Simultaneous Assay of Corticosterone and Cortisol in Plasma by Reversed-Phase Liquid Chromatography

1992 ◽  
Vol 38 (3) ◽  
pp. 346-352 ◽  
Author(s):  
M Hariharan ◽  
S Naga ◽  
T VanNoord ◽  
E K Kindt
Keyword(s):  
Extraction Method ◽  
Solid Phase ◽  
Internal Standard ◽  
Reversed Phase ◽  
Reversed Phase Liquid Chromatography ◽  
Ultraviolet Detector ◽  
Liquid Chromatographic Method ◽  
Analytical Recovery ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract We have developed a simple, specific, and sensitive reversed-phase liquid-chromatographic method for accurate and simultaneous analysis of corticosterone and cortisol in human plasma. We achieved a detection limit of 300 ng/L for both steroids by modifying the old solid-phase extraction method to make use of "Tef Elutor" C18 columns, using a minibore (100 x 2 mm) analytical column, and using an ultraviolet detector with a 10-mm-pathlength flow cell. With the new extraction method absolute extraction efficiencies were greater than 90% for all the analytes, including the internal standard, flumethasone. The mobile phase was water (containing 5 mL of triethylamine per liter and citric acid to adjust the pH to 6.5), tetrahydrofuran, and acetonitrile (82/10/8 by vol). The average interassay CV for corticosterone at 0-25 micrograms/L was 6.5%; that for cortisol at 0-300 micrograms/L was 3.8%. The analytical recovery relative to the internal standard was 100.2% for cortisol and 102.6% for corticosterone. Possible interferences from drugs and other steroids were studied.

scholarly journals Liquid Chromatographic Method for Determining Thiodicarb in Technical Products and Formulations: CIPAC Collaborative Study

1998 ◽  
Vol 81 (2) ◽  
pp. 341-343
Author(s):  
Alan R Hanks ◽  
◽  
J Abedi ◽  
E De Aguila ◽  
F Bodzian ◽  
...  
Keyword(s):  
Chromatographic Method ◽  
Collaborative Study ◽  
Internal Standard ◽  
Reversed Phase ◽  
Reversed Phase Liquid Chromatography ◽  
Liquid Chromatographic Method ◽  
Wettable Powder ◽  
Phase Liquid ◽  
Liquid Chromatographic ◽  
Technical Products

abstract A liquid chromatographic method for determining thiodicarb in technical products and formulations was evaluated by 25 participants from 19 laboratories. Data from 19 laboratories were used in statistical analysis to characterize method performance.Two technical materials, a suspension concentrate, a wettable powder, and a water dispersable granule were analyzed. Thiodicarb was determined by reversed-phase liquid chromatography using a mobile phase of methanol and water. Chromatography was performed on a C8 column with detection at 254 nm. Quantitation was achieved by using an internal standard and peak area ratios.

Simple, optimized liquid-chromatographic method for measuring total hydroxyproline in urine evaluated

1991 ◽  
Vol 37 (2) ◽  
pp. 285-290 ◽  
Author(s):  
P Reed ◽  
I B Holbrook ◽  
M L G Gardner ◽  
J R McMurray
Keyword(s):  
Solid Phase ◽  
Colorimetric Method ◽  
Internal Standard ◽  
Ion Exchange Resin ◽  
Reversed Phase ◽  
Standard Curve ◽  
Liquid Chromatographic Method ◽  
Analytical Recovery ◽  
Assay Time ◽  
Liquid Chromatographic

Abstract We have optimized a method for measuring total hydroxyproline (HYP) in urine by HPLC after release from urinary peptides by solid-phase hydrolysis on Dowex 50W x 8 ion-exchange resin. The HYP was derivatized with 4-chlor-7-nitrobenzo-2-oxa-1,3-diazole, and excess reagent was removed with the use of a 100-mg C18 Bond-Elut cartridge. The HYP derivative was separated isocratically at 30 degrees C on a 250 x 4.6 mm reversed-phase column containing 5-microns particles of Spherisorb S5 ODS-2, with S-carboxymethylcysteine as internal standard. Total assay time was 14 min. The standard curve for the method was linear from the detection limit for HYP, 3.6 mumol/L, to 10 mmol/L. The between-batch CV was less than 5.1% and the mean analytical recovery of HYP was 95% +/- 1.4%. Comparison with a commercially available colorimetric method showed good correlation: y = 1.158x + 19.76 mumol/L (Syx = 74, n = 120), but HPLC results were 15% higher, probably from incomplete hydrolysis with the colorimetric method. This method offers a considerable improvement in assay time, specificity, sensitivity, precision, and cost compared with the colorimetric method.

