Pentafluorobenzoyl Derivatives Research Articles

Comparing different gas chromatographic methods for the quantification of bisphenol A (BPA) trace levels in paper and cardboard products from the market

Bisphenol A (BPA; 4,4ʹ-(propane-2,2-diyl)diphenol), a suspected endocrine disruptor with weak estrogenic activity, is used in a variety of consumer products, including paper and cardboard products used as food contact materials. The present study compared four different gas chromatographic methods for the analysis of BPA in paper and cardboard food packages. Eighteen different food packages were extracted and BPA was determined using two different derivatisation reactions – trimethylsilylation with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) and halide alkylation with pentafluorobenzoyl chloride (PFBOCl) – and four different separation and detection techniques. The BSTFA derivatives were quantified with (1) GC-MS in single-ion monitoring (SIM) mode with electron ionisation (EI-GC-MS) and (2) GC-MS/MS in multiple reaction monitoring (MRM) mode using electron ionisation (EI-GC-MS/MS); while the PFBOCl derivatives were quantified with (3) GC-MS using electron ionisation (EI-GC-MS) as well as (4) GC-MS with negative chemical ionisation (NCI-GC-MS). All developed methods showed good linearity (R2 > 0.9938), precision (CV < 4.5% for reproducibility; CV < 2.2% for repeatability) and sensitivity, with limits of detection (LODs) between 0.02 µg kg−1 for the pentafluorobenzoyl derivatives measured with the NCI-GC-MS method and 6 µg kg−1 for the pentafluorobenzoyl derivatives determined with EI-GC-MS. Levels of BPA in the samples were in agreement for all methods, ranging from values below the limit of quantitation (LOQ) to 11.9 mg kg−1 paper. In a last step, the maximum potential migration into food products was calculated for all tested paper and cardboard samples, assuming a ‘worst case’ scenario of 100% migration.

Determination of hydroxylated fatty acids from the biopolymer of tomato cutin and their fate during incubation in soil

The plant cuticle is a thin, predominantly lipid layer that covers all primary aerial surfaces of vascular plants. The monomeric building blocks of the cutin biopolymer are mainly ω-hydroxy fatty acids. Analysis of ω-hydroxy fatty acids from cutin isolated from tomato fruits at different stages of decomposition in soil. Different derivatives and mass spectrometric techniques were used for peak identification and evaluation. Preparation of purified cutin involving dewaxing and HCl treatment. Incubation of purified cutin for 20 months in soil. Pentafluorobenzoyl derivatives were used for GC/MS operated in the electron capture negative ion (ECNI) mode and trimethylsilyl ethers for GC/MS operated in the electron ionisation (EI) mode for analysis of ω-hydroxy fatty acids. Six ω-hydroxy fatty acids were detected in the purified cutin, three of which were identified as degradation products of 9,16-dihydroxyhexadecanoic acid as a consequence of the HCl treatment involved in the purification step. Incubation of the isolated cutin in soil was accompanied with decrease in concentration of all hydroxyl fatty acids. We produced evidence that the HCl treatment only affected free hydroxyl groups and thus could be used for proportioning free and bound OH-groups on cutin fatty acids. The method enabled a direct quantification of the ω-hydroxy fatty acids throughout the incubation phase.

Lipid Extraction and Determination of Halogenated Phenols and Alkylphenols as Their Pentafluorobenzoyl Derivatives in Marine Organisms

A method was developed for the extraction of lipids and analysis of halogenated phenols and alkylphenols in marine organisms. The extraction efficiency was evaluated by comparing the extractable lipid content and the recovery of 13 added phenols from three different marine species (herring, cod, and blue mussel), with the corresponding results from three well-established extraction procedures, the Bligh and Dyer (B&D), the Smedes (S), and the Jensen (J) methods. The J method and the new method, Jensen centrifugation (Jc), gave phenol recoveries of 80-100% for all species, whereas the B&D and S methods gave relatively low recoveries for the most acidic phenols, with recoveries of only 20-50% for pentachlorophenol (PCP) depending on the species. It was concluded that this effect was governed by the dissociation of the phenols and adsorption to the protein tissue during the extraction (due to ionic interactions). To increase the sensitivity of the analysis, the phenols were converted to their pentafluorobenzoyl esters, by using a tetrabutylammonium-catalyzed extractive acylation. The reaction was quantitative within 2 min at room temperature, and the formed derivatives were persistent enough to withstand treatment with concentrated sulfuric acid.

