Capillary Gas Chromatography System Research Articles

Increasing Flame Ionization Detector Response by Silylation: The Effective Carbon Number of Carboxylic Acids

Detector response of carboxylic acids (C2–C12, straight and branched chain) were investigated using a flame ionization detector (FID) in a capillary gas chromatographic system. The response of the FID for hydrocarbons is almost directly proportional to the carbon quantity introduced into the flame. Heteroatoms in the molecule reduce signal magnitude, depending on their quality and on the bond they are involved in. We expressed this reduced response with the effective carbon number (ECN). We determined the ECN contribution (ΔECN) of the carboxyl group on the alkyl skeleton. We examined how the responses of carboxylic acids change if trimethylsilyl derivatives are evaluated and we compared the ECN of the neat and derivatized form.

The Effective Carbon Number of Chlorobenzenes

Detector response of 12 chlorobenzenes was investigated (mono-, di-, tri-, tetra-, penta-, and hexachlorobenzene, CBs) using flame ionization detector in a capillary gas chromatographic system. We determined the signal-reducing effect of the chlorine atom on the aromatic ring relative to the number of the chlorine substituents and expressed with the effective carbon number (ECN). Benzene was applied as a reference substance. Using the signal-modifying pattern of the chlorine atoms on the benzene's response, we developed an alternative calibration measurement method (CBs-ECN method) for the 12 CBs and compared it with classic calibration. The differences in the concentrations calculated by the two quantitative methods were under 4.5% for 11 CBs and 7% for one compound.Taking advantage of the opportunities provided by the CBs-ECN pattern it is not necessary to apply all of the 12 CBs but only one single component, the hexachlorobenzene for the calibration. With this simplification, the preparation of the calibration standards is faster, does not require purchasing all 12 CBs for each subsequent calibration, and the exposure to harm and expenses are reduced.

Investigation of polychlorinated biphenyls in breast milk from two regions in Bulgaria.

Human breast milk is an optimally balanced infant food and a suitable tool for assessing the burden of humans with lipophilic persistent organic pollutants. The aim of this study was to investigate the accumulation profile of polychlorinated biphenyls in breast milk of women living in Bulgaria and to assess the health risk to infants. Breast milk samples were obtained from 72 healthy primiparae and multiparae mothers, living in two regions in northeastern Bulgaria - Varna region and Dobrich region, in the period October 2019-July 2021. Important information for the study, such as age, body mass, smoking and dietary habits, was collected through a questionnaire. Fifteen congeners of PCBs, including six indicator congeners, were determined by capillary gas chromatography system with mass spectrometry detection. The lipid content of the tested samples was in the range from 0.5% to 6.7%, with average value 3.25%. The six indicator PCBs in human milk samples formed up to 89% of the total PCBs levels. The most abundant congener was PCB 153, followed by PCB 138 and PCB 180. Five of the 15 PCB congeners (77, 126, 128, 156, 169) were not detected in any of the milk samples. The arithmetic mean PCB levels in milk samples from Varna (32.7ng/g lw) were found higher than PCB levels in breast milk of mothers from Dobrich (22.5ng/g lw). The highest PCB levels were found in milk samples from primiparae mothers in 36-40 age group (for both regions). Infant exposure to PCBs present in human milk was estimated using toxic equivalents (TEQ). The health risk to infants was assessed and was compared to the tolerable daily intake (TDI). Positive correlation was found between the arithmetic mean PCBs levels and two important factors - the age and body mass index of the primiparae group. The mean values of the analyzed PCB congeners in breast milk samples from multiparae were lower than in those from primiparae mothers. The regional differences in PCB concentrations were small, suggesting similar exposures in the studied regions. The levels of PCBs in breast milk were found lower than levels from studies in other European countries. Statistical data does not show any association between PCB levels in milk and dietary habits. The results showed that infants are not at risk of any adverse effects caused by PCBs through breast milk.

