Direct analysis of the wild oat herbicide, asulam, in wheat samples by reversed-phase liquid chromatography at selected ultraviolet wavelengths.
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Carbamates↗
Biomedical subjects
J F Lawrence
Publications and source records attributed to J F Lawrence.
Determination of total non-sulphonated aromatic amines in tartrazine, sunset yellow FCF and allura red by reduction and derivatization followed by high-performance liquid chromatography.
Free and bound non-sulphonated aromatic amines (NSAA) are determined in the food colours tartrazine, sunset yellow FCF and allura red. After reduction of the bound amines with sodium dithionite, the NSAA are extracted into chloroform, then transferred to aqueous acid solution, diazotized with sodium nitrite and coupled with 2-naphthol-3,6-disulphonic acid, disodium salt (R-salt). Reversed-phase ion-pair liquid chromatography and an absorbance detector at 512 nm are used to analyse the coloured derivatives. Samples of dyes were spiked with known amounts of aniline, 1-naphthylamine, 2- and 4-aminobiphenyl, 4-aminoazobenzene, benzidine, p-cresidine or 4-nitro-p-cresidine bound to R-salt. Recoveries averaged 90% in tartrazine, 65% in sunset yellow FCF and 71% in allura red. Detection limits ranged between 2 and 32 ng/g. A survey of 24 commercial samples revealed levels up to 520 micrograms/g total NSAA. The majority of NSAA are bound to the coupling compound during the manufacturing process and less than 7% remain as free amines in the dye.
Amines↗
Determination of total non-sulphonated aromatic amines in soft drinks and hard candies by reduction and derivatization followed by high-performance liquid chromatography.
Utilizing elements of methodology developed previously for food colours, total free and bound non-sulphonated aromatic amines (NSAA) were determined in commercial samples of soft drink beverages and hard candies. Bound amines in the samples were reduced using sodium dithionite, then total NSAA were extracted into chlorofom, transferred to aqueous acid solution and diazotized with sodium nitrite before coupling with 2-naphthol-3,6-disulphonic acid, disodium salt (R-salt). The coloured derivatives were analysed using reversed-phase ion pair high-performance liquid chromatography (HPLC) and an absorbance detector set at 512 nm. Solid phase extraction cartridges were utilized for extraction and clean-up of the food colours present in the sample, and the concentration of each dye was determined quantitatively using HPLC and absorbance detector wavelengths of 426, 516 or 625 nm. Levels of total NSAA were compatible with those observed previously in food colours. Commercial soft drinks were found to contain (expressed in terms of total free plus bound NSAA in the beverage) 0.19-12.6 ng/ml of aniline, 0.83-8.25 ng/ml 1-naphthylamine and 0.62-1.12 ng/ml 2-naphthylamine. Levels of 0.66-9.15 ng/g of aniline and 2.48-10.6 ng/g 1-naphthylamine were found in commercial samples of hard candies. Bound NSAA in hard candies appeared to survive the manufacturing process. Recoveries averaged 96.9% for tartrazine and 89.6-97.2% for the bound amines when hard candies were prepared in the laboratory.
Amines↗
Determination of annatto in high-fat dairy products, margarine and hard candy by solvent extraction followed by high-performance liquid chromatography.
Utilizing solvents such as ethanolic aqueous ammonia, petroleum ether, hexane and chloroform, annatto components alpha- and beta-norbixin and alpha- and beta-bixin were extracted from cheese, butter, margarine and hard candy. After transferring the extract into a solution of aqueous acetic acid in methanol, bixin and norbixin were determined quantitatively using high-performance liquid chromatography (HPLC) and an absorbance detector set at 500 nm. Recovery of norbixin from spiked cheese samples averaged 92.6% over a range of 1 to 110 micrograms/g. Commercial cheese samples were found to contain 1.1-68.8 microgram/g total norbixin, and two samples also contained 5.1-5.6 micrograms/g total bixin. Samples of uncoloured butter were spiked with bixin and recovery averaged 93.2% over a range of 0.1 to 445 micrograms/g. Levels of 0.2 microgram/g total bixin and 0.91 microgram/g total norbixin were found in one commercial butter sample; the others contained trace levels of both compounds. Hard candies were prepared in the laboratory and recovery studies conducted. Recovery of norbixin averaged 88%.
Bixaceae↗
Ion chromatographic determination of cyanide released from flaxseed under autohydrolysis conditions.
