Gas Chromatography
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2021 ◽  
Vol 117 (11/12) ◽  
Author(s):  
Pabalala M. Mthembi ◽  
Ellen M. Mwenesongole ◽  
Michael D. Cole

Nyaope, a Tswana word for a mixture or ‘mish-mash’, describes a drug cocktail consisting of heroin, cannabis, and on occasion other controlled substances and warfarin. It is highly addictive with extremely unpleasant side effects caused by withdrawal from the drug. It is a problem drug especially in townships in South Africa. However, its prevalence in neighbouring southern African states and further afield is not yet known. There is currently no validated method for the analysis and comparison of nyaope. We describe a validated method for the gas chromatography – mass spectrometry analysis of nyaope so that within-batch and between-batch comparisons of nyaope can successfully be made for the first time. The validated method managed an accuracy within the range 80–120%, the precision was less than 20% for all analytes and managed linearity with R2≥0.99. The detection limits for diamorphine, efavirenz, nevirapine and Δ9-tetrahydrocannabinol were 14.2, 18.6, 18.7 and 9.94 pg on column, respectively, and the limits of quantitation were 43.1, 56.3, 56.6 and 30.1 pg on column, respectively. The simulated and casework samples were successfully discriminated into original batches using the identified nyaope components, the unsupervised chemometric methods principal component analysis and hierarchical clustering, as well as chromatographic profiles.


Author(s):  
Yaxiong Liu ◽  
Jiaxin Wen ◽  
Zhuoya Luo

AbstractHeadspace-gas-chromatography ion-mobility spectrometry (HS-GC-IMS) proved the diversity of volatile chlorinated compounds (VCCs) in frying oil in this work. First, the VCCs were obtained by headspace by heating the frying oil at 80 °C for 30 min. Then, those compounds were separated by GC capillary column in the first dimension and by IMS in the second dimension, respectively. And at last, those compounds were detected in negative ion mode for non-targeting. The study results indicated that VCCs' formation depends on the contents of NaCl and water, heating temperature and time, and the types of oil. The refining process does not affect the detection of VCCs, indicating the durability of such targets as indicators for assessing deep-frying oil. Using HS-GC-IMS, the VCCs were detected to evaluate 16 authentic refined deep-frying oils from the market with an accuracy of 100%.


Author(s):  
Vladimir Alexeevich Kholodov ◽  
Yulian Robertovich Farkhodov ◽  
Nadezhda Vasilievna Yaroslavtseva ◽  
Svyatoslav Vadimovich Maximovich ◽  
Sergei Anatolievich Yudin ◽  
...  

Reducing the amount of precipitation in summer in the Chernozems area alters soil organic matter (SOM). To compensate for the lack of moisture, farmers are introducing new agricultural technologies such as no-till cultivation. In turn, no-till practices influence the composition of SOM. We examined the impacts of the rise of aridity and no-till technology on the chemical composition of bioavailable and recalcitrant pools of OM. The properties of SOM were assessed using double-shot pyrolysis with gas chromatography/mass spectrometry (GC/MS). The thermolabile substances that are volatilised in the first stage of pyrolysis (300°C) are considered the bioavailable pool. Accordingly, substances are obtained in the second pyrolysis stage (500°C) were attributed to the recalcitrant pool. Identified in both steps of pyrolysis, products were assigned to different chemical groups (lignin-derivative, polysaccharide-fragments, indoles, etc.) and relative abundances were calculated. In work for the separation of substances, a polar column was used for chromatography of the thermolabile fraction. With an increase in aridity in Сhernozems, the content in the bioavailable pool of polysaccharide fragments decreased and the proportion of indoles increased. In the recalcitrant pool, the abundance of six-membered rings with nitrogen and aromatic compounds decreases at the same time the contents of unsubstituted and O-substituted acyclic compounds as well as pyridine increases. The influence of the NT was more noticeable in the recalcitrant OM. The NT practice promotes biological activity and to rich in nitrogen compounds the bioavailable OM; this process contributes to the accumulation of carbon in the recalcitrant OM.


Foods ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2888
Author(s):  
Shuang Chen ◽  
Jialing Lu ◽  
Michael Qian ◽  
Hongkui He ◽  
Anjun Li ◽  
...  

This paper proposes the combination of headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and chemometrics as a method to detect the age of Chinese liquor (Baijiu). Headspace conditions were optimized through single-factor optimization experiments. The optimal sample preparation involved diluting Baijiu with saturated brine to 15% alcohol by volume. The sample was equilibrated at 70 °C for 30 min, and then analyzed with 200 μL of headspace gas. A total of 39 Baijiu samples from different vintages (1998–2019) were collected directly from pottery jars and analyzed using HS-GC-IMS. Partial least squares regression (PLSR) analysis was used to establish two discriminant models based on the 212 signal peaks and the 93 identified compounds. Although both models were valid, the model based on the 93 identified compounds discriminated the ages of the samples more accurately according to the goodness of fit value (R2) and the root mean square error of prediction (RMSEP), which were 0.9986 and 0.244, respectively. Nineteen compounds with variable importance for prediction (VIP) scores > 1, including 11 esters, 4 alcohols, and 4 aldehydes, played vital roles in the model established by the 93 identified compounds. Overall, we determined that HS-GC-IMS combined with PLSR could serve as a rapid and accurate method for detecting the age of Baijiu.


Jurnal Ecolab ◽  
2021 ◽  
Vol 15 (2) ◽  
pp. 77-88
Author(s):  
Yunesfi Syofyan ◽  
◽  
Retno Puji Lestari ◽  
Yuriska Andiri ◽  
Sri Endah Kartiningsi ◽  
...  

