Analysis of γ-hydroxybutyric acid, DL-lactic acid, glycolic acid, ethylene glycol and other glycols in body fluids by a direct injection gas chromatography-mass spectrometry assay for wide use

A method for determining valproic acid in human whole blood and urine via gas chromatography-mass spectrometry and small-scale inter-laboratory trial

A simple and cost-effective method for analyzing valproic acid (VPA) in biological samples was developed. VPA was extracted in methyl tertiary-butyl ether (MTBE) and derivatized using trimethylsilyldiazomethane. The MTBE extract was analyzed by gas chromatography-mass spectrometry (GC-MS). The extraction recovery in human whole blood and urine was over 90 %, with good linearity in the range of 1.0 to 250 µg/mL of VPA. The RSD for 2.0, 20, and 200 μg/mL VPA in whole blood ranged from 0.9 to 4.7 % for intra-day and 1.5 to 5.9 % for inter-day. The RSD for 2.0, 20, and 200 μg/mL VPA in urine ranged from 1.9 to 2.6 % for intra-day and 1.2 to 2.9 % for inter-day. As a preliminary cross-validation study, a cross-check was conducted using blinded concentration samples. The results demonstrated that the assay data of the two laboratories were comparable.

Case Report: Early Recognition, Treatment, and Occupational Safety Protection are Crucial for Methanol Toxicity

Background

Despite significant progress in treating methanol poisoning, the lack of training, hazard communication, and occupational safety protection education contributes to the risk of occupational exposure and methanol toxicity. In addition, early diagnosis and timely medical care are essential to reduce the risk of morbidity and mortality, yet it remains a challenging procedure.

Case Report

A 35-year-old man working in a fireworks factory came to our emergency department with acute mental change and progressive disturbance of consciousness. The patient's vital signs were stable, and he presented with enlargement of both pupils with a weak reaction to light. Head computed tomography showed low signal intensities in the bilateral basal ganglia. He was admitted to the neurologic intensive care unit, where additional laboratory workup showed high anion-gap metabolic acidosis. Methanol poisoning was thus considered. Before being treated with sodium bicarbonate infusion, hemodialysis, folate, and high-dose vitamin B, the blood and urine samples were collected for toxicity tests, which turned out to be methanol poisoning. After 8 hours of hemodialysis, the patient's consciousness recovered, but he complained of a complete loss of vision in both eyes. Brain and optic nerve magnetic resonance images showed bilateral symmetric putamen lesions and optic neuropathy. Ophthalmic tests indicated visual pathway impairment and optic disc swelling but no fluorescein leakage. The right eye's vision was partially restored on the third day, but he could only count fingers at 20 cm. Unfortunately, his eyesight ceased to improve during the 6 months of follow-up.

Conclusions

Early diagnosis and prompt treatment will improve the prognosis of methanol poisoning in terms of vision and patient survival. Awareness and supervision of commercial alcohol use are indispensable for similar industrial processes.

Ethylene glycol: Evidence of glucuronidationin vivoshown by analysis of clinical toxicology samples

In the search for improved laboratory methods for the diagnosis of ethylene glycol poisoning, the in vivo formation of a glucuronide metabolite of ethylene glycol was hypothesized. Chemically pure standards of the β‐O‐glucuronide of ethylene glycol (EG‐GLUC) and a deuterated analog (d₄‐EG‐GLUC) were synthesized. A high‐performance liquid chromatography and tandem mass spectrometry method for determination of EG‐GLUC in serum after ultrafiltration was validated. Inter‐assay precision (%RSD) was 3.9% to 15.1% and inter‐assay %bias was −2.8% to 12.2%. The measuring range was 2–100 μmol/L (0.48–24 mg/L). Specificity testing showed no endogenous amounts in routine clinical samples (n = 40). The method was used to analyze authentic, clinical serum samples (n = 31) from patients intoxicated with ethylene glycol. EG‐GLUC was quantified in 15 of these samples, with a mean concentration of 6.5 μmol/L (1.6 mg/L), ranging from 2.3 to 15.6 μmol/L (0.55 to 3.7 mg/L). In five samples, EG‐GLUC was detected below the limit of quantification (2 μmol/L) and it was below the limit of detection in 11 samples (1 μmol/L). Compared to the millimolar concentrations of ethylene glycol present in blood after intoxications and potentially available for conjugation, the concentrations of EG‐GLUC found in clinical serum samples are very low, but comparable to concentrations of ethyl glucuronide after medium dose ethanol intake. In theory, EG‐GLUC has a potential value as a biomarker for ethylene glycol intake, but the pharmacokinetic properties, in vivo/vitro stability and the biosynthetic pathways of EG‐GLUC must be further studied in a larger number of patients and other biological matrices.