scholarly journals Liquid Chromatographic Method to Determine Narasin in Feedingstuffs and Premixtures: Development, Validation, and Interlaboratory Study

2004 ◽  
Vol 87 (6) ◽  
pp. 1278-1286 ◽  
Author(s):  
Alfred Thalmann ◽  
Klaus Wagner ◽  
Marinka Tomassen ◽  
Jaap Driessen ◽  
Jacob de Jong ◽  
...  
Keyword(s):  
Chromatographic Method ◽  
Reversed Phase ◽  
Feed Additives ◽  
Interlaboratory Study ◽  
Reversed Phase Liquid Chromatography ◽  
Extraction Solvent ◽  
Limit Of Determination ◽  
Liquid Chromatographic Method ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract A reversed-phase liquid chromatography (LC) method for narasin in feedingstuffs and premixtures was developed, validated, and interlaboratory studied. The extraction solvent was methanol–K2HPO4 solution (9 + 1, v/v). Narasin was detected at 600 nm after post-column derivatization with dimethylamino-benzaldehyde. Recovery was >90%. The repeatability (RSDr) in feed (20–140 mg/kg) ranged between 1.2 and 10.5%; the within-laboratory reproducibility (RSDR) ranged between 2.2 and 4.9%. The limit of determination was <20 mg/kg. Other feed additives did not interfere in the assay. The method showed ruggedness against changes in the composition of extraction solvent, eluent, and conditions for post-column reactions. In an interlaboratory study, 5 broiler feeds (4 positive, 1 blank) and 1 premixture were analyzed by 13 laboratories. The RSDr of the feedingstuffs (20–120 mg/kg) varied between 2.17 and 7.57%. The HORRAT ranged between 0.77 and 0.88, with recoveries between 82 and 104%. One laboratory detected small signals in the blank sample, calculated as 0.6 and 2.8 mg/kg. For the premixture, acceptable results for reproducibility could only be obtained after modification of the method: the RSDr was 4.42% and the HORRAT was 1.56 (12 laboratories).

Determination of Dicloxacillin Preparations by Liquid Chromatography

1992 ◽  
Vol 75 (1) ◽  
pp. 26-29 ◽  
Author(s):  
Mei-Chich Hsu ◽  
Yann-Jen Fann
Keyword(s):  
Internal Standard ◽  
Pharmaceutical Preparations ◽  
Standard Addition ◽  
Reversed Phase ◽  
Microbiological Method ◽  
Absorbance Detection ◽  
Liquid Chromatographic Method ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract A reversed-phase liquid chromatographic method was developed for the assay of dicloxacillin In bulk drugs and pharmaceutical preparations. The samples were analyzed on a μBondapak (C18) column with a mobile phase of methanol-4% acetic acid (60 + 40) at a flow rate of 1.5 mL/mln, with UV absorbance detection at 254 nm. An equation was derived showing a linear relationship between peak area ratios of dicloxacillin to dimethylphthalate (internal standard) and the dicloxacillin concentration over a range of 2-30 μg (r = 0.9999). Standard addition recoveries ranged from 98.65 to 100.74% (mean 99.70%, n = 6). The coefficient of variation was less than 0.24%. The assay results were compared with those obtained by the official microbiological method, which indicated that the proposed method Is a suitable substitute for the microbiological method for potency assays and stability studies of dicloxacillin preparations.

Simultaneous very fast liquid-chromatographic analysis of ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine in serum.

1983 ◽  
Vol 29 (3) ◽  
pp. 473-476 ◽  
Author(s):  
P M Kabra ◽  
M A Nelson ◽  
L J Marton
Keyword(s):  
Particle Size ◽  
Flow Rate ◽  
Chromatographic Analysis ◽  
Mobile Phase ◽  
Internal Standard ◽  
Reversed Phase ◽  
Ultraviolet Detector ◽  
Analytical Recovery ◽  
Liquid Chromatographic Analysis ◽  
Liquid Chromatographic