LEVELS OF INDICATOR POLYCHLORINATED BIPHENYLS IN HUMAN MILK FROM VARNA REGION, BULGARIA

Human milk is an appropriate tool for the assessment of the body burden of humans with lipophilic persistent organic pollutants such as polychlorinated biphenyls (PCBs). Purpose: The aims of the study were to determine the levels of polychlorinated biphenyls in the breast milk of women living in Varna, Bulgaria and to evaluate the association with demographic characteristics. Material and methods: Breast milk samples were collected in 2019 - 2020 from 28 healthy primiparae mothers. The six indicator PCB congeners were determined in individual mother's milk samples by capillary gas chromatography system with mass spectrometry detection (GC-MS). Results: The predominant PCB congener measured in human milk was PCB 153, followed by PCB 138 and PCB 180. The lower chlorinated congeners PCBs (28, 52 and 101) were found below the limit of detection in most individual samples. The median level of the Indicator PCBs in milk samples was 29.1 ng/g lipid weight. The highest PCBs levels were found in breast milk from primiparae mothers 36 – 40 age (36.8 ng/g lipid as a sum of six Indicator PCBs), suggesting bioaccumulation of these pollutants. Conclusions: Positive association was found between the Indicator PCBs levels and the age of mothers. The levels of the Indicator PCBs in breast milk were found to be lower than levels reported in other studies in the European countries.

Estimation of human health risk from polychlorinated biphenyls through consumption of fish from Black Sea, Bulgaria

INTRODUCTION: The present study evaluates the human daily intake of polychlorinated biphenyls (PCBs) through consumption of fish from the Black Sea, Bulgaria. The health risks were assessed using a risk quotient (RQ) of the fish consumption as the ratio of daily fish exposure level in relation to oral reference dose. MATERIALS AND METHODS: PCBs were determined in muscle tissue of four fish species widely consumed by the population of Bulgaria: goby ( Neogobius cephalargoides), sprat ( Sprattus sprattus ), horse mackerel (Trachurus Mediterraneus ponticus) and shad (Alosa pontica pontica) . Samples were collected from Bulgarian Black Sea coast during 2007 - 2011. The Indicator and dioxin-like PCBs were determined by capillary gas chromatography system with mass spectrometry detection. RESULTS: The sum of the six Indicator PCBs ranged from 7.2 to 27.3 ng/g ww (in goby and shad, respectively). The EDI of I-PCBs in fish from Black Sea was calculated between 1.36 and 5.14 ng/kg bw day through consumption of goby and shad, respectively. Dioxin - like PCBs were used in order to estimate the toxicity potential (TEQ) of PCB exposure. WHO-TEQs of the 6 `dioxin-like` PCB congeners were calculated from 0.03 pg TEQ/g ww (goby) to 0.28 pg TEQ/g ww (shad) and did not exceed the limit of 3 pg TEQ/g ww, according to European Commission. CONCLUSION: The estimated intake levels of dioxin-like PCBs in this study were several orders lower than their respective TDI for adults. The dietary intake of polychlorinated biphenyls through marine fish for the Bulgarian consumer does not pose a health risk.

Polychlorinated biphenyls in fish from Black Sea, Bulgaria

Polychlorinated biphenyls (PCBs) were measured in muscle tissue of six marine fish species: sprat (Sprattus sprattus sulinus), grey mullet (Mugil cephalus), bluefish (Pomatomus saltatrix), turbot (Psetta maxima), red mullet (Mullus barbatus) and garfish (Belone belone). Samples were collected from different parts of Bulgarian Black Sea coast. The PCBs were analyzed in order to evaluate the status of pollution in Bulgarian Black Sea coastal area and to assess the dietary intake through fish consumption. The PCBs (including Indicator and dioxin-like PCBs) were determined by capillary gas chromatography system with mass spectrometry detection. Total PCBs were found in all fish species at concentrations ranging between 134.2 ng/g lipid weight (lw) in bluefish and 571.9 ng/g lw in turbot. The sum of the six Indicator PCBs ranged from 100.3 to 453.8 ng/g lw (in bluefish and turbot, respectively). Dioxin – like PCBs were used in order to estimate the toxicity potential (TEQs) of PCB exposure. TEQs of the 6 “dioxin–like” PCB congeners were calculated from 0.04 pg TEQ/g wet weight (ww) (turbot) to 0.14 pg TEQ/g ww (bluefish) and did not exceed the limit of 3 pg TEQ/g ww, according to European Commission. The experimental results for PCBs in fish species from different sampling sites showed no significant differences between the North, Varna and South coast sampling area. The levels of PCBs in marine fish from Bulgarian Black Sea were found lower than those reported from the other regions. Estimated dietary intake of polychlorinated biphenyls through the analysed marine species does not seem to pose a health risk.

