Determination of Cyclohexylamine in Water by Solid Phase Extraction and Quantitative High Performance Thin Layer Chromatography

Abstract

Cyclohexylamine (CHA) was isolated from water by solid phase extraction on a C₁₈ microcolumn. The CHA in the column eluate was chromatographed on a high performance preadsorbent silica gel layer, detected with ninhydrin reagent and exposure to UV light, and quantified by reflectance scanning. Recovery from fortified distilled water samples at 10 ppm averaged 95.0% and at 1 ppm averaged 94.9%. Quantitative recoveries from tap water at 10 ppm and from lake water at 1 ppm were also demonstrated. Other boiler water additives permitted by FDA do not interfere.     

Determination of Chlorpyrifos and its Metabolite 3,5,6-Trichloro-2-Pyridinol in Tap Water and Bananas by Quantitative TLC on Preadsorbent Silica Gel

Abstract

Chlorpyrifos insecticide and its metabolite TCP were determined in tap water and banana samples by TLC of extracts on preadsorbent silica gel layers, detection with silver nitrate reagent, and densitometric scanning. Cleanup steps were required for the fruit sample extracts. Recovery of chlorpyrifos from tap water at 5 ppb averaged 87.5% and from banana at 0.05 ppm was 84.6%. Recovery of TCP from water at 5 ppb averaged 84.0% and from banana at 0.05 ppm was 86.8%. The sensitivity and precision of the method were shown to be adequate for routine residue analysis.     

Active TBC in Butadiene by HPLC

Abstract

A high performance liquid chromatographic method has been developed for the determination of active 4-tert-butyl-catechol (TBC) In 1,3-butadiene. Following evaporation of the butadiene from an aqueous m-nitrophenol internal standard solution, a 20-microliter aliquot is injected onto a reversed-phase liquid chromatographic column. Recovery op TBC was found to be quantitative over a 17-242 ppm range with a relative standard deviation of 3.8%.     

HPLC Determination of Utibapril and its Diacid FPL 63674XX in Rodent Laboratory Diet Using Selective Extraction and Gradient Elution Chromatography

Abstract

Utibapril is a novel thiadiazoline that is currently under investigation as an antihypertensive agent. The major degradation product, a diacid FPL 63674XX, is biologically active. An HPLC method has been developed to simultaneously determine both utibapril and its diacid in rodent laboratory diet used to dose animals in long term toxicology studies. The method is based on liquid-solid extraction of the compounds followed by direct injection of the extract. Gradient elution chromatography is utilized to better separate the diacid from interferences. Recovery of utibapril and the diacid from the lab diet was found to be 97.6 ± 0.44% and 99.7 ± 2.8%, respectively (n=3) at 0.43% w/w levels. The separation is achieved on a octadecylsilane column using a flow rate of 0.75 ml/min and a column temperature of 70°C. The UV detector was set at 260 nm. A linear and step gradient program was established using mobile phases consisting of 0.05 M     

High-Performance Liquid Chromatographic Determination of TCNB in Potatoes

Abstract

A high-performance liquid chromatographic (HPLC) method was developed for the determination of TCNB (tetrachloronitrobenzene), a sprout inhibitor, in potato peels and flesh fortified at levels of 0.16 to 53.5 ppm. TCNB was analyzed on a u Bondapak C₁₈ column with UV detection at 210 nm. The mobile phase was acetonitrile-methanol-water (35:35:30) at a flow rate of 1.0 ml/min. Retention time was approximately 10 min. TCNB was extracted by blending for 5 min in acetone. Samples at a level of 1 ppm or higher were directly injected whereas samples below 1 ppm were partitioned into hexane followed by passage through an alumina column. Average recoveries varied from 85.6 to 96.8% with coefficients of variation ranging from 2.18 to 11.68%. A study conducted to test 23 pesticides for possible interferences with TCNB demonstrated that none of them co-chromatographed. The lower limit of detection was 0.08 ppm.     

