scholarly journals Rapid Determination of Ampicillin in Bovine Milk by Liquid Chromatography with Fluorescence Detection

1997 ◽  
Vol 80 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Catharina Y W Ang ◽  
Luo Wenhong
Keyword(s):  
Fluorescence Detection ◽  
Rapid Determination ◽  
Bovine Milk ◽  
Skim Milk ◽  
Reversed Phase ◽  
Coefficients Of Variation ◽  
Whole Milk ◽  
Liquid Chromatographic ◽  
Clear Supernatant

Abstract A rapid and sensitive liquid chromatographic (LC) method was developed for the determination of am- picillin residues in raw bovine milk, processed skim milk, and pasteurized, homogenized whole milk with vitamin D. Milk samples were deprote- inized with trichloroacetic acid (TCA) and acetonitrile. After centrifugation, the clear supernatant was reacted with formaldehyde and TCA under heat. The major fluorescent derivative of ampicillin was then determined by reversed-phase LC with fluorescence detection. Average recoveries of ampicillin fortified at 5,10, and 20 ppb (ng/mL) were all >85% with coefficients of variation <10%. Limits of detection ranged from 0.31 to 0.51 ppb and limits of quantitation, from 0.66 to 1.2 ppb. After appropriate validation, this method should be suitable for rapid analysis of milk for ampicillin residues at the tolerance level of 10 ppb.

scholarly journals Determination of Amoxicillin in Catfish and Salmon Tissues by Liquid Chromatography with Precolumn Formaldehyde Derivatization

1996 ◽  
Vol 79 (2) ◽  
pp. 389-396 ◽  
Author(s):  
Catharina Y W Ang ◽  
Wenhong Luo ◽  
Eugene B Hansen ◽  
James P Freemana ◽  
Harold C Thompson
Keyword(s):  
Muscle Tissue ◽  
Fluorescence Detection ◽  
Solid Phase ◽  
Reversed Phase ◽  
Liquid Extraction ◽  
Liquid Liquid Extraction ◽  
Coefficients Of Variation ◽  
Liquid Chromatographic ◽  
Reversed Phase Lc

Abstract A liquid chromatographic (LC) method with fluorescence detection was developed for analysis of amoxicillin in catfish and salmon tissues. The tissue was extracted with phosphate buffer (pH 4.5), followed by trichloroacetic acid (TCA) precipitation of proteins and solid-phase (C18) extraction. Trace amounts of nonpolar interfering substances present after solid-phase extraction were removed by ether liquid-liquid extraction. The extract was reacted with formaldehyde and TCA at 100°C for 30 min. A fluorescent derivative was extracted with ether, concentrated, and analyzed by reversed phase LC with fluorescence detection. Average recoveries of amoxicillin spiked at 2.5-20 ppb were >80% for catfish and >75% for salmon muscle tissue, with coefficients of variation of <6%. Limits of detection (LOD) and quantitation (LOQ) for catfish tissue were 0.5 and 1.2 ppb, respectively. LOD and LOQ for salmon muscle tissue were 0.8 and 2.0 ppb, respectively.

Improved liquid-chromatographic determination of propranolol in plasma, with fluorescence detection.

1979 ◽  
Vol 25 (5) ◽  
pp. 777-779 ◽  
Author(s):  
P Jatlow ◽  
W Bush ◽  
H Hochster
Keyword(s):  
Fluorescence Detection ◽  
Internal Standard ◽  
Chromatographic Determination ◽  
Reversed Phase ◽  
Back Extraction ◽  
Micro Scale ◽  
Coefficients Of Variation ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract We describe an analysis for propranolol in plasma, with use of reversed-phase "high-pressure" liquid chromatography and fluorescence detection. Pronethalol is used as the internal standard. The procedure, which involves extraction into an organic solvent, evaporation, and clean-up by micro-scale back extraction from hexane into an aqueous phase, is specific and sensitive. The detection limit is less than 6 microgram/L (2.3 X 10(-8) mol/L). Within-day and between-day coefficients of variation are 1.8 and 4.4%, respectively. Commonly used drugs, including procainamide, N-acetylprocainamide, and quinidine, do not interfere.