Flaxseed is increasingly being used in some food products because of its high content of alpha-linolenic acid and dietary fibre. However, flaxseed contains cyanogenic glycosides which release toxic hydrogen cyanide in the presence of water (autohydrolysis). A method for estimation of cyanide in flaxseed under these conditions is described. The determination is carried out by homogenizing the sample with water, letting it stand, filtering it through a membrane and then injecting the filtrate into an HPLC system consisting of an anion exchange column and an electrochemical (amperometric, oxidation) detector. The homogenate is analysed at various intervals until a maximum value of cyanide is observed. The cyanide content of ten cultivars of flaxseed, when analysed by this method, was found to range from 124 to 196 micrograms/g. The release of cyanide showed a maximum at about 3 h of hydrolysis. Virtually no cyanide was detected on boiling the homogenate or the flaxseed before determination.
Anions↗
Lengthening of the humerus for upper extremity limb length discrepancy.
We present a case of humeral lengthening for a limb length discrepancy of 7.7 cm due to proximal humeral growth arrest in a 12-year-old boy. Lengthening of 69 mm was achieved using the Wagner technique. Bone grafting was not required. Humeral lengthening may be performed for upper extremity limb length discrepancy with good results. Objectives of treatment must include protection of the radial nerve from traction injury and from entrapment in the osteotomy site. Elbow extension may be lost during lengthening, but in the adolescent age group, full return of elbow motion can be expected.
Bone Diseases↗
Evaluation of silica- and sepharose-based immunoaffinity sorbents for sample cleanup in determination of fumonisins B1 and B2 in corn products.
Anti-fumonisin B1 polyclonal antibodies were isolated from the serum of rabbits, immobilized onto the surface of glutaraldehyde-activated silica or Sepharose CL-4B particles, and placed into empty small plastic solid-phase extraction cartridges. The immobilized antibodies were evaluated for their ability to retain fumonisin B1 and fumonisin B2. Cartridge capacity and elution conditions were determined, and the results were compared to those obtained with a commercially available cartridge. The cartridges, which were tested for their effectiveness to isolate the fumonisins from extracts of corn flour and nacho chips, detected fumonisins down to levels of about 20 ng/g. However, additional cleanup was required for detection at lower concentrations. With the use of a strong anion-exchange cartridge as a preliminary cleanup before immunoaffinity chromatography, the detection limit reached 2-5 ng/g in the products tested. The silica sorbent material exhibited strong interactions with the fumonisins, requiring acidified ethanol-water mixtures for elution and resulting in an additional degree of selectivity in isolating fumonisins from sample extracts. The silica-based immunoaffinity cartridges were successfully reused more than 10 times; the Sepharose-based cartridges were less robust. Liquid chromatography with fluorescence detection was used after prechromatographic derivatization with o-phthaldialdehyde-mercaptoethanol.
Animals↗
Effect of temperature and solvent composition on extraction of fumonisins B1 and B2 from corn products.
Fumonisins B1 and B2 were extracted from naturally contaminated corn products by using different extraction solvent compositions (methanol-water, acetonitrile-methanol-water, ethanol-water, and 100% water) and a range of temperatures from ambient to 150 degrees C. Ground samples of several corn products and 1 rice sample were mixed with an adsorbent material (Hydromatrix), and the fumonisins were extracted in 2 sequential 5 min static extractions at various temperatures. The combined extracts were cleaned up and analyzed by reversed-phase liquid chromatography with fluorescence detection after o-phthaldialdehyde-mercaptoethanol derivatization. The results showed a clear influence of temperature and solvent composition on recovery of fumonisins from some matrixes. With acetonitrile-methanol-water (1 + 1 + 2) the quantity of fumonisins extracted from naturally contaminated taco shells almost tripled in going from 23 degrees to 80 degrees C, and increased by another 30% when ethanol-water (3 + 7) was used as extraction solvent at 80 degrees C. Similar results were obtained with nacho chips. These effects were less pronounced with cornmeal, and small differences due to temperature and solvent composition were observed for corn flakes and rice. The ethanol-water extraction solvent combinations were specifically evaluated in an effort to use the cheapest, least toxic, and most environmentally friendly solvents for organic residue analysis. At 80 degrees C, ethanol-water combinations performed equally or better than methanol-water (8 + 2) or acetonitrile-methanol-water (1 + 1 + 2), combinations which are commonly used for fumonisin extractions. Even 100% water was successful for extracting fumonisins from the products, except for rice. However, increased amounts of water created technical problems and required an increased amount of Hydromatrix in the samples prior to extraction.