Polychlorinated biphenyls (PCBs) adalah senyawa kimia organoklorin buatan manusia yang berbahaya pada kesehatan manusia, mahluk hidup, dan lingkungan. Penggunaan PCBs telah dilarang secara internasional pada kesepakatan dunia dalam Konvensi Stockholm. Indonesia telah menandatangani Konvensi Stockholm pada tanggal 23 Mei 2001 dan meratifikasinya dengan Undang-Undang Nomor 19 Tahun 2009 tentang Ratifikasi Konvensi Stockholm mengenai Bahan Pencemar Organik yang Persisten. PCBs termasuk ke dalam kelompok persistent organic pollutants (POPs) yang terdaftar dalam Konvensi Stockholm, merupakan senyawa potensial sebagai penyebab kanker, mengganggu sistem imun, syaraf, reproduksi, dan kelenjar endokrin. Laboratorium Tanah dan Limbah Padat Pusat Standardisasi Instrumen Kualitas Lingkungan Hidup (PSIKLH) telah melakukan validasi metode pengujian 21 senyawa congener PCBs pada berbagai matriks lingkungan yaitu air, padatan (sedimen/tanah), dan biota sebagai bagian dari penyusunan rancangan metode standar. Pengukuran PCBs dalam sampel air, padatan, dan biota mengacu pada USEPA metode 8082A: Polychlorinated biphenyls (PCBs) by Gas Chromatography dan USEPA metode 3541: Automated Soxhlet Extraction. Modifikasi dilakukan dalam hal waktu pengujian yaitu proses ekstraksi dan clean up menggunakan alat otomatis (SOXTHERM® dan DEXTech ver 1.3). Dari waktu ekstraksi secara manual selama 18-20 jam dapat dipersingkat menjadi 2-3 jam, sedangkan untuk proses clean up membutuhkan waktu hanya 50 menit. Sampel dianalisis menggunakan instrumen Gas Chromatography – Electron Capture Detector (GC-ECD) Agilent 7890B dengan program temperatur GC menggunakan kolom non polar RTx5 (id 0,25 mm dan ketebalan 0,25 mm) yaitu T detektor: 300oC, T kolom 70oC, T injektor 250oC, dan mode injeksi splitless. Validasi pengujian mengacu pada kriteria yang ditetapkan dalam Prosedur Pelaksanaan, PP 19/P3KLL tentang validasi dan verifikasi metode yang meliputi penentuan limit deteksi, uji akurasi, presisi, dan reprodusibilitas. Hasil validasi contoh uji biota memenuhi syarat keberterimaan pada 21 congener dengan hasil uji akurasi RSD≤0,67 Horwitz, sementara uji presisi dan reprodusibilitas RSD≤0,5 Horwitz. Beberapa congener yang tidak memenuhi batas keberterimaan akurasi, presisi, dan reprodusibilitas untuk matriks air antara lain 2,3-diCB (5), 2,4,6-triCB (30), dan DecaCB (209), dan pada matriks padatan (sedimen/tanah) antara lain 2,2’5-triCB (18), 2,4,5-triCB (31), dan 2,2’,3,4,5-pentaCB (87). Metode ini dapat digunakan untuk pengujian PCBs untuk congener yang memenuhi syarat keberterimaan.


2021 ◽  
Vol 13 (22) ◽  
pp. 12856
Author(s):  
Yejin Choi ◽  
Sangjae Jeong ◽  
Young-Kwon Park ◽  
Huijeong Kim ◽  
Se-Jeong Lim ◽  
...  

The pyrolysis of waste electronically heated tobacco (EHT), consisting of tobacco leaves (TL), a poly-lactic acid (PLA) filter, and a cellulose acetate (CA) filter, was investigated using thermogravimetric (TG) and pyrolyzer–gas chromatography/mass spectrometry (Py-GC/MS) analysis. The pyrolytic properties of waste EHT obtained after smoking were comparable to those of fresh EHT. Although the maximum decomposition temperatures (TmaxS) of waste TL and CA were similar to those of fresh EHT components, the Tmax of waste PLA was slightly higher than that of fresh PLA due to smoldering. The Tmaxs of PLA and CA were lowered when they were co-pyrolyzed with TL due to interactions between pyrolysis intermediates. The apparent activation energies for the non-isothermal pyrolysis of waste EHT components were higher than those of fresh EHT components. Py-GC/MS analysis results indicated that considerable amounts of chemical feedstocks, such as nicotine and limonene from TL, caprolactone and lactide from PLA, and acetic acid and triacetin from CA, can be recovered by simple pyrolysis of EHT. Co-pyrolysis of TL, PLA, and CA revealed that the experimental amount of lactide was much larger than the calculated value, suggesting its synergistic formation.


Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4014
Author(s):  
Paulina Wiśniewska ◽  
Łukasz Zedler ◽  
Krzysztof Formela

In this paper, ground tire rubber was modified with dicumyl peroxide and a variable content (in the range of 0–15 phr) of ethylene-vinyl acetate copolymers characterized by different vinyl acetate contents (in the range of 18–39 wt.%). Modification of ground tire rubber was performed via an auto-thermal extrusion process in which heat was generated during internal shearing of the material inside the extruder barrel. The processing, performance properties, and storage stability of modified reclaimed ground tire rubber were evaluated based on specific mechanical energy, infrared camera images, an oscillating disc rheometer, tensile tests, equilibrium swelling, gas chromatography combined with a flame ionization detector, and gas chromatography with mass spectrometry. It was found that the developed formulas of modified GTR allowed the preparation of materials characterized by tensile strengths in the range of 2.6–9.3 MPa and elongation at break in the range of 78–225%. Moreover, the prepared materials showed good storage stability for at least three months and satisfied processability with commercial rubbers (natural rubber, styrene-butadiene rubber).


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