The determination of arsenic and selenium by HPLC combined with alternating current plasma detection and post-column hydride formation

A helium alternating current plasma detector in combination with HPLC has been evaluated for the determination of arsenic and selenium-containing compounds after post-column hydride generation. The construction, operation, and optimization of the system is presented. Detection limits for the compounds under study ranged from 45–60 pg/s. Determination of arsenic and selenium in spiked river water samples has been used to demonstrate the applicability of the technique.     

Selective determination of organofluorine compounds by capillary column gas chromatography with an atmospheric pressure helium microwave-induced plasma detector

Fluorinated analogs of compounds typical of those found in metabolic and other biological studies are detected with high selectivity using a gas chromatograph/microwave-induced plasma detector (GC-MIPD), which permits fluorine-selective detection by monitoring the emission at 685.6 nm. Using the described atmospheric pressure helium-sustained plasma detector, the minimum detectable level, fluorine selectivity (relative to carbon), and linear dynamic range of this GC-MIPD system were determined to be 4.8 pg-F/s, 1060, and 5000, respectively. The utility of this GC-MIPD system for the selective detection of organofluorine compounds is demonstrated by its application in the analysis of the metabolic fate of a fluorinated substrate administered to a mixture of wheat germ phosphatase and potato apyrase, as well as by analysis of synthetic mixtures.     

Simultaneous determination of organotin,organolead, and organomercury compounds in environmental samples using capillary gas chromatography with atomic emission detection

As part of a continuing evaluation of new analytical and sample preparation techniques conducted by the US Environmental Protection Agency (EPA), the use of capillary gas chromatography with atomic emission detection (GC-AED) for the simultaneous determination of organotin, organolead, and organomercury compounds in environmental samples was investigated. Pentylmagnesium bromide was used to pentylate ionic organotin, organolead, and organomercury compounds; the pentyl derivatives were then separated by GC and determined by AED. Several important GC-AED parameters, including the type of injector inlet, carrier gas flow rate, and helium make-up gas flow rate, were optimized for the simultaneous determination of these organometallic compounds. Their minimum detectable concentrations were approximately 1.0 to 2.5 ng/mL using a 0.5-μL on-column injection. The calibration curves exhibited good linearity between 2.5 and 2500 ng/mL for organotin and organolead compounds, and between 2.5 and 10000 ng/mL for organomercury compounds.     

Selectivity enhancement of a metal-sensitive flame ionization detector for capillary gas chromatography

A novel modification of a hydrogen-atmosphere flamo ionization detector (HAFID) is presented which attenuates response to hydrocarbon compounds, significantly enhancing selectivity towards organometallic compounds by more than an order of magnitude. Chromatograms of an organometallic compound test mixture and regular leaded gasoline are presented to depict the specificity of the response.     

Gas chromatographic determination of propyphenazone in plasma

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Combined immunological and thin-layer chromatographic method of the determination of morphine

     

Quantitative gas chromatographic analysis of perhalogenated compounds using a flame lonization detector

Summary In the determination of several perhalogenated compounds after gas chromatographic separation on an Apiezon L column, using a flame ionization detector, all the compounds tested gave linear area-mass plots although the coefficients observed do not lead to extrapolations which would permit quantitation of perhalogenated compounds for which no standard is available. Of the compounds tested, dibromodichloromethane, tetrachloroethene and tetrabromoethene gave good linear correlations of area ratio-mass ratio (using n-decane as the internal standard). Bromotrichloromethane and tetrabromomethane gave continuously curving area ratio-mass ratio plots which were very reproducible and could be used for graphical interpolation.     

Speciation analysis of triethyl-lead and tributyl-tin compounds in human urine by liquid-liquid extraction and gas chromatography microwave-induced plasma atomic emission detection

This work describes the development of a fast method for speciation analysis of triethyl-lead and tributyl-tin species in urine samples after in situ derivatization by tetraethyl- or tetrapropyl-borate reagents. The alkylation reaction is done in the aqueous and urine medium and the less-polar derivatives are extracted in hexane by liquid-liquid extraction. The species were extracted and the extract was efficiently collected from the aqueous phase after centrifugation. Finally, the organometallic species are separated by gas chromatography and determined from the emission signals of elemental lead and tin. Atomic lead and tin are formed from the organolead and organotin compounds during atomization of the column eluate in a microwave-induced helium plasma source. The simultaneous measurement of lead (Pb) at 405.780 nm and tin (Sn) at 303.419 nm was achieved by an atomic emission detector. Finally, the analytes were determined with satisfactory precision (<5%) and detection limits of 0.05 μg Pb/L and 0.48 μg Sn/L, respectively, when 10 mL of urine is extracted with 1 mL of hexane and 1 μL of extract is injected.     