Carboxylic Acids↗
Comparison of liquid chromatography/mass spectrometry, ELISA, and phosphatase assay for the determination of microcystins in blue-green algae products.
More than 100 samples of blue-green algae products (consisting of Aphanizomenon, Spirulina, and unidentified blue-green algae) in the form of pills, capsules, and powders were collected from retail outlets from across Canada. The samples were extracted with 75% methanol in water and centrifuged to remove solids. Aliquots of the extracts along with spiked blank sample extracts were sent to each participating laboratory and independently analyzed for microcystins by enzyme-linked immunosorbent assay (ELISA), protein phosphatase inhibition assay, and by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after sample cleanup using C18 solid-phase extraction. The results obtained by ELISA and LC-MS/MS agreed very well over a concentration range of about 0.5-35 microg/g. The colorimetric phosphatase results generally agreed with the other 2 methods. While the 2 biochemical assays measured total microcystin content compared with a standard of microcystin LR, the LC-MS/MS method measured specific microcystins (LA, LR, RR, YR) using external standards of these for identification and quantitation. Microcystin LR was found in all positive samples by LC-MS/MS. Microcystin LA was the only other microcystin found in the samples analyzed. These 2 microcystins represent essentially all the microcystins that were present in the extracts. Otherwise, the LC-MS/MS results would have been significantly lower than the results of the biochemical assays had other unknown microcystins been present.
Chromatography, Liquid↗
Quantitative determination of paralytic shellfish poisoning toxins in shellfish by using prechromatographic oxidation and liquid chromatography with fluorescence detection.
The prechromatographic oxidation LC method developed by Lawrence [J. Assoc. Off. Anal. Chem. 74, 404-409(1991)] for the determination of paralytic shellfish poisoning (PSP) toxins has been tested for the quantitative determination of PSP toxins in shellfish. All aspects of the method were studied and modified as necessary to improve its performance for routine regulatory purposes. The chromatographic conditions were changed to shorten analysis time. The oxidation reaction was tested for repeatability and the influence of the sample matrix on quantitation. An important part of the study was to quantitatively evaluate an ion exchange (-COOH) cleanup step using disposable solid-phase extraction cartridges that separated the PSP toxins into 3 distinct groups for quantitation, namely the C toxins, the GTX toxins, and the saxitoxin group. The cleanup step was very simple and used increasing concentrations of aqueous NaCl for elution of the toxins. The C toxins were not retained by the cartridges and thus were eluted unretained with water. The GTX toxins (GTX1 to GTX6 as well as dcGTX2 and dcGTX3) eluted from the cartridges with 0.05M NaCl while the saxitoxin group (saxitoxin, neosaxitoxin, and dcsaxitoxin) required 0.3M NaCl for elution. Each fraction was analyzed by LC after oxidation with periodate or peroxide. All of the compounds could be separated and quantitatively determined in spiked samples of mussels, clams, and oysters. The nonhydroxylated toxins could be quantitated at concentrations as low as about 0.02 microg/g (2 micro/100 g) of tissue while the hydroxylated toxins could be quantitated at concentrations as low as about 0.1 microg/g (10 microg/100 g). Average recoveries of the toxins through the complete cleanup procedure were 85% or greater for spiked extracts of oysters and clams and greater than 73% for mussels.
Animals↗
A study of ten toxins associated with paralytic shellfish poison using prechromatographic oxidation and liquid chromatography with fluorescence detection.
Ten paralytic shellfish toxins [saxitoxin, neosaxitoxin, B-1, B-2, gonyautoxin 1, 2, and 3 (i.e., GTX-1, GTX-2, and GTX-3), C-1, C-2, and C-3] were oxidized at room temperature under mildly basic conditions with hydrogen peroxide or periodic acid. The products were then analyzed by liquid chromatography (LC). The N-1-hydroxylated toxins (neosaxitoxin, B-2, GTX-1, and C-3) formed fluorescent products after periodate oxidation at ca pH 8.7, but did not form fluorescent derivatives with peroxide oxidation. The non-N-1-hydroxylated toxins (saxitoxin, B-1, GTX-2, GTX-3, C-1, and C-2) formed highly fluorescent derivatives with both peroxide and periodate oxidations. Individual toxins produced mainly single fluorescent peaks by reverse-phase LC. However, all GTX toxins eluted with the same retention time. Also, C-1 and C-2 eluted together, as did neosaxitoxin and B-2. The non-N-1-hydroxylated toxins could be detected in quantities as low as 20-50 pg/injection, while the N-1-hydroxy analogues could be detected at levels as low as 100-500 pg/injection. UV absorption and fluorescence emission spectra were similar for the oxidation products of all toxins examined (max. 333 +/- 2 nm absorption, 389 +/- 4 nm fluorescence emission).
