Biomedical subjects

A R Long

Publications and source records attributed to A R Long.

At least 37 records · Page 2Linked to original sources

PubMedDate not supplied

Analysis of beta-carotene in medical food by liquid chromatography with matrix solid-phase dispersion.

A liquid chromatographic method is described for analysis of beta-carotene in medical food. The nutrient is extracted from medical food without saponification by matrix solid-phase dispersion and quantitated by isocratic normal-phase chromatography with a Si 60 column and a mobile phase of hexane containing 0.125% (v/v) isopropyl alcohol. The limit of quantitation is 0.02 microgram/mL at 436 nm. Standard response was linear over the concentration range of 0.02-1.0 microgram/mL (r2 = 0.99998). Recoveries were determined on a zero control reference material containing added beta-carotene at various levels. Recoveries averaged 91.2% (n = 25) with coefficients of variation from 0.50 to 3.10%. The method provides a rapid, specific, sensitive, and easily controlled assay for analysis of beta-carotene in fortified medical food. In addition, retinyl palmitate can be assayed simultaneously with an in-line fluorescence detector.

Chromatography, Liquid↗

PubMedDate not supplied

Determination of lipids in infant formula powder by direct extraction methylation of lipids and fatty acid methyl esters (FAME) analysis by gas chromatography.

Fatty acid methyl esters (FAMEs) of pure triglyceride standards, oils, and fat from dry matrixes were formed by transesterification using sodium methoxide in methanol-hexane. FAMEs were produced by direct addition of sodium methoxide-hexane to samples and heating to simultaneously extract and transesterify acyl lipids. FAMEs were quantitated by capillary gas chromatography (GC) over a fatty acid concentration range of 0 to 1.7 mg/mL (r > or = 0.9997). Total fat was calculated as the sum of individual fatty acids expressed as triglyceride equivalents, in accordance with nutrition labeling guidelines. Saturated, polyunsaturated, and monounsaturated fats were calculated as sums of individual free fatty acids. Absolute recoveries determined from individual fatty acids in test samples ranged from 69.7 to 106%. Recoveries (relative to the C13:0 internal standard) for individual fatty acids in test samples ranged from 95 to 106%. Reproducibility was constant at each fatty acid level in the reaction mixture (n = 5, coefficient of variation [CV] < 2%). Absolute recovery determined from the sum of total fatty acids in standard reference material (SRM) 1846 (powdered infant formula) was 96.4%. Analysis of SRM 1846 gave results that agreed closely with the certified fat and fatty acid values. Analysis of commercial infant formula gave results that were comparable to those obtained with AOAC Method 996.01. The direct extraction methylation procedure is rapid, and the transesterification of acyl lipids to form FAMEs is complete within 15 min. Classical saponification and refluxing are not required. This method provides FAMEs free of interferences and easily quantitated by GC or confirmed by GC/mass spectrometry (MS). Unambiguous MS identification of individual FAMEs derived from pure standards, SRM 1846, and powdered infant formula product was obtained.

Chromatography, Gas↗

PubMedDate not supplied

Liquid chromatographic analysis of vitamin K1 in milk-based infant formula with matrix solid-phase dispersion.

A liquid chromatographic method for vitamin K1 in milk-based infant formula is described. The vitamins are extracted from infant formula by matrix solid-phase dispersion and quantitated by reversed-phase chromatography with fluorescence detection. Vitamin K1 is converted to the fluorescent hydroquinone with a postcolumn zinc reductive reactor. The limit of detection is 12 pg, and the limit of quantitation is 38 pg on-column. Linear responses were obtained in the range 0.55-22.1 ng/ml (r2 = 0.9998). Recoveries of vitamin K1 from an analyte-fortified blank material for milk-based infant formula averaged 91.7% (n = 25). The method provides a rapid, specific, and easily controlled assay for vitamin K1 in fortified infant formula.

Animals↗

PubMedDate not supplied

Determination of vitamin K1 in medical foods by liquid chromatography with postcolumn reduction and fluorometric detection.

A liquid chromatographic (LC) method is described for the determination of vitamin K1 in medical foods. The sample is enzymatically digested with lipase and alpha-amylase and extracted with 1% sodium bicarbonate solution-isopropanol (1 + 1). After C18 solid-phase extraction, vitamin K1 is separated by nonaqueous reversed-phase LC, converted to the hydroquinone by postcolumn zinc reduction, and quantitated by fluorescence detection. The limit of detection is 8 pg (3 sigma), and the limit of quantitation is 27 pg (10 sigma) on column. Linear response ranged from 0.1 to 1.0 ng vitamin K1 (r= 0.9999). The mean recovery (n = 38) for all spiking levels was 101.6 +/- 2.85%. Analysis of Standard Reference Material 1846, Infant Formula, gave a mean value of 0.95 +/- 0.088 mg vitamin K/kg (K or K1?) (n = 31) with a coefficient of variation of 9.26.

