Octadecylsilyl Research Articles

Methods for concentration of urinary immunoreactive insulin.

Insulin is readily concentrated from 10 to 50 ml of urine with better than 75% recovery using octadecylsilyl (ODS) silica columns (C18Sep-Pak cartridge) and can then be measured by radioimmunoassay. Fractionation on Sephadex G50 gel filtration reveals that the apparent immunoreactivity corresponds for the most part to 6000 dalton insulin. Renal clearance of insulin in 5 normal subjects does not appear to differ in the fasted or fed state and ranged from 0.34 to 0.58 ml/min with an average of 0.44 +/- 0.10 (S.D.) ml/min. Increased urinary insulin output was observed following feeding and fell during prolonged fasting. Insulin output in urine from 7 non-diabetic subjects ranged from 11 to 39 mU/24 hr, averaging 25 +/- 10 mU/24 hr. In normal subjects without renal disease a single determination of renal insulin clearance and a timed urinary insulin output appear to be sufficient for determination of mean plasma insulin during that time period. Concentration of urine using this methodology could provide the material for HPLC screening for abnormal insulins and for their subsequent purification to determine the site of change in amino acid sequence.

High Performance Liquid Chromato-Graphic Method For The Determination Of Permethrin Deposits In A Forestry Spray Trial

Abstract A convenient and sensitive reversed-phase high performance liquid Chromatographie method has been developed for the determination of perraethrin [3-phenoxybenzyl (±)- cis,trans -3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] insecticide. Various isocratic and gradient mobile phases, consisting of acetonitrile:water (CH3CN:H2O) and methanol:water (CH3OH:H2O) solvent systems at two flow rates, were tested to separate and quantify the Isoners of permethrin using octadecylsilyl (ODS) (Regis 5μ m) and octylsilyl (OS) (RP-8, 10 μ m) bonded columns. The optimal mobile phase for perraethrin using the ODS column was 70:30 (v/v) CH3CN:H2O mixture at flow rates of either 1.0 or 1.5 mL/min. The measurement was done with a UV detector at 200 nm and 50°C. The OS column gave a less satisfactory separation than the ODS. Gradient elution systems examined did not improve the iso-meric separation of perraethrin. Using the method developed, deposit levels obtained on various sampling units during a perra...

Solute Retention in Column Liquid Chromatography. VII. Reduction of Mass-Transfer Non-Equilibrium and Analysis Time

Abstract Retentions are reported for the test solutes benzene and the polycyclic aromatic hydrocarbons (PAH) naphthalene, biphenyl, anthracene, and fluoranthene with columns containing mechanical mixtures of (inert diluent) Spherisorb silica + (active sorbent) Spherisorb octadecylsilyl (ODS) derivatized silica with methanol:water mobile phase. All solutes elute in one column volume with neat silica diluent packing, while both the extent of separation as well as analysis time increase as the amount of ODS phase is increased. Plots of the reduced plate height h against the reduced linear carrier velocity v show that the column efficiency with pure diluent phase is a factor of two superior to that containing neat active sorbent at vopt. However, an anomalous rise in h is found at v less than vopt. The capacity factors of the solutes increase linearly from zero as the amount of active phase is increased, hence limiting the permissible sample size at high packing dilution; there also occur some inversions of retention order. Dilution of lc sorbents with inert packings is thereby shown to provide quantitative control over column efficiency, analysis time and, potentially, selectivity. The technique is claimed to offer particular advantage in microbore-column liquid chromatography.

Development and validation of a specific radioimmunoassay for PHI in plasma

A sensitive and specific radioimmunoassay for the recently isolated neuropeptide with N-terminal histidine and C-terminal isoleucine amide (PHI) has been developed which can detect 3.0 pmol/l of the peptide in plasma. The routine antiserum produced in rabbit had a titre of 1 : 800 000 and recognized the sequence 3–8 of the 27 amino acid peptide. Labelling of PHI with 125I was performed by the chloramine T method, and labelled PHI was separated from unlabelled on an octadecylsilyl (ODC)-silica column. Non-specific interference in the assay was excluded by extraction of plasma with ethanol to a mean recovery of 82.4%. Plasma samples diluted parallel to the standard curve and behaved as PHI on ODC-silica column. The intra-assay and inter-assay coefficient of variation (CV) values at a level of 24.0 pmol/l were 6.3% and 13.1%, respectively. In 75 normal adults, the fasting PHI concentration ranged from 3.5–30.0 pmol/l with a mean of 14.2 pmol/l. In 235 children, the PHI concentration varied with age. Ingestion of a meal caused a rapid and short-lived increase in the PHI concentration.

