Flame Photometric Detector Research Articles

Levels of tin and organotin compounds in human urine samples from Iowa, United States

Exposure to tin in the general US population is near ubiquitous, as determined using urinary tin levels measured by inductively coupled plasma mass spectrometry (ICP-MS). Urinary tin levels are associated with chronic health outcomes, such as diabetes; however, it is unclear if these associations are due to the presence of inorganic and organic forms of tin in urine. To address this knowledge gap, levels of total tin and several organotin compounds (OTCs) were measured in convenience urine samples from pregnant women and adults from Iowa, United States. Total tin and OTC levels in urine samples were quantified using ICP-MS and gas chromatography with pulsed flame photometric detection (GC-PFPD), respectively. ICP-MS detected tin in almost all urine samples from both study populations. Low levels of dibutyltin were detected in two out of fifty human urine samples. Importantly, storage of urine samples in plastic containers, but not HNO3-pretreated glass vials drastically reduced the recoveries of OTCs, in particular, tributyltin. Although their detection frequency is low, exposures to OTC should be considered when studying associations between human exposures to tin compounds and adverse health outcomes; however, urinary OTC levels measured in banked urine samples may not be suitable as biomarkers of OTC exposure.

Micro-Flame Photometric Detection in Miniature Gas Chromatography on a Titanium Tile

A novel miniaturized gas chromatography–flame photometric detection device built within a titanium platform (Ti µGC–FPD) is presented. The 7.5 cm × 15 cm monolithic Ti device contains both an OV-101 coated separation column (5 m × 100 µm i.d.) and a shielded cavity to house the hydrogen-rich detector flame. The FPD employs a micro counter-current flame (about 250 µm in diameter) that is stabilized by opposing relatively low flows of oxygen and hydrogen (7–10 mL/min O2 and 40 mL/min H2). Under optimal conditions, the minimum detectable limits are about 70 pg S/s for sulfur and 8 pg P/s for phosphorous. The natural (i.e., unfiltered) selectivity for these responses over carbon is near 104.3 for S/C and 105 for P/C. Even greater selectivity over hydrocarbons can further still be obtained by employing conventional interference filters. Overall, good separations with stable and sensitive detector performance are obtained with the device, and its sturdy Ti structure supports robust operation. Results indicate that this Ti µGC–FPD device may be a useful alternative approach for incorporating selective FPD sensing in µGC analyses.

Exposure of chlorpyrifos in toddlers living in an agricultural area in Sakon Nakhon province, North-East Thailand

Purpose Children living in agricultural areas are exposed to pesticides in their living areas and through activities of daily living. These exposures may lead to adverse health effects. The purpose of this paper is to investigate household environmental and behavioural factors associated with chlorpyrifos exposure and resultant adverse health effects in children living in an agricultural community. Design/methodology/approach A cross-sectional study was conducted including 65 toddlers (age of 12–36 months) and their parents were face-to-face interviewed from January to February 2016. Toddler’s hands and feet, toys and floors were wiped for chlorpyrifos residue analysis. The wipes were extracted and analysed by gas chromatography with a flame photometric detector, and blood cholinesterase activity was measured by the EQM Test-mate (model 400). Findings The average age (± standard deviation) of children was 19.9 (±5.9) months. Chlorpyrifos detections were 61.5 per cent (hands), 57.1 per cent (toys), 53.8 per cent (floors) and 30.8 per cent (feet). The highest chlorpyrifos residue concentration was detected on toy surface (3.022 µg/m2). Chlorpyrifos residues on hands and feet were positively correlated with concentrations on floors and toys (Spearman’s ρ, p<0.01). Multiple linear regression analysis revealed that more frequent hand washing (β=−0.236, p=0.067) and showering (β=−0.240, p=0.056) was negatively associated with chlorpyrifos residue on children’s body. House cleaning frequency was significantly associated with an increase in haemoglobin-adjusted erythrocyte cholinesterase (β=0.251, p<0.05). Originality/value Chlorpyrifos exposures found in the children household area through their activities and behaviours can cause several adverse health effects. The circumstances associated with chlorpyrifos exposure should be mitigated and reduced to improve the household environment of children living agricultural areas.

