Trace level determination of 1,4-benzodiazepines in blood by differential pulse polarography

Ma, Brooks; Mr, Hackman

doi:10.1021/ac60362a036

Cited by 20 publications

(8 citation statements)

References 19 publications

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“…This may confirm the reduction of the azomethine group of pymetrozine via the wellknown 2e /2H + mechanism (Halvorsen and Jacobsen 1972;Brooks and Hackman 1975;Livertoux and Bessiere 1987;Mercan, Yilmaz, and Inam 2007), which is represented by Figure 5. However, in this work, the mechanism was not investigated experimentally and further studies are needed to confirm these proposals.…”

Section: Influence Of Phsupporting

confidence: 73%

Voltammetric Behavior of the Insecticide Pymetrozine on a Mercury Meniscus Modified Silver Solid Amalgam Electrode

et al. 2015

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A novel sensitive voltammetric method for the determination of the insecticide pymetrozine was designed using a solid working electrode. A mercury meniscus modified silver solid amalgam Downloaded by [University of Leeds] at 12:58 03 October 20152 electrode in connection with differential pulse voltammetry was found to be appropriate for the determination of the insecticide. Pymetrozine provided one well-developed reduction peak suitable for analytical purposes at approximately 800 millivolts (versus the Ag/AgCl electrode)in an acidic medium. The voltammetric behavior of pymetrozine as a function of the pH of the supporting electrolyte and scan rate was investigated using cyclic voltammetry and direct current voltammetry, respectively. The optimum conditions for determination using differential pulse voltammetry were in a Britton-Robinson buffer at pH 3.0 with a limit of detection of 5.4 × 10 8 moles per liter and a linear dynamic range from 2 × 10 7 to 1 × 10 4 moles per liter. The relative standard deviations of repeated determinations (n = 5) at various concentrations of pymetrozine did not exceed 3 percent. The results obtained using silver solid amalgam electrode were compared with those achieved on hanging mercury drop electrode. The influence of possible interfering agents was also studied. The practical application of the method was verified by analysis of pesticide preparations and fortified river water. Keywordshanging mercury drop electrode, insecticide, mercury meniscus modified silver solid amalgam electrode, pymetrozine, voltammetry

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Section: Influence Of Phsupporting

confidence: 73%

Voltammetric Behavior of the Insecticide Pymetrozine on a Mercury Meniscus Modified Silver Solid Amalgam Electrode

et al. 2015

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“…The pulse polarography method enabling determination of even water-soluble metabolites without extraction, may be suitable for studying urinary metabolites, although it is rarely applied (Brooks and Hackman, 1975;de Silva, 1976;Ellaithy et al, 1977).…”

Section: Determination Of Nitrazepam and Its Metabolites In Urinementioning

confidence: 99%

Clinical Pharmacokinetics of Nitrazepam

Kangas

Breimer

1981

Clinical Pharmacokinetics

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Nitrazepam is one of the oldest benzodiazepines and is widely used as an hypnotic throughout the world, except North America, where it is not available. It is a safe hypnotic, with low acute toxicity and minor side effects. Development of tolerance or dependence and withdrawal symptoms are rare and very few known interactions with other drugs exist.The absorption of nitrazepam from the gastrointestinal tract is fairly rapid (t mJJx ranging 0.5 to 7 hours). The bioavailability after oral intake averages about 80 % . Maximum plasma concentrations after a single 5mg dose are of the order of 40ng/ml. As a Iipaphilic drug, nitrazepam is distributed rapidly in the body. The plasma levels can be filled to a 2-compartment open model. The a-phase is rather rapid and the elimination phase is characterised by a long half-life of about 30 hours; accumulation with daily use therefore occurs. Marked interindividual variation (up to JO-fold) is found in all pharmacokinetic parameters. Age and immobilising diseases may influence the parameters. evidently increasing Vd~ and tI12~'A similar amount of protein-free drug found in the plasma. i.e. JO to 15 % of the total plasma level. is found in the cerebrospinal fluid. In saliva the concentrations are significantly smaller. Nitrazepam penetrates the human placenta. In early pregnancy. the ratio of cord to maternal plasma concentration is about 0.5, 12 hours after drug administration. In late pregnancy, the ratio reaches 1 within afew hours. Breast milk concentrations are about one-half of those in maternal plasma.Nitrazepam has no clinically active metabolites. It is excreted mainly as conjugated and non-conjugated 7-aminonitrazepam and 7-acetamidonitrazepam. Polymorphic acetylation is not likely to be of clinical importance. Enzyme induction or significant loss of efficacy have not been found with long term use.There is no significant correlation between plasma concentrations and clinical effects (or side effects) of nitrazepam. Plasma level monitoring is therefore of no benefit clinically (except for special cases, e.g. in epileptic patients). Increased responsiveness in terms of therapeutic effects and side effects is evident in the elderly. Therefore, small doses not exceet!ing 5mg daily should be prescribed for geriatric patients.

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“…Levels of various diazepines in blood were accurately monitored at the 20-ng/ml (2 X 10" 8 M) level. 95 The absolute limit of the technique was the 10 ng contained in the cell.…”

Section: Nadh + (Dcpip) Ox D I°p H O R a S L Nad* + (Dcplp) Redmentioning

confidence: 99%