Stability of Chlorophenols and Their Acetylated Derivatives in Water: Sample Storage Procedures

2014 ◽  
Vol 97 (1) ◽  
pp. 179-182
Author(s):  
Paulo de Morais ◽  
Teodor Stoichev ◽  
M Clara P Basto ◽  
Pedro N Carvalho ◽  
M Teresa S D Vasconcelos
Keyword(s):  
Sodium Chloride ◽  
Acetic Anhydride ◽  
Water Samples ◽  
Storage Conditions ◽  
Storage Space ◽  
Sample Storage ◽  
Different Temperatures ◽  
Low Levels ◽  
The Stability

Abstract The determination of chlorophenols (CPs) in water samples is a subject of increasing interest. Reduction of sample storage space and the stability of CPs when present at very low levels are still problems that deserve research. The stability of CPs at ng/L levels at different temperatures and in the presence or absence of sodium carbonateand acetic anhydride was studied for up to 39 days. Stable and reproducible CP concentrations for about a month of storage in both river and wastewater were achieved in two storage conditions as follows: at –18°C with addition of 10% sodium chloride; and at 4°C with addition of both 10% sodium chloride and 10 mg/mL sodium carbonate. These sample treatments are good alternatives to the immobilization of CPs on SPE cartridges in terms of both analyte stability and saving of storage space.

scholarly journals Investigation and Validation of Detection of Storage Stability of Difenoconazole Residue in Mango

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Fangfang Zhao ◽  
Jingkun Liu ◽  
Bingjun Han ◽  
Jinhui Luo
Keyword(s):  
Food Safety ◽  
Pesticide Residue ◽  
Storage Stability ◽  
Sample Solution ◽  
Sample Storage ◽  
Fruit Samples ◽  
Different Temperatures ◽  
The Stability ◽  
Food Safety And Quality ◽  
Accuracy And Stability

To investigate the stability of the pesticide residue in storage samples is a part of detection, which is also an improvement to the accuracy of analytical results. In this work, the UPLC-MS/MS method with perfect accuracy and stability was established for determining residues of difenoconazole in mango. The stability of the residue under different temperatures (4°C and −20°C) and media (fruit samples and pretreated sample solution) was investigated. At 0.1 mg/kg, the residue degraded in 6 months by 12% when at −20°C, while in a week by only 12.2% at 4°C. However, when pretreated and preserved in the solution, the residue remained more than 90% for 6–8 weeks. The results indicated that the main causes of degradation are biochemical factors, and the factors are affected by temperature. The findings also provided appropriate conditions for sample storage. This investigation promotes the accuracy in detection and hence guarantees food safety and quality.

scholarly journals The Influence of Serum Sample Storage Conditions on Selected Laboratory Parameters Related to Oxidative Stress: A Preliminary Study

Diagnostics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 51
Author(s):  
Lilla Pawlik-Sobecka ◽  
Katarzyna Sołkiewicz ◽  
Izabela Kokot ◽  
Aleksandra Kiraga ◽  
Sylwia Płaczkowska ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Serum Sample ◽  
Storage Conditions ◽  
Wilcoxon Test ◽  
Reference Ranges ◽  
Sample Storage ◽  
Serum Samples ◽  
The Stability ◽  
The Individual ◽  
The Impact

The present work aims at accessing the stability of biological material stored for diagnostic and scientific purposes. The influence of the temperature, storage time, and cyclic thawing on concentration stability of selected oxidative stress parameters in human serum was investigated. The study group consisted of 20 serum samples collected from healthy volunteers aged 18–52. The parameters whose reference ranges were not determined and to which validated determination methods did not correspond were examined by manual methods (FRAP and AOPP). Automatic methods were used to determine routine laboratory tests (albumin, total protein, bilirubin, uric acid) using the Konelab 20i® analyzer. The samples were stored at various temperatures (room temperature, 4 °C, −20 °C, −80 °C) for max 6 months and were subjected to cyclic thawing at 1 month intervals. In order to check whether any differences between the concentrations of the studied parameters existed when the samples were stored in various conditions, the paired Student t-test or Wilcoxon test and comparison to desirable bias were applied. Based on the obtained results, it was found that the temperature and time of serum sample storage significantly affected the stability of the analyzed parameters and determined different shelf lives of serum samples for oxidative stress examination. Therefore, continuing the investigation concerning the impact of storage conditions on various serum parameters seems justified due to the discrepancy between the individual results obtained by different researchers and the inconsistencies between the results of scientific research and the applicable recommendations.

