Gas Chromatography-mass Spectrometry With Selected Ion Monitoring Research Articles

Selective and sensitive GC-MS analysis of carcinogenic N-nitrosodimethylamine in pharmaceuticals using a magnetic coconut carbon composite as a solid-phase extraction sorbent

The aim of the present research was to develop a magnetic coconut carbon composite (Fe2O3/Fe3O4@CNC) as a solid-phase extraction (SPE) sorbent for the analysis of carcinogenic N-nitrosodimethylamine (NDMA) in pharmaceuticals. Coconut composites modified with Fe2O3 and Fe3O4 were prepared and applied as SPE sorbent for the extraction of NDMA in pharmaceuticals. The sorbent was characterized with X-Ray, infrared spectroscopy and nitrogen porosimetry. The best ions for the Gas Chromatography-Mass Spectrometry with Selected Ion Monitoring (GC-MS/SIM) analysis were m/z 74 and 42 for NDMA, and m/z 80 and 46 for NDMA-d6 internal standard. System has offered great method performance in terms of sensitivity limit of quantitation (LOQ) 16 ng kg−1. The developed sorbent has enhanced the sensitivity and speed of analysis. The developed method was applied to authenticate the presence of NDMA in various pharmaceutical samples. Among the analyzed samples, NDMA impurities were relatively identified at high amounts in nizatidine samples. Highlights NDMA was verified in ranitidine, metformin and nizatidine Fe2O3/Fe3O4@CNC composite was used for NDMA identification without pretreatment SPE sorbent enhance sensitivity, reduce analysis time, sustain accuracy & precision High level of NDMA impurity were found in nizatidine pharmaceuticals.

The development of plasma pseudotargeted GC-MS metabolic profiling and its application in bladder cancer.

Bladder cancer (BC) is a fatal malignancy with considerable mortality. BC urinary metabolomics has been extensively investigated for biomarker discovery, but few BC blood metabolomic studies have been performed. Hence, a plasma pseudotargeted metabolomic method based on gas chromatography-mass spectrometry with selected ion monitoring (GC-MS-SIM) was developed to study metabolic alterations in BC. The analytical performance of the developed method was compared with that of a nontargeted method. The relative standard deviation (RSD) values of 89 and 70.7% of the peaks obtained using the pseudotargeted and nontargeted methods, respectively, were less than 20%. The Pearson correlations of 90.7 and 78.3% of the peaks obtained using the pseudotargeted and nontargeted methods, respectively, exceeded 0.90 in the linearity evaluation. Compared with the nontargeted method, the signal-to-noise ratios (S/N) of 97.9 and 69.3% of the peaks increased two- and fivefold, respectively. The developed method was fully validated, with good precision, recovery, and stability of the trimethylsilyl (TMS) derivatives. The method was applied to investigate BC. Significant increases in the contents of metabolites involved in, for example, the pentose phosphate pathway (PPP) and nucleotide and fatty acid synthesis were found in the high-grade (HG) BC group compared to the healthy control (HC) group. These differences imply that the activated PPP may regulate BC cell proliferation by promoting lipid and nucleotide biosynthesis and the detoxification of reactive oxygen species (ROS). These results illustrate that the plasma pseudotargeted method is a powerful tool for metabolic profiling. Graphical abstract The plasma pseudotargeted metabolic profiling suggested the metabolic alterations in bladder cancer (BC) and the significantly differential metabolites for BC discrimination.

Determination of chlorinated by-products of parabens in swimming pool water

We describe the determination of trace amounts of chlorinated parabens, i.e. disinfection by-products, in swimming pool water, using gas chromatography-mass spectrometry with selected ion monitoring (GC-MS-SIM). A dichlorinated by-product of isopropylparaben was detected at levels of up to 25 ng L−1. Further, a dichlorinated by-product of methylparaben and a monochlorinated by-product of benzylparaben were present in concentrations lower than the limit of quantification. Benzylparaben, the parent compound, was also detected at concentrations of up to 28 ng L−1. Thus, in this study, chlorinated parabens were detected and quantified for the first time as disinfection by-products in swimming pool water. The results of this study have raised concerns regarding the chlorinated by-products of active ingredients used in personal care products.