Abstract We describe a sensitive, specific, and very fast liquid-chromatographic assay for simultaneously determining five anticonvulsants (ethosuximide, primidone, phenobarbital, phenytoin, and carbamazepine) by using commercially available 5- or 3-microns particle size reversed-phase columns and a microflow-cell-equipped ultraviolet detector. The anticonvulsant drugs are extracted from 200 microL of serum containing 50 mg of cyclopal per liter as an internal standard, by elution from a Bond-Elut (Analytichem International, Harbor City, CA 90710) column with 300 microL of methanol. A 5-microL aliquot of the eluate is applied to an analytical column and eluted with a mobile phase of acetonitrile/methanol/phosphate buffer, 20 mmol/L, pH 3.7 (13.5/35/51.5 by vol), at a flow rate of 3.0 mL/min and at 50 degrees C. Detection is at 210 or 195 nm. The chromatography is complete in less than 2.5 min with the 5-microns-particle column, and in less than 1.4 min with the 3-microns-particle column. The sensitivity of the method for all drugs is less than 1 mg/L. Analytical recovery of drugs added to serum ranged from 92 to 109% for concentrations up to 200 mg/L. Between-run precision (CV) ranged from 1.3 to 4.1%.

A simple liquid-chromatographic method applied to determine caffeine in plasma and tissues.

1988 ◽  
Vol 34 (11) ◽  
pp. 2345-2348 ◽  
Author(s):  
I Biaggioni ◽  
S Paul ◽  
D Robertson
Keyword(s):  
High Pressure ◽  
Extraction Method ◽  
Mobile Phase ◽  
Chromatographic Method ◽  
Solid Phase ◽  
Reversed Phase ◽  
Simple Liquid ◽  
Liquid Chromatographic Method ◽  
The Mean ◽  
Liquid Chromatographic

Abstract In this simple, reliable assay for quantifying caffeine in plasma and tissues, methylxanthines are first partly purified from plasma and acid extracts of tissue by passage through solid-phase columns. The ease of this extraction method permits a relatively large number of samples to be processed daily. Quantification is by reversed-phase high-pressure liquid chromatography (mobile phase: acetic acid/acetonitrile/water, 2/6/92 by vol). Caffeine is eluted in 20 min. The reliability of this method allows its automation. This method has been adapted to measure caffeine in brain and kidney extracts and in as little as 10 microL of plasma. After 10 days of oral administration of caffeine (1 g/L, in drinking water) to six rats, the mean (+/- SEM) concentrations of caffeine in plasma, brain, and kidney were 18.6 +/- 6.0 micrograms/mL, 16.2 +/- 1.5 micrograms/g, and 18.9 +/- 2.0 micrograms/g, respectively. Correlations were linear between concentrations of caffeine in plasma and brain (r = 0.86) and between concentrations in plasma and kidney (r = 0.91). This method should be useful in studying the effects and mechanisms of actions of methylxanthines.

scholarly journals Determination of Methomyl in Insecticidal Formulations by Reversed-Phase Liquid Chromatography: Collaborative Study

1996 ◽  
Vol 79 (4) ◽  
pp. 941-948
Author(s):  
James E Conaway ◽  
J B Audino ◽  
E Bane ◽  
S K Carrigan ◽  
R Glinsky ◽  
...  
Keyword(s):  
Liquid Chromatography ◽  
Coefficient Of Variation ◽  
Mobile Phase ◽  
Collaborative Study ◽  
Internal Standard ◽  
Reversed Phase ◽  
Reversed Phase Liquid Chromatography ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract A reversed-phase liquid chromatographic (LC) method for methomyl was studied. Twelve collaborators analyzed 3 solid and 4 liquid formulations on both a Zorbax octadecylsilane (ODS) column and a similar column of their choice. Methomyl and the internal standard were separated by using a mobile phase consisting of approximately 8% acetonitrile in water, which was monitored at 254 nm. The coefficient of variation on the Zorbax column ranged from 0.70 to 5.23%, while the range on the collaborators' house columns was 1.08 to 6.01%. Results with the Zorbax ODS column fell within the 5% 2-tail limits, and 10 of 11 collaborators' results fell within these limits on house columns. The LC method for determination of methomyl in insecticidal formulations has been adopted first action by AOAC INTERNATIONAL.

scholarly journals Chlortetracycline, Oxytetracycline, and Tetracycline in Edible Animal Tissues, Liquid Chromatographic Method: Collaborative Study

1996 ◽  
Vol 79 (2) ◽  
pp. 405-417 ◽  
Author(s):  
James D MacNeil ◽  
Valerie K Martz ◽  
Gary O Korsrud ◽  
Craig D C Salisbury ◽  
Hisao Oka ◽  
...  
Keyword(s):  
Chromatographic Method ◽  
Solid Phase ◽  
Collaborative Study ◽  
Reversed Phase ◽  
Animal Tissues ◽  
Liquid Chromatographic Method ◽  
Phase Liquid ◽  
Tetracycline Residues ◽  
Liquid Chromatographic

