Characterization of the flame photometric detector in the sulphur mode

Summary The effect of experimental conditions such as gas flow rates, detector and column temperatures on sulphur response are discussed. It is concluded that the response of the flame photometric detector is affected by the O/H ratio and the total gas flow. Column temperature has an important influence upon S₂ emission. It is shown that the sulphur response of the FPD is dependent on the compound containing the sulphur.     

Method for analysis of heavy sulphur compounds using gas chromatography with flame photometric detection

A method for analysis of heavy sulphur compounds in wines, based on gas chromatography (GC) with flame photometric detection, is reported. Wine samples preparation includes a dichloromethane liquid-liquid extraction followed by concentration under a nitrogen atmosphere. The extracted fraction was also analysed by GC-mass spectrometry. The method enables high recovery of sulphur compounds in wine and satisfies the requirements of repeatability and sensitivity. Applications of the method to red, white and Port wines are reported.     

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.     

Critical appraisal of the flame photometric detector in petroleum analysis

Summary This paper summarises experience gained at the British Petroleum Limited Research Centre, Sunbury-on-Thames, with sulphur selective gas chromatography (GC) detectors. A single flame photometric detector (SFPD) has been in use for three years for research and routine applications. Three areas of interest are described demonstrating in turn different characteristics of the detector. Firstly, a determination of trace levels of individual organo-sulphur compounds in the 15–65°C cut of crude oils illustrates the complexity of using an SFPD in a rigorously quantitative manner. Secondly, the use of an SFPD as a qualitative tool for the comparison of the sulphur distribution of crude oils up to the temperature limit of GC is cited. Finally, a third section describes the properties of a dual flame photometric detector (DFPD) which are compared and contrasted with those of the SFPD.     

Application of a flame photometric detector to the gas chromatographic measurement of sulphur compounds in hydrocarbon fractions

Summary Analysis of individual sulphur compounds in a complex hydrocarbon matrix is complicated either by quenching or by simultaneous hydrocarbon response. In the latter case the hydrocarbon response can be subtracted by opposing the signals from two different detectors, leaving a simplified chromatogram of the sulphur compounds.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Determination of the boiling point distribution of sulfur compounds in light cycle oil using GC with a flame photometric detector and pyrolyzer

A method has been developed to determine the boiling point distribution of sulfur compounds in light cycle oils (LCO'S). The method chosen for this analysis was GC with a flame photometric detector (FPD) and pyrolyzer. Tests were carried out to evaluate the recovery efficiency, repeatability, and accuracy of the method. Repeatabilities within 2% were obtained. The recovery of benzothiophenes and dibenzothiophenes was close to 100%; this was important because these are the major sulfur components in LCO's. No hydrocarbon or solvent interferences were observed with the use of the pyrolyzer, even for a 95% solvent level. Comparison with results from other techniques showed that the method accurately determined the levels of sulfur compounds in the LCO boiling point range.     

Chromatographic parameters derived for the non-linear response of a flame photometric detector

Summary A mathematical derivation of efficiency and resolution equations for use in conjunction with flame photometric detection of sulphur compounds is presented. These equations are similar to those for linear detection apart from the incorporation of the exponential response factor, n, in the denominator of the respective expressions for non-linear detection. The latter equations reduce to those usually recognised for linear detection if the value n=1 is substituted. Equating the column efficiency equations for linear and non-linear detection permits direct determination of the value of n.     

Evaluation of comprehensive two-dimensional gas chromatography with flame photometric detection: Potential application for sulfur speciation in shale oil

Flame photometric detection in the sulfur channel has been evaluated for sulfur speciation and quantification in comprehensive two-dimensional gas chromatography [GC × GC-FPD(S)] for S-compound speciation in shale extracts. Signal non-linearity and potential quenching effects were reportedly major limitations of this detector for analysis of sulfur in complex matrices. However, reliable linear relationships with correlation coefficient >0.99 can be obtained if the sum of the square root of each modulation slice in GC × GC is plotted vs. sulfur concentration. Furthermore, the quenching effects are reduced due to essentially complete separation of S-containing components from the hydrocarbon matrix. An increase of S/N of up to 150 times has been recorded for benzothiophene and dibenzothiophene in GC × GC-FPD when compared to GC-FPD due to the modulation process. As a consequence, 10 times lower detection limits were observed in the former mode. The applicability of the method was demonstrated using shale oil sample extracts. Three sulfur classes were completely separated and the target class (thiophenes) was successfully quantified after the rest of the sample was diverted to the second detector by using a heart-cut strategy. Based on the proposed method, 70% of the sulfur in the shale oil was assigned to the thiophenes, 24% to benzothiophenes, and 5% to dibenzothiophene compounds.     