Concentrations of medium-chain 2- and 3-hydroxy fatty acids in foodstuffs

Medium chain 2-hydroxy fatty acids and 3-hydroxy fatty acids (2-OH-FAs and 3-OH-FAs with 8–20 carbons) are widespread in nature but little was known about the quantities of these minor fatty acids in food. For this reason, the concentrations and composition of 2- and 3-OH-FAs in several foodstuffs (milk and dairy products, animal brains, suet, vegetable oils) and two non-food samples (wool wax and vernix caseosa) were determined by gas chromatography with electron-capture negative ion mass spectrometry in the selected ion monitoring mode. Lipids were isolated from samples by accelerated solvent extraction. After transesterification the obtained fatty acid methyl esters (FAMEs) were separated into OH-FAMEs and non-OH-FAMEs. The OH-FAMEs were converted into pentafluorobenzoyl (PFBO) derivatives (PFBO- O-FAMEs). 2- and 3-OH-FAs were detected in all samples analysed. Chain-length ranged from 8–20 carbons. In general, 3-OH-FAs dominated in milk and dairy products (maximum concentration 17.7 mg/100 g l.w. in goat milk) whereas 2-OH-FAs were more abundant in animal brains and suet. The lowest concentrations were determined in vegetable oils (0.21–2.42 mg/100 g l.w.) whereas the highest concentrations of 2-OH-FAs were determined in wool wax (1180 mg/100 g l.w.) and vernix caseosa (34.5 mg/100 g l.w.). The OH-FA pattern was varied and use of specific OH-FAs was proposed as tracers for authenticity controls. Based on the concentrations determined, it was estimated that the daily uptake of OH-FAs via food is in the milligram range.

Gas chromatography–mass spectrometry determination of the pentafluorobenzoyl derivative of methylhydrazine in false morel ( Gyromitra esculenta) as a monitor for the content of the toxin gyromitrin

The main toxic compound found in false morel ( Gyromitra esculenta) is acetaldehyde- N-methyl- N-formylhydrazone (gyromitrin). This paper describes a method of determining the total hydrazones content based on acid hydrolysis of gyromitrin and other related hydrazones in air-dried false morel followed by derivatisation of methylhydrazine with pentafluorobenzoyl chloride. The derivative, tris-pentafluorobenzoyl methylhydrazine ( tris-PFB-MH) is analyzed by gas chromatography–mass spectrometry. The overall precision of the method is better than 10% (relative standard deviation) for 0.5 ng/μl methylhydrazine in solution. The minimum detectable concentration of methylhydrazine ( tris-PFB-MH) by this method is estimated to be approximately 12 pg/μl, which is equal to 0.3 μg/g dry matter (DM) of false morel.

Analysis of estrogens in river water and effluents using solid-phase extraction and gas chromatography–negative chemical ionisation mass spectrometry of the pentafluorobenzoyl derivatives

A procedure was developed for the analysis of estrogens in environmental water and effluents. Samples were extracted by passing through polymer-impregnated solid-phase extraction discs or C 18 cartridges, followed by gas chromatography–negative chemical ionisation mass spectrometry of the pentafluorobenzoyl derivatives. The derivatives were stable and gave diagnostic negative molecular ions as the base peak for each of the major estrogens studied. The absolute recovery of estrogens spiked into clean groundwater using the disc procedure was 84–116% at the 10 ng l −1 level (calculation not based on use of internal standards). Using doubly deuterated estradiol as internal standard added prior to extraction, the % relative standard deviation of estrogen extraction and analysis in spiked groundwater at the 10 ng l −1 level was 2.6–9.8%. Detection limits were 0.2 ng l −1 or below for the major estrogens, based on a 2.5 litre sample. The most abundant estrogen was estrone, with concentrations over the range 6.4–29 ng l −1 in effluents, and 0.2 to 17 ng l −1 in water from the River Thames.

Quantitative analysis of estrogens in human urine using gas chromatography/negative chemical ionisation mass spectrometry.

A sensitive procedure for the determination of estrogens in urine has been developed, using enzymatic hydrolysis and ether extraction followed by capillary gas chromatography with negative chemical ionisation mass spectrometry (GC/NCI-MS) of the pentafluorobenzoyl derivatives. These derivatives were superior for GC/NCI-MS to trifluoroacetyl, heptafluorobutyl, pentadecafluorooctanoyl and perfluorotolyl derivatives, giving characteristic negative molecular ions as the base peak for each of the naturally occurring estrogens estrone, estradiol and estriol, and for the synthetic estrogen ethynylestradiol used in contraceptive pills. The method was also suitable for determination of some metabolites of estrone and estradiol. The specificity and sensitivity of the GC/NCI-MS method simplifies sample preparation. Recovery of spiked samples was in the range 84-101% for the natural estrogens based on additions to increase the concentration by 5 and 1 microg L(-1). The repeatability of the method was 1-8% for all estrogens.