Organochlorine contaminants (PCBs, DDTs, HCB & HBDE) in fish from the Lake Varna and Lake Beloslav, Bulgaria

Abstract Concentrations of organochlorine compounds such as polychlorinated biphenyls (PCBs), DDT and its metabolites, hexachlorobenzene (HCB) and hexachlorobutadiene (HBDE) were determined in three fish species: goby (Neogobius melanostomus), golden grey mullet (Mugil auratus) and silverside (Atherina boyeri). Samples were collected from the Lake Varna and the Lake Beloslav in 2014. The edible fish tissues were analyzed in order to investigate the presence of pollutants in species from the lakes near Varna City, Bulgaria and compared the results to the levels in other aquatic ecosystems. The fifteen congeners of PCBs, HCB, HCBD, DDT and its two main metabolites DDE and DDD were determined by capillary gas chromatography system with mass spectrometry detection. The OCPs levels in the wild fish were found in the order DDTs > PCBs. The other contaminants HCB and HCBD were not detected or were below the analytical detection limit. Among the pesticides, essentially only the metabolites p, p’- DDE and p, p’- DDD were found. The concentrations of DDTs were determined from 2.66 to 17.97 ng/g wet weight and PCBs concentrations were found from 0.43 to 8.05 ng/g ww (in goby and golden grey mullet, respectively). The sum of the six Indicator PCBs did not exceed the European maximum limit 75 ng/g wet weight. The concentrations of DDTs and PCBs were found lower compared to those in similar fish species from other aquatic ecosystems.

Experimental investigation of the efficiency of triple rinsing of agricultural containers regarding their characterization as non-hazardous wastes

The efficiency of water rinsing for removing fenthion from non-combustible used pesticide containers was investigated. Four hundred empty containers from four olive oil producing areas in Greece were studied. Following triple rinsing cleaning procedures, the amount of fenthion retained in the container ranged from 0.01% to 0.1% w/w of its initial concentration. Extraction was accomplished with acetone, and the extracts were analyzed with a capillary gas chromatographic system coupled with flame ionization detector. The results obtained showed that triple rinsing is an effective procedure for removing fenthion from used pesticide containers, since the remaining pesticide concentration was below the legislated threshold value. Consequently, the containers can be handled as non-hazardous solid wastes.

Narrow Bore Packed Column Designed for Capillary Gas Chromatograph

A narrow-bore packed column (packed-capillary column) that designed for a direct installation in conventional capillary gas chromatographic (GC) system had been developed. In this column, particulate sorbents that employed in typical GC packed columns were packed into a stainless-steel capillary of 1.0 mm i.d. By attaching a pair of stainless-steel capillaries of 1.27 mm o.d. at both ends of the column, the packed-capillary column can be directly installed into the conventional capillary GC system. In this article, fundamental of the packed-capillary column developed by our research group is mainly reviewed, along with the various applications, such as column switching analysis and evaluation of catalytic property based on the determinations of CO and CO2.

