Reversed-phase Solid-phase Extraction Cartridge Research Articles

Analyses of the brominated vegetable oil in soft drinks using gas chromatography–flame ionization detector and atmospheric pressure gas chromatography–quadrupole/time-of-flight mass spectrometry

Herein, a new method for quantifying the brominated vegetable oil content in commercial soft drinks was developed, which accelerated the sample preparation process and improved analytical efficiency. First, simple and accurate chromatographic separation techniques were performed using a VF-5ht column for both GC-FID (quantitative) and APGC-QTOF (qualitative) analyses. The samples were subjected to chromatography on a reversed-phase solid-phase extraction cartridge. (PoraPak™RxnRP). Transesterification using a boron trifluoride methanol complex in methanol solution was performed. When validating this method, the analyte recovery percentages were between 82.2% and 99.9%, and the recovery and standard deviation of repeatability values were between 1.2% and 3.5%. Using an isotope library, the bromostearic acid methyl esters (9,10-dibromostearic acid methyl ester, 9,10,12,13-tetrabromostearic acid methyl ester, and hexabromostearic acid methyl ester) in the sample mixtures were qualitatively confirmed via APGC-QTOF. A novel aqueous ammonium adduct, which has not been previously reported, was also confirmed. These results indicated that this new method was simple, accurate, and also allowed for precise qualitative and quantitative confirmation as well as high reproducibility.

High Flow-Rate Sample Loading in Large Volume Whole Water Organic Trace Analysis Using Positive Pressure and Finely Ground Sand as a SPE-Column In-Line Filter.

By using an innovative, positive pressure sample loading technique in combination with an in-line filter of finely ground sand the bottleneck of solid phase extraction (SPE) can be reduced. Recently published work by us has shown the proof of concept of the technique. In this work, emphasis is put on the SPE flow rate and method validation for 26 compounds of emerging environmental concern, mainly from the 1st and 2nd EU Watch List, with various physicochemical properties. The mean absolute recoveries in % and relative standard deviations (RSD) in % for the investigated compounds from spiked pure water samples at the three investigated flow rates of 10, 20, and 40 mL/min were 63.2% (3.2%), 66.9% (3.3%), and 69.0% (4.0%), respectively. All three flow rates produced highly repeatable results, and this allowed a flow rate increase of up to 40 mL/min for a 200 mg, 6 mL, reversed phase SPE cartridge without compromising the recoveries. This figure is more than four times the maximum flow rate recommended by manufacturers. It was indicated that some compounds, especially pronounced for the investigated macrolide molecules, might suffer when long contact times with the sample glass bottle occurs. A reduced contact time somewhat decreases this complication. A very good repeatability also held true for experiments on both spiked matrix-rich pond water (high and low concentrations) and recipient waters (river and wastewater) applying 40 mL/min. This work has shown that, for a large number of compounds of widely differing physicochemical properties, there is a generous flow rate window from 10 to 40 mL/min where sample loading can be conducted. A sample volume of 0.5 L, which at the recommended maximum flow rate speed of 10 mL/min, would previously take 50 min, can now be processed in 12 min using a flow rate of 40 mL/min. This saves 38 min per processed sample. This low-cost technology allows the sample to be transferred to the SPE-column, closer to the sample location and by the person taking the sample. This further means that only the sample cartridge would need to be sent to the laboratory, instead of the whole water sample, like today’s procedure.

Analysis of Azodicarbonamide in Wheat Flour and Prepared Flour Mixes.

Azodicarbonamide (ADA) is used in some countries as a flour bleaching agent and a dough conditioner. However, ADA is prohibited for use as a food additive in Japan. Therefore, it is necessary to establish an efficient and sensitive method to determine ADA in wheat flour. A simple and practical procedure to analyze ADA in wheat flour and prepared flour mixes was developed. ADA was extracted from samples by ultrasonication with acetone. ADA in the solution was derivatized with triphenylphosphine (TPP). The ADA-TPP derivative was concentrated and cleaned up using a reversed-phase solid-phase extraction cartridge, and the ADA-TPP derivative was analyzed using HPLC for determination and LC-MS/MS for identification. Good linearity was achieved over the concentration range of 0.25-100 ppm ADA in wheat flour and prepared flour mixes. The mean recoveries from wheat flour and prepared flour mixes fortified at the levels of 1 and 10 ppm ranged from 86.9 to 101.0%, and the coefficients of variation ranged from 1.9 to 3.4%.