Representative commodity for six leafy vegetables based on the determination of six pesticide residues by gas chromatography

A residue analytical method was developed for the determination of trichlorfon, chlorpyrifos, dimethoate, β cypermethrin, deltamethrin, and chlorothalonilin in six leafy vegetables by gas chromatography–electron capture detector (GC–ECD) and gas chromatography–flame photometric detector (GC–FPD). The method had a good linearity (R2 ≥ 0.9924) and precision (RSD ≤ 14.0%). The limits of quantification (LOQ) of six pesticides were all 0.01 mg/kg. Average recoveries of six pesticides ranged from 81% to 119%. The developed method was successfully applied to study the initial deposits, degrade characteristics, and terminal residues for six pesticides applied to six leafy vegetables under the same dose of formulation. The half-life of six pesticides was in the range of 0.8–8.8 days. The highest initial deposits, maximal residues, and terminal residues were found on leaf mustard and sweet potato leaves as the same pesticides were applied in different crops. Therefore, leaf mustard can be selected as representative commodity in the same subgroup to realize the residual extrapolation. This conclusion should be considered as a complement on crop classification of China.

Review of the analysis of insecticide residues and their levels in different matrices in Ghana

This review reports on how Ghanaian scientists analyse insecticide residues in various matrices in their laboratories as well as the levels of insecticides found in Ghana. It covers different sample preparation methods such as solid-liquid and liquid-liquid extraction. The main technique used for this analysis was gas chromatography (GC) with various detectors such as electron capture, flame photometric, nitrogen phosphorus, and mass spectrometric detection. Liquid chromatography (LC) with mass spectrometric detection was sometimes used to determine the levels of very polar insecticide residues. From the articles reviewed 74% of the insecticides detected were organochlorines with DDTs, lindanes, and endosulfans as most abundant ones. Levels of the insecticides of interest analysed, varied from below the detection limits to clearly above the safety limits. The lowest detected concentration of insecticide residues reported in fruits and vegetables was δ-lindane in pawpaw (0.06 mg/kg) while the highest was fenvalerate (25.6 mg/kg). Insecticide residues reported in sediment were predominantly organochlorines with concentrations ranging from 9.68 ng/kg to 10.98 µg/kg. Endosulfan and its metabolites were the main insecticides found in water bodies with concentrations ranging from 0.036 µg/L to 62.3 µg/L. DDT and its metabolites were the dominant insecticides found in human fluids.

Persistence of pesticides in green vegetables of Satna District of Madhya Pradesh

Astudy was conducted forthe qualitative and quantitative estimation of 51 pesticides comprising 16 organochlorines, 23 organophosphates, eight synthetic pyrethroids and four herbicides in commonly consumed green vegetables i.e spinach, coriander, chilli, ladyfinger, bottle gourd and bitter gourd collected from various tehsils of Satna district, Madhya Pradesh. Gas chromatography-Electron Capture Detector (GC-ECD), Flame Photometric Detector (GC-FPD) were used for estimation of pesticides and Gas chromatography-Mass Spectrometry (GC-MS) was used for confirmation. Out of 144 samples, 59 samples were found contaminated with pesticide residue. It was observed that most of the bitter gourd samples were contaminated with chlorpyrifos whereas spinach and okra were contaminated with cypermethrin. Nagod samples were found most contaminated (10 out of 18) whereas Rampur Baghelan were least contaminated (6 out of 18). Contamination of chlorpyrifos was predominant in samples of Nagod, Raghurajnagar and Birsinghpur whereas cypermethrin contamination was so in Majhagawa samples. Profenofos and monocrotophos were detected only in Nagod and Raghurajnagar samples.

