Single Ion Monitoring Mode Research Articles

Efficient and sensitive method for the quantification of saturated monoacylglycerols in biodiesel by gas chromatography–mass spectrometry

The experimental approach of this work was to develop a new method for the quantification of saturated MAGs in biodiesel using GC–MS. The method was established on a 30 m 5% phenyl phase column and ensured satisfying separation of the target MAGs. The quantification of the saturated MAGs was carried out in single ion monitoring (SIM) mode using the quantitation ions for the target MAGs: m/z 218 (2‐C16:0), m/z 371 (1‐C16:0), m/z 385 (1‐C17:0), and 399 (1‐C18:0) as well as m/z 413 for 1‐C19:0, serving as an internal standard (IS). The analytical procedure involved mixing the biodiesel sample with the IS and a silylating agent before applying GC–MS analysis. Response factors for the individual target MAGs related to the IS were determined. Prior to the quantification of saturated MAGs in real biodiesel samples, derived from used cooking oil (UCO) and waste animal fats (WAF), the linearity (R2>0.99) and the limits of detection and quantification (LOD: 8–20 ng/g, LOQ: 26–61 ng/g) of the method were determined.Practical applications: The European Committee for Standardization (CEN) contemplates to establish a limit value specifically for saturated MAGs in biodiesel, primarily requiring a specific analysis method. At present, there is no suitable test method for the determination of saturated monoglycerol content in FAME. Therefore, the approach of this work was to develop a new method for the quantification of saturated MAGs in biodiesel using GC–MS. In contrast to the currently valid European standard method EN 14105 for the determination of free glycerol, mono‐, di‐ (MAGs, DAGs), and triacylglycerols (TAGs), this new method features a very high sensitivity and enables the exclusion of interfering substances, both due to performing the analysis in single ion monitoring mode (SIM).

Development of a new biochemical test to diagnose and monitor neuroblastoma in Vietnam: Homovanillic and vanillylmandelic acid by gas chromatography–mass spectrometry

ObjectivesThe aim of this study was to develop an accurate robust testing method to simultaneously measure urine levels of HVA and VMA using gas chromatography mass spectrometry (GCMS) and to establish age-specific reference intervals of HVA and VMA in random urines for Vietnamese children. Design and methodsThe assay for urinary HVA and VMA was developed based on a classical urinary organic acid profiling method. Briefly, this incorporated 3-phenyl butyric acid as the internal standard and liquid–liquid extraction with ethyl acetate followed by derivatization with BSTFA. The Agilent 7890A GC and 5975C Mass Selective Detector in single ion monitoring mode was used for analysis.Reference intervals were developed from random urine samples collected from 634 disease free Vietnamese children and compared to 50 known neuroblastoma patient samples. Results were reported relative to creatinine concentration. Age related 95% reference intervals for urinary HVA and VMA were estimated from sample quantiles. The analytes (expressed as analyte/creatinine ratios) diagnostic values were determined by calculating the related sensitivity, specificity and likelihood ratios. ResultsHVA and VMA were linear to at least 193 and 221μmol/L, respectively. The limit of quantitation for both analytes was 0.9μmol/L. Using the bi-level control (n=15), the within-batch coefficients of variations (CVs) were less than 3% for both analytes across the assay range. The between-batch CVs (n=20 over three months), were 3.6% at 11μmol/L and 2.1% at 88μmol/L for HVA, 6.6% at 18.2μmol/L and 2.6% at 90.6μmol/L for VMA.Vietnamese age related reference intervals were established for urinary HVA and VMA per creatinine. HVA for children <6months (n=91) was 5.3–37.0μmol/mmol; 6months to <1year (n=141) was 2.7–27.7μmol/mmol; 1 to 5years (n=139) was 3.4–17.9μmol/mmol; 6 to 10years (n=136) was 2.7–8.8μmol/mmol; and 11 to 15years (n=127) was 1.1–9.4μmol/mmol. VMA for children <6months was 1.8–12.2μmol/mmol; 6months to <1year was 1.5–9.3μmol/mmol; 1 to 5years was 1.9–7.8μmol/mmol; 6 to 10years was 1.6–5.1μmol/mmol; and 11 to 15years was <0.9–6.3μmol/mmol. ConclusionsA robust testing method for simultaneous quantitation of urinary HVA and VMA by GCMS was developed. This method is accurate, precise and fit for its clinical purpose and suitable for developing countries. Age-related reference intervals of urinary HVA and VMA were established for Vietnamese children and the intervals declined progressively with increasing age for each analyte.

