Determination of carbofuran and its metabolites in rice paddy water by using solid phase extraction and liquid chromatography

A procedure for the determination of carbofuran and its metabolites (carbamate and phenolic) in rice paddy water is described. Water samples are concentrated on a C-18 solid phase extraction (SPE) column and eluted with methanol-water. The eluate is analyzed by reverse-phase liquid chromatography (LC) and measured by a wavelength programmable ultraviolet (UV) detector. The limit of detection for the method is 0.4 micrograms/L. Recovery studies were carried out at levels ranging from 1 to 15 micrograms/L in both rice paddy water and distilled water; recoveries ranged from 85.9 to 112.9%.     

Determination of neonicotinoid pesticide residues in vegetables and fruits with solid phase extraction and liquid chromatography mass spectrometry

A rapid and simple extraction method for the simultaneous analysis of five neonicotinoid insecticides has been developed. Twelve different fruit and vegetable matrixes were extracted with methanol and cleaned up using a graphitized carbon solid phase extraction cartridge loading with a 20% methanol solution. The concentrated eluate after methanol elution was then analyzed for pesticide residues by liquid chromatography/mass spectrometry in the APCI positive mode. The five pesticides including nitenpyram, thiamethoxam, imidacloprid, acetamiprid, and thiacloprid were recovered at 70-95% at spike levels of 0.1 and 1 mg/kg in bell pepper, cucumber, eggplant, grape, grapefruit, Japanese radish, peach, pear, potato, rice, and tomato. Relative standard deviations were less than 10% for all of the recovery tests. The proposed method is fast, easy to perform, and could be utilized for regular monitoring of pesticide residues.     

Analysis of fat-soluble vitamins. XXIII. High performance liquid chromatographic assay for vitamin D in vitamin D3 and multivitamin preparations.

Vitamin D is determined in preparations containing other fat-soluble vitamins by high performance liquid chromatography (HPLC). The unsaponifiable residue is extracted and separated from interferences by reverse phase chromatography; the fraction corresponding to vitamin D3 is collected and quantitated using normal phase chromatography (amylalcohol-n-hexane as mobile phase) by measuring the vitamin D3 and pre-vitamin D3 peaks at 254 nm. Previtamin D3 content is calculated as vitamin D3 with a conversion factor (determined on the equipment used). Application of the method to vitamin AD3 mixtures in oils gives 98-102% recovery. The reproducibility, using an external standard, is 2-3%, calculated as the coefficient of variation; with an internal standard, the coefficient of variation is 1-1.5%. The method measures potential vitamin D3 content in preparations containing greater than or equal to 200 IU/g in the presence of all known vitamin D3 isomers, vitamin A, and vitamin E.     

Determination of saccharin, sodium benzoate, and caffeine in beverages by reverse phase high-pressure liquid chromatography.

A reverse phase high-pressure liquid chromatographic method is presented for the simultaneous separation and determination of sacchrain, sodium benzoate, and caffeine in soft drinks, fruit juices, fruit cocktails, fruit punches, coffee, and artificial sweetener concentrates. Decarbonated soft drinks, fruit punches, and artificial sweetener concentrates are injected directly into the chromatograph. Fruit juices and coffee solutions require filtration through a 0.45 mum pore membrane filter prior to injection. Samples are eluted from a mu-Bondapak/C18 column with 5% glacial acetic acid and are quantitated with an ultraviolet detector. The results of saccharin, sodium benzoate, and caffeine determinations in 34 soft drinks (representing 11 manufacturers and 20 flavors); 8 fruit juices, cocktails, and punches; 7 coffees; and 6 artificial sweetener concentrates are presented. Average recoveries of saccharin, sodium benzoate, and caffeine from soft drinks are 99.0, 99.3, and 100.2%, respectively.     

