Phenyl-methylpolysiloxane Column Research Articles

Effective and Reusable Monolith Capillary Trap of Nitrosamine Extraction by Superheated Water from Frankfurter Sausage

A novel, simple, rapid, and inexpensive method of extraction and cleanup of nitrosamines from frankfurter sausage was achieved with a capillary filled with monolith of either polystyrene-co-divinylbenzene (PS-DVB), Polydivinylbenzene (P-DVB), or silica that had been fabricated. The study of capability in trapping nonpolar matrix and monolith capillaries with varied lengths revealed that a silica monolith gave the best result for nitrosamine determination. With an online coupling between superheated water extraction (SWE) and silica monolith capillary connected to a 5% phenyl-methylpolysiloxane column, factors affecting the extraction and determination, namely, sensitivity with and without the monolith, reusability, injection-injection repeatability, capillary-capillary precision, and chromatographic separation, were investigated. This confirmed the feasibility of the method. The optimal length of silica monolith capillary was 30 mm, offering reuse more than 20 times. Separation and quantification of selected volatile nitrosamines were carried out using gas chromatography (GC) coupled with either a flame ionization detector (FID) or mass spectrometer (MS). The overall extraction and determination method determined by GC-MS allowed for a recovery of 75-88% with a <5% relative standard deviation (RSD) and detection limit of 2-5 ng of injected nitrosamine.

Two‐dimensional gas chromatography with heart‐cutting for isotope ratio mass spectrometry analysis of steroids in doping control

The accuracy and precision of gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) measurements are highly dependent on analyte purity. Reliable analysis of urinary steroids for doping control therefore requires extensive and time-consuming sample preparation (i.e. liquid chromatography fraction collection) prior to GC-C-IRMS analysis. The use of two-dimensional GC (GC-GC) with heart-cutting (Deans Switch) as a possible approach to reduce the sample purification required for IRMS analysis is described herein. The system uses a low thermal mass oven (LTM) incorporated into an existing GC-C-IRMS system. GC-GC allowed the use of a cyanopropyl/phenyl column in the first dimension to optimize the separation of underivatized steroids, while a phenyl-methylpolysiloxane column in the second dimension focuses the selectively cut analytes into narrower peaks for more sensitive and reliable MS analysis. In addition, to confirm analyte identity, eluent from the second GC was split, with 20 % entering a scanning MS, and 80 % flowing to the IRMS. As a proof concept, the developed method was then used to analyze a single spot urine (5 ml) from an individual receiving T therapy (2 × 50 mg sachets of Testogel(®)). The T delta value (-27.8 ‰, [T] = 38 ng/ml) was clearly distinct from 11-ketoetiocholanolone (-22.5 ‰) (used as an endogenous reference compound (ERC)), indicating T as being of exogenous origin. The simultaneous analysis by the scanning MS yielded a full scan mass spectrum of the same chromatographic peak, thus confirming the peak to be T.

Determination of polycyclic aromatic hydrocarbons (PAHs) from organic aerosols using hollow fiber micro – porous membrane liquid – liquid extraction (HF-MMLLE) followed by gas chromatography–mass spectrometry analysis

A method for determination of polycyclic aromatic hydrocarbons (PAHs) from aerosols was developed. Instead of conventionally used non-polar or slightly polar phenylmethylpolysiloxane column a highly polar, highly substituted, cyanopropyl column (VF-23 MS) was used for separation of PAHs. Based on hollow fiber micro-porous membrane liquid–liquid extraction (HF-MMLLE) a method was developed for sample clean up and pretreatment. An enrichment factor of 617–1022 was obtained with extraction efficiency 10.2–18.9% for different PAHs analyzed in this study. The optimized method was successfully applied to aerosol samples and limits of detection between 1.2 pg m −3 and 180 pg m −3 was obtained. Almost all PAHs were found in most of the aerosol samples.