Simultaneous and cost-effective determination of ethylene glycol and glycolic acid in human serum and urine for emergency toxicology by GC-MS

OBJECTIVES

A simple, cost-effective, and fast gas chromatography method with mass spectrometry detection (GC-MS) for simultaneous measurement of ethylene glycol, 1,2-propylene glycol and glycolic acid was developed and validated for clinical toxicology purposes.

DESIGN AND METHODS

Successful derivatization of glycolic acid with isobutyl chloroformate was achieved directly in serum/urine while glycols are simultaneously derivatized by phenylboronic acid. The entire sample preparation procedure is completed within 10 min.

RESULTS

The assay was proved to be quadratic in the range of 50 to 5000 mgL(-1) with adequate accuracy (96.3-105.8%) and precision (CV ≤ 8.9%).

CONCLUSION

The method was successfully applied to quantify the selected compounds in serum of patients from emergency units and the results correlated well with parallel GC-FID measurements (R(2) 0.9933 for ethylene glycol and 0.9943 for glycolic acid).

Near-fatal persistent anion- and osmolal-gap acidosis due to massive gamma-butyrolactone/ethanol intoxication

We report a case of an ethanol and massive gamma-butyrolactone (GBL) intoxication, the precursor of the recreational drug gamma-hydroxybutyric acid (GHB), resulting in life-threatening metabolic acidosis (pH 6.5) with a highly increased anion- and osmolal gap. Rapid analysis using gas chromatography revealed a GHB plasma concentration of 4400 mg/L, far above the upper limit concentration of 1000 mg/L found in adult fatalities attributed to GBL. Full recovery was established following supportive treatment including haemodialysis. This is the first report of a combined ethanol/GBL intoxication as a cause of high serum anion- and osmolal-gap metabolic acidosis.

Enzymatic assay for GHB determination in forensic matrices

Current procedures for the determination of gamma-hydroxybutyric acid (GHB) require time-consuming extraction and derivatization steps before chromatographic detection, making a high-throughput alternative desirable. Bühlmann Laboratories offers an enzymatic assay for the quantitative determination of GHB in urine and serum. We report the adaptation of this photometric assay to the Thermo Scientific MGC-240 analyzer and its use in the determination of GHB in forensic matrices including urine, whole blood and vitreous humour. Most matrices require only a brief centrifugation before analysis, while blood requires an additional protein precipitation step. A variety of cases (sexual assaults, impaired drivers and death investigations) have been analyzed alongside the gas chromatography-mass spectrometry (GC-MS) reference method. Correlation with the GC-MS has been found to be acceptable, with no false negatives and few false positives, although postmortem samples appear more prone to testing false positive than do antemortem samples. Simple sample preparation and high throughput allow for a significant reduction in analysis time relative to chromatographic methods. This assay is used as a screening method in our laboratory, with a quantitative GC-MS method serving for the confirmation of positive results. To our knowledge, this represents the first evaluation of an enzymatic assay for GHB in a forensic context.

Ethylene glycol poisoning: quintessential clinical toxicology; analytical conundrum

Ethylene glycol poisoning is a medical emergency that presents challenges both for clinicians and clinical laboratories. Untreated, it may cause morbidly or death, but effective therapy is available, if administered timely. However, the diagnosis of ethylene glycol poisoning is not always straightforward. Thus, measurement of serum ethylene glycol, and ideally glycolic acid, its major toxic metabolite in serum, is definitive. Yet measurement of these structurally rather simple compounds is but simple. This review encompasses an assessment of analytical methods for the analytes relevant for the diagnosis and prognosis of ethylene glycol poisoning and of the role of the ethylene glycol metabolites, glycolic and oxalic acids, in its toxicity.