Determination of isoxaflutole (balance) and its metabolites in water using solid phase extraction followed by high-performance liquid chromatography with ultraviolet or mass spectrometry

Balance (isoxaflutole, IXF) belongs to a new family of herbicides referred to as isoxazoles. IXF has a very short soil half-life (<24 h), degrading to a biologically active diketonitrile (DKN) metabolite that is more polar and considerably more stable. Further degradation of the DKN metabolite produces a nonbiologically active benzoic acid (BA) metabolite. Analytical methods using solid phase extraction followed by high-performance liquid chromatography-UV (HPLC-UV) or high-performance liquid chromatography-mass spectrometry (HPLC-MS) were developed for the analysis of IXF and its metabolites in distilled deionized water and ground water samples. To successfully detect and quantify the BA metabolite by HPLC-UV from ground water samples, a sequential elution scheme was necessary. Using HPLC-UV, the mean recoveries from sequential elution of the parent and its two metabolites from fortified ground water samples ranged from 68.6 to 101.4%. For HPLC-MS, solid phase extraction of ground water samples was performed using a polystyrene divinylbenzene polymer resin. The mean HPLC-MS recoveries of the three compounds from ground water samples spiked at 0.05-2 microg/L ranged from 100.9 to 110.3%. The limits of quantitation for HPLC-UV are approximately 150 ng/L for IXF, 100 ng/L for DKN, and 250 ng/L for BA. The limit of quantitation by HPLC-MS is 50 ng/L for each compound. The methods developed in this work can be applied to determine the transport and fate of Balance in the environment.     

Separation and identification of nine penicillins by reverse phase liquid chromatography

A simple and rapid high performance liquid chromatographic method was developed for the separation and identification of amoxicillin, ampicillin, cloxacillin, dicloxacillin, methicillin, oxacillin, nafcillin, penicillin G potassium, and penicillin V potassium. The antibiotics were separated at ambient temperature on a Chromegabond 10 microns C18 column with acetonitrile-methanol-0. 01M potassium dihydrogen phosphate buffer, pH 4.7 (19 + 11 + 70), at 1 mL/min. A variable wavelength detector set at 225 nm, 0.16 AUFS , and a recorder set at 0.25 cm/min were used for the detection. Individual antibiotics and their mixtures were dissolved in the mobile phase and injected into the chromatograph through a 20 microL injection loop. Baseline separation was observed for virtually all 9 antibiotics. The entire mixture was resolved in less than 30 min. The method was sensitive, reproducible, and applicable to the qualitative analysis of commercial dosage forms.     

Separation and purification of sulforaphane from broccoli seeds by solid phase extraction and preparative high-performance liquid chromatography

A novel, rapid, and economical method to isolate and purify natural sulforaphane from broccoli seeds is described. The procedure involves solvent extraction of autolyzed seed meal, followed by separation by solid phase extraction (SPE) and purification by preparative high-performance liquid chromatography (HPLC). The SPE method provides higher yield of sulforaphane from crude extracts compared to conventional liquid-liquid extraction. High purity and recovery of sulforaphane product can be obtained by preparative HPLC with a C 18 column and 30% methanol in water as the mobile phase. The purified compound was characterized by MS and (1)H and (13)C NMR. The techniques described here are useful tools in the preparative-scale isolation of sulforaphane in a fast, cost-effective, and waste-conscious manner.     

Determination of organochlorine and organophosphorus pesticide residues in eggs using a solid phase extraction cleanup

A multiresidue solid phase extraction (SPE) method for the isolation and subsequent gas chromatographic determination of nonpolar organochlorine and polar organophosphorus pesticide residues in eggs is described. The method uses an acetonitrile extraction followed by an SPE cleanup using graphitized carbon black and aminopropyl SPE columns. Organophosphorus pesticides are determined by gas chromatography with flame photometric detection. After further cleanup of the extract using Florisil SPE columns, organochlorine pesticides are determined by gas chromatography with electron capture detection. Studies were performed using eggs containing both fortified and incurred pesticide residues. The average recoveries were 86-108% for 8 fortified organochlorine pesticide residues and 61-149% for 28 fortified organophosphorus pesticide residues.     