scholarly journals Determination of Ceftiofur in Bovine Milk by Liquid Chromatography

1996 ◽  
Vol 79 (4) ◽  
pp. 844-847 ◽  
Author(s):  
Patrick J Mcneilly ◽  
Valerie B Reeves ◽  
E J Ian Deveau
Keyword(s):  
Ammonium Acetate ◽  
Methanol Extract ◽  
Solid Phase ◽  
Bovine Milk ◽  
Reversed Phase ◽  
Acetate Solution ◽  
Coefficients Of Variation ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic

Abstract A liquid chromatographic procedure is described for determination of ceftiofur (CEF) residues in milk. Milk samples were diluted with ammonium acetate solution and extracted on a C18 solid-phase extraction (SPE) column. After the analyte was eluted from the SPE column with methanol, extract volumes were reduced under nitrogen, diluted to 2.0 mL with acetate buffer, and filtered. CEF was determined after separation of milk components by reversed-phase chromatography with UV detection at 293 nm. Recoveries of CEF from bovine milk fortified at 25,50, and 100 ppb were 86.1,90.8, and 92.0%, respectively, with coefficients of variation (CVs) of 6.4, 7.3, and 3.9%, respectively. Values of CEF obtained from analysis of milk containing 2 levels of biologically incurred residues were 26.1 and 67.3 ppb with CVs of 3.8 and 4.4%, respectively. The limits of detection and quantitation were estimated to be 4 and 7 ppb, respectively.

Optimized liquid-chromatographic determination of metronidazole and its metabolites in plasma.

1984 ◽  
Vol 30 (5) ◽  
pp. 784-787 ◽  
Author(s):  
R A Gibson ◽  
L Lattanzio ◽  
H McGee
Keyword(s):  
Rapid Determination ◽  
Chromatographic Determination ◽  
Reversed Phase ◽  
Detector Response ◽  
High Pressure Liquid Chromatographic ◽  
Liquid Chromatographic Method ◽  
Wide Range ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract Metronidazole and its known metabolites in plasma can be rapidly separated by a "high-pressure" liquid-chromatographic method that can also be adapted for rapid determination of tinidazole. Samples deproteinized with trichloroacetic acid (50 g/L final concentration) undergo isocratic separation on a reversed-phase C18 column eluted with an 8/92 (by vol) mixture of acetonitrile/KH2PO4 (5 mmol/L, pH 3.0). The method is sensitive, reliably detecting as little as 25 micrograms of metronidazole and (or) its metabolites per milliliter of plasma. The detector response varied linearly with concentration for all compounds tested over a wide range (25-500 micrograms/L). Within-day and between-day variation was generally less than 2.5% for all concentrations of all compounds tested. Various other antibiotics tested did not interfere.

Determination of Acesulfam-K in Foods

1993 ◽  
Vol 76 (2) ◽  
pp. 268-274 ◽  
Author(s):  
Jacques Prodolliet ◽  
Milene Bruelhart
Keyword(s):  
Fruit Juice ◽  
Soft Drink ◽  
Food Additives ◽  
Reversed Phase ◽  
Uv Absorbance ◽  
Phase Detection ◽  
Coefficients Of Variation ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic

Abstract A liquid chromatographic method was evaluated for the determination of the intense sweetener acesulfam-K in tabletop sweetener, candy, soft drink, fruit juice, fruit nectar, yogurt, cream, custard, chocolate, and biscuit commercial preparations. Samples are extracted or simply diluted with water and filtered. Complex matrixes need a clarification step with Carrez solutions. An aliquot of the extract is analyzed on a reversed-phase μBondapak C18 column using 0.0125M KH2PO4 (pH 3.5)-acetonitrile (90 + 10) as mobile phase. Detection is performed by UV absorbance at 220 nm. Recoveries ranged from 95.2 to 106.8%. With one exception, all analyzed values were within ±15% of the declared levels. The repeatabilities and the repeatability coefficients of variation were, respectively, 0.37 mg/100 g and 0.98% for products containing less than 40 mg/100 g acesulfam-K and 2.43 mg/100 g and 1.29% for other products. The same procedure also allowed detection of many food additives or natural constituents, such as other intense sweeteners, organic acids, and alkaloids, in a single run without interfering with acesulfam-K. The method is simple, rapid, precise, and sensitive; therefore, it is suitable for routine analyses.