Highly sensitive quantification of 7α-hydroxy-4-cholesten-3-one in human serum by LC-ESI-MS/MS

We describe a highly sensitive and specific method for the quantification of serum 7alpha-hydroxy-4-cholesten-3-one (C4), which has been used as a biomarker for bile acid biosynthesis. This method is based upon a stable isotope dilution technique by liquid chromatography-tandem mass spectrometry (LC-MS/MS). C4 was extracted from human serum (2-50 mul) by a salting-out procedure, derivatized into the picolinoyl ester (C4-7alpha-picolinate), and then purified using a disposable C(18) cartridge. The resulting picolinoyl ester derivative of C4 was quantified by LC-MS/MS using the electrospray ionization mode. The detection limit of the C4 picolinoyl ester was found to be 100 fg (signal-to-noise ratio = 10), which was approximately 1,000 times more sensitive than the detection limit of C4 with a conventional HPLC-ultraviolet method. The relative standard deviations between sample preparations and between measurements by our method were calculated to be 5.7% and 3.9%, respectively, by one-way layout analysis. The recovery experiments were performed using serum spiked with 20.0-60.0 ng/ml C4 and were validated by a polynomial equation. The results showed that the estimated concentration with 95% confidence limit was 23.1 +/- 2.8 ng/ml, which coincided completely with the observed X(0) +/- SD = 23.3 +/- 1.0 ng/ml with a mean recovery of 93.4%. This method provides highly reliable and reproducible results for the quantification of C4, especially in small volumes of blood samples.

Disrupted coordinate regulation of farnesoid X receptor target genes in a patient with cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX), sterol 27-hydroxylase (CYP27A1) deficiency, is associated with markedly reduced chenodeoxycholic acid (CDCA), the most powerful activating ligand for farnesoid X receptor (FXR). We investigated the effects of reduced CDCA on FXR target genes in humans. Liver specimens from an untreated CTX patient and 10 control subjects were studied. In the patient, hepatic CDCA concentration was markedly reduced but the bile alcohol level exceeded CDCA levels in control subjects (73.5 vs. 37.8 +/- 6.2 nmol/g liver). Cholesterol 7alpha-hydroxylase (CYP7A1) and Na+/taurocholate-cotransporting polypeptide (NTCP) were upregulated 84- and 8-fold, respectively. However, small heterodimer partner (SHP) and bile salt export pump were normally expressed. Marked CYP7A1 induction with normal SHP expression was not explained by the regulation of liver X receptor alpha (LXRalpha) or pregnane X receptor. However, another nuclear receptor, hepatocyte nuclear factor 4alpha (HNF4alpha), was induced 2.9-fold in CTX, which was associated with enhanced mRNA levels of HNF4alpha target genes, CYP7A1, 7alpha-hydroxy-4-cholesten-3-one 12alpha-hydroxylase, CYP27A1, and NTCP. In conclusion, the coordinate regulation of FXR target genes was lost in CTX. The mechanism of the disruption may be explained by a normally stimulated FXR pathway attributable to markedly increased bile alcohols with activation of HNF4alpha caused by reduced bile acids in CTX liver.

Iron Supplementation and Oxidative Damage to DNA in Healthy Individuals with High Plasma Ascorbate