Search for Optimal Parameters for Gas Chromatographic Complex When Determining Sarin in Water Samples by Flame Photometric Detection Method

Sarin is considered to be an instrument for chemical terror by the extremist organizations due to the availability of technologies and components for its production. This fact became evident after the use of sarin by several members of the extremist organization «Aum Shinrikyo» for air infection of the capital`s subway in 1995 in Japan and by ISIL bands in Syria in 2013. Because of its physical and chemical properties, as well as its ability to be dissolved in water in any ratios, sarin can infect water sources for the long period of time. But the sensitivity of flame photometric detectors (FPD) is not always sufficient for the analysis of water samples for the presence of sarin, its precursors and products of destruction, especially in cases of necessity to detect the concentrations less than 0,03 ppm (3×10 -5 mg/ml). We have found out that higher sensitivity of the detector can be achieved in case of the increase of the gas carrier (helium) pressure in the injector up to 25 psi, and the temperature – to 250 °C, single-segment temperature rise in the thermostat with a speed of 10 °C/min from 40 °C (1 min) to 280 °C (5 min) at a hydrogen stream in PFD – 75 ml/min, air – 100 ml/min, helium – 60 ml/min. In comparison with the initial method, the offered one is more sensitive in case of sarin concentration in water in the range from 6×10 -6 to 1×10 -4 mg/ml to 1,7 times. The approbation of the offered optimal parameters was carried out during the gas chromatographic detection of sarin in water samples during the OPCW Proficiency Tests, during the analysis of arbitration samples, during the scientific research and the obtaining of national accreditation of the Laboratory of Chemical Analytical Control of the 27 Scientific Centre of the Minstry of Defence of the Russian Federation. These parameters can be used successfully during the studies of any organophosphorous chemicals by GC analysis with flame photometric detection

Fabrication of graphene oxide incorporated polymer monolithic fiber as solid phase microextraction device for determination of organophosphate esters in soil samples

A novel solid phase microextraction fiber named graphene oxide incorporated poly acrylamide-ethylene glycol dimethacrylate (GO-poly AM-EDGMA) monolithic fiber has been successfully prepared in a fused silica capillary tube (250 μm, i.d.) via thermally initiated polymerization using acrylamide (AM) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, dimethylformamide dispersed by GO as porogens, and then obtained by removing 1 cm wall from one end of the fused silica capillary tube. The fiber has large surface area (536 m2 g−1), pore capacity (0.694 cm3 g−1) good thermal stability (up to 320 ℃), long service life and good reproducibility (RSD ＜5% throughout 110 times) which facilitated for high throughput headspace solid phase microextraction (HS-SPME) coupled to gas chromatograph (GC) analysis. The HS-SPME/GC method using the new fiber was evaluated by the determination of five organophosphate esters (OPEs) in soil samples coupled to flame photometric detector (FPD). The proposed HS-SPME-GC/FPD method yielded satisfactory limits of quantification (0.03 ng g−1∼0.24 ng g−1); linearity (≥0.99), good intra- and inter-day precision expressed as relative standard deviations for a single fiber were in the range of 5.2–9.0% and 4.8–9.0%, respectively, and fiber-to-fiber reproducibility was in the range of 5.9–9.7%. The method was applied for the analysis of OPEs in environmental soil samples and the relative recoveries were found to be in the range from 80.1 to 105.6%. Based on these features, the new fiber has great potential for widespread use as a high throughput trace analysis tool.

A Rapid Analytical Method for the Selective Quenching-Free Determination of Thiols by GC-FPD

A rapid method is introduced, which facilitates the selective gas chromatography–flame photometric detection (GC–FPD) analysis of thiols. The method uses lead oxide particles or plumbite solution to complex thiols into a solid lead thiolate moiety that can be physically separated from complex sample matrices and then reconstituted as the original thiol in a simple replacement solvent for analysis. While both red or yellow forms of lead oxide are found to remove thiols from sample solutions, the latter does so about 10 times faster than the former. Comparatively, though, plumbite solution is most rapid in this regard and is still 10 fold faster than solid yellow lead oxide. For example, 98 ± 1% (n = 3) of a 1-butanethiol standard in hexane (600 ng µL− 1) was extracted after only 2 min of contact with a 0.06 M plumbite solution. The method allows thiols to be selectively isolated from co-eluting peaks and other sulfur species, which can simplify their determination. It also allows thiols to be removed from complex hydrocarbon matrices for analysis, which can greatly reduce interference from signal quenching when using a conventional FPD. For instance, analysis of a thiol standard in a commercial gasoline by this method showed that the FPD sulfur signal increased from 16 to 97% of its expected value by removing the quenching hydrocarbon interference. Accordingly, results indicate that this method could be a useful alternative approach for the selective analysis of such thiol-containing samples.