Residual 1,2-dibromoethane in mango, capsicum, passionfruit and papaw after fumigation against Queensland fruit fly, Dacus tryoni (Froggatt)

1985 ◽  
Vol 25 (1) ◽  
pp. 214
Author(s):  
KJ Melksham ◽  
HE Munro
Keyword(s):  
Fruit Fly ◽  
Storage Conditions ◽  
Residue Level ◽  
Gas Chromatography Mass Spectrometry ◽  
X Ray ◽  
Maximum Residue Level ◽  
Low Levels ◽  
Rate Of Dissipation ◽  
Time Required

Residual 1,2-dibromoethane (EDB) was measured in mango, capsicum, passionfruit and papaw following treatment with biologically effective levels of EDB. Post-fumigation forcedairing periods, storage conditions and times of storage were varied. The duration of the forced-airing period after fumigation had no significant effect on the rate of dissipation of EDB from mango. Fumigated mango required storage at 21� for at least 3 days before EDB levels fell to the maximum residue level (MRL) of 0.1 mg/kg. Cool storage of mango extended the time required for the EDB level to fall to the MRL to at least 6 days. Fumigated capsicum stored at 21�C required 2 days for EDB levels to fall to the MRL while, with fumigated papaw, this took at least 4 days. Even after storage for 7 days, EDB levels in fumigated passionfruit exceeded the MRL so the fumigation procedure was unsuitable for use with passionfruit. A kinetic model was proposed which explained the behaviour of EDB in the various trials and in other literature reports. All samples were analysed by X-ray fluorescence spectrometry (X-RF) and many results were confirmed more specifically and more sensitively by gas chromatography-mass spectrometry. Comparison ofresults by these two methods, including the results of samples spiked with low levels of EDB, helped remove doubts about the suitability of X-RF for the determination of residual EDB.

Effect of storage of plasma and serum on enzymatic determination of non-esterified fatty acids

2001 ◽  
Vol 38 (3) ◽  
pp. 252-255 ◽  
Author(s):  
Luis García Menéndez ◽  
Ana L Fernández ◽  
Alfredo Enguix ◽  
Constanza Ciriza ◽  
Juan Amador
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Storage Conditions ◽  
The Other ◽  
Specific Reference ◽  
Enzymatic Method ◽  
Esterified Fatty Acids ◽  
Enzymatic Determination ◽  
The Stability

Many contradictory results have been published on the stability of total non-esterified fatty acids in blood, plasma and serum under different storage conditions. The present study was undertaken to investigate the stability of non-esterified fatty acids, measured with an enzymatic method, in samples of EDTA-treated plasma and serum under different temperature conditions. We conclude that EDTA-treated plasma and serum can both be used for analysis. Specific reference values should be established depending on the type of sample chosen. Samples that cannot be analysed immediately can be stored at -20°C for at least 14 days without significant changes in the concentration of total non-esterified fatty acids. None of the other storage conditions and periods studied are suitable for the measurement of non-esterified fatty acid concentration.

scholarly journals Evaluation of Synthetic Cannabinoid Metabolites in Human Blood in the Absence of Parent Compounds: A Stability Assessment

2020 ◽  
Author(s):  
Alex J Krotulski ◽  
Sandra C Bishop-Freeman ◽  
Amanda L A Mohr ◽  
Barry K Logan
Keyword(s):  
Accurate Determination ◽  
Synthetic Cannabinoids ◽  
The United States ◽  
Storage Conditions ◽  
Synthetic Cannabinoid ◽  
Blood Samples ◽  
Flight Mass Spectrometry ◽  
Acid Metabolites ◽  
The Stability