PERSISTENT ORGANIC POLLUTANTS - PCBs AND DDTs IN FISH FROM DANUBE RIVER AND FROM BLACK SEA, BULGARIA

Persistent organochlorine pollutants (POPs) like polychlorinated biphenyls (PCBs) and DDT residues (DDTs) can still be a problem for the aquatic environment and the human health. PCBs and DDTs were determined in three freshwater fish species: common carp (Cyprinus carpio), catfish (Silurus glanis), pike-perch (Sander lucioperca) and two marine fish: shad (Alosa pontica pontica) and grey mullet (Mugil cephalus). The freshwater fish samples were collected from the Danube River and from Black Sea, Bulgaria in 2010. The POPs were analyzed in order to investigate the presence of PCBs and DDTs in fish species from Danube River and compared the results to the levels in marine fish species from Black Sea. The fifteen congeners of PCBs, p,p’-DDT and its two main metabolites p,p’-DDE and p,p’-DDD were determined by capillary gas chromatography system with mass spectrometry detection. DDTs were the predominant contaminants in investigated species, with the p,p’- DDE contributing to more than 67% to the total DDTs. In freshwater fish concentrations of DDTs were found from 19.2 to 30.3 ng/g ww and PCBs concentrations - from 6.2 to 12.6 ng/g ww. The highest levels of PCBs and DDTs were determined in shad. The levels of DDTs and PCBs were determined lower than those found in similar fish species from other aquatic ecosystems.

Determination of monomethylmercury in low- and high-polluted sediments by microwave extraction and gas chromatography with atomic fluorescence detection

The analysis of monomethylmercury (MMHg) in sediments is a difficult task because both very low concentrations and interconversion between species especially in highly polluted samples are frequent. This work features a general strategy for real sediment analysis with preconcentration and/or clean-up steps for both low- and high-polluted sediments to control these specific problems. The extraction conditions have been optimized using closed-vessel microwave-assisted heating with acidic extractants. The analysis has been carried out by the injection of ethylated derivatives of the analytes into a capillary gas chromatographic system coupled to fluorescence spectrometry. When using 6 M HNO 3, the most labile inorganic mercury fraction as well as MMHg were extracted from the sediment but there was still some inorganic mercury that remained un-extracted. MMHg was stable and quantitatively recovered by applying this procedure. The role of the labile inorganic fraction on artifact MMHg generation has been evaluated and it has been found to be highly variable depending on the sediments’ geochemical characteristics. Therefore, for high-polluted sediments (inorganic mercury concentration above 500 ng g −1) a clean-up step with dichloromethane has been used before ethylation, whereas for low content samples, preconcentration under nitrogen stream at room temperature has been optimized. Both steps can be combined if necessary. MMHg content has been found in good agreement with the certified value for the reference materials (IAEA-405 and ERM-CC580).

Determination of 14C/ 12C of acetaldehyde in indoor air by compound specific radiocarbon analysis

A method of compound-specific radiocarbon analysis (CSRA) for acetaldehyde in indoor air was established for the source apportionment purpose and the methodology was applied to indoor air samples. Acetaldehyde in indoor air samples was collected using the conventional 2,4-dinitrophenylhydrazine (DNPH) derivatization method. Typically 24-h air sampling at 5–10 L min −1 allowed collection of adequate amount of acetaldehyde for radiocarbon analysis by accelerator mass spectrometry (AMS). The 14C abundance of acetaldehyde in indoor air was measured by AMS after solvent extraction of derivatized acetaldehyde and sequential purification by a preparative liquid chromatography system and a preparative capillary gas chromatography system. The recovery and purity of the derivatized acetaldehyde was satisfactory for 14C analysis by AMS. 14C abundance of acetaldehyde was calculated by considering that of derivatizing agent DNPH. Our preliminary survey showed that percent modern carbon (pMC) values of acetaldehyde isolated from indoor air sampled in newly built, unoccupied housings ( n=5) in the suburb of Tokyo ranged from 49.4 to 67.0. This result indicated that contribution of anthropogenic source was greater than previously expected.