2-Propanol↗

PubMedDate not supplied

Matrix solid phase dispersion (MSPD) extraction and gas chromatographic screening of nine chlorinated pesticides in beef fat.

A multiresidue technique is presented for the extraction and quantitative gas chromatographic screening of 9 insecticides (lindane, heptachlor, aldrin, heptachlor epoxide, p,p'-DDE, dieldrin, endrin, p,p'-TDE, and p,p'-DDT) as residues in beef fat. Beef fat was fortified by adding the 9 insecticides, plus dibutyl chlorendate as internal standard, to 0.5 g portions of beef fat and blending with 2 g C18 (octadecylsilyl)-derivatized silica. The C18/fat matrix blend was fashioned into a column by adding the blend to a 10 mL syringe barrel containing 2 g activated Florisil. The insecticides were then eluted from the column with 8 mL acetonitrile, and a 2 microL portion of the acetonitrile eluate was then directly analyzed by gas chromatography with electron capture detection. Unfortified blank controls were treated similarly. The acetonitrile eluate contained all of the pesticide analytes (31.25-500 ng/g) and was free of interfering co-extractants. Correlation coefficients for the 9 extracted pesticide standard curves (linear regression analysis, n = 5) ranged from 0.9969 (+/- 0.0021) to 0.9999 (+/- 0.0001). Average relative percentage recoveries (85 +/- 3.4% to 102 +/- 5.0%, n = 25 for each insecticide), inter-assay variability (6.0 +/- 1.0% to 14.0 +/- 6.7%, n = 25 for each insecticide), and intra-assay variability (2.5-5.1% n = 5 for each insecticide) indicated that the methodology is acceptable for the extraction, determination, and screening of these residues in beef fat.

Animals↗

PubMedDate not supplied

Multiresidue matrix solid phase dispersion (MSPD) extraction and gas chromatographic screening of nine chlorinated pesticides in catfish (Ictalurus punctatus) muscle tissue.

A multiresidue technique for extraction and gas chromatographic screening of 9 insecticide (lindane, heptachlor, aldrin, heptachlor epoxide, p,p'-DDE, dieldrin, endrin, p,p'-TDE, and p,p'-DDT) residues in catfish (Ictalurus punctatus) muscle tissue is presented. The 9 insecticides, plus dibutyl chlorendate internal standard, were fortified into catfish muscle tissue (0.5 g) and blended with 2 g C18 (octadecylsilyl derivatized silica reverse-phase material). The C18/muscle tissue matrix blend was fashioned into a column by adding the blend to a 10 mL syringe barrel containing 2 g activated Florisil. The insecticides were then eluted from the column with acetonitrile (8 mL), and a portion (2 microL) of the acetonitrile eluate was then directly analyzed by gas chromatography with electron capture detection. Unfortified blank controls were treated similarly. The resultant extracts contained pesticide analytes (31.25-500 ng/g) free of interfering compounds when analyzed. Correlation coefficients for the 9 extracted pesticide standard curves (linear regression analysis, n = 5) ranged from 0.9967 (+/- 0.0018) to 0.9999 (+/- 0.0001). Average percentage recoveries (82 +/- 4.8% to 97 +/- 3.6%, n = 25 for each insecticide), interassay (5.0 +/- 2.7% to 16.9 +/- 6.5%, n = 25 for each insecticide) and intraassay (1.8 to 4.7%, n = 5 for each insecticide) variabilities were indicative of an acceptable methodology for the analysis and screening of these residues in catfish muscle tissue.

Animals↗

PubMedDate not supplied

Matrix solid phase dispersion (MSPD) isolation and liquid chromatographic determination of furazolidone in pork muscle tissue.

A method for the isolation and liquid chromatographic (LC) determination of furazolidone in pork muscle tissue is presented. Blank or furazolidone-fortified pork muscle tissue samples (0.5 g) were blended with octadecylsilyl (C18, 18% load, endcapped, 2 g) derivatized silica. A column made from C18/pork matrix was first washed with hexane (8 mL), followed by elution of furazolidone with ethyl acetate. The ethyl acetate extract was then passed through an activated alumina column. The eluate contained furazolidone that was free from interfering compounds when analyzed by LC with UV detection (photodiode array, 365 nm). Detector response with increasing concentrations of furazolidone isolated from fortified samples was linear (r = 0.998 +/- 0.002) with an average percentage recovery of 89.5 +/- 8.1% for the concentration range (7.8-250 ng/g) examined and resulted in a minimum detectable limit of 390 pg on column, and a detector response of more than 5 times baseline noise. The inter-assay variability was 9.9 +/- 5.4% with an intra-assay variability of 1.5%.