Halogenated compound response in an oxygen doped ion mobility detector for capillary gas chromatography

An ion mobility detector that has been specifically developed for interfacing with capillary gas chromatography is investigated in the negative ion mode. Like the electron capture detector, to which this instrument is closely related, the ion mobility detector shows an enhanced response to low molecular weight halogenated compounds when a small quantity of oxygen is doped into the make-up gas flow. Under O₂ doping conditions, the device can operate in a reactant ion monitoring mode responding universally to compounds capable of capturing thermal electrons and in a tunable selective product ion mode providing increased selectivity over that achieved by the ECD. At an oxygen concentration of 0.5%, minimum detectable amounts as low as 600 femtograms have been realized for carbon tetrachloride. Selectivity of chloro- versus bromo- compounds is demonstrated using a mixture of p-dichlorobenzene and p-dibromobenzene.     

High resolution gas chromatographic determination of permanent gases with a helium ionization detector

The capability of the helium ionization detector (HID) to operate in connection with capillary columns for trace gas analyses has been evaluated. Two different capillary columns were considered: a PLOT fused silica column with molecular sleve and a thick film WCOT glass column with PS-255. The determination of trace impurities in gases can be achieved with evident advantages over classical adsorption columns, even using a split injection system. Direct on-column injections also have been investigated with promising results.     

Gas chromatographic determination of impurities in nitromethane

Summary Impurities in commercially available nitromethane have been determined by gas-liquid chromatography using six different column packings. Besides nitromethane, 1-nitropropane, 2-nitropropane, acetonitrile, methanol, small amounts of ethanol and acetaldehyde have been detected. The presence of formaldehyde, ethyl acetate and acetone is probable. Mixtures containing comparable amounts of the four nitroalkanes could be separated on all columns, but plots of logarithms of the retention times vs. carbon number or boiling points of the nitroalkanes or column temperatures were linear only in case of columns packed with Porapak R and Q.     

New studies of the plasma emission detector

Being an element-selective detector, the plasma emission detector was used to determine carbon in organic compounds. Experiments were carried out with the aid of osculating interference filters and lock-in amplifiers. The obtained signals were processed by a fast-Fourier-transform analyzer to study their frequency spectra. Results are given for the detection of carbon. Furthermore studies on the influence of angle-adjustment, microwave power, photomultiplier voltage and oscillation frequency on the determination of fluorine in organic compounds were carried out and results for detection limits and dynamic range of this method are presented.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Determination of butyl- and phenyltin compounds in human urine by HS-SPME after derivatization with tetraethylborate and subsequent determination by capillary GC with microwave-induced plasma atomic emission and mass spectrometric detection

A headspace solid-phase micro-extraction (HS-SPME) method was developed and optimized for gas chromatographic separation and determination of commonly found organotin compounds in human urine after potential exposure. Butyl- and phenyltin compounds were in situ derivatized to ethylated derivatives by sodium tetraethylborate (NaBEt₄) directly in the urine matrix. The relevant parameters affecting the yield of the SPME procedure were examined using tetrabutyltin as internal standard. The method was optimized for direct use in the analysis of undiluted human urine samples and mono-, di- and tri-substituted butyl- and phenyltin compounds could be determined after a 15-min headspace extraction time at room temperature. The selectivity of the microwave-induced plasma atomic emission detector (MIP-AED) as an element specific detector in combination with the relatively selective sample preparation technique of HS-SPME allowed the interference-free detection of the organotin compounds in all cases. A quadrupole mass spectrometer was used in parallel experiments as a detector for the confirmation of the identity molecular structure of the eluted compounds. The performance characteristics of the developed method are given for the determination of mixtures of these compounds. Finally the proposed method was applied to the analysis of several human urine samples.     

气相色谱用氩微波等离子体炬发射光谱检测器——对Sn,P,Si和B金属有机化合物响应特性的研究

报道了一种气相色谱用氩微波等离子体炬原子发射光谱检测器(GC-MPT-AED),以氩气为载气、等离子体工作气和尾吹气,探讨了不同气体作等离子体清洗气和屏蔽气时对Sn,P,Si,B等元素响应特性的影响.研究了系统对Sn,P,Si,B等元素的检出限、线性范围和精密度,并对乐果乳油中磷元素的含量进行了测定.     