Characterization of the key aroma compounds in peach by gas chromatography–olfactometry, quantitative measurements and sensory analysis

The volatile compounds of peaches (Prunus persica L.) obtained from five cultivars (Chongyanghong, Y1; Ruiguang 19, Y2; Zaohongxia, Y3; Zaohong 2, Y4; and Wuyuehuo, Y5) were analyzed by gas chromatography–olfactometry (GC–O), gas chromatography–mass spectrometry (GC–MS) and GC–flame photometric detection (FPD). A total of 40 odor-active volatile compounds were observed in the GC–O experiments. Amongst those compounds, hexanal, (Z)-3-hexen-1-ol, (E)-2-hexenal, 3-mercaptohexanol, nonanal, γ-nonalactone, and γ-decalactone contributed greatly to aroma of peach. In addition, thirty-four quantified compounds were demonstrated as important odorants according to odor activity values (OAVs > 1). Amongst these compounds, hexanal (OAV: 28–89), pentanal (OAV: 9–16), (E)-2-heptenal (OAV: 19–60), (E)-2-hexenal (OAV: 26–86), (E)-2-octenal (OAV: 10–42), (E)-2-nonenal (OAV: 8–94), γ-decalactone (OAV: 13–34), δ-decalactone (OAV: 2–19), (R)-(−)-linalool (OAV: 29–76) and phenyl acetaldehyde (OAV: 4–59) were the most powerful compounds in five varieties of peach.

Development and Validation of an Analytical Method to Quantitate Tris(chloroisopropyl)phosphate in Rat and Mouse Plasma using Gas Chromatography with Flame Photometric Detection.

Tris(chloropropyl)phosphate (TCPP) is an organophosphorus flame retardant (OPFR) and plasticizer increasingly used in consumer products and as a replacement for brominated flame retardants. Commercially available TCPP is a mixture of four structural isomers the most abundant of which is tris(1-chloro-2-propyl)phosphate (TCPP-1). Although there is a widespread use of TCPP and potential for human exposure, there is limited data on the safety or toxicity of TCPP. The National Toxicology Program is conducting long-term studies to examine the toxicity of the TCPP in rats after lifetime exposure, including perinatal oral exposure. Quantitative estimates of internal dose are essential to interpret toxicological findings in rodents. To aid in this, a method was fully validated to quantitate the most abundant isomer, TCPP-1, in female Harlan Sprague Dawley (HSD) rat and B6C3F1 mouse plasma with partial validation in male rat plasma, and male and female mouse plasma. The method used protein precipitation using trichloroacetic acid followed by the extraction with toluene, and analysis by gas chromatography with flame photometric detection. The performance of the method was evaluated over 5-70 ng TCPP-1/mL plasma. The method was linear (r ≥ 0.99), accurate (inter-day relative error: ≤ ± -7.2) and precise (inter-batch relative standard deviation: ≤27.5%). The validated method has lower limits of quantitation and detection of ~5 and 0.9 ng/mL, respectively, in female HSD rat plasma and can be used on samples as small as 50 μL demonstrating the applicability to plasma samples from toxicology studies.

Assessment of spontaneous combustion status of coal based on relationships between oxygen consumption and gaseous product emissions