Animals↗
Liquid chromatographic determination of paralytic shellfish poisons in shellfish after prechromatographic oxidation.
A liquid chromatographic method for quantitating paralytic shellfish poison toxins in shellfish has been developed in which the toxins are converted to fluorescent purines by prechromatographic oxidation under mildly basic conditions with hydrogen peroxide or periodate. The addition of ammonium formate to the periodate oxidation reaction greatly improved the yield of fluorescent derivatives for neosaxitoxin, gonyautoxin-1, B-2, and C-3 compared to the same reaction without ammonium formate. As little as 3-6 ng of each of the nonhydroxylated toxins and 7-12 ng of the hydroxylated compounds per gram of shellfish could be detected. Reversed-phase chromatography using ammonium formate in the mobile phase improved the chromatography of neosaxitoxin and B-2 compared to results obtained earlier. Because the oxidation products of neosaxitoxin and B-2 could not be separated, parent compounds were separated before oxidation by using an SPE-COOH ion exchange cartridge. The repeatability coefficient of variation for the oxidation reactions ranged from 3 to 8% for the peroxide reaction, and from 4 to 11% for the periodate reaction, depending upon the individual toxin determined and its concentration in the extract (0.04-0.55 micrograms/g). The method was compared to the mouse bioassay and the postcolumn oxidation method. In most cases, results were comparable.
Chromatography, Liquid↗
Liquid chromatographic determination of domoic acid in mussels, using AOAC paralytic shellfish poison extraction procedure: collaborative study.
A liquid chromatographic method using the AOAC paralytic shellfish poison (PSP) extraction procedure for domoic acid, a marine toxin, in mussel tissue was collaboratively studied in 10 laboratories. Domoic acid is extracted by boiling the homogenized tissue for 5 min with 0.1N HCl. The mixture is cooled, diluted to a known volume, and then centrifuged. An aliquot of the supernate is diluted, filtered, and analyzed by reverse-phase liquid chromatography with a mobile phase containing acetonitrile and water adjusted to about pH 2.5. Each collaborator received a prepared standard solution, a practice sample, and 7 randomly numbered unknown samples (1 blank mussel tissue, 1 spiked at 14.1 micrograms domoic acid/g, 1 spiked at 18.9 micrograms/g, and duplicate samples with naturally incurred domoic acid at 75 micrograms/g and at 186 micrograms/g). Five of the laboratories had little or no experience in domoic acid analysis. Ten of 11 laboratories completed the study and submitted results. Two individual values out of a total of 70 were found to be outliers. Mean recovery of domoic acid from the spiked extracts was 75%. Relative standard deviations between laboratories (RSDR) ranged from 7.5 to 19.4%; within-laboratory RSDs (RSDr) for the 2 blind duplicate pairs were 1.9 and 4.8%. The detection limit was about 1 microgram domoic acid/g. The method has been adopted official first action by AOAC.
Animals↗
Comparison of three liquid chromatographic methods with FDA optimized Monier-Williams method for determination of total sulfite in foods.
Three liquid chromatographic (LC) methods employing amperometric detection were compared with the collaboratively studied FDA optimized Monier-Williams distillation method for the determination of total sulfite in 5 food types. The foods included lemon juice, white wine, instant mashed potatoes, golden raisins, and onion flakes. Two of the LC methods (one employing headspace sampling and the other direct injection) used ion-exchange chromatography with a basic mobile phase (pH about 10.8) and a glassy carbon electrode; the third (employing direct injection) used ion-exclusion chromatography with an acidic mobile phase (pH about 2) and a platinum electrode. All 4 methods produced similar results for the wine, lemon juice, and raisins. Results were different for instant mashed potatoes and onion flakes. The headspace-LC method and direct ion-exclusion LC method, both of which employed an alkaline sample extraction, yielded significantly higher values for sulfite in instant potatoes than did the other 2 methods. A large interfering peak with both direct LC methods prevented quantitation of sulfite in the onion flakes. All methods can detect sulfite as low as about 1 microgram/g in 4 of 5 food types examined.