Determination of iV-Methylcarbamate Pesticides in Liver by Liquid Chromatography

1989 ◽  
Vol 72 (4) ◽  
pp. 586-592 ◽  
Author(s):  
Sher M Ali
Keyword(s):  
Liquid Chromatography ◽  
Simultaneous Determination ◽  
Fluorescence Detection ◽  
Methylene Chloride ◽  
Gel Permeation Chromatography ◽  
Purification Technique ◽  
Coefficients Of Variation ◽  
Gel Permeation ◽  
Liquid Chromatographic

Abstract A liquid chromatographic (LC) method using a 2-step purification technique for the simultaneous determination of 10 carbamates in bovine, swine, and duck livers has been developed. Carbamates are extracted from liver samples with methylene chloride. After evaporation, the residues from the extract are dissolved in methylene chloride- cyclohexane (1 + 1) and cleaned up by gel permeation chromatography. The eluate containing carbamate residues is evaporated to dryness, reconstituted in methylene chloride, further purified by passing it through an aminopropyl Bond Elut extraction cartridge, and analyzed by liquid chromatography using post-column derivatization with orthophthalaldehyde and fluorescence detection. Excitation and emission are set at 340 and 418 nm, respectively. Liver samples for beef, pork, and duck were fortified with 5, 10, and 20 ppb of mixed carbamate standards. The average of 10 recoveries of 10 carbamates at all 3 levels of fortification was greater than 80% with coefficients of variation less than 17%.

Determination of Aspartame and Its Major Decomposition Products in Foods

1993 ◽  
Vol 76 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Jacques Prodolliet ◽  
Milene Bruelhart
Keyword(s):  
Soft Drink ◽  
Food Additives ◽  
Reversed Phase ◽  
Food Samples ◽  
Phase Detection ◽  
Decomposition Products ◽  
Coefficients Of Variation ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic

Abstract A liquid chromatographic procedure already evaluated in a preceding study for the analysis of acesulfam-K is also suitable for the determination of the intense sweetener aspartame in tabletop sweetener, candy, fruit beverage, fruit pulp, soft drink, yogurt, cream, cheese, and chocolate preparations. The method also allows the determination of aspartame’s major decomposition products: diketopiperazine, aspartylphenylalanine, and phenylalanine. Samples are extracted or diluted with water and filtered. Complex matrixes are centrifuged or clarified with Carrez solutions. An aliquot of the extract is analyzed on a reversed-phase μBondapak C18 column using 0.0125M KH2P04 (pH 3.5)-acetonitrile ([85 + 15] or [98 + 2]) as mobile phase. Detection is performed by UV absorbance at 214 nm. Recoveries ranged from 96.1 to 105.0%. Decomposition of the sweetener was observed in most food samples. However, the total aspartame values (measured aspartame + breakdown products) were within -10% and +5% of the declared levels. The repeatabilities and the repeatability coefficients of variation were, respectively, 1.00 mg/100 g and 1.34% for products containing less than 45 mg/100 g aspartame and 4.11 mg/100 g and 0.91 % for other products. The technique is precise and sensitive. It enables the detection of many food additives or natural constituents, such as other intense sweeteners, organic acids, and alkaloids, in the same run without interfering with aspartame or its decomposition products. The method is consequently suitable for quality control or monitoring.

Elimination of caffeine interference in HPLC determination of urinary nicotine and cotinine.