An Improved Gas-Liquid Chromatographic Method for the Analysis Of 1,1,1-Trichloro-2,2-BIS(p-Chlorophenyl) Ethane(p,p′-DDT) and Its Metabolites in Milk

Abstract

A rapid method has been developed, in which p,p′-DDT residues are extracted from milk samples with n-hexane, following treatment of the milk with concentrated sulfuric acid. The extract, containing p,p′-DDT residues is then cleaned up on a silica gel column. Electron capture gas chromatography was used to measure the efficiency of the extraction and cleanup procedure. An overall average recovery of 97% was obtained on samples at concentration levels of 0.05 to 1.00 ppm.     

Simultaneous Determination of Cadmium,Cobalt, Copper,Lead, Mercury and Nickel in Zinc Sulfate Plant Electrolyte Using Liquid Chromatography with Electrochemical and Spectrophotometric Detection

Abstract

The current efficiency (cost) of electrolytic production of high purity metallic zinc from zinc sulfate plant electrolyte is critically dependent on the concentration of a number of trace elements. The matrix, containing a very large concentration excess of zinc sulfate in concentrated sulfuric acid presents difficulties for determining low concentrations of other metals with many analytical methods. In this work it is shown that Cd, Co, Cu, Pb, Hg and Ni impurities may be simultaneously determined at concentrations less than or equal to 1 ppm using a combination of solvent extraction, high performance liquid chromatography and electrochemical or spectrophotometrie detection. Solvent extraction utilizes the formation of pyrrolidine dithiocarbamate complexes, which after removal of zinc complexes and excess ligand on an anion exchange column can be separated on a C-18 reverse phase chromatographic column and detected by UV/Visible spectrophotometrie or electrochemical detection. Other combinations of chromatographic and detection procedures were thwarted by the very large concentration excess of zinc and other problems.     

Analysis of Indenolol In Biological Fluids By High Performance Liquid Chromatography

Abstract

The analysis of indenolol in plasma and urine is described. The method involves extraction of the drug from plasma or urine using chloroform at basic pH. The separation was performed on CN column using methanol and 0.01M potassium dihydrogen phosphate solution 50:50. The efficiency of extraction was 97%. Minimum detectable amount by fluorescence was 20 ng/ml.     

Ion-Paired Liquid Chromatographic Determination of Cefazolin in Canine Serum and Tissues

Abstract

Cefazolin is commonly used as a prophylactic antibiotic in dogs undergoing total hip arthroplasty.

A sensitive high-performance liquid chromatographic method was developed for the determination of cefazolin in canine serum and tissues. The tissues were those in contact with the hip prothesis; namely, the coxofemoral joint capsule, cancellous bone from the acetabulum and bone marrow from the femoral canal.

The method involved filtration of diluted serum or tissue extracted with ethanol:acetonitrile:water (40:10:50) through a 30,000 molecular weight cut-off filter. Separation of cefazolin from other components was by ion-paired (dodecanosulfonate) high performance liquid chromatography using a reversed-phase column eluted with acetonitrile/water solution. The ultraviolet absorbance of the column effluent was monitored at 230 nm. Recovery of cefazolin spiked at 10 μg/ml from serum was 89.8% with a coefficient of variation (CV) of 5.3% (n=10). Recovery of cefazolin spiked at 5 μg/ml from tissue extracts of joint capsule, cancellous bone and bone marrow was: 93.9%, 98.2%, and 104.2% respectively, with a CV of 6.7%, 10.2% and 10.6% respectively (n=10). A correlation coefficient of 0.9999 occurred with cefazolin in aqueous solution (n=5). The limit of detection for cefazolin was approximately 10 ng/ml of serum or tissue extract.     

Comparison of Octadecyl-Bonded Alumina and Other Stationary Phases for Lipophilicity Estimation by High Performance Liquid Chromatography

Abstract

A recently developed octadecyl-bonded alumina stationary phase (ODA) was evaluated for determining the lipophilicities of organic compounds by high performance liquid chromatography. Using a column packed with this material and mobile phases consisting of methanol and aqueous buffers, the correlation between the octanol-water partition coefficients (log P's) of compounds of various chemical classes and the logarithms of their chromatographic capacity factors (log k's) was found to be superior to that obtained using columns packed with octadecylsilica, poly butadiene-coated alumina or octadecyl-derivanzed polystyrene-divinylbenzene copolymer. In contrast to results obtained with other columns, phenols and other hydrogen-bonding compounds did not need to be treated as a separate data set on the ODA column to obtain good correlations between log k's and log P's. The resistance of ODA to degradation by alkaline solvents allowed the use of a basic mobile phase (pH > 10) for suppressing ionization and determining the lipophilicities of organic bases which could not be evaluated within the stable pH range of ODS (pH 2–8). The log P's of five basic pharmaceutical compounds determined in this manner were found to be significantly higher than previously reported values. Evidence is presented which indicates that the previously reported log P values of these compounds are inaccurate, due to improper correction for ionization.     

