bienzyme reactor was detected fluorimetrically. Sufficient L-malate conversion could be achieved using the coupled transferase reaction to transform the reaction product oxaloacetate. The linear range of the unmodified flow injection system, 5 – 100 μ M of L-malate, could be increased up to 50 mM by means of zone sampling so that untreated samples could be analyzed directly. From 12 – 20 samples per hour could be analyzed with a standard deviation of less than 2 % depending on variation in the degree of dilution. The activity of the bienzyme reactor decreased less than 4% over an analysis period of 3 weeks with more than 1200 injections.

Suzuki, Masayasu; Suzuki, Hiroaki; Karube, Isao; Schmid, Rolf D.

doi: 10.1080/00032718908052406pmid: N/A

Abstract A disposable type micro enzyme sensor was constructed using a Clark-type micro oxygen electrode and immobilized xanthine oxidase (EC 1.1.3.22) for the assay of hypoxanthine which is an important marker for the fish freshness estimation. The sensor showed a good response to hypoxanthine and allowed the determination of hypoxanthine in the concentration range between 6.7 – 180 μM.

Glazier, S. A.; Rechnitz, G. A.

doi: 10.1080/00032718908052407pmid: N/A

Abstract This report describes the construction and characterization of an oxalate-sensing electrode. The electrode is based on the incorporation of ground beet stem into the graphite paste of a graphite paste electrode. The hydrogen peroxide generated by enzymatic degradation of oxalate is monitored at a working voltage of 0.900 V vs SCE. All measurements were conducted in a succinic acid/EDTA buffer at pH 4.00. Under these conditions, the electrodes exhibit reproducible responses to oxalate. The lower limit of oxalate detection was less than 1.03 × 10−4 M. The time to achieve a steady state response after exposure to a step change in oxalate concentration in solution is less than one minute. The magnitude of response to oxalate over the oxalate concentrations studied varies among several electrode tested as does the degree of linearity of response. An electrode studied still exhibited analytically useful responses to oxalate on the 15th day of its use. The beet stem-based electrodes display little response to glycolic acid, glucose, DL-valine, or pyruvate.

Yokoyama, Kenji; Tamiya, Eiichi; Karube, Isao

doi: 10.1080/00032718908052408pmid: N/A

Abstract An integrated micro-glucose sensor which was apparently unaffected by the concentration of dissolved oxygen was developed. This sensor consisted of both a mediated glucose sensor (MGS) and an O2-based glucose sensor (OGS) using glucose oxidase. The responses of both MGS and OGS were affected by concentration of dissolved oxygen. However, the responses of MGS were corrected on the basis of those of OGS. Then the precise glucose concentration was obtained from the following equations under several oxygen concentrations. Y+2. 1×10−1 Z+1.9×10−3Z2−6.4×10−5Z3+5. 7×10−9Z4= 6.5×10−1G+2.5×10−3G2−2. 0×10−5G3+4.7×10−8G4−3.7×10−11G 5 X = 104/(103V+G) where X, Y, Z, G and V are glucose concentration (mg/dl), response of MGS (nA), response of OGS (nA), injection volume of 10 g/dl glucose solution (μl) and initial volume (ml), respectively.

Mandenius, Carl Fredrik; Chollet, Andre; Mecklenburg, Michael; Lundström, Ingemar; Mosbach, Klaus

doi: 10.1080/00032718908052409pmid: N/A

Abstract Detection of DNA-binding and hybridization using pseudo-Brewster angle reflectometry and ellipsometry is described. DNA was attached to planar silicon surfaces coated with a 150 Å layer of nitrocellulose or with a monolayer of aminosilane. Poly-L-lysine was used as a linker between the modified surfaces and the DNA. The course of the reassociation was monitored continuously with the reflectometry method. A reassociation time of approximately one hour was observed for polynucleotides of 0.5–1.0 kb.

Alvarado, José; Cavalli, Paolo; Omenetto, Nicolo; Rossi, Guglielmo; Ottaway, John M.; Littlejohn, David

doi: 10.1080/00032718908052410pmid: N/A

Abstract A carbon rod atomizer was used for sample introduction into a commercial inductively coupled plasma for the determination of lead in whole blood. Samples of known lead concentration were either treated with Triton-X or nitric acid or diluted 1+5 with distilled water and analyzed by comparison against graphs obtained using aqueous solutions and using the standard additions method. Both approaches produced similar results indicating no appreciable matrix influence. The Pb concentration values obtained were in close agreement with those previously determined by ETA-AAS, Delves′ cup-FAAS and anodic stripping voltammetry. Signal integration and careful selection of the measurement period were critical to obtain accurate results. Derived concentrations were shown to be essentially independent of the heating rate of the vaporization unit and the length of tubing used to transport the material into the plasma. Using a 1 μg ml−1 lead aqueous standard, a signal to background ratio of 5.5 was obtained under optimized conditions. Relative standard deviations of the blank and the analytical signal were 0.2 and 1.8%., respectively. An aqueous solution detection limit of 0.007 μg ml−1 was calculated for lead.

Fu, Chauhwei J.; Mason, William D.

doi: 10.1080/00032718908052411pmid: N/A

Abstract A simplified high performance liquid chromatographic method was developed to determine the levels of nifedipine in human plasma. Nifedipine and the internal standard, 11-ketoprogesterone, are extracted from alkalinized plasma into organic solvent. The organic solvent is then evaporated to total dryness and the analytes are reconstituted with mobile phase and chromatographed. The limit of quantitation is 10 ng/ml using a 1.0 ml plasma sample.

Al-rikabi, A. M. K.; Al-jabri, F. M.; Hasoon, S. J.

doi: 10.1080/00032718908052412pmid: N/A

Abstract Titrimetric method for the determination of (1–100) mg/L iron(II) as pure solutions and in its dosage forms was investigated and found to offer an improvement in ease, speed and accuracy. This method is based on the direct visual titration of iron(II) with ceric amnonium sulphate and employs chlorpromazine hydrochloride in a mixture of sulphuric and phosphoric acids as a redox indicator. An interference study is carried out for the differant acids and cations. Data obtained for sevceral pharmaceuticals are reported and compared with those obtained potentiometrically. Formal redox potential was determined to be 285 mv.

Zakhari, N. A.; Hassan, S. M.; El-shabrawy, Y.

doi: 10.1080/00032718908052413pmid: N/A

Abstract A sensitive colorimetric method has been devised for microdetermination of six indole derivatives; ergotamine tartrate, methylergometrine maleate, dihydroergocornine methanesulphonate, dihydroergocristine methanesulphonate, dihydroergocryptine methanesulphonate and pindolol, both in pure form and in pharmaceutical preparations. The method is based on the reaction of indole moiety with diazotised 4-nitroaniline in buffer solution of pH 6 to produce a stable yellow monoazo dye. Beer's law is obeyed over final concentration ranges 8–32 μgm1−1 for ergotamine tartrate, 4–48 μgml−1 for methylergometrine maleate, 8–56 μgml−1 for dihydro-ergot alkaloids and 1–10 μgml−1 for Pindolol with apparent molar absorptivity range (7.62 × 103−2.61 × 104) 1.mole−1.cm−1. A study has been made to determine the optimum conditions of the colour reaction.