Passive sampling for target and nontarget analyses of moderately polar and nonpolar substances in water

The applicability of silicone rubber and low-density polyethylene (LDPE) as passive sampling materials for target and nontarget analyses of moderately polar and nonpolar substances was assessed through a field deployment of samplers along a small, polluted stream in Oslo, Norway. Silicone and LDPE samplers of identical surface area (but different volumes) were deployed at 6 sites in the River Alna for 49 d. Quantitative target analysis by gas chromatography-mass spectrometry (quadrupole, single-ion monitoring mode) demonstrated that masses of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine compounds absorbed in the 2 polymeric materials were consistent with the current understanding of the control and mode of accumulation in these sampler materials. Some deviation was observed for decabromodiphenyl ether (BDE-209) and may be linked to the large molecular size of this substance, resulting in lower diffusivity in the LDPE. Target and nontarget analyses with gas chromatography coupled to high resolution time-of-flight mass spectrometry allowed the identification of a wide range of chemicals, including organophosphate compounds (OPCs) and musk compounds (galaxolide and tonalid). Semiquantitative analysis revealed enhanced quantities of the OPCs in silicone material, indicating some limitation in the absorption and diffusion of these substances in LDPE. Overall, silicone allows nontarget screening analysis for compounds with a wider range of log octanol-water partition coefficient values than what can be achieved with LDPE.

Highlighting the tricarboxylic acid cycle: Liquid and gas chromatography–mass spectrometry analyses of 13C-labeled organic acids

The tricarboxylic acid (TCA) cycle is involved in the complete oxidation of organic acids to carbon dioxide in aerobic cells. It not only uses the acetyl-CoA derived from glycolysis but also uses breakdown products of proteins, fatty acids, and nucleic acids. Therefore, the TCA cycle involves numerous carbon fluxes through central metabolism to produce reductant power and transfer the generated electrons to the aerobic electron transport system where energy is formed by oxidative phosphorylation. Although the TCA cycle plays a crucial role in aerobic organisms and tissues, the lack of direct isotopic labeling information in its intermediates (organic acids) makes the quantification of its metabolic fluxes rather approximate. This is the major technical gap that this study intended to fill. In this work, we established and validated liquid and gas chromatography–mass spectrometry methods to determine 13C labeling in organic acids involved in the TCA cycle using scheduled multiple reaction monitoring and single ion monitoring modes, respectively. Labeled samples were generated using maize embryos cultured with [13C]glucose or [13C]glutamine. Once steady-state labeling was reached, 13C-labeled organic acids were extracted and purified. When applying our mass spectrometric methods to those extracts, mass isotopomer abundances of seven major organic acids were successfully determined.

Preliminary identification and quantification of steroid hormones in the red palm weevil, Rhynchophorus ferrugineus

In the present preliminary study, we used a gas chromatography–mass spectroscopy (GC-MS) method to identify and quantify steroid hormones, their precursors and metabolites in whole body of red palm weevil (RPW) R. ferrugineus adults. We identified a total of seven steroids by single ion monitoring mode (SIM) analysis and compared them to the National Institute of Standards and Technology (NIST) library. The steroids include: dehydroepiandrosterone (DHEA), estrone, estradiol-17β, testosterone, progesterone, cortisol and cholesterol, whereas pregnenolone, pregnan-20-one-17-hydroxy and corticosterone were not detected. This study shows that some invertebrate groups seem to use partially or totally comparable hormones to vertebrates and produce vertebrate-type steroids with functional roles. However, some steroids of the endocrine system of invertebrates are still lacking or yet to be identified in most phyla.