Development and single-laboratory validation of a new gas chromatographic multi-pesticide method of analysis of commercial emulsifiable concentrate formulations containing alachlor, chlorpyrifos methyl, fenthion and trifluralin as active ingredients

A multi-pesticide (MP) method was developed and single-laboratory validated for the quality control of commercial pesticide products containing alachlor, chlorpyrifos methyl, fenthion and trifluralin as active ingredients (a.i.). A capillary gas chromatographic system with flame ionization detection (FID) and a programmable temperature vaporising split injector was used. The performance characteristics (specificity, linearity, precision and repeatability) of the method satisfied international acceptability criteria.

‘Single-laboratory’ validation of a method of quantitative analysis of alachlor, chlorpyriphos-methyl, fenthion, and trifluralin

A simple, new gas-chromatography method was developed and validated by a single-laboratory for quantitative determination of four active ingredients (alachlor, chlorpyriphos-methyl, fenthion, and trifluralin) in their commercially available emulsifiable concentrate formulations, widely used in Greece. This method enables the analysis of a number of pesticides with the same chromatographic conditions and internal standard. A capillary gas-chromatographic system equipped with a flame ionization detector and a split injector was used. The linearity of response, specificity, repeatability and other performance characteristics of the method are presented. As a result, the method is validated.

Analysis of volatile compounds in some typical Brazilian fruits and juices by SPME-GC method

This paper describes the analysis of volatile organic compounds (VOC) in typical Brazilian fruit and fruit juices by a solid-phase microextraction (SPME) method using a capillary gas chromatography system with flame ionization detection and mass spectrometry (GC-MS). A SPME holder with a 100-µm polydimethilsiloxane fibre coating was utilized. The optimal conditions were desorption at 220°C for 1 min, absorption at 50°C for 20 min and 4.00 ml of sample in the headspace vial. The method gave good precision and showed a linear response. More than 100 VOC were identified in the fruit and juices studied by GC-MS. The method was employed to quantify ethanol, naphthalene and benzoic acid in four different species of Brazilian fruit and their juices.

Dual column capillary gas chromatographic system for the in situ analysis of volatile organic compounds on a cometary nucleus.

Two Wall Coated Open Tubular capillary columns, coated with poly(cyanopropylphenyl-dimethyl)siloxane and poly(diphenyl-dimethyl)siloxane stationary phases, have been selected for use in the COmetary SAmpling and Composition space experiment for the separation and identification of the wide range of volatile organic compounds which could be present in cometary nuclei. This article presents the main characteristics of the tandem column system for the analysis of solutes of cometary interest within the constraints of space instrumental operating conditions. The high efficiency of the columns is demonstrated and the influence of the operating conditions on their separation properties are investigated. The studied columns exhibit complementary retention pattern: their use in a dual column system makes it possible to achieve the separation and the identification of the compounds of interest. Finally, the good analytical behavior of the columns when analyzing samples which include large amounts of water, the main presumed volatile in comets, is demonstrated. The presented results thus show the suitability of the selected tandem columns system for the desired analyses, and their performance on adaptation to in-situ cometary chemical investigation.

Determination of some local anesthetics in human serum by gas chromatography with solid-phase extraction

A method of analysis based on solid-phase extraction coupled with capillary gas chromatographic system for determination of mepivacaine, bupivacaine and lidocaine from human serum was developed. As extraction sorbents were used Chromosorb 103, Tenax-GC and Chromosorb T. The best extraction sorbent proved to be Chromosorb 103. Their recoveries ranged from 91 to 94% at the target concentrations of approx. 1.5 μg ml −1 in serum. Relative standard deviation of the recoveries ranged from 3.11 to 5.30 at these concentrations. As internal standard was used lidocaine. The chromatographic analysis was performed on a gas chromatograph equipped with a capillary column, HP-Innowax, and flame ionisation detector. Samples were injected in splitless mode. This method was applied in a stomatological clinic to healthy volunteers to whom superior–posterior alveolar nerve block anesthesia with mepivacaine was administered.