It is imperative to have an in-depth understanding of the relationship between oxygen consumption and gaseous product emissions during coal self-heating not only for preventing fires in the coal industry but also for reducing emissions of hazardous gases. Two typical coal samples with high tendency of spontaneous combustion were heated to 230 °C with a programmed temperature of 1.0 K min−1 using a pilot-scale test apparatus. The trends for oxygen consumption and gaseous product emissions were obtained from continuous measurements of the gas samples at the reactor outlet via a gas chromatography equipped with a Flame Photometric Detector. Based on the rates of oxygen consumption and gaseous product emissions, the relationship between oxygen consumption and each gaseous product emission was studied. Multi-linear regressions of the oxygen consumption and gaseous product emissions were performed. The coefficients for the emission rates of CO2, CO and H2 in the regression equations of the two coals with three different particle sizes are found to be all positive, while the coefficients for the CH4 emission rates are all negative. These results indicate that the oxygen consumption of coal facilitates the release of CO2, CO and H2, while the increase of oxygen consumption rate may not enhance the release of hydrocarbon gas. Based on the results, an evaluation index defined as the ratio of oxygen consumption rate to the gaseous product emission rate is proposed to assess the state of coal spontaneous combustion.

Magnetic dispersive micro solid-phase extraction and gas chromatography determination of organophosphorus pesticides in strawberries

Magnetic nanoparticles (MNPs) with different sizes and characteristics were synthesized to be used as a QuEChERS sorbents for the determination of seven organophosphorus pesticides (OPPs) in strawberries by gas chromatography analysis with flame photometric and mass spectrometry detection. To achieve the optimum conditions of modified QuEChERS procedure several parameters affecting the cleanup efficiency including the amount of the sorbents and cleanup time were investigated. The results were compared with classical QuEChERS methodologies and the modified QuEChERS procedure using MNPs showed the better performance. Under the optimum conditions of the new methodology, three spiking levels (25, 50 and 100 μg kg−1) were evaluated in a strawberry sample. The results showed that the average recovery was 93% and the relative standard deviation was less than 12%. The enrichment factor ranged from 111 to 145%. The good linearity with coefficients of determination of 0.9904–0.9991 was obtained over the range of 25–250 μg kg−1 for 7 OPPs. It was determined that the MNPs have an excellent function as sorbent when purified even using less amount of sorbents and the magnetic properties allowed non-use of the centrifugation in cleanup step. The new methodology was applied in strawberry samples from conventional and organic farming. The new sorbents were successfully applied for extraction and determination of OPPs in strawberries.

Verification of <i>Aspergillus Niger</i> as a Myco-remediation Agent of Lambda-Cyhalothrin and Associated Heavy Metals in <i>Lactuca Sativa</i> (L.) Leaf

Pesticide residue constitutes a danger to soil micro and macro fauna and flora and to humans. This study assessed the impact of the application of Aspergillus niger as a pesticide remediating agent on Lambda-cyhalothrin and some of its associated heavy metals translocated to the leaves of Lactuca sativa . A Complete Randomized Design (CRD) experiment using three Treatments was conducted. Lambda-cyhalothrin was extracted from the Samples using the multiple residue technique and its residue determined using Gas Chromatography with Pulsed Flame Photometric Detector (PFPD). The associated heavy metals were determined using the Atomic Absorption Spectrophotometric method. Data so generated were means from five replicates, and were subjected to a one way analysis of variance - ANOVA with Tukey HSD Test for differences between means at 99% confidence interval (P≤0.01). The results show that the highest mean value of Lambda-cyhalotrhrin residue in L. sativa leaves was found in Treatment A (1.50 mg/kg), a value which was significantly higher (P≤0.01) than the residue found in Treatments B (1.0 mg/kg) and C(0.02 mg/kg). Mean Lambda-cyhalothrin residue in Treatment A alone was above the Maximum Residue Level (MRL) of 1.0 mg/kg in vegetable set in the legal EU regulation.The application of A. niger also precipitated a significant reduction (P≤0.01) in the level of all the heavy metals evaluated except Arsenic. All the heavy metals evaluated were however below the WHO/FAO safe limit. The result from this study posits A. niger as a promising mycoremediation agent of pesticide pollution.