Liquid chromatography–mass spectrometry method for the analysis of 1,4‐dimethylpyridinium in rat plasma – application to pharmacokinetic studies

A sensitive and specific liquid chromatography electrospray ionization-mass spectrometry method for determination of 1,4-dimethylpyridinium (1,4-DMP) in rat plasma has been developed and validated. Chromatography was performed on an Aquasil C(18) analytical column (4.6 × 150 mm, 5 µm, Thermo Scientific, Rockford, IL, USA) with isocratic elution using a mobile phase containing acetonitrile and water with an addition of 0.1% of formic acid. Detection was achieved by an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 2000 triple quadrupole mass spectrometer. Electrospray ionization was used for ion production. The limit of detection in the single ion monitoring mode was found to be 10 ng/mL. The limit of quantification was 50 ng/mL. The precision and accuracy for both within-day and between-day determination of 1,4-dimethylpyridinium was 2.4-7.56 and 90.93-111.48%. The results of this analytical method validation allow pharmacokinetic studies to be carried out in rats. The method was used for the pilot study of the pharmacokinetic behavior of 1,4-DMP in rats after intravenous administration.

UHPLC–MS Analysis of Juvenile Hormone II in Mediterranean Corn Borer (Sesamia nonagrioides) Hemolymph Using Various Ionization Techniques

The juvenile hormones (JHs) have been considered the most versatile hormones in the animal kingdom. JH-II is the most abundant JH in Sesamia nonagrioides, important maize pests in the Mediterranean basin. This study compared the sensitivities and matrix effects of four ionization modes on analyzing JH-II in S. nonagrioides hemolymph using ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS) in single ion monitoring (SIM) mode. The ionization techniques tested were electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), and APPI with the lamp turned off, which corresponds to atmospheric pressure thermospray ionization (APTSI). ESI was discarded because of the high matrix effect. APPI was discarded because the correlation responses between solvent and matrix on the instrumental quality parameters were worse than those for APTSI and APCI. In our analytical conditions, APCI has shown the best validation parameter values. APCI ionization is widely available in instrumental laboratories.

Sensitive analysis of metal cations in positive ion mode electrospray ionization mass spectrometry using commercial chelating agents and cationic ion-pairing reagents

Metals play a very important role in many scientific and environmental fields, and thus their detection and analysis is of great necessity. A simple and very sensitive method has been developed herein for the detection of metals in positive ion mode ESI-MS. Metal ions are positively charged, and as such they can potentially be detected in positive ion mode ESI-MS; however, their small mass-to-charge (m/z) ratio makes them fall in the low-mass region of the mass spectrum, which has the largest background noise. Therefore, their detection can become extremely difficult. A better and well-known way to detect metals by ESI-MS is by chelating them with complexation agents. In this study eleven different metals, Fe(II), Fe(III), Mg(II), Cu(II), Ru(III), Co(II), Ca(II), Ni(II), Mn(II), Sn(II), and Ag(I), were paired with two commercially available chelating agents: ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS). Since negative ion mode ESI-MS has many disadvantages compared to positive ion mode ESI-MS, it would be very beneficial if these negatively charged complex ions could be detected in the positive mode. Such a method is described in this paper and it is shown to achieve much lower sensitivities. Each of the negatively charged metal complexes is paired with six cationic ion-pairing reagents. The new positively charged ternary complexes are then analyzed by ESI-MS in the positive single ion monitoring (SIM) and single reaction monitoring (SRM) modes. The results clearly revealed that the presence of the cationic reagents significantly improved the sensitivity for these analytes, often by several orders of magnitude. This novel method developed herein for the detection of metals improved the limits of detection (LODs) significantly when compared to negative ion mode ESI-MS and shows great potential in future trace studies of these and many other species.