Analysis of Dexamethasone Acetate in Pharmaceutical Formulations by HPLC

Abstract

A rapid and effective high-pressure liquid chromatographic method has been developed for the quantitative determination of dexamethasone 21 acetate in pharmaceutical formulations. Sample preparation employs a simple extraction procedure and analysis is carried out on a reversephase chromatographic system using a LiChrosorb RP 18 column and a water-acetonitrile as mobile phase. The extraction procedure gives quantitative recovery and chromatographic results show that drug levels of as 0.1 ppm can be conveniently analyzed without significant background interferences.     

A Stability Indicating HPLC Assay for Prednisolone Sodium Phosphate in Implantable Infusion Pumps

Abstract

A stability indicting assay for prednisolone sodium phosphate (PSP) in solutions for implantable infusion pumps was developed. PSP and its major breakdown product, prednisolone, were separated from formulation excipients by reverse phase chromatography on a phenyl-bonded phase column using an acetonitrile-phosphate buffer mobile phase. Detection was by ultraviolet absorbance at 243 mm. Recovery from a synthetic formulation was 101.0 ± 0.4% (n=6). The method was used to monitor the stability of PSP solutions in implantable infusion pumps maintained at 37°C over a 21 day period.     

High Performance Liquid Chromatographic Determination of Emetine in Corn

Abstract

A High performance liquid chromatographic (HPLC) method for the quantitative analysis of emetine in corn is described. Corn kernels are removed from the ears, blended, and extracted with methanol. The extract is filtered through a 0.45 um Acrodisc filter and analyzed by HPLC using a LC-18-DB column. For detection, a fluorescence detector set at excitation of 285 and emission at 316 nm is used. The recoveries of samples fortified between 0.1 ppm to 20 ppm with emetine ranged from 95.5% to 103.3%.     

Simultaneous Determination of Five Antibacterials in Swine Muscle by High Performance Liquid Chromatography

Abstract

A high performance liquid chromatographic method (HPLC) for the determination of olaquindox, morantel, furazolidone, nitrofurazone and carbadox residues in swine muscles was developed. The drugs were extracted from muscles with acetonitrile and cleaned up by alumina column. HPLC analysis was carried out on an Inertsil C8 column with a mobile phase of acetonitrile-water-acetic acid (3:97:1), and the drugs were detected at 340 nm. The average recoveries of all drugs added to muscles at 0.1 ppm level were more than 75% and the detection limit of each drug was 0.03 ppm in muscles.     

Determination of chlorotoluron, isoproturon and metoxuron in soil by GLC-NPD and confirmation using GLC-MS

Summary The analysis of several phenyl urea herbicides in soil by GLC-NPD, directly or after alkylation, and the confirmation of residues by GLC-ITD is reported. Soil was extracted with methanol, the organic solvent evaporated, the residue dissolved in hexane and then analyzed by gas chromatography on a 3% OV-17 glass packed column. An aliquot of the extract was ethylated overnight with EtI, NaH and Me₂SO as solvent. The mixture was hydrolyzed, the ethylated compounds extracted with hexane and determinated by GLC-NPD on a BP-5 fused silica capillary column. Values obtained with the direct GLC analysis were reproducible and similar to those obtained after ethylation. Recovery of each herbicide was higher than 80% and the limit of detection was 0.01 ppm. These compounds were also analyzed by GLC-ITD. The sensitivity in the SIM mode was near 0.1 ng and the residues can be confirmed with this technique down to 0.01 ppm.     