1989 ◽  
Vol 35 (7) ◽  
pp. 1456-1459 ◽  
Author(s):  
N T Thuan ◽  
M L Migueres ◽  
D Roche ◽  
G Roussel ◽  
G Mahuzier ◽  
...  
Keyword(s):  
Reversed Phase ◽  
Gas Liquid Chromatography ◽  
Tobacco Exposure ◽  
Coefficients Of Variation ◽  
Chromatographic Procedure ◽  
Phase Liquid ◽  
Liquid Chromatographic ◽  
Minimum Detectable Amount ◽  
Column Extraction

Abstract We report an analytical reversed-phase liquid-chromatographic procedure for quantifying nicotine and cotinine in urine, taking into account the presence of interfering caffeine frequently encountered in such specimens. These analytes are extracted from the alkalinized urine with chloroform. After evaporation of the chloroform, the residue is dissolved in methanol and injected into a chromatographic C18 column. Extraction recoveries averaged 80% to 97%. Chromatographic conditions were investigated to obviate caffeine interference. The proposed eluent mobile phase is a polar mixture of water, acetonitrile, methanol, and a pH 4 acetoacetate buffer (65/2/29/4 by vol) adjusted to pH 4.30 +/- 0.02 with triethylamine. High resolution and linearity were obtained for each analyte up to a concentration of 200 mg/L. The minimum detectable amount of each compound was 20 ng per injection, corresponding to 10 micrograms per liter of urine. Correlation with results of gas-liquid chromatography was excellent (r = 0.99). This simple, rapid procedure allows routine screening of tobacco exposure with acceptable precision: within- and between-run coefficients of variation were less than 2% and less than 5%, respectively.

Determination of Ractopamine Hydrochloride in Swine, Cattle, and Turkey Feeds by Liquid Chromatography with Coulometric Detection

1994 ◽  
Vol 77 (4) ◽  
pp. 840-847 ◽  
Author(s):  
Michael P Turberg ◽  
Thomas D Macy ◽  
Jerry J Lewis ◽  
Mark R Coleman
Keyword(s):  
Solid Phase ◽  
Reversed Phase ◽  
Free Base ◽  
Coulometric Detection ◽  
Solid Phase Extraction Cartridge ◽  
Coefficients Of Variation ◽  
Ractopamine Hydrochloride ◽  
Cattle Feeds ◽  
Liquid Chromatographic

Abstract A liquid chromatographic method is described for the determination of ractopamine hydrochloride (LY31537) in swine, turkey, and cattle feeds in the 1.25–100 ppm range and in swine supplement at 100 ppm. Feed samples were extracted with acidified methanol. An aliquot of the feed extract was diluted with water and buffered to pH 10.5 ± 0.5 with sodium carbonate to convert ractopamine hydrochloride to a free base. The free base was extracted from the buffered sample with ethyl acetate. The extract was further purified on an acid-washed, silica solid-phase extraction cartridge. After conversion of the free base back to the salt form with pH 4.5 buffer, analytical separation and quantitation of ractopamine hydrochloride were accomplished on IBM phenyl and Whatman ODS reversed-phase columns with coulometric detection at +600 mV. Mean daily recovery levels ranged from 85 to 100% for feeds fortified at 1.25 to 100 ppm. The coefficients of variation ranged from 1 to 6% for feeds fortified at 2.5 to 100 ppm.

Improved liquid-chromatographic method for determination of serum cortisol.

1979 ◽  
Vol 25 (7) ◽  
pp. 1293-1296 ◽  
Author(s):  
P M Kabra ◽  
L L Tsai ◽  
L J Marton
Keyword(s):  
Limit Of Detection ◽  
Internal Standard ◽  
Serum Cortisol ◽  
Peak Height ◽  
Reversed Phase ◽  
Column Temperature ◽  
Coefficients Of Variation ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic

Abstract We describe a specific and precise method for measuring concentrations of cortisol in serum or plasma by liquid chromatography. Cortisol, together with an internal standard, equilenin, is extracted from 1 mL of serum or plasma and analyzed isocratically on a reversed-phase column with a mobile phase of acetonitrile/phosphate buffer (30/70, by vol.), at a flow rate of 2.0 mL/min. The eluted cortisol is detected by its absorption at 254 nm and quantitated by peak height measurements. Each analysis requires no longer than 15 min at the optimum column temperature of 50 degrees C. The lower limit of detection for cortisol is about 2 ng/sample for a standard solution; sensitivity is routinely 5 micrograms/L of serum. Analytical recoveries exceeded 95%, with good day-to-day precision (coefficients of variation between 4 and 7%). Of more than 50 drugs and steroids tested for possible interference, only the steroids cortisone, prednisone, and prednisolone may interfere with the analysis of cortisol.

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