Novel designs of dielectric barrier discharge hydride atomizers for atomic spectrometry

Eight designs of dielectric barrier discharge (DBD) atomizers have been constructed and optimized. Subsequently, their performance with atomic absorption (AAS), atomic fluorescence (AFS) and atomic emission (AES) detectors was investigated employing arsane as a model analyte. Although being all based on a planar shaped quartz body, the individual DBD designs differed from each other in the style of electrode attachment, electrode shape and area as well as electrode distance. All the designs studied were found compatible with AAS detection giving comparable sensitivity (between 0.38 and 0.47 s ng−1 As) and detection limit (around 0.2 ng ml−1 As) under optimum atomization conditions. However, significant differences in optimum conditions were found among the designs in terms of the applied voltage that strongly depends on the style of electrode attachment and electrode distance. The design with metal strip electrodes glued to a quartz body requires >14 kV to be operated. The design with sputtered electrodes of the same shape can reach the same sensitivity with 8.5 kV. These values can be further reduced to 6.5 kV, when decreasing the electrode distance from 3 to 1 mm. Selected DBD designs tested have been proven to be compatible with other spectrometric detectors such as AFS reaching detection limit 0.05 ng ml−1 As or AES with detection limit of 30 ng ml−1 As showing the universality of the planar DBD designs and its potential to further applications as well as mechanistic studies.

Residue behaviour of profenofos and triazophos in okra (Abelmoschus esculentus) and their decontamination using culinary processes

The persistence pattern and risk assessment of profenofos and triazophos in okra (Abelmoschus esculentus (L.) Moench) and cropped soil were studied in the present study. The insecticides were applied twice at 10 days interval @ 500 and 1000 g a.i./ha. Residues were quantified at 0, 1, 3, 5, 7, 10, 15 and 20 days of second application using GC equipped with Flame Photometric Detector (FPD). The average initial deposits of triazophos (1.838 mg/kg) in okra fruits were higher than profenofos (1.418 mg/kg) at the recommended application rates. Both the insecticides followed a first order kinetics with half-lives of 1.6 and 1.4 days, respectively on okra fruits. The initial deposits of 0.483 and 0.500 mg/kg, for respective insecticides, disappeared to BDL on 5th and 7th day in okra cropped soil. Microwave oven cooking proved more promising than other household processing in dislodging the residues of test insecticides from okra fruits. On the basis of this study, waiting periods of 7.6 and 7.4 days were suggested for consumption of okra sprayed with profenofos and triazophos, respectively.

Efficient derivatization of methylphosphonic and aminoethylsulfonic acids related to nerve agents simultaneously in soils using trimethyloxonium tetrafluoroborate for their enhanced, qualitative detection and identification by EI-GC–MS and GC–FPD

Trimethyloxonium tetrafluoroborate (TMO·BF4) has been used in the simultaneous derivatization of phosphonic and 2-aminoethylsulfonic acids related to nerve agents in different soils for their enhanced detection and identification by electron ionization gas chromatography-mass spectrometry (EI-GC–MS). The panel of acids consisted of five Schedule 2 phosphonic acids (methyl methylphosphonic acid, ethyl methylphosphonic acid, isopropyl methylphosphonic acid, pinacolyl methylphosphonic acid and cyclohexyl methylphosphonic acid) along with two sulfonic acids, N,N-diethyl-2-aminoethylsulfonic acid and N,N-diisopropyl-2-aminoethylsulfonic acid. The acids were converted to their corresponding methyl esters at ambient temperature when present at a 10μgg−1 concentration in three separate soils: Virginia type A soil, Ottawa sand and Nebraska EPA soil. The concentration of the acids reflects values typically encountered during proficiency tests (PTs) administered annually by the Organisation for the Prohibition of Chemical Weapons (OPCW). Derivatization times to yield detectable signals for the methyl ester products for all the acids was found to vary among all three soil samples, however, it was found that generally the most optimal time across all the matrices involved was 3h after the addition of TMO·BF4. Concomitantly, the analysis of the samples was complemented using GC coupled to flame photometric detection (GC–FPD). The inclusion of GC–FPD in the analysis yielded stronger signals for all seven methylated analytes making their detection after merely 3h possible relative to the ones initially obtained with EI-GC–MS. Regarding the three soils employed in our study, a greater methylating efficiency was found in the Virginia type A soil and Ottawa sand yielding results that were significantly larger in magnitude to those found during the same time points for the Nebraska EPA soil sample. Prolonged reaction times (up to 72h) were explored to find the time for the highest yield of methyl ester production were found instead to be deleterious to the process showcasing the importance of the fast yielding nature of the process specifically in situations where time-sensitive analysis is crucial (e.g. OPCW-PT).