A New Rapid and Sensitive LC-MS Assay for the Determination of Sorafenib in Plasma: Application to a Patient Undergoing Hemodialysis

A simple liquid chromatography-mass spectrometry method was developed and validated for quantification of sorafenib (Nexavar) in human plasma. After a solid-phase extraction procedure, the separation was performed within 2 minutes using an isocratic flow of a mobile phase consisting of formic acid/acetonitrile applied on a C18 analytical column. The analyte was detected by mass spectrometry in the single-ion monitoring mode. The method was validated according to the recommendations of the US Food and Drug Administration. The method was linear (r² > 0.99) between 10 and 10,000 ng/mL. The lower limits of detection and quantification were 5 and 10 ng/mL, respectively. Within-day and between-day imprecisions were less than 10.4%, and inaccuracy did not exceed 8.7%. The mean extraction recovery was 92.2%. The method also provided satisfactory results in terms of time stability and dilution integrity. Sorafenib plasma concentrations of the studied patient ranged between 1831 and 3459 ng/mL. This new technique is rapid, sensitive, and was applied to the determination of sorafenib plasma concentrations in a patient undergoing hemodialysis. Our results indicate that sorafenib is not cleared from plasma by hemodialysis, although analysis should be delayed after dialysis to avoid erratic fluctuations.

A validated LC-MS/MS method for the determination of vinflunine in plasma and its application to pharmacokinetic studies

A rapid, simple and sensitive LC-MS/MS method for the quantification of vinflunine in plasma was developed and validated. The analysis involved a simple liquid-liquid extraction. After making alkaline with NaOH, plasma was extracted with methyl tert-butyl ether and the organic extract was then evaporated and the residue was reconstituted in mobile phase. The reconstituted solution was injected into an HPLC system and was subjected to reverse-phase HPLC on a 5 µm ODS-3 column at a flow-rate of 0.2 mL/min. The mobile phase consisted of ammonium acetate (0.02 mol/L, pH = 3.0) and acetonitrile (20:80). Vinflunine was detected in the single ion monitoring mode using target ions at m/z 817.4/160.1/142.3 for vinflunine and m/z 447.2/128.3/112.1 for gefitinib (internal standard). Standard curves were linear over the concentration range of 5-1000 ng/mL. The mean predicted concentrations of the quality control samples deviated by less than 2% from the corresponding nominal values; the intra-assay and inter-assay precisions of the assay were within 7% relative standard deviation. The extraction recovery of vinflunine was more than 80%. The validated assay was applied to a pharmacokinetic study of vinflunine in plasma following the administration of a single vinflunine injection (2 mg/kg).

Evidence of mephedrone chronic abuse through hair analysis using GC/MS

Mephedrone is a synthetic derivative of cathinone which is becoming more common on the recreational drug market. Several intoxications following mephedrone abuse have been reported though published papers have focused essentially on analytical approaches for biological fluids and only one has involved a hair sample. After the development and validation of a new method, the first series of positive results for mephedrone in hair specimens is reported here. After decontamination of the hair strand in methylene chloride, hair segments were cut into small pieces with scissors, weighed and incubated overnight in Soerensen buffer pH 7.0 in the presence of deuterated 3,4-methylenedioxymethamphetamine (MDMA) at 40°C. The incubation medium was extracted using ethyl acetate after alkalinisation with 1N sodium hydroxide (NaOH). Before injection, the dry extract was derivatized using a mixture of heptafluorobutyric anhydride/ethyl acetate (100:50, v/v), evaporated and dissolved in ethyl acetate (25μl). After introduction of 1μl of the extract onto a splitless injector, chromatographic separation was achieved on a HP 6890 gas chromatograph equipped with a 5-MS capillary column. Detection was achieved in single ion monitoring mode (m/z 254-119-210 for mephedrone, m/z 258-213 for MDMA-d5) using a 5973 MSD operating in electron impact mode. Sixty-seven hair specimens were tested for mephedrone. Thirteen of them were found positive for mephedrone with concentrations ranging from 0.2 to 313.2ng/mg with a mean concentration of 26.8ng/mg. It was difficult to compare our findings due to a lack of reference data, nevertheless mephedrone seems well incorporated into hair (concentrations in the ng/mg range) like other stimulant drugs such as amphetamines or cocaine. The aim of this work was to develop a specific and accurate method for mephedrone analysis in hair specimens and its application to a large number of samples (n=67). The developed analytical method appears sensitive enough to reveal occasional to regular use of mephedrone.