Certain Malvaceae Plants Have a Unique Accumulation of myo-Inositol 1,2,4,5,6-Pentakisphosphate.

Methods used to quantify inositol phosphates in seeds lack the sensitivity and specificity necessary to accurately detect the lower concentrations of these compounds contained in the leaves of many plants. In order to measure inositol hexakisphosphate (InsP6) and inositol pentakisphosphate (InsP5) levels in leaves of different plants, a method was developed to concentrate and pre-purify these compounds prior to analysis. Inositol phosphates were extracted from leaves with diluted HCl and concentrated on small anion exchange columns. Reversed-phase solid phase extraction cartridges were used to remove compounds that give peaks that sometimes interfere during HPLC. The method permitted the determination of InsP6 and InsP5 concentrations in leaves as low as 10 µM and 2 µM, respectively. Most plants analyzed contained a high ratio of InsP6 to InsP5. In contrast, certain members of the Malvaceae family, such as cotton (Gossypium) and some hibiscus (Hibiscus) species, had a preponderance of InsP5. Radiolabeling of cotton seedlings also showed increased amounts of InsP5 relative to InsP6. Why some Malvaceae species exhibit a reversal of the typical ratios of these inositol phosphates is an intriguing question for future research.

Elimination of LC–MS/MS Matrix Effect Due to Phospholipids Using Specific Solid-Phase Extraction Elution Conditions

The objective is to find elution conditions using different solid-phase extraction chemistries to reduce the amount of phospholipids in plasma extract, which is associated with matrix effect in LC-MS. Phospholipids' recovery was reduced by decreasing the eluents' methanol content applied to silica-based and polymer-based reversed-phase solid-phase extraction cartridges while 100% acetonitrile applied to the silica-based cartridges drastically minimized the phospholipids' elution. Silanol interactions are involved in the increased retention of phospholipids with silica-based reversed-phase cartridges when using high percentages of ACN in eluents. The bioanalytical usefulness of these findings was confirmed by successful extraction recovery of pharmaceutical compounds. Combinations of specific eluents and reversed-phase solid-phase extraction cartridges were found to prevent matrix effect due to phospholipids.

Improving the Determination of Nitrovin in Feeds by Reversed-Phase LC with SPE

A simple reversed-phase liquid chromatographic method with ultraviolet detector (378 nm) for the determination of nitrovin in feeds was improved and validated. The mobile phase was a mixture of acetonitrile and 0.1% formic acid solution (v/v) in the ratio of 50:50 (v/v), and the flow rate was set at 1.2 mL min−1. The extraction solution was a mixture of dimethyl formamide, acetonitrile and methanol (50:25:25, v/v), the sample was cleaned-up with reversed-phase solid phase extraction cartridge. The standard nitrovin was purified with crude nitrovin product by ethylene glycol monoethyl ether and identified by elemental analyzer. The limit of detection was 0.05 mg kg−1 and the limit of quatification was 0.2 mg kg−1 in feeds. The assay had satisfactory selectivity, recovery, linearity and precise repeatability and trueness.