Sample preparation and liquid chromatographic determination of vitamin D in food products

Vitamin D in different fortified foods is determined by using liquid chromatography (LC). Sample preparation is described for fortified skim milk, infant formulas, chocolate drink powder, and diet food. The procedure involves 2 main steps: saponification of the sample followed by extraction, and quantitation by LC analysis. Depending on the sample matrix, additional steps are necessary, i.e., enzymatic digestion for hydrolyzing the starch in the sample and cartridge purification before LC injection. An isocratic system consisting of 0.5% water in methanol (v/v) on two 5 microns ODS Hypersil, 12 X 0.4 cm id columns is used. Recovery of vitamin D added to unfortified skim milk is 98%. The results of vitamin D determination in homogenized skim milk, fortified milk powder, fortified milk powder with soybean, chocolate drink powder, and sports diet food are given.     

A simple method for the determination of trace levels of alkylphenolic compounds in fish tissue using pressurized fluid extraction, solid phase cleanup, and high-performance liquid chromatography fluorescence detection

A simple automated extraction method for the determination of alkylphenolic compounds in fish tissue is reported. Pressurized fluid extraction is used to extract ground fish tissue, and the resulting extract is purified on aminopropyl silica (APS) extraction cartridges. With no further sample preparation, nonylphenol (NP) and its ethoxylates, up to nonylphenol pentaethoxylate, are quantitated using normal phase (APS Hypersil) high-performance liquid chromatography with fluorescence detection. The major advantage of this technique is elimination of the conventional gel permeation cleanup step, a lengthy procedure designed to remove fish lipids. Spiked recoveries with lake trout averaged 85% for the six NP and NP ethoxylates that were investigated. Tissue concentrations of NP and NP ethoxylates determined in fish from various locations of the Great Lakes region ranged from 18 to 2075 ng/g, wet weight.     

Quantitative amino acid analysis of feedstuff hydrolysates by reverse phase liquid chromatography and conventional ion-exchange chromatography

Corn, soybean meal, and isolated soybean protein samples were acid-hydrolyzed and analyzed for amino acid content by reverse phase liquid chromatography (LC) and by conventional ion-exchange chromatography (IEC) using an amino acid analyzer. The former method employed pre-column derivatization with orthophthalaldehyde (OPTA)/ethanethiol and fluorescence detection. In the LC procedure, glycine and threonine were not resolved, and proline and cyst(e)ine were not detected. In general, amino acid values obtained by LC and IEC compared closely within and across feedstuffs, and both agreed well with published amino acid composition data. The notable exceptions were aspartic acid, glutamic acid, and alanine. Results of this study suggest that reverse phase LC with pre-column OPTA derivatization can be applied to accurately measure primary amino acids in individual feedstuffs.     

基质固相分散萃取-高效液相色谱串联质谱法测定土壤中残留的磺酰脲类除草剂

建立了基质固相分散萃取-高效液相色谱串联质谱法(MSPD-HPLC-MS/MS)测定土壤中3种磺酰脲类除草剂(氯磺隆、甲磺隆、苯磺隆)残留的分析方法。对基于球磨的基质固相分散萃取条件进行了详细优化,最终确定最佳条件为:0.2 g土壤样品、0.8 g HC-C18粉末状分散剂与直径为8 mm的小钢珠一起球磨10 min后,转移至空的玻璃萃取小柱,用10 m L乙腈洗脱,氮气吹干后用甲醇定容至0.6 m L,再经0.22μm的滤膜抽滤后装入自动进样瓶中。用Syncronis C18反相色谱柱分离,以甲醇(A)~1‰甲酸溶液(B)为流动相进行梯度洗脱,选择反应监测(SRM)模式下进行检测。氯磺隆在20~200μg·kg~(-1),甲磺隆和苯磺隆在10~200μg·kg~(-1)范围内线性良好,相关系数r在0.997 9~0.999 5。土壤样品的平均加标回收率在84.7%~104.6%,相对标准偏差在4.5%~7.9%(n=5)。方法的检出限(S/N=3)0.32~0.68μg·kg~(-1)。该方法简单、效率高、干扰少、回收率高,满足土壤中除草剂的残留分析要求。     

Combined use of supercritical fluid extraction, micellar electrokinetic chromatography, and reverse phase high performance liquid chromatography for the analysis of antioxidants from rosemary (Rosmarinus officinalis L.)