The potential of on-line flame photometric detection in microcolumn liquid chromatography

The potential of an interface for the on-line coupling of microcolumn liquid chromatography (LC)and a flame photometric detector (FPD) has been further investigated. With the micro-LC/FPD system, relatively high-molecular-weight polar compounds such as cyclic adenosine monophosphate, guanosine monophos- phate, glucose monophosphate, fructose monophosphate, and phytic acid were separated and selectively detected. In order to increase the sensitivity, on-line preconcentration with a microprecolumn inserted in the rotorof a Valcovalve has been applied. Preliminary results have shown that an injection volume of at least 500 1-11 water containing organophosphorus acids at a 5–50 ng/rnl concentration level is possible.     

Determination of cyanogen and cyanogen chloride using gas chromatography with a flame ionisation detector

Summary The response of a flame ionisation detector (FID) to cyanogen ((CN)₂) and cyanogen chloride (CNCI) has been studied. The lower limits of detection for (CN)₂ and CNCl were 6×10⁻¹² moles and 2×10⁻¹¹ moles respectively. In a comparative study a thermal conductivity detector gave as its lower limit of detection for both (CN)₂ and CNCl 4×10⁻¹¹ moles. Both detectors showed excellent linearity over the range 0 to 10 micromoles. The ratio of the gradients of the FID calibrations (CN)₂/CNCI were found to be approximately two suggesting the response depended on the cyanide group. The response and stability of the FID was investigated as a function of air and hydrogen flow-rates. The response increased with increasing air flow-rate for both (CN)₂ and CNCI up to 300cm³min⁻¹, thereafter no significant increase was observed. On raising the hydrogen flow from 10 to 25cm³min⁻¹ only a slight increase in the sensitivity of the FID towards both (CN)₂ and CNCI was observed. At higher flow rates the response for (CN)₂ increased markedly whereas at the same flow rates the response for CNCI increased only slightly.     

Development and validation of a multiresidue method for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection

A multiresidue method has been developed and validated for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection. Limits of quantification of the method varied between 0.007 and 0.01 μg/g. Ethyl acetate based extraction followed by dispersive solid‐phase extraction cleanup with primary secondary amine yielded internationally acceptable recoveries of acephate, chlorpyrifos, dichlorvos, monocrotophos, malathion, malaoxon, phorate, phorate‐sulfoxide, phorate‐oxon, phorate‐sulfone, and quinalphos from selected matrices. The recoveries of target analytes from cane juice were 75.55 ± 0.5–102.57 ± 4.2, 77.45 ± 4.7–103.33 ± 3.3, and 80.55 ± 6.6–105.82 ± 9.8% at 0.01, 0.02, and 0.1 μg/g levels of fortification, respectively. The recoveries from cane sugar were 73.24 ± 3.5–104.47 ± 1.9, 75.23 ± 1.5–116.10 ± 3.7, and 70.75 ± 5.7–110.15 ± 2.7%, respectively at 0.01, 0.02, and 0.1 μg/g levels of fortification. Matrix effect and measurement uncertainty were within the permissible limit (less than 20%) as prescribed for pesticide residue analysis.     

Determination of anthraquinone in a photometric detector

Anthraquinone can be determined, following gas chromatographic separation, by photometry of its luminescence in excited nitrogen. The spectrum consists of some broad bands, the most prominent of which peak at 460–480 nm. The minimum detectable amount (S/N=2), using a packed column, is surprisingly low at ca. 0.5 pg or 0.24 fmol/s (2.4×10^–16mol/s); the linear range spans three to four orders of magnitude; and the detector is capable of operating under temperature-programmed GC conditions.While anthraquinone is the strongest responding analyte of its kind, similar though somewhat weaker responses are produced by certain types of aroyl compounds. All other tested groups of organics give only extremely weak, negative responses (decreases in background luminescence) at some 10⁵ to 10⁶ higher concentrations. Quenching of anthraquinone luminescence can occur: As a typical example, a 50% reduction in response is produced by a ca. 100 ppmv/v level of co-elutingn-butane in the nitrogen carrier (a more than millionfold weight excess for a 1 pg peak of anthraquinone).Material taken from the Ph. D. thesis of Y.-Z. Tang (Dalhousie University, 1987)     

Chromatographic determination of phosphine (PH3) and hydrogen sulfide (H2S) in the headspace of anaerobic bacterial enrichments using flame photometric detection

Summary A gas chromatographic method is presented which distinguishes phosphine from hydrogen sulfide and other possible headspace gases of anaerobic microbial cultures. In anaerobic cultures spiked with phosphine, this gas is recovered in the liquid and gaseous phase down to 10 pg per ml of gas or liquid. No biogenically produced phosphine was found. Phosphine in amounts as small as 30 ng per 1 can be stored for several days in glass bottles covered with rubber septa, filled with nitrogen, in the presence or absence of water or of an anaerobic bacterial culture. Due to the selectivity of the detector and the retention characteristics of the porous layer open tubular polymer column alkanes, alkenes and organosulfur compounds routinely found in anaerobic bacterial headspaces do not interfere with the analytical quantification of phosphine.     

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.     