Validation of a chromatographic method to determine E-6006 and its metabolite E-6332 in rat and dog plasma by solid-phase extraction and capillary gas chromatography. Application in pharmacokinetics.

E-6006, 5-(alpha-[2-(dimethylamino)ethoxy]-2-thienylmethyl)-1-methyl-1H-pyrazole is a new antidepressive compound and E-6332, 5-(alpha-[2-(methylamino)ethoxy]-2-thienylmethyl)-1-methyl-1H-pyrazole is its desmethylate metabolite. With the aim of quantifying E-6006 and E-6332, simultaneously in rat or dog plasma, a method of analysis based on solid-phase extraction coupled with capillary gas chromatographic system with N-P detection was developed and validated. E-6006, E-6332 and its internal standard (E-4018) were isolated from plasma using an off-line semiautomatic solid-phase extraction method. Gas chromatography separations were carried out by means of 12 m length, 0 2 mm (i.d.) and 0.33 microm (f.t.) ULTRA 1 type capillary column in splitless mode of injection at 190 degrees C, with a TSD or specific nitrogen--phosphorus detector. No peaks interfering with the quantification of E-6332 and E-6006 were observed. The limit of quantification was 5 ng/ml with a precision and accuracy <17%. The peak height ratios were proportional to E-6332 and E-6006 concentration over the range from 5 to 600 ng/ml (r(2)>0.998). Mean recoveries of E-6332, E-6006 and internal standard from rat plasma were between 57.1 and 82.6. Intra-assay precision coefficients were <8.0 and <11.8%, respectively, for E-6332 and E-6006, with an accuracy <12.6 and <9.7%. Both inter-assay precision and accuracy were within acceptable limits (<15%). In dog, the results were very similar to those obtained in rat. To show an example of the suitability of the method to determine E-6332 and E-6006, plasma profiles obtained after single oral and intravenous administration of 20 mg/kg to rats and 25 mg/kg to dogs are reported.

Quantification of the rice aroma compound, 2-acetyl-1-pyrroline, in uncooked Khao Dawk Mali 105 brown rice.

Volatile components of uncooked Khao Dawk Mali 105 brown rice were extracted using indirect steam distillation under reduced pressure and controlled temperature in order to prevent cooking. Analysis of the fresh extract by capillary gas chromatography-mass spectrometry revealed that there were >140 volatile constituents. Among these, 70 volatiles were identified, including 2-acetyl-1-pyrroline (2AP), a key aroma compound of cooked rice. Further study concentrated on an improved method for the quantification of 2AP in uncooked brown rice. The method was simplified by utilizing a solvent extraction procedure. Quantitative analysis was performed using a capillary gas chromatographic system employing a flame ionization detector with the aid of a more selective column, CP-Wax 51, for amines. This improved chromatographic system had remarkable detection sensitivity for 2AP in the rice extracts so that 2AP in an extract of only 0.5 g of uncooked Khao Dawk Mali 105 brown rice could be detected.

Simultaneous Determination of Chlorothalonil and Hexachlorobenzene in Technical and Formulated Materials by Capillary Gas Chromatography: Collaborative Study

A collaborative study was conducted for the capillary gas chromatographic (GC) method for the simultaneous determination of the fungicide chlorothalonil (CTL) and the accompanying impurity, hexachlorobenzene (HCB), in technical and formulated materials. The method calls for the dissolution of technical and dry formulations of CTL and HCB from the aqueous flowable formulation. The 10 participating laboratories were asked to analyze the samples by adhering to the method as closely as their instrumentation and data systems allowed, and to note any deviations from the method. Collaborators were asked to prepare the standards and samples, set up the capillary GC systems, analyze the samples, and calculate the results. CTL produced reproducibility relative standard deviations (RSDR) of 0.4-2.5 (active ingredient concentrations ranged from approximately 52 to 98% by weight). HCB produced RSDR values of 5.2-22% (HCB concentrations were 0.02-0.04% by weight). The method was adopted First Action by AOAC INTERNATIONAL.