Dried blood spot punches for confirmation of suspected γ-hydroxybutyric acid intoxications: validation of an optimized GC–MS procedure

Background: γ-hydroxybutyric acid ( GHB ), notorious as a club- and date-rape drug, was quantified in dried blood spots (DBS) by punching out a disc, followed by ‘on-spot’ derivatization and analysis by GC–MS. Results: A homogenous distribution in DBS was demonstrated and accurate results were obtained when analyzing a disc punched out from a 20–35 µl spot, regardless the hematocrit of the blood sample. Validation based on US FDA and European Medicines Agency guidelines was performed, with a calibration range covering 2–100 µg/ml. Conclusion: A sensitive GC–MS method for GHB analysis in DBS was successfully optimized and validated. The successful analysis of DBS collected from GHB abusers suggests the routine applicability of the DBS sampling technique for GHB analysis in toxicological cases.

Adsorption of organic matter at mineral/water interfaces: 7. ATR-FTIR and quantum chemical study of lactate interactions with hematite nanoparticles

The interaction of the l-lactate ion ( l-CH3CH(OH)COO(-), lact(-1)) with hematite (alpha-Fe2O3) nanoparticles (average diameter 11 nm) in the presence of bulk water at pH 5 and 25 degrees C was examined using a combination of (1) macroscopic uptake measurements, (2) in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and (3) density functional theory modeling at the B3LYP/6-31+G* level. Uptake measurements indicate that increasing [ lact(-1)]aq results in an increase in lact(-1) uptake and a concomitant increase in Fe(III) release as a result of the dissolution of the hematite nanoparticles. The ATR-FTIR spectra of aqueous lact(-1) and lact(-1) adsorbed onto hematite nanoparticles at coverages ranging from 0.52 to 5.21 micromol/m2 showed significant differences in peak positions and shapes of carboxyl group stretches. On the basis of Gaussian fits of the spectra, we conclude that lact(-1) is present as both outer-sphere and inner-sphere complexes on the hematite nanoparticles. No significant dependence of the extent of lact(-1) adsorption on background electrolyte concentration was found, suggesting that the dominant adsorption mode for lact(-1) is inner sphere under these conditions. On the basis of quantum chemical modeling, we suggest that inner-sphere complexes of lact(-1) adsorbed on hematite nanoparticles occur dominantly as monodentate, mononuclear complexes with the hydroxyl functional group pointing away from the Fe(III) center.

Comparative analysis of gamma-hydroxybutyrate and gamma-hydroxyvalerate using GC/MS and HPLC

This paper describes two analytical techniques used to separate and quantify gamma-hydroxybutyrate (GHB) and gamma-hydroxyvalerate (GHV). The first technique was a N,O-bis(trimethylsilyl)triflouro-acetimide-trimethylchlorosilane derivatization, followed by gas chromatography/mass spectrometry analysis using an HP-5 capillary column at a rate of 1.0 mL/min with a run time of 9.25 min. This technique was found to be sensitive (LOD 1 pg on column) and gave a low average error (5%) in a beverage study. When supplemented by a surrogate spike, the method yielded 97% analyte recovery from beverages. The second technique was high-performance liquid chromatography/UV (HPLC/UV) using a C-18 column with a (20:80% v/v) methanol:dibasic phosphoric buffer (10 mM, pH 3) at a rate of 1.00 mL/min with a run time of 7.5 min. UV detection occurred at 254 nm. This method was found to be less sensitive (LOD 0.05 microg on column) for direct analysis of aqueous samples. To remove interferences seen in the beverage study, a liquid-liquid extraction before HPLC analysis was tested. However, a decreased sensitivity (LOD 100 microg on column) and irreproducible peak profiles resulted.