Influence of Deep Frying on the Unsaponifiable Fraction of Vegetable Edible Oils Enriched with Natural Antioxidants

The influence of deep frying, mimicked by 20 heating cycles at 180 °C (each cycle from ambient temperature to 180 °C maintained for 5 min), on the unsaponifiable fraction of vegetable edible oils represented by three characteristic families of compounds (namely, phytosterols, aliphatic alcohols, and triterpenic compounds) has been studied. The target oils were extra virgin olive oil (with intrinsic content of phenolic antioxidants), refined sunflower oil enriched with antioxidant phenolic compounds isolated from olive pomace, refined sunflower oil enriched with an autoxidation inhibitor (dimethylpolysiloxane), and refined sunflower oil without enrichment. Monitoring of the target analytes as a function of both heating cycle and the presence of natural antioxidants was also evaluated by comparison of the profiles after each heating cycle. Identification and quantitation of the target compounds were performed by gas cromatography-mass spectrometry in single ion monitoring mode. Analysis of the heated oils revealed that the addition of natural antioxidants could be an excellent strategy to decrease degradation of lipidic components of the unsaponifiable fraction with the consequent improvement of stability.

Liquid chromatography‐mass spectrometric method for determination of the non‐imidazole H3‐receptor antagonist UPR1056 in rat plasma

The non-imidazole H3 receptor antagonist UPR1056 was dosed in plasma samples from rats individually administered with a single i.p. dose of 1.25 mg/kg by means of a newly validated HPLC-MS method. UPR1056 was extracted from rat plasma by protein precipitation with acetonitrile and was separated by linear gradient elution, employing water and methanol both additioned with 0.05% trifluoroacetic acid as mobile phases. UPR1056 was detected in MS using an electrospray ion source operating in positive ion mode. Acquisition was performed in single ion monitoring mode at m/z=349.3. The method was validated over the concentration range of 17.43-1743 ng/mL (50-5000 pmol/mL). Within- and between-run precision for the low, mid and high quality controls (QC) levels were 6.75% or less and accuracy ranged from 95.8 to 107.6%. The lower limit of quantification was 17.43 ng/mL. The analysis of the time course of UPR1056 concentrations over the 24-h period revealed a C(max) of 1147 ng/mL after 2 h from peripheral administration of the non-imidazole H(3)-receptor antagonist, with a prolonged elimination half-life of over 9 h.

Mass Spectrometry-based Proteomics Using Q Exactive, a High-performance Benchtop Quadrupole Orbitrap Mass Spectrometer

Mass spectrometry-based proteomics has greatly benefitted from enormous advances in high resolution instrumentation in recent years. In particular, the combination of a linear ion trap with the Orbitrap analyzer has proven to be a popular instrument configuration. Complementing this hybrid trap-trap instrument, as well as the standalone Orbitrap analyzer termed Exactive, we here present coupling of a quadrupole mass filter to an Orbitrap analyzer. This “Q Exactive” instrument features high ion currents because of an S-lens, and fast high-energy collision-induced dissociation peptide fragmentation because of parallel filling and detection modes. The image current from the detector is processed by an “enhanced Fourier Transformation” algorithm, doubling mass spectrometric resolution. Together with almost instantaneous isolation and fragmentation, the instrument achieves overall cycle times of 1 s for a top10 higher energy collisional dissociation method. More than 2500 proteins can be identified in standard 90-min gradients of tryptic digests of mammalian cell lysate— a significant improvement over previous Orbitrap mass spectrometers. Furthermore, the quadrupole Orbitrap analyzer combination enables multiplexed operation at the MS and tandem MS levels. This is demonstrated in a multiplexed single ion monitoring mode, in which the quadrupole rapidly switches among different narrow mass ranges that are analyzed in a single composite MS spectrum. Similarly, the quadrupole allows fragmentation of different precursor masses in rapid succession, followed by joint analysis of the higher energy collisional dissociation fragment ions in the Orbitrap analyzer. High performance in a robust benchtop format together with the ability to perform complex multiplexed scan modes make the Q Exactive an exciting new instrument for the proteomics and general analytical communities.