Abstract Synthetic cannabinoids represent a chemically diverse class of novel psychoactive substances (NPS) responsible for large analytical and interpretative challenges for forensic toxicologists. Between 2016 and 2019, the three most prevalent synthetic cannabinoids in the United States were MMB-FUBINACA (FUB-AMB), 5F-MDMB-PINACA (5F-ADB) and 5F-MDMB-PICA, based on results from seized drug and toxicology testing. In 2018, accurate determination of synthetic cannabinoid positivity was brought into question as it was determined that the metabolites of these drug species were present in the absence of parent compounds in forensically relevant blood samples. During this study, the stability of MMB-FUBINACA, 5F-MDMB-PINACA and 5F-MDMB-PICA was evaluated, as well as the characterization of breakdown products. A liquid–liquid extraction method was assessed for recovery of basic parent compounds and acidic metabolites and deemed fit for use in this study. Analysis was performed by liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOF-MS) using a SCIEX TripleTOF® 5600+. All three synthetic cannabinoids were found to be unstable when stored in blood at either room temperature or refrigerated; all analytes were considerably more stable when stored in the freezer. All three synthetic cannabinoids degraded to their respective butanoic acid metabolites: MMB-FUBINACA 3-methylbutanoic acid, 5F-MDMB-PINACA 3,3-dimethylbutanoic acid and 5F-MDMB-PICA 3,3-dimethylbutanoic acid. All three of these metabolites were studied and determined to be stable in blood at all storage conditions. Considering these results, our laboratory continued testing for synthetic cannabinoid metabolites in blood samples and found 83 positives (21%) for only a synthetic cannabinoid metabolite. A case report is presented herein where 5F-MDMB-PINACA 3,3-dimethylbutanoic acid was identified in the absence of 5F-MDMB-PINACA. Forensic toxicologists should be aware of the results of this study as they directly impact analytical consideration for test development and implementation, as well as interpretation of findings.

Gas-Liquid Chromatographic-Mass Fragmentographic Determination of Low Levels of Diethylcarbonate in Beverages

1979 ◽  
Vol 62 (2) ◽  
pp. 253-256
Author(s):  
Ben H Van Lierop ◽  
Hans Nootenboom
Keyword(s):  
Sodium Chloride ◽  
Electron Impact ◽  
Coefficient Of Variation ◽  
Detection System ◽  
Gas Chromatograph ◽  
Low Levels ◽  
Liquid Chromatographic ◽  
Impact Mode ◽  
Chromatographic Mass

Abstract Sodium chloride and ethanol (omitted for samples with >10% alcohol) are added to the beverage sample and the sample is allowed to equilibrate in a 30°C water bath. An aliquot of the headspace is injected into a gas chromatograph containing a column packed with 0.2% Carbowax 1500 on 80—100 mesh Carbopack C. During the elution of diethylcarbonate (DEC), an impurity that is present in diethylpyrocarbonate, the column effluent is vented to a mass spectrometer with a multiple ion detection system and operated in the electron impact mode. The ions at m/e 63 and 91 are monitored. Lemonade, fruit drinks, wine, and beer samples (138 total) were analyzed for DEC. Sixteen samples had >30 ppb DEC. Eight analyses of a lemonade sample gave a mean of 88 ppb with a coefficient of variation of 11 % .

Kinetic Study of the Decomposition of Nitrite to Nitrate in Acid Samples Using Raman Spectroscopy

1996 ◽  
Vol 50 (8) ◽  
pp. 991-994 ◽  
Author(s):  
J. F. van Staden ◽  
M. A. Makhafola ◽  
D. de Waal
Keyword(s):  
Raman Spectroscopy ◽  
Flow Injection ◽  
Flow Injection Analysis ◽  
Decomposition Rate ◽  
Water Samples ◽  
Acidic Medium ◽  
Storage Conditions ◽  
Ph Values ◽  
The Mean ◽  
The Stability

Raman spectroscopy was employed as a means of determining the rate of decomposition of nitrite in solutions at various pH values. Nitrite decomposes with time in acidic medium, with an increase in decomposition rate as the concentration of acid increases. The mean decomposition rate of 0.625 mol/L NO−2 in 1 mol/L HCl is 1.18 × 10−5 s−1, with t1/2 = 16 h. This rate explains the problems encountered when the flow injection analysis (FIA) version of the Shinn reaction is applied to certain nitrite samples mainly from acidic origin. Nitrite is potentially unstable, and all food and water samples should be analyzed as soon as possible after collection. If it is necessary to store the samples prior to analysis, the effects of the storage conditions on the stability of the analyte must be established in prior trials.

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