Extraction of Aflatoxins B1 and G1 from Maize by Using Aqueous Sodium Dodecyl Sulfate

Aflatoxins are potent carcinogens produced by certain Aspergillus fungi. The aflatoxins were first discovered in the 1960s, and since then have been found to be distributed worldwide in a variety of commodities, foods, and feeds. Many of the early techniques for detecting aflatoxins involved extraction with halogenated solvents. With the increased availability and use of reversed-phase solid-phase extraction cartridges and the availability of immunoaffinity columns, aqueous mixtures of nonhalogenated solvents have been frequently used. To further reduce the need for solvents, we examined the effects of eliminating solvents during the extraction of maize, using aqueous mixtures of the detergent sodium dodecyl sulfate. After extraction and filtration, aflatoxins B1 (AFB1) and G1 (AFG1) were isolated by using commercially available immunoaffinity columns. The isolated AFB1 and AFG1 were derivatized with trifluoroacetic acid before separation by liquid chromatography with fluorescence detection. In spiked maize, the limits of detection were 0.5 and 1 ng/g for AFB1 and AFG1, respectively. Recoveries of AFB1 from maize spiked at 1-20 ng/g averaged 87.5% (range, 76.3-99.0%), with an average repeatability relative standard deviation (RSDr) of 4.0%. Recoveries of AFG1 from maize spiked at 2-20 ng/g averaged 80.4% (range, 70.3-85.8%), with an average RSDr of 3.5%. This is the first reported demonstration of an effective solvent-free extraction of aflatoxins from maize at ambient pressure, and this extraction procedure may serve to help reduce solvent consumption during aflatoxin analysis.

Direct measurement of the glucuronide conjugate of 1-hydroxypyrene in human urine by using liquid chromatography with tandem mass spectrometry

To evaluate human exposure to polycyclic aromatic hydrocarbons (PAHs), we developed a rapid, simple and sensitive method for determining 1-hydroxypyrene-glucuronide (1-OHP-G) in human urine. To improve precision, a deuterated glucuronide was used as an internal standard. The method requires only 1 mL of urine. The urine was treated with a mixed-mode anion-exchange and reversed-phase solid-phase extraction cartridge (Oasis MAX). The analytes were analyzed with a C 18 reversed-phase column with a gradient elution, followed by tandem mass spectrometry with electrospray ionization in negative ion mode. The detection limit of 1-OHP-G (corresponding to a signal-to-noise ratio of 3) was 0.13 fmol/injection. Urinary concentrations of 1-OHP-G determined by this method were strongly correlated ( r 2 = 0.961) with concentrations of 1-hydroxypyrene by conventional HPLC with fluorescence detection.

Peer Validation of a Method to Confirm Chloramphenicol in Honey by Liquid Chromatography-TandemMass Spectrometry

Chloramphenicol (CAP) is extracted from an aqueous dilution of honey using ethyl acetate. The extracts are evaporated and redissolved in water. CAP is then extracted from the aqueous solutions using reversed-phase solid-phase extraction cartridges. CAP is eluted from the reversed-phase cartridges with acetonitrile-water and re-extracted into ethyl acetate. The ethyl acetate is evaporated, and the residue is reconstituted in an aqueous solution. Extracts are chromatographed using a reversed-phase column and analyzed by electrospray negative mode tandem mass spectrometry. Four product ions of precursors m/z 321 or 323 are monitored. The method meets confirmation criteria recommended by the U.S. Food and Drug Administration and 4-point identification criteria established by the European Union. With slight modifications to accommodate different equipment, the method was validated in 2 laboratories.

Multiresidue Determination of Eleven Quinolones in Milk by Liquid Chromatography with Fluorescence Detection

A liquid chromatographic method with fluorescence detection was developed for simultaneous determination of norfloxacin, ofloxacin, ciprofloxacin, pefloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid, and flumequine in milk The samples were extracted with 10% trichloroacetic acid/acetonitrile (9 + 1, v/v) and cleaned by Strata-X reversed-phase solid-phase extraction cartridges. The 11 quinolones were separated on a reversed-phase C18 column (Hypersil BDS-C18) with mobile phase gradient elution and detected with fluorescence by means of a wavelength program. The recoveries for milk fortified with the 11 quinolones at 3 levels were 69-88% with acceptable relative standard deviations of <9% (intraday) and <14% (interday). The limits of detection were 23 microg/L for enrofloxacin, and 1-9 microg/L for the other 10 quinolones.