Inflammatory Platelet-activating Factor-like Phospholipids in Oxidized Low Density Lipoproteins Are Fragmented Alkyl Phosphatidylcholines

Oxidation of human low density lipoprotein (LDL) generates proinflammatory mediators and underlies early events in atherogenesis. We identified mediators in oxidized LDL that induced an inflammatory reaction in vivo, and activated polymorphonuclear leukocytes and cells ectopically expressing human platelet-activating factor (PAF) receptors. Oxidation of a synthetic phosphatidylcholine showed that an sn-1 ether bond confers an 800-fold increase in potency. This suggests that rare ether-linked phospholipids in LDL are the likely source of PAF-like activity in oxidized LDL. Accordingly, treatment of oxidized LDL with phospholipase A(1) greatly reduced phospholipid mass, but did not decrease its PAF-like activity. Tandem mass spectrometry identified traces of PAF, and more abundant levels of 1-O-hexadecyl-2-(butanoyl or butenoyl)-sn-glycero-3-phosphocholines (C(4)-PAF analogs) in oxidized LDL that comigrated with PAF-like activity. Synthesis showed that either C(4)-PAF was just 10-fold less potent than PAF as a PAF receptor ligand and agonist. Quantitation by gas chromatography-mass spectrometry of pentafluorobenzoyl derivatives shows the C(4)-PAF analogs were 100-fold more abundant in oxidized LDL than PAF. Oxidation of synthetic alkyl arachidonoyl phosphatidylcholine generated these C(4)-PAFs in abundance. These results show that quite minor constituents of the LDL phosphatidylcholine pool are the exclusive precursors for PAF-like bioactivity in oxidized LDL.

Quantitation of monosaccharide isotopic enrichment in physiologic fluids by electron ionization or negative chemical ionization GC/MS using di-O-isopropylidene derivatives.

The aldonitrile pentaacetate and other derivatives lack ions in the electron ionization (EI) spectra possessing an intact hexose structure and thus must be analyzed by chemical ionization GC/MS in order to study multiple isotopomers. We report methods for quantitation of hexose di-O-isopropylidene acetate (IPAc) or pentafluorobenzoyl (PFBz) esters. These were prepared in a two-step procedure using inexpensive reagents that do not adversely impact the isotopomer structure of the sugar. The acetate derivative possesses an abundant [M - CH3] ion in the EI spectrum which is suitable for quantitative analysis of isotopomers. The negative chemical ionization (NCI) spectrum of the corresponding pentafluorobenzoyl derivative has a dominant molecular anion. Moreover, the PFBz derivative is about 100-fold more sensitive than the acetate, which offers some advantages for analysis of minor hexoses found in plasma. Isotopic calibration curves of [U-13C]glucose are linear over the 0.1-60% tracer/tracee range tested. The useful range for isotopic tracer studies is 25-2500 pmol for EI analysis of the acetate derivative and 0.1-55 pmol for NCI analysis of PFBz derivative (sample amount injected). For most studies where sample size is not limited, EI-GC/MS analysis of the IPAc derivative is preferred. NCI-GC/MS analysis is reserved when sample size is limiting or when studies involve hexoses other than glucose that are normally present at low concentration.

Negative-ion Chemical Ionization of Amphetamine Derivatives

The negative-ion chemical ionization (NICI) mass spectra of the heptafluorobutyryl (HFB) and pentafluorobenzoyl (PFBz) derivatives of several amphetamines and N-substituted amphetamines were obtained. The HFB derivatives of amphetamine and its ring-substituted congeners were each found to undergo predominant loss of one molecule of hydrogen fluoride, while the corresponding PFBz derivatives each underwent sequential loss of two molecules of hydrogen fluoride followed by the loss of either a methyl or an aryl group. The HFB derivatives of the N-substituted amphetamines were found to undergo sequential loss of four molecules of hydrogen fluoride while the corresponding PFBz derivatives produced high-abundance molecular ions. NICI mass spectra of deuterium-labelled amphetamine derivatives were obtained and the order of hydrogen elimination was studied. These findings explain previous observations of hydrogen fluoride loss by the amphetamine derivatives and define potential applications of NICI mass spectrometry to the analysis of these compounds.