Animals↗

PubMedDate not supplied

Matrix solid-phase dispersion (MSPD) isolation and liquid chromatographic determination of oxytetracycline, tetracycline, and chlortetracycline in milk.

A multiresidue method for the isolation and liquid chromatographic determination of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) antibiotics in milk is presented. Blank and tetracycline (OTC, TC, and CTC) fortified milk samples (0.5 mL) were blended with octadecylsilyl (C18, 40 microns, 18% load, endcapped, 2 g) derivatized silica packing material containing 0.05 g each of oxalic acid and disodium ethylenediaminetetraacetic. A column made from the C18/milk matrix was first washed with hexane (8 mL), following which the tetracyclines were eluted with ethyl acetate-acetonitrile (1 + 3; v/v). The eluate contained tetracycline analytes that were free from interfering compounds when analyzed by liquid chromatography with UV detection (photodiode array, 365 nm). Correlation coefficients of standards curves for individual tetracycline isolated from fortified samples were linear (from 0.982 +/- 0.009 to 0.996 +/- 0.004) with average percentage recoveries from 63.5 to 93.3 for the concentration range (100, 200, 400, 800, 1600, and 3200 ng/mL) examined. The inter-assay variability ranged from 8.5 +/- 2.4% to 20.7 +/- 13.0% with an intra-assay variability of 1.0-9.3%.

Animals↗

PubMedDate not supplied

Matrix solid phase dispersion isolation and liquid chromatographic determination of five benzimidazole anthelmintics in fortified beef liver.

A multiresidue method for isolation and liquid chromatographic determination of 5 benzimidazole anthelmintics (thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) in beef liver tissue is presented. Blank or benzimidazole-fortified liver samples (0.5 g) were blended with octadecylsilyl derivatized silica packing material (C18, 18% load, endcapped, 2 g). A column made from the C18/liver matrix was first washed with hexane (8 mL), following which the benzimidazoles were eluted with acetonitrile. The acetonitrile extract was then passed through an activated alumina column. The eluate contained benzimidazole analytes that were free from interfering compounds as determined by UV detection (photodiode array, 290 nm). Correlation coefficients of standard curves for individual benzimidazoles isolated from fortified samples, using internal standardization, were linear (0.996 +/- 0.002 to 0.999 +/- 0.001) with average relative percentage recoveries from 62.0 +/- 6.7 to 86.8 +/- 8.6% for the concentration range (100-3200 ng/g) examined. The interassay variability was 7.0 +/- 4.1 to 12.9 +/- 10.2% with an intra-assay variability from 2.2 to 4.0%.

Animals↗

PubMedDate not supplied

Matrix solid phase dispersion isolation and liquid chromatographic determination of oxytetracycline in catfish (Ictalurus punctatus) muscle tissue.

A method for isolation and liquid chromatographic determination of oxytetracycline in catfish (Ictalurus punctatus) muscle tissue is presented. Blank control and oxytetracycline-fortified fish muscle tissue samples (0.5 g) were blended with octadecylsllyl (C18, 40 microns, 18% load, endcapped) derivatized silica packing material (2 g) containing 0.05 g each of oxalic acid and disodium ethylenediaminetetraacetate. A column made from the C18/fish tissue matrix was first washed with hexane (8 mL), following which the oxytetracycline was eluted with acetonitrile-methanol (1 + 1, v/v) containing 0.06% w/v each of butylated hydroxyanisole and butylated hydroxytoluene. The eluate contained oxytetracycline analyte that was free from interfering compounds when analyzed by liquid chromatography with UV detection (photodiode array set at 365 nm). Standard curves for oxytetracycline isolated from fortified samples were linear (0.998 +/- 0.002) with an average absolute percentage recovery of 80.9 +/- 6.6% for the concentration range (50, 100, 200, 400, 800, 1600, and 3200 ng/g) examined. The interassay variability was 11.3 +/- 5.2% with an intra-assay variability of 1.1%.

Animals↗

PubMedDate not supplied

Matrix solid phase dispersion isolation and liquid chromatographic determination of sulfadimethoxine in catfish (Ictalurus punctatus) muscle tissue.