Identification and Quantification of the Osmodiuretic Mannitol in Urine for Sports Drug Testing Using Gas Chromatography-Mass Spectrometry

The osmodiuretic mannitol can be potentially misused in sports, owing to its urine diluting effect and the possibility to decrease bodyweight. To reveal a doping offence, resulting urinary mannitol concentrations after a prohibited intravenous application and a permitted oral intake have to be differentiated. Therefore, a reliable gas chromatography-mass spectrometry (GC-MS) method was established based on peracetyl derivatives of the analytes. All possible hexitols (allitol, galactitol, iditol, altritols, sorbitol and mannitol) that can occur in human urine were separated and identified on a phenyl-methylpolysiloxane column (HP-5MS) within 10.75 min, and the method demonstrated its capability for quantification purposes. The lower limit of detection and lower limit of quantification were estimated at 0.9 microg mL(-1) and 2.4 microg mL(-1), respectively, and the assay was validated for mannitol and sorbitol regarding the parameters specificity, linearity, intra- (<10%) and inter-day precision (<15%) and accuracy (92-102%). To investigate urinary mannitol concentrations after oral intake the method was applied to an excretion study, providing a mean urinary excretion of mannitol of 19.5%. Comparison of theoretically expected urinary levels after a common therapeutic dose of mannitol and preliminary results on physiological urinary mannitol levels were promising, regarding a threshold level for mannitol that can be utilised for doping control purposes.

Gas‐chromatographic separation of stereoisomers of dipeptides

Synthetic dipeptides comprising mixtures of enantiomers, diastereomers, or sequential isomers were converted into their N-perfluoroacetyl dipeptide esters (perfluoroacetyl: trifluoroacetyl, pentafluoroacetyl, heptafluorobutyryl; ester: methyl, 1-propyl, 2-propyl, 2,2,2-trifluoroethyl) and analyzed by GC-MS on the chiral stationary phases Chirasil-L-Val and Lipodex-E using helium as carrier gas. Further, dipeptides were converted into their N-trifluoroacetyl dipeptide S-(+)-2-butyl esters and separated on achiral phenylmethyl polysiloxane column (HP-5 MS). Derivatization of dipeptides was performed at ambient temperature in order to avoid formation of the corresponding diketopiperazines. The best separation of stereoisomers was achieved with TFA and PFP methyl esters on Chirasil-L-Val.

Determination of Trichlorfon and Dichlorvos Residues in Shrimp Using Gas Chromatography with Nitrogen−Phosphorus Detection

A method capable of quantifying trichlorfon and dichlorvos in shrimp at concentrations of 20−80 ng/g has been developed. Ground shrimp is homogenized in ethyl acetate and centrifuged. The supernatant is dried completely on a rotatory evaporator. The extract is dissolved in petroleum ether, concentrated on a solid phase extraction column, and analyzed by gas chromatography using a cool on-column inlet and a nitrogen−phosphorus detector. The analytes are separated from matrix components using a thermal gradient on a (cyanopropyl)phenyl-methylpolysiloxane column. The method was validated with control shrimp fortified at 20, 40, and 80 ng/g trichlorfon and dichlorvos. The average recoveries and intralaboratory coefficients of variations were 50−83% and 15−21% respectively. Keywords: Trichlorfon; dichlorvos; shrimp; gas chromatography; nitrogen−phosphorus detector

Gas chromatographic retention behaviour of polychlorinated naphthalenes on non-polar, polarizable, polar and smectic capillary columns

Six commercially available gas chromatography columns were investigated for performance in separating polychlorinated naphthalenes (PCNs). Retention behaviour on the investigated phases is compared and retention data for 40 congeners on a 5% phenyl—methylpolysiloxane column is reported. For all columns, except the octylmethylpolysiloxane and the smectic, a relation between substitution pattern and retention was found, where substitution in adjacent positions as well as α-substitution increase the retention time. A mathematical model based on these findings was developed and used to predict the relative retention of all congeners from di- up to octachloronaphthalene, on a 5% phenyl—methylpolysiloxane column.

GC-MS Characterization of the Compounds in Some Essential Oils

The composition of different essential oils (menthe, basil, lavender, rose) was investigated by gas chromatographic–mass spectrometry (GC–MS) method to identify those compounds responsible for the characteristic, pleasant floral or aroma odour or taste of some valuable oils. Three different rose oils presented monoterpenes as fragrance target compounds and some aliphatic hydrocarbons with fixative effects responsible for a longer-lasting odour impression. Chromatography was performed on a 5% phenyl methylpolysiloxane column (15 or 30 m x 0.25 mm I.D., 0.25 µm) operated in suitable temperature programs.