Negativeion Chemical Ionization of Amphetamine Derivatives

The negative-ion chemical ionization (NICI) mass spectra of the heptafluorobutyryl (HFB) and pentafluorobenzoyl (PFBz) derivatives of several amphetamines and N-substituted amphetamines were obtained. The HFB derivatives of amphetamine and its ring-substituted congeners were each found to undergo predominant loss of one molecule of hydrogen fluoride, while the corresponding PFBz derivatives each underwent sequential loss of two molecules of hydrogen fluoride followed by the loss of either a methyl or an aryl group. The HFB derivatives of the N-substituted amphetamines were found to undergo sequential loss of four molecules of hydrogen fluoride while the corresponding PFBz derivatives produced high-abundance molecular ions. NICI mass spectra of deuterium-labelled amphetamine derivatives were obtained and the order of hydrogen elimination was studied. These findings explain previous observations of hydrogen fluoride loss by the amphetamine derivatives and define potential applications of NICI mass spectrometry to the analysis of these compounds.

Determination of 4-(4-chlorophenyl)-4-hydroxypiperidine, a metabolite of haloperidol, by gas chromatography with electron-capture detection

An electron-capture gas chromatographic procedure was developed for the analysis of 4-(4-chlorophenyl)-4-hydroxypiperidine (CPHP), a metabolite of haloperidol. The assay involved basic extraction of this metabolite from the biological samples, followed by back-extraction with HCl. After basification of the acid phase, extractive derivatization with pentafluorobenzoyl chloride in toluene was conducted. The pentafluorobenzoyl derivative was quantified on a gas chromatograph equipped with a fused-silica capillary column, an electron-capture detector and a printer-integrator. N-(3-Trifluoromethylphenyl)piperazine was carried through the procedure as an internal standard and calibration curves were determined for each assay run. The procedure was demonstrated to be linear and reproducible and was utilized to detect and quantify CPHP in urine, plasma, brain and liver samples from rats treated with haloperidol. The structure of the derivatized metabolite was confirmed by gas chromatography-mass spectrometry.

Distinguishing Ephedrine and Pseudoephedrine from Methamphetamine as 4-Carbethoxyhexafluorobutyryl or Pentafluorobenzoyl Derivatives and Analysis by GC/CI-MS: Microwave-Induced Rapid Derivatization

Distinguishing Ephedrine and Pseudoephedrine from Methamphetamine as 4-Carbethoxyhexafluorobutyryl or Pentafluorobenzoyl Derivatives and Analysis by GC/CI-MS: Microwave-Induced Rapid Derivatization

Differential electron capture mass spectral response of pentafluorobenzoyl derivatives of platelet activating factor alkyl chain homologs.

The electron capture mass spectrometric response of pentafluorobenzoyl ester derivatives of platelet-activating factor alkyl chain homologs has been found to be inversely proportional to their alkyl chain length. This phenomenon was observed when either the gas chromatograph or direct insertion probe was utilized for sample introduction. A similar differential response was also obtained for a series of fatty alcohols, analyzed as pentafluorobenzoyl esters. These studies demonstrate that multiple standard curves must be prepared for analysis of platelet-activating factor and related lipids in order to obtain accurate quantification.

Secondary fatty alcohols of Mycobacterium xenopi.

Secondary alcohols of Mycobacterium xenopi were studied by gas chromatography and gas chromatography-mass spectrometry. Mycobacterial cells were hydrolysed and the liberated alcohols separated by extraction and analysed both underivatized and as trimethylsilyl, methyl ether- and pentafluorobenzoyl derivatives. Seven straight-chain secondary alcohols containing from 18 to 24 carbon atoms and two branched-chain secondary alcohols with 21 and 23 carbon atoms were present in all of the studied strains.

Gas chromatography-mass spectrometry of lipopolysaccharide 3-hydroxy fatty acids: comparison of pentafluorobenzoyl and trimethylsilyl methyl ester derivatives

3-Hydroxytetradecanoic and 3-hydroxyhexadecanoic acids were used as chemical markers for the determination of lipopolysaccharides by gas chromatography-mass spectrometry of their pentafluorobenzoyl and trimethylsilyl methyl ester derivatives. The latter derivatives were simpler to prepare than the former, although both were chemically stable. Analysis of pentafluorobenzoyl derivatives (chemical ionization mode with negative ion detection) provided somewhat better sensitivity than analysis of trimethylsilyl derivatives (electron impact mode): 1 pg (injected amount) of pentafluorobenzoyl derivatives was detectable under routine conditions. Both types of derivative gave similar values when used to measure lipopolysaccharides in a bacteria-contaminated pharmacological product. The described methods are useful for the determination and characterization of lipopolysaccharides in various environments.

