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)     

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.     

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.     

Effects of hydrocarbon quenching in gas chromatography when using the flame photometric detector

Summary The long time retardation of the main hydrocarbon peak in the chimney of the flame photometric detector greatly reduces the responses of later-eluting sulfur compounds. In the absence of hydrocarbons in the flame, the slope (s) of the log I vs. log [S] plot (where I is the sulfur response and [S] is the sulfur concentration in the sample) is of the highest value and is constant for all experimental conditions tested. Flame hydrocarbons cause the s value to decrease, and this is dependent on the oxygen to hydrogen ratio in the flame (O/H) and, under certain conditions, also on the sulfur to carbon ratio (S/C) of the sample. The abnormalities observed in the determination of methyl thiol in natural gas are explained on the basis of the present study.     

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.     

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     

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。     

Multi-beam polarized photometric detector for high-performance liquid chromatography

A novel multi-beam polarized photometric detector (PPD) for high-performance liquid chromatography (HPLC) is described. By pairing a polarizing prism with a thin quartz plate as a retarder, many linear polarized beams are produced at every 1/2 wavelength of the plate, and the polarizing axes of the adjacent beams intersect each other. The addition of another prism inclining its polarizing axis by π/4 against the first one enables the simultaneous measurement of optical rotations based on the PPD at many wavelengths. The combination of these optics with a photo-diode array detector can be used to construct a modulated type polarimeter. This detector is designed to measure the optical rotation of an analyte at its absorption band. The spline function connecting the points at 1/4 wavelengths of the plate was used as a baseline to extract the PPD waves. The use of the similarity factor as a noise filter gave high sensitivity. Application of the proposed technique to an analyte carrying the Cotton absorption band provided good results.     

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.     

Determination of phosphate using a highly sensitive paired emitter-detector diode photometric flow detector

The use of a novel inexpensive photometric device, a paired emitter-detector diode (PEDD) has been applied to the colorimetric determination of phosphate using the malachite green spectrophotometric method. The novel miniaturized flow detector applied within this manifold is a highly sensitive, low cost, miniaturized light emitting diode (LED) based detector. The optical flow cell was constructed from two LEDs, whereby one is the light source and the second is the light detector, with the LED light source forward biased and the LED detector reversed biased. The photocurrent generated by the LED light source discharges the junction capacitance of the detector diode from 5 V (logic 1) to 1.7 V (logic 0) and the time taken for this process to occur is measured using a simple timer circuit.The malachite green (MG) method employed for phosphate determination is based on the formation of a green molybdophosphoric acid complex, the intensity of which is directly related to phosphate concentration. Optimum analytical parameters such as reaction kinetics, reagent to sample concentration ratio and emitter wavelength intensity were investigated for the spectrophotometric method. Linear calibration plots that obeyed the Beer-Lambert law were obtained for phosphate in the range of 0.02-2 μM. The dynamic range, sensitivity and limits of detection are reported.     

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.     

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     

顶空固相微萃取-气相色谱表面发射火焰光度检测法测定底泥中的丁基锡化合物

固相微萃取可用于多种样品基体中挥发、半挥发性有机化合物的测定。将固相微萃取技术应用于底泥样品中丁基锡化合物的富集和萃取,以气相色谱分离结合表面发射火焰光度检测器检测,方法灵敏、快速,一丁、二丁、三丁基锡的检测限可达16.9、1.58和0.17ng/g。     

Indirect photometric detection of anions in nonaqueous capillary electrophoresis employing Orange G as probe and a light-emitting diode-based detector

A method based on indirect photometric detection (IPD) in CE employing a blue LED (473 nm) as a light source and the highly absorbing (478 nm) anionic dye, Orange G, as the probe ion was developed for the sensitive analysis of inorganic and organic anions. The use of nonaqueous solvents was examined as a simple way to reduce the adsorption of the dye onto the capillary wall and to thereby improve the baseline stability. The benefits of this approach were confirmed by experiments using BGEs in methanol (MeOH) and DMSO in which superior baselines were obtained relative to those achieved using aqueous electrolyte systems. A range of commercial LEDs was tested to improve the detection performance, with a difference of 25% in sensitivity being observed between the best and worst performing LED. The final system (4 mM Orange G, 0.05% w/v hydroxypropylcellulose (HPC), 20 mM triethanolamine (TEA) in pure MeOH) exhibited stable baselines and very low LODs (0.10-0.18 microM) for a test mixture comprising nine inorganic and organic anions. These values represent a two- to six-fold improvement over previous studies and the proposed method provides the most sensitive IPD method for the determination of anions using CE published to date. RSDs for ten replicates were in the ranges of 0.42-0.62% for migration time, 1.41-3.46% for peak area and 3.20-5.78% for peak height.     