Urinary immunoreactive gastrin in normal subjects.

Gastrin can readily be concentrated from 10 to 50 ml of urine with better than 90% recovery using octadecylsilyl (ODS) silica columns (C18 Sep-Pak cartridge) and then measured by radioimmunoassay. Fractionation on Sephadex G50 gel filtration reveals that the apparent immunoreactivity is not due to nonspecific interference in the assay system but does correspond to the two known forms of gastrin, the 17 and 34 amino acid peptides. Renal clearance of gastrin in 5 normal subjects does not appear to differ in the fasted and fed state and ranged from 0.09 to 0.26 ml/min with an average of 0.16 +/- 0.05 (S.D.) ml/min. Urinary gastrin excretion in the overnight fasting state was generally less than 0.005 pmol/hr/kg body weight and fell to lower levels after a 20-hour fast. Increased urinary gastrin output was observed following feeding. Gastrin output in urine in 7 subjects ranged from 6.8 to 10.2 pmol/24 hr with an average of 8.5 +/- 1.5 (S.D.) pmol/24 hr. A single determination of renal gastrin clearance and 24-hour gastrin urinary output appears to be sufficient for the determination of averaged plasma gastrin levels in normal subjects without renal disease. Similar methodology should be applicable to a variety of other peptidal hormones as well.

Pharmacokinetics and biotransformation of the prostacyclin analogue, ZK 36 374 III. Development of a radioirmunoassay and its application to the pharmacokinetics of ZK 36 374 in the rat

The development of a radioimmunoassay for ZK 36 374, a chemically stable prostacyclin analogue, and its application to the pharmacokinetics of the drug in the rat is described. Antiserum against ZK 36 374 was raised in rabbits by immunization with ZK 36 374 coupled to bovine serum albumine via the carboxylic group. ZK 36 374 is extracted from plasma samples and purified from matrix constituents by means of octadecyl silyl cartridges. At a plasma concentration of 2.5 ng/ml intra- and interassay variations are 6 and 7 %, respectively. The limit of detection is 0.5 ng/ml. After intravenous administration of 200 μg/kg to female Wistar rats a biphasic decline of the drug concentration in the plasma was observed with half-lives of 5 min and 3 h. Oral doses of 200 and 2000 μg/kg were very rapidly absorbed reaching maximum plasma levels of 3 and 32 ng/ml as early as 10–15 min p.admin.. Bioavailability at the two dose levels was calculated to be 8 and 13 % of dose. Disposition was biphasic, as well, with a somewhat prolonged β-phase after the highest dose.

Evidence against insulin synthesis BY IM-9 lymphocytes.

Insulin concentrated from acid/ethanol extracts of IMg lymphocytes by the use of octadecylsilyl (ODS) silica cartridges averaged 0.13 ng/ml cell volume compared with the 0.12 ng insulin/ml cell culture medium. The insulin content of these cells appears to be less than 1% of previously reported values and probably could be accounted for by concentration of insulin from the incubation medium on cell receptors.

The retention mechanism of some alkane and benzene derivatives on octadecylsilyl and trimethysilyl silica in gas chromatographic columns

Gas chromatography net retention data of a number of mono-substituted alkane and benzene derivatives on trimethylsilyl, octadecylsilyl (ODS) and trimethylchlorosilane treated ODS Porasil C have been measured at 160° and interpreted in terms of the adsorption model of Snyder. On the basis of plausible assumptions, the interaction of apolar samples with the ODS chains is separated from that with the adsorbent surface underneath. For polar samples, the effects of these two interaction mechanisms cannot be distinguished.