Gas chromatography — mass spectrometry methods for analysis of secondary alcohols present in the Mycobacterium avium complex

Secondary alcohols of mycobacteria belonging to the Mycobacterium avium complex were studied by gas chromatography and gas chromatography — mass spectrometry. After hydrolysis of the mycobacterial cells followed by extraction of the alcohols, trimethylsilyl, trifluoroacetyl, heptafluorobutyryl and pentafluorobenzoyl derivatives were formed. In the electron impact mode the trimethylsilyl derivative of 2-eicosanol was detected down to 10 pg, whereas in the negative ion chemical ionization mode the pentafluorobenzoyl derivative was detected at the 1 pg level. An alcohol not previously detected in mycobacteria was found in all of the studied strains; it was identified as 2-nonadecanol. The methods described may be useful for the detection of certain mycobacteria, including the M. avium complex, in clinical or environmental samples.

An evaluation of the negative ion mass spectra of electron-capturing derivatives of the biogenic trace amines I—phenylethylamine

A series of fluorinated derivatives have been examined for their suitability of use for quantification of biogenic trace amines, in particular phenylethylamine, in biological samples at the picogram (femtomolar) level using negative ion mass spectrometry. The negative ion mass spectra of the pentafluoropropionyl, heptafluorobutyryl, perfluorosuccinimido, pentafluorobenzyl and pentafluorobenzoyl derivatives of phenylethylamine are characterized by intense high-mass fragment ion peaks due to loss of HF, whereas the spectra of the 3-trifluoromethylbenzoyl, 4-trifluoromethylbenzoyl and 3,5-di-trifluoromethylbenzoyl derivatives exhibited fragment ions due to loss of H or 2H and the pentafluorobenzoyl derivative did not form a detectable molecular ion. After acetylating the fluorobenzoyl derivatives of phenylethylamine, the spectra of the resultant amides were found to contain primarily molecular ions, and the electron capture cross-sections and negative ion sensitivities increased. The most suitable derivatives were found to be the N-acetyl-N-pentafluorobenzoyl, which could be detected at the 75 fg (0.5 attomolar) level of phenylethylamine and the N-acetyl-N-3,5-di- (trifluoromethyl)benzoyl derivative.

Determination of hydrogen peroxide in fish products and noodles (Japanese) by gas-liquid chromatography with electron-capture detection

A sensitive and practical method for the determination of hydrogen peroxide (H2O2) in various fish products and noodles (Japanese) is described. The method is based on the gas chromatographic measurement of 2-hydroxyanisole, as its pentafluorobenzoyl (PFB) derivative, which is a product of the hydroxylation of anisole by reaction with H2O2 and potassium hexacyanoferrate(III) [K3Fe(CN)6] in the acid solution. The PFB derivative of 2-hydroxyanisole is determined by gas-liquid chromatographic separation on a 5% OV-17, 5% OV-210 mixed-phased column using an electron-capture detector (GLC-ECD). The calibration curve for H2O2 in the range 0.1-1.0 micrograms/mL is linear and sufficiently reproducible for quantitative determination; the detection limit for H2O2 is 0.06 micrograms/mL of sample extract. The coefficient of variation (n = 5) of the values determined is below 4.9%, and the average recovery rate throughout the procedure, including derivatization and gas-liquid chromatography, was above 87.1% in the fish products and noodles investigated. Although various possible metal ions and organic substances in the samples to be analyzed were tested at relatively high levels, all of them did not interfere with the production of 2-hydroxyanisole. The derivatization process was simple and rapid, requiring about 60 min, and the resulting derivative was stable for at least 1 week if stored under appropriate conditions.

Determination of nonylphenol and nonylphenol ethoxylates as their pentafluorobenzoates in water, sewage sludge and biota

A method has been developed for the determination of nonylphenol and nonylphenol ethoxylates containing one to three ethoxy units in water, sludge and biota. After isolation the substances are converted into their corresponding pentafluorobenzoyl derivatives and quantified by GC/ECD or GC/MS. Results from investigations of secondary sludge from eight municipal sewage treatment plants in Sweden revealed concentrations of 4-nonylphenol from 26 to 1100 mg/kg d.m. An uptake study on blue mussels ( Mytilus edulis ) was carried out near the waste water outlet of a manufacturer of nonylphenol ethoxylates. The concentrations of 4-nonylphenol in the mussels ranged from 0.20 to 0.40 μg/g wet weight.