Antioxidants from rosemary were determined by the combined use of supercritical fluid extraction (SFE) prior to reverse-phase high-performance liquid chromatography (RP-HPLC) or micellar electrokinetic chromatography (MEKC). The separation of antioxidants found in the SFE fractions was achieved by using a new MEKC method and a published HPLC procedure, both with diode array detection. The characterization of the different antioxidants was further done by HPLC-mass spectrometry. Advantages and drawbacks of HPLC and MEKC for analyzing the antioxidants found in the different extracts are discussed. From the results it is concluded that HPLC renders higher peak area and is better in its reproducibility than MEKC; both techniques provide similar analysis time reproducibility. The main advantage of MEKC is its much higher separation speed, which is demonstrated to be useful for the quick adjustment of SFE conditions, allowing rosemary fractions of higher antioxidative power to be obtained quickly. Moreover, the possibilities of this approach for following the degradation of antioxidants are discussed.     

Reverse phase high pressure liquid chromatography of vitamin A in margarine, infant formula, and fortified milk

Retinal was determined in margarine (50 mg), infant formula (1 ml), and fortified milk (1 ml) by saponification in centrifuge tubes, extraction of the unsaponifiable lipid with hexane, and high pressure liquid chromatography (HPLC) in 90% methanol on a 25 cm x 3.2 mm column containing 10 micrometer LiChrosorb reverse phase. beta-Carotene was determined using the same column and 99% methanol as eluant. The vitamins in the eluate were identified and measured from their absorption at 325 (retinol) and 453 nm (beta-carotene), using a computing integrator. Retinol and carotene were prominent peaks in the chromatograms from properly fortified samples and were satisfactorily separated from other materials. In a survey of 12 different margarines for retinol, the results from liquid chromatography agreed with those of a variety of spectrophotometric and fluorometric procedures but they were obtained with greater ease and they could be interpreted more confidently. The recovery of retinol from oil was better than 99%. The coefficients of variation was 6.8% for 12 replicate analyses of a margarine for retinol and 5.4% for 10 replicate analyses of a margarine for beta-carotene.     

Analysis of fat-soluble vitamins. XX. Determination of vitamin D in multivitamin preparations. Second collaborative study.

The official first action method for determining vitamin D in multivitamin preparations was modified. The method was collaboratively studied by 7 laboratories, using 6 preparations in oil. The preparations consisted of vitamin D at various levels and at various ratios (in w/w) in vitamin A. Three samples contained cholecalciferol and 3 samples contained vitamin D3 from vitamin D3 resin. After outliers were eliminated by the Dixon test, data were analyzed and averages were compared with amounts of vitamin D known to be in each sample. For samples with vitamin D: vitamin A ratios of 1:0.5, 1:5, and 1:10, the mean vitamin D recoveries were 98.8, 94.6, and 90.7%, respectively. The method has been adopted as official final action.     