Direct Measurement of Elemental Mercury Using Multidimensional Gas Chromatography with Microwave-Induced Helium Plasma Atomic Emission Spectroscopy

Microwave-induced helium plasma atomic emission spectroscopy permits direct measurement of picogram levels of elemental mercury in various matrices when combined with multidimensional gas chromatography. Two columns with different stationary phases provide excellent separation for elemental mercury, and multidimensional analysis improves the reliability, performance, and system cleanliness of atomic emission detection. The possibility of false positive identification is substantially eliminated, and excellent sensitivity for the target compound was attained with the use of two selective columns and atomic emission detection at 254 nm. A flame ionization detector was incorporated as part of the system configuration to increase analytical platform capability and flexibility. Elemental mercury was measured in gas matrices over a range of 0.1–170 μg/m3 having a correlation coefficient of R2 = 0.9995, a precision of less than 5% relative standard deviation (n = 10), and a measured recovery exceeding 99% in natural gas as a model matrix. The total analysis time is less than 10 min. Only a small 1 mL sample volume is needed, and the described approach does not rely on any form of sample enrichment. The utility of multidimensional gas chromatography with microwave-induced helium plasma atomic emission spectroscopy is demonstrated with challenging industrial applications, such as the measurement of elemental mercury in natural gas, industrial solvents, and vapor generated from ruptured compact fluorescent light bulbs.

Identification of Sulfur‐Containing Impurities in Biodiesel Produced From Brown Grease

AbstractFatty acid methyl esters (FAME) from waste grease usually contain higher concentrations of sulfur (S) than allowed to meet the specified quality standard for biodiesel (<15 ppm). Brown grease lipid‐derived FAME was produced and fractionated by two passes through a wiped‐film evaporator (WFE) to produce three fractions: (1) a 120 °C pass distillate, (2) a 170 °C pass distillate, and (3) a heavy residue. Solid phase extraction (SPE) was used to concentrate the S species from the distillate fractions so that they could be detected by a gas chromatography–pulsed flame photometric detector (GC–PFPD) and GC–mass spectrometry (MS). The ethyl acetate and methanol (MeOH) fractions obtained by SPE of the 120 °C WFE distillate and methyl tert‐butyl ether and acetone fractions obtained by SPE of the 170 °C WFE distillate had the highest concentration of S and were, therefore, the best candidates for GC–PFPD analysis. GC–PFPD methods were developed to separate the S species adequately enough for those peaks to be analyzed by GC–MS which matched fragmentation patterns identified by the MS chemical library as tetrahydrothiophenes, dithiolanes, and thiophenes. MS fragmentation patterns were used to identify other, larger, S‐bearing species as sulfides and disulfides cross‐linking between two FAME molecules. The results obtained from this study provide a foundation for developing effective purification methods to remove S‐containing impurities from waste grease‐derived biodiesel.

English

This study investigates the impact of clarification process on the nutritional, mineral and vitamin composition of the cashew apple juice. The proximate composition in percentage for moisture, dry matter, ash, crude fibre, ether extract, crude protein and carbohydrate were determined in line with the recommended methods of Association of Official Analytical Chemist (AOAC), and vitamin profile was analysed using Gas Chromatography coupled with the Pulsed Flame Photometric Detector (GC-FPD). The mineral analysis also followed the recommendation of AOAC. The clarified cashew apple juice had values in mg/100 of 10.1, 6.1, 2.2, 28.8, 10.2 and 0.22 for calcium, magnesium, sodium, potassium, phosphorus and iron, respectively. The study showed that cashew apple juice is rich in nutrient and contains a good level of trace elements necessary for healthy living. Rice gruel as a natural sourced clarifying agent can better replace industrial clarification agents for a safer drink production. ords: Clarification process, nutritional composition, mineral composition, vitamin composition, cashew apple juice.