A method for the isolation and liquid chromatographic determination of sulfadimethoxine in catfish (Ictalurus punctatus) muscle tissue is presented. Blank control and sulfadimethoxine-fortified fish muscle tissue samples (0.5 g) were blended with octadecyisilyl (C18, 40 micrograms, 18% load, endcapped) derivatized silica packing material. A column made from the C18/fish tissue blend was first washed with hexane (8 mL), following which the sulfadimethoxine was eluted with dichloromethane (8 mL). The eluant contained sulfadimethoxine analyte that was free from interfering compounds when analyzed by liquid chromatography with UV detection (photodiode array, 270 nm). Standard curves for sulfadimethoxine isolated from fortified samples were linear (0.999 +/- 0.001) with an average relative percentage recovery of 101.1 +/- 4.2% for the concentration range (50, 100, 200, 400, 800, and 1600 ng/g) examined using sulfamethoxazole as the internal standard. The interassay variability was 10.7 +/- 8.2% with an intra-assay variability of 2.2%.

Animals↗

PubMedDate not supplied

Multiresidue method for isolation and liquid chromatographic determination of seven benzimidazole anthelmintics in milk.

A multiresidue method for the isolation and liquid chromatographic determination of 7 benzimidazole anthelmintics (thiabendazole, oxfendazole, para-hydroxyfenbendazole, fenbendazole sulfone, mebendazole, albendazole, and fenbendazole) in milk is presented. Blank or benzimidazole-spiked milk samples (0.5 mL) were blended with octadecylsilyl (C-18, 18% load, end-capped) derivatized silica packing material. A column made from the C-18/milk matrix was first washed with hexane (8 mL), and then the benzimidazoles were eluted with methylene chloride-ethyl acetate (1 + 2, v/v; 8 mL). The eluate contained benzimidazole analytes which were free from interfering compounds as determined by UV detection (photodiode array, 290 nm). Correlation coefficients of standard curves for individual benzimidazoles isolated from spiked samples were linear (0.989 +/- 0.003 to 0.998 +/- 0.001) with recoveries ranging from 70 +/- 9% to 107 +/- 2% for the concentration range (62.5-2000 ng/mL) examined. The inter-assay variabilities ranged from 4 +/- 1% to 9 +/- 7% with intra-assay variabilities of 3-6%.

Animals↗

PubMedDate not supplied

Isolation and gas chromatographic determination of chlorsulfuron in milk.

A method for the isolation and gas chromatographic determination of chlorsulfuron in milk is presented. Blank or chlorsulfuron-spiked milk samples were blended into C-18 (octadecylsilyl derivatized silica, ODS) packing material. A column made from the C-18/milk matrix was washed with hexane after which chlorsulfuron was eluted with dichloromethane (DCM). The DCM eluate contained chlorsulfuron which was free from interfering co-extractants when analyzed by gas chromatography utilizing a nitrogen/phosphorus detector. Chlorsulfuron was found to undergo a thermally induced decomposition to give 2-amino-4-methoxy-6-methyl-1,3,5-triazine, which was detected and quantitated by this method. Standard curves for these analyses were linear (r = 0.992 +/- 0.004, n = 5), with an average percentage recovery of 91.6 +/- 10.8%, over the concentration range examined (62.5-2000 ng/mL). The inter- and intra-assay variabilities were 11.6 +/- 7.5% and 6.2%, respectively.

Animals↗

PubMedDate not supplied

Liquid chromatographic determination of simazine, atrazine, and propazine residues in catfish.

A liquid chromatographic (LC) method is described for the simultaneous determination of the triazine herbicides, simazine (SIM), atrazine (ATZ), and propazine (PRO) in the 12.5-100 ppb range in catfish. The herbicides are extracted from catfish homogenates with ethyl acetate, followed by solvent partitioning between acetonitrile and petroleum ether and additional cleanup on a C18 cartridge. A Supelcosil LC-18-DB column is used for LC separation, and UV determination is at 220 nm. The isocratic mobile phase is a mixture of methanol, acetonitrile, and water. Mean recoveries from catfish were 88.7, 96.9, and 91.7%; standard deviations were 6.84, 7.78, and 6.26%; and coefficients of variation were 7.72, 8.03, and 6.82% for SIM, ATZ, and PRO, respectively.

Animals↗

PubMedDate not supplied

Determination of flunixin in milk by liquid chromatography with confirmation by gas chromatography/mass spectrometry and selected ion monitoring.