A photometric detector based on a blue light-emitting diode

The suitability of blue light-emitting diodes as radiation sources in molecular absorption spectroscopy was evaluated. Electronic as well as spectral considerations are discussed. A transducer based on a blue light-emitting diode and a photodiode is described which yields direct absorbance readings by passing the photocurrent to an integrated circuit logarithmic converter. The performance of this device was tested for commonly used spectrophotometric procedures for Cr, Mn, Zn, Fe and Cl and compared with conventional molecular absorption spectroscopy. Also investigated was the application of the transducer as a detector in flow-injection analysis.     

Optimization of GC detector parameters using electronic pressure control

HP 5890 Series II Gas Chromatographs are equipped with prototype hardware enabling electronic pressure programming of all detector and carrier gases. A method of using electronic pressure control (EPC) to optimize detector performance (sensitivity, selectivity, and baseline stability) is demonstrated. With EPC, sample introduction, column separation, and detector performance can be optimized simultaneously without the classical trade-offs in performance. An example is also presented of the use of a new automated system which enables cool on-column injection into 250 or 320 μm columns without the need for a retention gap.     

A radio-frequency moving-boundary detector

A new type of moving-boundary detector is described in which boundaries are detected at platinum ring electrodes situated on the outside of a moving-boundary tube. These rings are part of a bridge circuit operating at radio frequencies. Impedance changes in the region of the rings are converted by a phase-sensitive detector to a voltage output which, when operating in the differential mode, takes the form of a sharp peak as a boundary passes through the rings. Boundary displacements of less then 20 m can be detected, and a precision of better than 0.02% is obtained in the measurement of boundary velocities in typical transference measurements. The fact that only three electrical leads are required in the detecting circuit gives this detector a decided advantage for high-pressure work. Equally important is the elimination of electrode polarization problems associated with other types of electrical detectors.Taken, in part, from a Ph.D. thesis, Carnegie-Mellon University, 1971.     

胶束电动毛细管色谱间接紫外光检测法分离胆汁酸

利用间接紫外光检测法在254 nm进行胆汁酸胶束电动毛细管色谱分离的研究.在对氨基苯磺酸为背景电解质和十二烷基硫酸钠作胶束的体系中,加入高浓度的尿素,有效地改善了两类胆汁酸5组份的分离度,在优化分离缓冲体系10 mmol/L对氨基苯磺酸-5 mmol/L硼砂-30 mmol/LSDS-7 mol/L尿素-10%乙醇(pH 7.5)中,13 min内获得基线分离,分离效率为8.4×104～1.1×105.所建立的方法无需衍生化处理,为胆汁酸的分离提供了新的通用的方法.     

Detection of osmocene by gas chromatography-flame photometry

Following gas chromatographic separation, bis(cyclopentadienyl) osmium (osmocene) can be selectively determined by a flame photometric detector. The luminescence is broad and spectrally complex, with the highest emission intensity observed in the red and near infrared. The minimum detectable amount (S/N=2) of osmocene is 0.5 ng or 0.15 pmol/s (0.2 ng by the IUPAC definition), and its linear range spans close to three orders of magnitude. The selectivity within linear range vis-à-vis naphthalene, through a 650-nm cut-on filter, is about 1.7 × 10³ on a compound weight basis, or 4.3 × 10⁴ on an elemental (mol Os/mol C) basis. The molar response ratios for the bis(cyclopentadienyl) derivatives of the iron group metals Fe Ru Os are approximately 3 60 1, at a set of conditions roughly suited to the simultaneous detection of all three elements in one chromatographic run.Part of doctoral thesis requirements of first author