Abstract Thirteen laboratories analyzed samples of edible animal tissues for tetracycline residues. The method included extraction of analytes into buffer, elution from a C18 solid-phase extraction (SPE) cartridge, and reversed-phase liquid chromatographic (LC) analysis, including use of a confirmation column. An additional laboratory, using an alternative LC assay based on a different sample cleanup, also analyzed the samples. Results showed the 2 methods are comparable. The LC method for determination of cholortetracycline, oxytetracycline, and tetracycline in edible animal tissues has been adopted by AOAC INTERNATIONAL. Results from 13 laboratories indicate that the method under study provides generally better results at the higher concentrations tested than at concentrations near the detection limit and that there is less problem with interferences in muscle tissue than in kidney. The method can achieve reliable results for analytes and matrixes studied at concentrations from 0.1 to 0.6 ppm and above, depending on the analyte-matrix combination, with generally better performance to be expected with muscle than with kidney. The poorer performance for fortified samples, particularly kidney, was attributed to additional homogenization steps required to prepare these samples. Recovery of analytes from different

Analysis of 5-Vinyl-l,3-Oxazolidine-2-Thione by Liquid Chromatography

1992 ◽  
Vol 75 (3) ◽  
pp. 529-536 ◽  
Author(s):  
Alain Quinsac ◽  
Daniel Ribaillier ◽  
Patrick Rollin ◽  
Michel Dreux
Keyword(s):  
Liquid Chromatography ◽  
Solid Phase ◽  
Internal Standard ◽  
Rapeseed Meal ◽  
Reversed Phase ◽  
Mercury Acetate ◽  
Phase Liquid ◽  
Biological Environment ◽  
Liquid Chromatographic

Abstract 5-Vlnyl-1,3-oxazolldlne-2-thlone (5-VOT) Is a goltrlgenlc compound released by enzymatic degradation of progoltrln, the major glucoslnolate occurring In rapeseed meal. A liquid chromatographic (LC) method for determination of 5-VOT in a biological environment Is presented. Complete extraction of 5-VOT has been carried out by complexatlon with phenyl mercury acetate under cyclohexanlc conditions, and then by decomplexation using an aqueous sodium thlosulfate solution. These reactions displace 5-VOT from an aqueous to an organic medium, and then back again to the aqueous condition, thus assuring high selectivity of the extraction. Precise quantitation of 5-VOT Is completed in 10 mln by reversed-phase liquid chromatography using an isocratic elutlon with UV detection and a specially made synthetic Internal standard. Concentration steps by solid-phase chromatography and evaporation can be introduced In the analytic procedure to lower the detection limit of 5-VOT in the sample used from 100 to 0.5 ppb. Using sow milk samples, the method was tested by small measured additions of 5-VOT. The recovery rate of the product was very good (>97%). Different phases used to achieve a sensitive, rapid, and precise method are described.

scholarly journals Determination of Total Avermectin B1 and 8,9-Z-Avermectin B1 Residues in Wine by Liquid Chromatography

1996 ◽  
Vol 79 (5) ◽  
pp. 1158-1161 ◽  
Author(s):  
Janice A Cobin ◽  
Nelson A Johnson
Keyword(s):  
Liquid Chromatography ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Signal To Noise Ratio ◽  
Reversed Phase ◽  
Liquid Chromatographic Method ◽  
Limit Of Quantitation ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract A liquid chromatographic method was developed and validated for determination of avermectin Bi and 8,9-Z-avermectin B1 residues in wine. The sample is extracted with hexane-acetonitrile and the hexane layer containing the avermectins is concentrated/ purified on an aminopropyl solid-phase extraction (SPE) column. The purified extract is derivatized with trifluoroacetic anhydride and the derivatized avermectins are analyzed by reversed-phase liquid chromatography with fluorescence detection. Recoveries of avermectins from wine fortified with approximately 1-25 ng/g avermectin B1a or 8,9-Zavermectin B1a averaged 88 and 102%, respectively. The limit of quantitation is 1 ng/g (signal-to-noise ratio [S/N] > 10) and the limit of detection is 0.5 ng/g (S/N > 3) for each analyte. This procedure provides a simple, rapid, and sensitive method for monitoring the total amount of avermectin residues in wine.

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