High-performance liquid chromatographic determination of (−)-cathinone in plasma

Summary High-performance liquid chromatography (HPLC) for the determination of (–)-cathinone in rabbit and human plasma has been studied. The problem of dimerization during extraction from plasma was satisfactorily resolved. Detection was by UV at 257 nm. Concentration levels as low as 24 ng ml^–1 were satisfactorily determined. This level of sensitivity should be adequate for the detection of (–)-cathinone in the blood of khat users and also for the quantitative determination of (–)-cathinone in blood for pharmacokinetic purposes. The applicability of the assay procedure to pharmacokinetic studies is demonstrated.     

Pulsed discharge emission detector — Application to analytical spectroscopy of permanent gases

Summary This publication contains our initial development of a pulsed discharge emission detector (PDED) (patent pending). It uses a pulsed high voltage discharge in helium, which provides a stable source for atomic and polyatomic emission spectroscopy. We have evaluated this detector for both quantitative and qualitative analysis of a range of chemical compounds. Emission spectra observed from the pulsed high voltage discharge are valuable for spectral analysis. The results obtained for selected permanent gases in the ultraviolet, visible and infrared regions of the optical spectrum indicate that these spectra can be used for compound identification after a chromatographic separation. The data are unique in our opinion and serve as a basis for the future development and investigation of the analytical significance of this detection method.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Applications of gas chromatography with an atomic emission detector

An atomic emission detector for gas chromatography has been developed which is, in principle, capable of detecting selectively any element (except helium) which can elute from a gas chromatographic column. Software methods have been developed so far for 23 elements and on isotope, including all of the organic elements along with mercury, lead, tin, silicon, and deuterium. Element-specific analyses are shown for several petroleum, environmental, and aroma samples. A table for the detector's element-specific detection limits, selectivities, and linear dynamic ranges is given for 12 elements and deuterium.     

Gas chromatographic detection of organometallic compounds by reactive-flow photometry

The response of the reactive flow detector (RFD) toward organometallic compounds of several transition metals has been explored, and several of its strong elemental responses have been characterized in detail. The RFDs minimum detectable flow (measured in picograms of metal per second at S/N_p-t-p=2) is 0.1 for ruthenium, 3 for chromium, 10 for manganese, 5 for nickel, 15 for iron, and 2 for osmium. Typically, the linearity of response spans four orders of magnitude, with atomic selectivity of metal versus carbon ranging from 2 to 3 orders. Response quenching by co-eluting hydrocarbons is not observed. As a demonstration experiment, the common analysis of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline is carried out on an RFD system modified for dual-channel operation. The results show that dual-channel operation of the RFD can increase the native elemental selectivity of manganese over carbon by a factor of 100, in accordance with earlier results obtained on a special version of the flame photometric detector (FPD). Significant differences exist between the optical spectra of carbon flame species resulting from various combustion modes carried out in the RFD capillary, and also between conventional FPD and typical RFD spectra. Consideration of these spectral differences suggests that the virtual absence of in the reactive flow may be the primary reason why analyte response quenching by hydrocarbons, while prominent in the FPD, is not observed in the RFD.     

A high-performance liquid chromatographic method for determination of flecainide in human plasma using fluorescence detection

Summary A high performance liquid chromatographic method for the determination of flecainide in serum has been developed. The analysis is performed on a microparticulate silica column. The eluate is monitored by fluorescence detection at an excitation wavelength of 300nm and an emission wavelength of 370nm. No sources of interference were identified and a coefficient of variation of less than 8% was observed on repeated flecainide determinations. The method has a good reproducibility, specificity and accuracy, and can be applied in therapeutic drug monitoring of flecainide in patients.     

High-performance liquid chromatographic determination of busulfan in plasma

Summary Busulfan (Myleran; 1,4-bis-(methanesulfonyloxy) butane; BU) is a bifunctional alkylating agent used in clinical practice since 1959. It is currently included at high doses in conditioning regimens for bone marrow transplantation, usually in combination with cyclo-phosphamide. A high-performance liquid chromatographic method has been developed for the determination of BU in plasma. The basis of the assay is a derivatization with sodium diethyldithiocarbamate at 32°C in the presence of 1-bromo-1-deoxy-3,6-anhydrogalactitol as internal standard. Analysis is performed on a cyano column with heptane-isopropanol-glacial acetic acid as mobile phase and UV detection at 280 nm. The calibration graph was linear in the concentration range 0.18–46.40 μM BU in plasma. The limit of detection was 0.1 μM. The precision and accuracy were between the limits required by good laboratory practice. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, september 1–3, 1999