Rapid Chromatography for the Determination of Polychlorinated Biphenyls by GC-MS in Environmental Monitoring

A method for determination of polychlorinated biphenyls (PCBs) in environmental and biological materials has been developed. This method includes rapid chromatography requiring less than 10 min using an HT-8 capillary column at 30 m × 0.25 mm i.d. Rapid chromatography was performed using a column temperature gradient from 80 to 310°C at a rate of 40°C/min. Low-resolution mass spectrometry in single ion monitoring mode of simultaneous detection of 12 target ions is suggested for detection of PCBs peaks. The method not only enabled us to reduce time of analysis but also to increase the efficiency of separating PCB peaks from interferences and to reduce levels of detection of analytes resulting in a minimized sample preparation stage. The last includes extraction of the PCBs using organic solvents, preliminary alkaline hydrolysis in the case of biological objects, and cleaning up the extracts on compact cartridges. The method was tested in monitoring studies for these contaminants in soils, sediments, snow cover, fish tissues, and seal blubber. Total PCBs and isomer congener groups of the same chlorination degree and seven indicator congeners (IUPAC No.'s 28, 52, 101, 118, 138, 153, and 180) are determined with a high degree of certainty. The PCB concentrations were in the range of 1–700 ng/g dry weight for environmental samples and 500–25000 ng/g lipids for biota. The method yields measurements of total PCBs and isomer groups with a precision no greater than 10% and no greater than 15% for the indicator congeners.

Quantification of 4 antidepressants and a metabolite by LC–MS for therapeutic drug monitoring

A liquid chromatography method coupled to mass spectrometry was developed for the quantification of bupropion, its metabolite hydroxy-bupropion, moclobemide, reboxetine and trazodone in human plasma. The validation of the analytical procedure was assessed according to Société Française des Sciences et Techniques Pharmaceutiques and the latest Food and Drug Administration guidelines. The sample preparation was performed with 0.5 mL of plasma extracted on a cation-exchange solid phase 96-well plate. The separation was achieved in 14 min on a C18 XBridge column (2.1 mm × 100 mm, 3.5 μm) using a 50 mM ammonium acetate pH 9/acetonitrile mobile phase in gradient mode. The compounds of interest were analysed in the single ion monitoring mode on a single quadrupole mass spectrometer working in positive electrospray ionisation mode. Two ions were selected per molecule to increase the number of identification points and to avoid as much as possible any false positives. Since selectivity is always a critical point for routine therapeutic drug monitoring, more than sixty common comedications for the psychiatric population were tested. For each analyte, the analytical procedure was validated to cover the common range of concentrations measured in plasma samples: 1–400 ng/mL for reboxetine and bupropion, 2–2000 ng/mL for hydroxy-bupropion, moclobemide, and trazodone. For all investigated compounds, reliable performance in terms of accuracy, precision, trueness, recovery, selectivity and stability was obtained. One year after its implementation in a routine process, this method demonstrated a high robustness with accurate values over the wide concentration range commonly observed among a psychiatric population.

Improved extraction method to evaluate the degradation of selected PAHs by marine fungi grown in fermentative medium

An improved method to evaluate the degradation of polycyclic aromatic hydrocarbons (PAHs) for filamentous fungi is hereby proposed. The PAH adsorption through fungal mycelia implies the use of an exhaustive extraction, which is usually performed through a combination of different techniques applied separately to the liquid medium and to the mycelia. This work proposes a simplified extraction procedure with reduced analysis time and sample manipulation, thereby guaranteeing its precision and accuracy. The selected PAHs, pyrene and benzo[a]pyrene, were quantified by gas chromatography using a mass selective detector operating in single ion monitoring mode. The method was validated presenting accuracy within the scope of this study and it was used for evaluating the potential of PAHs degradation by thirteen fungi derived from marine environment. This study selected the fungus Aspergillus sclerotiorum CBMAI 849 for being able to degrade 85% of pyrene and 61% of benzo[a]pyrene after 4 and 8 days, respectively, and the fungus Mucor racemosus CBMAI 847 for being able to degrade 44% of benzo[a]pyrene after 8 days