Determination of Captan,Folpet, and Captafol in Water,Apples, and Lettuce By Quantitative Thin-Layer Chromatography

Abstract

Captan, folpet, and captafol were determined in water, lettuce, and apples by TLC of extracts on preadsorbent silica gel layers, detection with silver nitrate reagent, and densitometric scanning. The fungicides were extracted from water on Chromosorb 102 raicrocolumns. Cleanup on a Florisil column was required for the food extracts. Recoveries from distilled and tap water ranged from 76–98% at 0.02 ppm and 81–94% at 0.007 ppm. Recoveries from lettuce ranged from 88–94% and from apples 84–90%, both at 0.25 ppm. The selectivity, sensitivity, and precision of the method are adequate for routine residue analysis.     

Quantitation of the Triazine Herbicides Atrazine and Simazine in Water by Thin Layer Chromatography with Densitometry

Abstract

A TLC-densitometric method for determination of the triazine herbicides atrazine and simazine in natural and tap water is described. Separation was carried out on silica gel G, followed by detection with silver nitrate and UV exposure. Alumina column cleanup was required for tap water. Recovery of samples fortified at 10 ppb was > 80%, and the relative standard deviation was better than 7.5%.     

Quantification of trovafloxacin in serum by high-performance liquid chromatography with on-line solid-phase extraction

Summary A rapid, simple, accurate and sensitive liquid chromatographic assay with on-line solid-phase extraction is described for determination of trovafloxacin in human serum. Samples were deproteinized with acetonitrile and injected on to an NH₂ extraction column for sample clean-up. Thereafter, an on-line column-switching system was used for quantitative transfer of the drug to a C₁₈ analytical column. Separation was performed by ion-pair chromatography and detection was by ultraviolet absorbance at 275 nm. Recovery was 98.5%. The linear range was from 0.25 to 20μg mL⁻¹, with a correlation coefficient of 0.999. Detection limit was 0.1 μg mL⁻¹ from extraction of 25 μL serum.     

Multiclass detection and quantitation of antibiotics and veterinary drugs in shrimps by fast liquid chromatography time-of-flight mass spectrometry

A fast liquid chromatography time-of-flight mass spectrometry (LC-TOFMS) method has been developed for simultaneous quantitative multiclass determination of residues of selected antibiotics and other veterinary drugs (benzalkonium chloride, ethoxyquin, leucomalachite green (LMG), malachite green (MG), mebendazole, sulfadiazine, sulfadimethoxine, sulfamethazine, sulfamethizole, sulfanilamide, sulfapyridine, sulfathiazole and trimethoprim) in shrimps. Different sample treatment methodologies were tested for the extraction of the targeted species based on either liquid partitioning with different solvents, solid-phase extraction or and matrix solid-phase dispersion. The final selected extraction method consisted of solid-liquid extraction protocol using acetonitrile as solvent followed by a clean-up step with primary secondary amine (QuEChERS). Recovery rates for the extraction of the selected multiclass chemicals were in the range 58-133%. Subsequent identification, confirmation and quantitation were carried out by LC-TOFMS analysis using a reverse-phase C₁₈ column with 1.8 μm particle size. The confirmation of the target species was based on accurate mass measurements of the protonated molecules ([M+H]⁺) and their fragment ions, obtaining routine accuracy errors lower than 2 ppm in most cases. The optimized LC-TOFMS method displayed excellent sensitivity for the studied analytes, with limits of detection (LODs) in the range 0.06-7 μg kg⁻¹. Finally, the proposed method was successfully applied to the analysis of 12 shrimp samples collected from different supermarkets, showing the potential applicability of the method for ultratrace detection of these chemicals in such complex matrix.     

Residues Analysis of Post-Harvest Imidazole Fungicides in Citrus Fruit by H PLC and GLC

Abstract

The determination of imazalil and prochloraz fungicide residues has been carried out by HPLC with an UV detector at 204 nm and by GLC with an electron capture detector (ECD).

In both cases fungicide residues were extracted with hexane/acetone (90:10, v/v) after pH adjustment and purified by a liquid-liquid partitioning process. When HPLC was used for prochloraz and imazalil analysis, it was necessary to eliminate the interfering substances with a further clean-up process. This was also required when samples with low residue levels were analyzed by GLC.

Recovery was always higher than 70%. The detection limit was 0.04 ppm for the HPLC method and 0.02 for the GLC method.

Imazalil and prochloraz residues in “Washington Navel” oranges and “Hernandina” clementine fruits, dipped in a 1000 ppm fungicide solution, are reported.