Browsing by Author "Vuko, Loyiso"

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    Development of a GC-MS method to determine toxic alcohols and their metabolites in postmortem blood
    (2024) Grevel, Carl; Vuko, Loyiso; Davies Bronwen
    The intentional and accidental ingestion of toxic alcohols represents a health care and potential public health concern within South Africa. Household and industrial antifreezes and brake fluids contain ethylene glycol (ETG) and diethylene glycol (DEG), which cause toxicity within humans. Other toxic alcohols such as 1,4-butanediol (1,4-BD) and propylene glycol (PGL) also show toxicity within the human body. Some of these analytes have previously been implicated in cases of fatal poisoning. However, the extent to which toxic alcohols contribute to death in South Africa is yet to be determined, as these are not routinely investigated in forensic toxicological analysis of biological samples. The purpose of this study was to modify and characterise a gas chromatography-mass spectroscopy (GC-MS) method for the quantitative determination of ETG, DEG, 1,4-BD, PGL, and the toxic metabolite of ETG, glycolic acid (GCA), in postmortem whole blood samples at the Forensic Toxicology Unit (FTU) in the Western Cape, South Africa. We describe the alteration of an existing method that examines most of these target analytes among others by Meyer, Weber and Maurer (2011), utilising a lower quantity of N,O-bis-(trimethylsilyl) trifluoroacetamide (BSTFA) and post-mortem whole blood rather than plasma. The method was characterised according to parameters of calibration model, limit of detection, limit of quantification, bias, precision, processed sample stability, and carryover. Linearity was observed for all analytes between 25– 100 µg/mL with preliminary limits of detection at 25 µg/mL. Preliminary limits of quantification were 25 µg/mL for 1,4-BD, and 50 µg/mL for ETG, PGL, GCA and DEG. Recovery was calculated at ~40% for all analytes, and processed sample stability was calculated to be acceptable for up to 72 hours. The developed method was applied to several post-mortem cases of toxic alcohol ingestion at the Observatory Forensic Pathology Institute (OFPI). In conclusion, the method for the determination of toxic alcohols in post-mortem samples was successfully developed and characterised for a government forensic toxicology laboratory in the Western Cape. Future work will include the validation of this method to streamline analytical determination of the morbidity and mortality related to toxic glycols in the Western Cape
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    Investigating the use of CO-oximetry for simultaneous measurement of carboxyhaemoglobin and methaemoglobin in post-mortem blood
    (2022) Muleya, Jane Mahlatse; Vuko, Loyiso; Mader, Jade; Davies, Bronwen
    Carbon monoxide (CO) is a gas that exerts its toxicity on humans, when inhaled, by bonding with haemoglobin (Hb) to produce carboxyhaemoglobin (COHb). This results in tissue hypoxia which can be fatal at high blood saturation levels. Carboxyhaemoglobin may be measured using a Radiometer ABL825 FLEX analyser, a spectrophotometric instrument that applies a technique called CO-oximetry to measure Hb derivatives such as COHb and methaemoglobin (MetHb). The latter is an oxidised form of Hb that can cause or contribute to mortality at high concentrations. Methaemoglobin is notorious for its instability in vitro. This study, therefore, sought to determine handling conditions best suited for the stability of MetHb in post-mortem blood such that the ABL825 FLEX analyser may be used for the simultaneous measurement of COHb and MetHb. To this end, blood samples collected from 15 cases of potential CO poisoning at Salt River Mortuary were aliquoted into red (no additive)-, green (containing lithium heparin)-, and purple (containing ethylenediaminetetraacetic acid)-top tubes. The samples were stored at 4°C or –80°C and retrieved from storage on days 0, 1, 4, 7, 14, and 30, for analysis. While COHb remained stable in all storage conditions over a 30-day period, this was not true for MetHb. When samples were stored at 4°C, a rapid increase followed by a gradual decline was observed for MetHb in all the tube types investigated. The MetHb content was at its lowest after two weeks of storage, which was consistent with COHb levels at the same time period and temperature. At –80°C, continuous increase of MetHb was observed, with the samples stored in green-top tubes showing the least amount of overall change from the reference (day zero) values. The study provided useful data regarding the stability of MetHb under the considered storage conditions, the investigators concluded that refrigerating blood samples in either red-, purple-, or green-top tube was suitable for the accurate simultaneous determination of both COHb and MetHb, if the analytes are measured immediately after collection or after two weeks of storage. Given that the nature of post-mortem forensic casework is such that suitable blood specimens are not always available for toxicological analyses, for the second aim of the study, the researchers sought to investigate the suitability of thoracic cavity fluid as an alternative specimen for the measurement of COHb. For this aim, thoracic cavity fluid collected into green-top tubes from the aforementioned cases was analysed immediately after collection. The results were compared to those obtained from the analysis of blood collected into green-top tubes and analysed on day zero (before storage). The statistical analyses used for this assessment indicated that thoracic cavity fluid would be a suitable alternative to blood for the measurement of COHb using the ABL825 FLEX analyser.
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    Post-mortem toxicological analysis of hair in violent fatalities: an investigation into long-term drug exposure
    (2022) Mnisi, Precious Zemvelo; Davies, Bronwen; Vuko, Loyiso
    Violence-related injuries are a major cause of mortality in the Western Cape (South Africa). Previous research has demonstrated an association between violent mortalities and drug use. Furthermore, long-term drug use has been shown to alter behaviour that may lead to violence. Hence, this study aimed to investigate the effect of long-term drug use on violence-related mortalities. Due to the drug retention properties of hair, it is the gold standard for demonstrating the historical pattern of drug use. Hair samples were collected from 92 violent death cases admitted to Salt River Mortuary (South Africa). A qualitative toxicological analysis was performed in 90 hair samples using a SCIEX X500R QTOF. Variables pertaining to the colour and length of the hairs were recorded. The majority of the hair samples were black (n=79), while others were black and white (n=5), greyish (n=3), light grey and reddish brown (n=1) and strong brown hair (n=1). Various toxicologically relevant substances were detected in 74 cases (82.2 %) in which a total of 54 different substances were detected in hair samples. Acetaminophen was the most prominent licit substance (47%) detected, followed by caffeine (18.9%) and diphenhydramine (12%). Methamphetamine was the most common illicit detected substance (54%), followed by methaqualone (43%). Segmented hair samples showed historical use in 81.2 % of cases. These results show that hair can be used as a supplementary sample during toxicological investigation in violent fatalities in the local context.