Chromatography, Gel↗
Determination of sodium dioctylsulfosuccinate in dry beverage bases by liquid chromatography with post-column ion-pair extraction and absorbance detection.
Sodium dioctylsulfosuccinate (DSS) is extracted as an ion pair with methylene blue from finished drinks prepared from dry beverage bases. The complex is quantitatively determined colorimetrically in chloroform-acetone solution by a standard procedure. DSS is specifically identified by analyzing an aliquot of the extract by reverse phase liquid chromatography (LC). The compound is detected by using a simple post-column dynamic extraction system in which DSS is extracted from the aqueous mobile phase into chloroform as a methylene blue ion pair. The chloroform phase passes through the absorbance detector for measurement at 546 nm (filter detector). The absolute detection limit was 5-10 ng DSS, while in beverage bases as low as 0.1 microgram/g was detected. Extraction of the beverage bases with mobile phase followed by filtration and direct LC analysis with the described system was also successful, although not evaluated on a routine basis.
Beverages↗
Determination of sulfite in foods by headspace liquid chromatography.
Sulfite was determined in a variety of foods by liquid chromatography (LC) after the samples were mixed with a solution containing mannitol, FeSO4, and Na2HPO4, adjusted to pH 11, and left to stand for 15 min at room temperature. An aliquot of the mixture was placed in a headspace vial and mixed with 50% H3PO4. After 15 min, a portion of the headspace was removed with a syringe containing LC mobile phase without acetonitrile. The syringe was shaken and an aliquot of the solution was analyzed on an anion exchange column with a mobile phase of 0.03M methane sulfonate (pH 10.8) containing 5% acetonitrile. Sulfite was detected amperometrically (glassy carbon electrode) at +0.7 V. The method was successfully compared to the FDA-modified Monier-Williams procedure for a variety of foods. Minimum detectable levels were about 1 microgram/g, based on a 15 g sample.
Animals↗
Determination of seven artificial sweeteners in diet food preparations by reverse-phase liquid chromatography with absorbance detection.
The artificial sweeteners aspartame, saccharin, cyclamate, alitame, acesulfam-K, sucralose, and dulcin are determined in diet soft drinks and tabletop sweetener preparations. Samples are diluted, filtered, and analyzed directly by liquid chromatography on a C-18 reverse-phase column with a mobile phase gradient ranging from 3% acetonitrile in 0.02M KH2PO4 (pH 5) to 20% acetonitrile in 0.02M KH2PO4 (pH 3.5). Diet puddings and dessert toppings are extracted with ethanol, filtered, and diluted with mobile phase for analysis. The sweeteners, except sucralose and cyclamate, were detected by UV absorbance at either 200 or 210 nm. Sucralose was determined at 200 nm or by refractive index. Cyclamate was determined after post-column ion-pair extraction. The sweeteners stevioside and talin were not detected. Additives such as caffeine, sorbic acid, and benzoic acid did not interfere.
Beverages↗
Capillary column gas chromatographic determination of ethyl carbamate in alcoholic beverages with confirmation by gas chromatography/mass spectrometry.
A method is described for determining ethyl carbamate at low microgram/kg levels in several types of alcoholic beverages by capillary column gas chromatography with Hall electrolytic conductivity detection and confirmation by mass spectrometry. Samples are diluted to obtain a uniform concentration of ethanol (ca 10%) then saturated with NaCl and extracted with methylene chloride. Extracts are evaporated to a small volume and injected in ethyl acetate solution for chromatographic analysis. The method was evaluated by 5 laboratories, 4 employing the Hall detector and one using mass spectrometric detection. Overall between-laboratory mean percent recoveries were: wine, 85.3 +/- 21.0% coefficient of variation (CV) (spiking level 20-45 micrograms/kg); sherry, 83.8 +/- 16.1% CV (spiking level, 81-142 micrograms/kg); whiskey, 79.5 +/- 13.9% CV (spiking level 127-190 micrograms/kg); and brandy, 85.0 +/- 12.5% CV (spiking level 297-446 micrograms/kg). Mass spectrometric results agreed well with the Hall results for all commodities. Detection limits were about 5 micrograms/kg for the Hall detector and about 0.5 microgram/kg for mass spectrometric detection.
Alcoholic Beverages↗