Previously, we have investigated the potential for a pro-oxidant interaction of iron and ascorbate in vivo in iron and ascorbate cosupplementation or ascorbate supplementation studies. In this study, for the first time, the effects of iron supplementation on oxidative damage to DNA in healthy individuals with plasma ascorbate levels at the upper end of the normal range were examined. Forty female and male volunteers (mean plasma ascorbate ≈70 μmol/L) were supplemented with a daily dose of syrup (ferrous glycine sulphate equivalent to 12.5 mg iron) for 6 weeks. Serum ferritin, transferrin bound iron, % saturation of transferrin and plasma ascorbate were assessed and the mean dietary intakes of all subjects were estimated through food frequency questionnaires. Oxidative damage to DNA bases from white blood cells was measured by gas chromatography/mass spectrometry with selected-ion monitoring (GC/MS-SIM), using isotope-labelled standards for quantification. Iron supplementation did not affect any of the iron status parameters. There were also no detrimental effects, over the period under investigation, in terms of oxidative damage to DNA. However, the effects of larger doses or of longer supplementation periods should also be investigated.

Determination of fatty acids (C8–C22) in urban wastewater by GC-MS

A simple method for determination of fatty acids (C8–C22) in wastewater, extracted with dichloromethane, was developed. The extraction time was drastically reduced using ultrasound. Fatty acids were esterified using BF3 methanolic solution followed by an 11min run using gas chromatography-mass spectrometry with selected ion monitoring (GC/MS-SIM). A clean-up is not necessary using SIM Mode. Tridecanoic acid was used as a surrogate internal standard. Detection limits go from 0.008 to 0.016mgl−1. The applicable concentration range was 0.010 to 10mgl−1. The method was validated by using the Standard Addition Methodology and it was applied satisfactorily to wastewater from Granada (Spain).

Determination of endosulfan and some pyrethroids in waters by micro liquid-liquid extraction and GC-MS

A simple, rapid and reproducible method for the determination of some pesticide residues in water was developed using micro liquid-liquid extraction and gas chromatography - mass spectrometry with selected ion monitoring (GC/MS-SIM). The chlorinated insecticides α- and β-endosulfan and endosulfan-sulfate as well as the synthetic pyrethroids bifenthrin, permethrin, cypermethrin, fenvalerate and deltamethrin can be separated from a 500 mL sample water extracted with 0.5 mL of n-hexane containing anthracene-d10 as internal standard without clean-up in only 13 min. The recovery efficiencies of the tested compounds yielded more than 93.0% at a fortification level of 5 ng mL–1 and their relative standard deviations were between 1.9 and 11.7%. Detection limit of each compound ranged between 3 and 35 pg mL–1. The method was applied to ground, sea and tap waters from Almeria (Spain). The solubilities in water at 20° C were determined.

Oxidative DNA base damage and its repair in kidneys and livers of nickel(II)-treated male F344 rats.

DNA base damage was assayed using gas chromatography/ mass spectrometry with selected ion monitoring (GC/MS-SIM) in renal and hepatic chromatin of male F344 rats up to 14 days after a single i.p. injection of 90 micromol Ni(II) acetate/kg body wt. Ten different damaged bases were quantified. No damage was found in either organ 12 h after Ni(II) treatment. The damage became significant only from day 1, with magnitude and persistence depending on the organ and base. In livers, levels of five DNA base products were significantly elevated over those in control rats. They were: 8-oxoguanine (by 46% at day 1 postinjection); 2,6-diamino-4-hydroxy-5-formamidopyrimidine (by 107% at day 1); 5-(hydroxymethyl)uracil (by 94% at day 1); 5,6-dihydroxyuracil (by 128% at day 1); and 5-hydroxyhydantoin (by 39% in terms of the overall adjusted means for days 1-14 post-injection). The elevation was highest at day 1 post-injection followed by a decrease at later days, except for 5-hydroxyhydantoin. In kidneys, the levels of only three damaged bases, 8-oxoguanine, 5-hydroxyhydantoin and 5,6-dihydroxyuracil were increased significantly (by 31, 73 and 60%, respectively) and one base, 8-oxoadenine, was increased by 26%, just below significance, all in terms of overall adjusted means for days 1-14 post-injection. Hence, unlike those in the liver, the renal increases persisted for 14 days. The results reveal a tissue specific response to Ni(II)-mediated oxidative DNA base damage with apparently faster DNA repair in liver than in kidney, the main target of Ni(II) carcinogenicity.