Linearity of a flame ionisation detector for capillary gas chromatography

Summary The influence of the nitrogen and hydrogen flow rates on the linearity of the flame ionisation detector is investigated and flow-rates which give a linear response over five orders of magnitude are determined.     

Improvements in flame photometric detector design and operation. Determination of organophosphorus pesticide residues at low picogram levels

The molecular emission of heteroelements such as phosphorus and sulfur is the basis of the selective response of the flame photometric detector. The behavior of the FPD towards phosphorus compounds has been studied and design improvements sought with regard to burner configuration and temperature distribution. The possibility of differentiating between compounds containing phosphorus atoms and those containing both phosphorus and sulfur atoms has also been examined. Detection limits and response characteristics have been reported for organophosphorus pesticide residues in samples of natural origin     

气相色谱-脉冲火焰光度法测定水产品中的二硫氰基甲烷残留

建立了气相色谱-脉冲火焰光度法(GC-PFPD)测定水产品中二硫氰基甲烷(MBT)残留的分析方法。用二氯甲烷-正己烷溶液(1∶1,v/v)在超声条件下提取水产品中的MBT,然后用中性氧化铝固相萃取小柱对提取物进行净化和富集,通过HP-5MS石英毛细管柱(30 m×0.32 mm×0.25μm)分离,最后采用配有脉冲火焰光度检测器的气相色谱仪进行测定,外标法定量。MBT在1.0~20.0 mg/L范围内线性关系良好,相关系数为0.997 1;检出限为0.1 mg/kg;加标回收率为65.6%~97.6%,精密度为6.32%~12.8%(n=7)。该法能很好地满足水产品中药物残留检测的需求。     

Analysis of sulfur-containing compounds in ambient air using solid-phase microextraction and gas chromatography with pulsed flame photometric detection

A new analysis method for sulfur-containing compounds in air using solid-phase microextraction (SPME), gas chromatography and pulsed flame photometric detection (PFPD), SPME-GC-PFPD method, has been developed. The analysis method is simple, fast and easily performed. To demonstrate the usefulness and versatility of the method air samples collected in geothermal areas in Rotorua, at a muddy beach in Auckland (cities in New Zealand), and in a wastewater treatment plant were analysed. COS, H₂S, CS₂, SO₂, CH₃SH, (CH₃)₂S and CH₃(CH₂)₂CH₂SH were identified in the samples from Rotorua. It was noted that air quality in residential areas with respect to sulfur compounds was better than that around geothermal sources. Samples from the wastewater treatment plant contained COS, H₂S, CS₂, SO₂, CH₃SH, (CH₃)₂S and (CH₃)₂S₂. It was found that the emission of sulfur compounds was reduced in the course of the wastewater treatment process. The potential impact of the detected sulfur compounds on human health is briefly discussed.     

The fundamental properties of the direct injection method in the analysis of gaseous reduced sulfur by gas chromatography with a pulsed flame photometric detector

In this study, the fundamental aspects of gas chromatography with a pulsed flame photometric detector were investigated through the calibration of gaseous reduced sulfur compounds based on the direct injection method. Gaseous standards of five reduced sulfur compounds (hydrogen sulfide, methane thiol, dimethyl sulfide, carbon disulfide, and dimethyl disulfide) were calibrated as a function of injection volume and concentration level. The results were evaluated by means of two contrasting calibration approaches: fixed standard concentration method (variable volumetric injection of standard gases prepared at a given concentration) and fixed standard volume method (injection of multiple standards with varying concentrations at a given volume). The optimum detection limit values of reduced sulfur compounds, when estimated at 100 μL of injection volume, ranged from 2.37 pg (carbon disulfide) to 4.89 pg (dimethyl sulfide). Although these detection limit values improved gradually with decreasing injection volume, the minimum detectable concentration (e.g., in nmol mol⁻¹ scale) remained constant due to a balance by the sample volume reduction. The linearity property of pulsed flame photometric detector also appeared to vary dynamically with changes in its sensitivity. According to this study, the performance of pulsed flame photometric detector, when tested by direct injection method, is highly reliable to precisely describe the behavior of reduced sulfur compounds above ∼20 nmol mol⁻¹.     

Development of a simple desulfurization procedure for the determination of butyltins in complex sediment samples using gas chromatography-pulsed flame photometric detection

In this study a rapid solid phase extraction (SPE) procedure was developed to minimize the effect of different sulfur species for the determination of butyltin in sediments. The organosulfur species and organotins were firstly retained on C8 cartridges and then organotins were selectively eluted and analyzed by gas chromatography-pulsed flame photometric detection (GC-PFPD). Optimal conditions for the SPE procedure were obtained using an experimental design approach. The method's accuracy was established by analyzing a certified reference material (CRM), BCR-646 freshwater sediment. The experimental values were found to be in agreement with the assigned values for butyltins. Finally, complex sediment samples collected from a Chilean harbor were analyzed using this methodology to demonstrate its analytical potential for the determination of butyltin in environmental samples.