Determination of glucosinolates in canola seeds using anion exchange membrane extraction combined with the high-pressure liquid chromatography detection

A rapid, simple, and reliable method for the determination of individual glucosinolates in canola seeds was developed using a semiquantitative extraction of glucosinolates with anion exchange membranes and HPLC detection. In this one-step extraction procedure, a membrane (7 cm(2)) is placed in the seed suspension prepared by grinding and boiling 0.8 g of seeds in 20 mL of water. After 10 min of shaking on the mechanical shaker, the membrane is removed from the suspension, washed, and transferred to a vial containing 5 mL of 1 N tetramethylammonium chloride. The glucosinolates are eluted from the membrane by shaking the membrane for 10 min with the eluting solvent. The glucosinolate content in membrane eluates is determined by HPLC using sinigrin standards. A coefficient of variation ranging from 1.9 to 7.6% for aliphatic glucosinolates indicated very good reproducibility of the method. Because of the instability of 4-hydroxyglucobrassicin, the coefficient of variation for the determination of this indolyl glucosinolate was 13.9%. To verify the results of the membrane extraction/HPLC detection, this new method was compared with the existing colorimetric and GC procedures. Very good correlation (R(2) = 0.98) was obtained between the total glucosinolates determined by the membrane extraction/HPLC method and the palladate colorimetric procedure for 17 canola varieties. Concentrations of individual glucosinolates in five canola varieties were compared with the GC data. Very good agreement between these two methods was obtained for aliphatic glucosinolates. However, the membrane extraction/HPLC method yielded slightly higher values for 4-hydroxyglucobrassicin than the GC method, possibly indicating that the decomposition of this glucosinolate was reduced during the sample extraction with the membranes. The simplicity and low cost of the membrane extraction/HPLC method make it an attractive alternative to the existing procedures for glucosinolate analysis in canola seeds.     

Separation and analysis of pilocarpine, isopilocarpine, and pilocarpic acid by reverse phase liquid chromatography: collaborative study

A method for separating and determining pilocarpine and 2 degradation products was developed and subjected to collaborative study. Pilocarpine, isopilocarpine, and pilocarpic acid were isolated on a reverse phase liquid chromatographic phenyl bonded column and detected by UV spectrophotometry at 220 nm. Nine collaborators received commercial samples labeled to contain 2, 1, and 0.5% pilocarpine and a 2% practice sample. The collaborative results for pilocarpine were excellent; coefficients of variation ranged from 3.20 to 4.10%. The method was adopted official first action for determination of the active component, pilocarpine, in the presence of isopilocarpine and pilocarpic acid. Although quantitative results for the degradation products were not as good, the method is suitable as a limits test for these substances.     

Determination of neomycin in animal tissues, using ion-pair liquid chromatography with fluorometric detection

A liquid chromatographic (LC) method is described for the determination of neomycin in animal tissues. Tissues are homogenized in 0.2M potassium phosphate buffer (pH 8.0); the homogenate is centrifuged, and the supernate is heated to precipitate the protein. The heat-deproteinated extract is acidified to pH 3.5-4 and directly analyzed by LC. The LC method consists of an ion-pairing mobile phase, a reverse phase ODS column, post-column derivatization with o-phthalaldehyde reagent, and fluorometric detection. The LC method uses paromomycin as an internal standard, and separates neomycin from streptomycin or dihydrostreptomycin because they have different retention times. The LC column separates neomycin in 25 min; the detection limit is about 3.5 ng neomycin. The overall recovery of neomycin from kidney tissues spiked at 1-30 ppm was 96% with a 9.0% coefficient of variation. The method was also applied to muscle tissue.     

Determination of malachite green residues in fish using a highly sensitive electrochemiluminescence method combined with molecularly imprinted solid phase extraction

An electrochemiluminescence (ECL) inhibition method combined with molecularly imprinted solid phase extraction (MISPE) was developed for quantitative determination of malachite green (MG) residues in fish. It was found that MG could strongly inhibit the ECL signal of luminol. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of MG was in good linear relationship over a concentration range from 20 to 5000 ppt. The method detection limit was found to be about 6 ppt. Molecularly imprinted polymers (MIPs) were synthesized as solid phase extraction (SPE) sorbents, and MISPE was used for the selective extraction and purification of MG. By carrying out the oxidation reaction with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), which could convert leucomalachite green (LMG) into MG, this method was successfully applied to determine MG residues in fish. A possible mechanism for the quenching effects of MG on luminol was also proposed.