Estimation of selected phenols in drinking water with In situ acetylation and study on the DNA damaging properties of polychlorinated phenols

Gas chromatography/mass spectrometry with selected-ion monitoring (GC/MS-SIM) method were used to analyze 23 selected phenols in natural and drinking waters by an in situ acetylation technique. This method was suitable for determining phenol concentrations at the ng/L level because of less background interference and better recoveries. The application range for all these phenols was from 0.01 or 0.04 to 10 micrograms/L, using a 800 ml water sample. The levels of trace phenols in four Taiwan water treatment plants were in the range of 12-312 ng/L. The polychlorinated phenols, namely 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, and pentachlorophenol, were evaluated for their ability to induce deoxyribonucleic acid (DNA) damage using a DNA precipitation assay employing mouse embryonic fibroblast cells (C3H10T1/2) with or without a liver microsomal activation system. These agents exhibited a weak positive response when microsomal activation enzymes were present in this assay. When the tetrachlorohydroquinone, a toxic metabolite of pentachlorophenol, was measured by the same method without the activation system, a significant and dose-dependent DNA damage was found. This result indicates that in the evaluation of the carcinogenic potential of these agents, their corresponding metabolites should be taken into consideration. DNA strand breakage caused by these active metabolites may play an important role in the tumorigenetic process of polychlorinated phenols.

Fourier-transform infrared spectroscopy and gas chromatography-mass spectrometry reveal a remarkable degree of structural damage in the DNA of wild fish exposed to toxic chemicals.

The use of gas chromatography-mass spectrometry with selected ion monitoring (GC-MS/SIM) and Fourier-transform infrared (FT-IR) spectroscopy revealed a remarkable degree of damage in the hepatic DNA of fish exposed to toxic environmental chemicals, compared with controls. The exposed fish, which were neoplasm-free, were part of a population with a high incidence of liver cancer. GC-MS/SIM showed markedly high concentrations of hydroxyl radical-induced ring-opening products (e.g., 2,6-diamino-4-hydroxy-5-formamidopyrimidine) and 8-hydroxy adducts of adenine and guanine (e.g., 8-hydroxyguanine) in the DNA. FT-IR spectroscopy revealed substantial changes in spectral areas, such as those assigned to NH vibrations of nucleotide bases and CO vibrations of deoxyribose. This diverse and extensive damage to DNA provides a perspective of premalignant changes resulting from xenobiotic exposure and a promising basis for predicting cancer risk in animals and humans.

Rapid diagnosis of bacterial meningitis by the detection of a fatty acid marker in CSF with gas chromatography-mass spectrometry and selected ion monitoring

A chemical marker of bacterial meningitis was sought by comparing derivatives of sterile cerebrospinal fluid (CSF) with cultures of organisms in spinal fluid and artificial media. The technique of gas chromatography-mass spectrometry with selected ion monitoring (GC-MS-SIM) was used, optimised for the analysis of fatty acids. Twenty candidate ions were screened, and an ion of mass: charge ratio (m/e) 268 was chosen for detection in clinical specimens. The origin of this marker is unknown, but it is probably the molecular ion of a C16:1 fatty acid. In 135 clinical specimens of CSF examined, the m/e 268 ion was found to be a useful marker for the common organisms that cause bacterial meningitis, giving a sensitivity of 88% and a specificity of 98%. The method was more rapid and more sensitive than conventional microscopy and culture, but CSF containing coagulase-negative staphylococci, Mycobacterium tuberculosis, Cryptococcus neoformans and some other uncommon pathogens gave inconsistent results. Many organisms produced characteristic ion profiles with multiple-ion monitoring, and this method of chemical analysis holds promise for the rapid diagnosis of bacterial infections to genus or species level.

The use of gas chromatography/negative ion chemical ionization mass spectrometry for the determination of lorazepam in whole blood.