A liquid chromatographic (LC) method was developed for the determination of flunixin (FNX) in raw bovine milk. The milk was acidified and mixed with silica gel, and the mixture was packed into a chromatographic column. The column was defatted with water-saturated dichloromethane-hexane (30 + 70, v/v), and the analyte was eluted with EtOAc. The EtOAc extract was washed with water at pH 3.5, the water was discarded, and the EtOAc layer was then extracted with 0.1M NaOH. The aqueous layer was drained, passed through a primed C18 solid-phase extraction (SPE) column, and eluted with EtOAc. The EtOAc layer was dried under N2, taken up in a solution of MeOH-(5 mM tetrabutylammonium [TBA]-H2PO4 + 2 mM NaOH) (50 + 50), sonicated, and filtered. FNX was determined by LC using a C18 column (ODS Hypersil), a mobile phase mixture of 58% A (MeOH) and 42% B (5 mM TBA-H2PO4 + 2 mM NaOH), and a diode-array ultraviolet detector at 285 nm. FNX was determined in raw milk at 5 spiking levels (5, 10, 20, 40, and 80 ng drug/mL milk). Absolute recoveries ranged from 69.6 to 74.4%, and relative standard deviations ranged from 1.1 to 6.9%. The limit of quantitation was 1.7 ng drug/mL milk. A lactating cow was dosed intravenously (2.2 mg/kg) with flunixin meglumine (Banamine) to generate incurred milk residues. FNX residues ranged from 7.34 ng/mL at 16 h postdose to 1.74 ng/mL at 24 h postdose. Both levels were obtained with additional beta-glucuronidase treatment (almost no incurred drug was detected at these low levels without the enzyme treatment).(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗

PubMedDate not supplied

Gas chromatographic/mass spectrometric confirmation of leucomalachite green in catfish (Ictalurus punctatus) tissue.

A gas chromatographic/mass spectrometric (GC/MS) method was developed to confirm the presence of leucomalachite green (LMG), a metabolite of the triphenylmethane dye malachite green (MG), in catfish tissue. Residues were isolated according to a previously described liquid chromatographic (LC)/VIS spectrometric analysis of MG and LMG in fish. In our isolation procedure, analytes are extracted from tissue with acetonitrile-buffer, partitioned into CH2Cl2, and applied to neutral alumina and propylsulfonic acid solid-phase extraction cartridges. Before GC/MS analysis, extracts prepared for the LC determinative method are eluted from a cyano solid-phase extraction cartridge, extracted into organic solvent, and concentrated for GC/MS analysis. Selected ion monitoring was performed by using 5 diagnostic ions (m/z 330, 329, 253, 210, and 165) of LMG. The method was validated by confirming LMG in tissue fortified with mixtures of MG and LMG (5 and 10 ng/g each) and in tissue from fish that had been exposed to low levels of MG.

Aniline Compounds↗

PubMedDate not supplied

Liquid chromatographic determination of the anticoccidial drug halofuginone hydrobromide in eggs.

A liquid chromatographic (LC) method is described for the determination of 5-100 ppb halofuginone hydrobromide (HFG) in eggs. HFG as the free base is extracted from eggs with ethyl acetate. The extract is cleaned up on an acidic Celite 545 column. A Waters C18 column is used for LC separation with UV determination at 243 nm. The isocratic mobile phase is a mixture of water-acetonitrile-ammonium acetate buffer (12 + 5 + 3) and acetic acid. The interassay average recovery from eggs was 90.4%, with a standard deviation of 5.11 and a relative standard deviation of 5.65%.

Animals↗

PubMedDate not supplied

Determination of malachite green and its metabolite, leucomalachite green, in catfish (Ictalurus punctatus) tissue by liquid chromatography with visible detection.

To determine residues of malachite green (MG) and its metabolite, leucomalachite green (LMG), in catfish tissue, analytes are extracted with acetonitrile-buffer and the extract is partitioned into methylene chloride. Final cleanup and isolation are performed on neutral alumina solid-phase extraction (SPE) and propylsulfonic acid cation-exchange SPE columns before analysis by liquid chromatography with visible detection. PbO2 postcolumn oxidation is performed by isocratic elution with a buffered mobile phase from a cyano column. Recoveries and relative standard deviations (RSDs) from fortified catfish tissues were 72.9% (RSD, 1.92%; 23 ppb), 75.5% (RSD, 6.85%; 11 ppb), and 69.6% (RSD, 6.93%; 5.7 ppb) for MG and 87.4% (RSD, 2.92%; 21 ppb), 88.1% (RSD, 5.94%; 10 ppb), and 82.6% (RSD, 11.5%; 5.3 ppb) for LMG. The method was applied to MG-incurred catfish at depuration times of 0, 2, 4, 8, and 24 h. Average levels of residual MG and LMG in the 24 h depuration catfish tissue were 73.4 and 289 ppb, respectively.

Animals↗