Separation and quantitation of milk whey proteins of close isoelectric points by on-line capillary isoelectric focusing—Electrospray ionization mass spectrometry in glycerol–water media

On-line coupling between CIEF and ESI/MS based on the use of bare fused-silica capillaries and glycerol–water media, recently developed in our laboratory, has been investigated for the separation of milk whey proteins that present close p I values. First, a new rinsing procedure, compatible with MS detection, has been developed to desorb these rather hydrophobic proteins (α-casein (α-CN), bovine serum albumin (BSA), lactoferrin (LF)) from the inner capillary wall and to avoid capillary blockages. Common hydrochloric acid washing solution was replaced by a multi-step sequence based on the use of TFA, ammonia and ethanol. To achieve the separation of major whey proteins (β-lactoglobulin A (β-LG A), β-lactoglobulin B (β-LG B), α-lactalbumin (α-LA) and BSA, which possess close p I values (4.5–5.35), CIEF parameters i.e. carrier ampholyte nature, capillary partial filling length with ampholyte/protein mixture and focusing time, have been optimized with respect to total analysis time, sensitivity and precision on p I determination. After optimization of sheath liquid composition (80:20 (v/v) methanol–water + 1% HCOOH), quantitation of β-LG A, β-LG B, α-LA and BSA was performed. The limits of detection obtained from extracted ion current (EIC) and single ion monitoring (SIM) modes were in the 57–136 nM and 11–68 nM range, respectively. Finally, first results obtained from biological samples demonstrated the suitability of CIEF–MS as a potential alternative methodology to 2D-PAGE to diagnose milk protein allergies.

Determination of Fumonisins in Milled Corn Grains Using HPLC-MS

A new method for determination of fumonisins in corn samples was developed and validated. The mycotoxins were extracted by a mixture of methanol-acetonitrile-water (1:1:2, v/v/v) and determined on a liquid chromatograph with mass spectrometric detection. The separation was performed on Zorbax XDB-C(18) column (150 x 4.6 mm; 5 microm) with a Metaguard ODS-2 precolumn (30 x 4.6 mm; 5 mum) using gradient elution with mobile phase consisting of acetonitrile and 5 mmol/L ammonium acetate (adjusted by acetic acid to pH 3.0). For detection of (M+H(+)) ions, a quadrupole mass spectrometer in single ion monitoring mode was applied. Developed method showed very good linearity in a tested range of concentration. Detection limit is 62.0 microg FB(1)/kg and 58.5 microg FB(2)/kg of maize grains. Because the detection limits lie under the maximum permitted EU levels, the method is suitable for determination of fumonisins in milled corn grains.

Dihydroartemisinin loaded nanostructured lipid carriers (DHA-NLC): evaluation of pharmacokinetics and tissue distribution after intravenous administration to rats.

A simple and rapid LC-MS/MS method was established for the determination of dihydroartemisinin (DHA) in plasma and tissues of rats. Sample preparation was achieved by liquid-liquid extraction with aether and analysis was performed on LC-MS/MS in positive ion mode using electrospray ionization (ESI) as an interface. Target compounds were quantified in a single ion-monitoring (SIM) mode. DHA was monitored at m/z 267.1 and the internal standard finasteride at m/z 305.2. Chromatography was carried out using a Synergi fusion RP 80 column with a mixture of ethanol and 0.1% formic acid mixture (75:25) as the mobile phase. The pharmacokinetics and tissue distribution after intravenous administration of DHA in nanostructured lipid carrier (NLC) and in solution were then compared. The mean residence times (MRT) of the DHA-NLC was much longer than that of the DHA solution. In the tested organs, the AUC values of the DHA-NLC were higher than that of the DHA solution in liver, spleen, lung, brain and muscle, and lower than the DHA solution in heart and kidney. DHA-NLC prepared in this study is a promising sustained-release and drug-targeting system for antitumor drugs. It may also allow a reduction in dosage and a decrease in systemic toxicity.