The determination of lorazepam in blood by gas chromatography/mass spectrometry with selected ion monitoring (GC/MS/SIM) in the negative chemical ionization mode (NICI) was investigated. The method involves a single extraction with Amberlite XAD-2 resin and the use of [2H6]triazolam as an internal standard. The limit of detection is 0.5 ng/mL and standard curves are linear from 6.25 to 250 ng/mL. The applicability of the method to forensic toxicology is reported.

Structure of hydroxyl radical-induced DNA-protein crosslinks in calf thymus nucleohistone in vitro.

Hydroxyl radicals are known to produce DNA-protein crosslinks in chromatin in vivo and in vitro. Here we investigated DNA-protein crosslinks formed between aliphatic amino acids and thymine in calf thymus nucleohistone exposed predominantly to hydroxyl radicals in gamma-irradiated N2O-saturated aqueous solution. Aliphatic amino acids are the predominant types of amino acids in the core histones of calf thymus, and thus are likely to form crosslinks with DNA. For identification of the crosslinks we first investigated hydroxyl radical-induced crosslinking of thymine to aliphatic amino acids in model systems, i.e. an aqueous mixture of thymine and a single amino acid. Samples were analyzed for possible thymine-amino acid crosslinks by gas chromatography-mass spectrometry. Using this approach the structure of the crosslinks was elucidated, and information on their gas chromatographic and mass spectral properties was obtained. Gas chromatography-mass spectrometry with selected-ion monitoring (GC-MS/SIM) was then used to identify DNA-protein crosslinks in acidic hydrolysates of calf thymus nucleohistone exposed to ionizing radiation in buffered aqueous solution. DNA-protein crosslinks involving thymine and the amino acids Gly, Ala, Val, Leu, Ile and Thr were identified. In some cases several isomers of the same crosslink were observed. The yield of the crosslinks was measured by GC-MS/SIM and was found to be a linear function of radiation dose in the range 49 to 436 Gy. The mechanism for the formation of these DNA-protein crosslinks is thought to involve hydrogen atom abstraction by hydroxyl radicals from the aliphatic amino acid followed by addition of the amino acid radical to the carbon(6)-position of thymine and subsequent oxidation of the adduct radical.

Gibberellins, Amylase, and the Onset of Heterosis in Maize Seedlings

Rood, S. B. and Larsen, K. M. 1988. Gibberellins, amylase, and the onset of heterosis in maize seedlings.—J. exp. Bot. 39: 223-233. The possible involvement of gibberellins and amylase in heterosis of maize seedlings was investigated in two parental inbreds, CM7 and CM49, and their single cross F, hybrid, CM7 x CM49. Germination of all three genotypes was complete within 36 h after the onset of imbibition. By 48 h, heterosis (hybrid vigour) for increased shoot and root length was consistently observed. The endogenous concentration of gibberellin (GA;) was measured in 48 h seedlings by gas chromatography-mass spectrometry with selected ion monitoring (GC-SIM) using pHJ-GAj as an internal standard. The GA3 concentration was highest in the hybrid (59 ng g~' dry wt.), intermediate in CM49 (9-Ongg-1), and lowest in CM7 (<50ngg_1). Amylase activities in all three genotypes were very low at 24 h, but increased during the next 24 h, after which time amylase activity in the hybrid was significantly higher than that of either parental inbred. Inhibitors of gibberellin (GA) biosynthesis, AMO-1618 or CCC, inhibited germination, shoot and root growth, and amylase activity in all three genotypes. Conversely, exogenous gibberellic acid (GA3) increased amylase activity, particularly in the inbred CM7. Amylase isozymes were separated through polyacrylamide gel electrophoresis and generally similar profiles of starch degrading enzymes were observed in the three genotypes. Since GA is known to control a-amylase biosynthesis in some cereals, these results are consistent with the hypothesis that GAs are involved in the regulation of heterosis in maize. A higher endogenous GAt concentration in the hybrid could result in increased amylase activity in the hybrid seedlings and consequently, more rapid starch hydrolysis which fuels heterosis for early growth.