Analysis of plasticizers in PVC medical devices: Performance comparison of eight analytical methods.

A wide variety of medical devices (MDs) used in hospitals are made of flexible plasticized polyvinylchloride (PVC). Different plasticizers are present in variable amounts in the PVC matrix of the devices and can leach out into the infused solutions and may enter into contact with the patients. The ARMED1 project aims to assess the migration of these plasticizers from medical devices and therefore the level of exposure in patients. For the first task of the project, eight methods were developed to directly detect and quantify the plasticizers in the PVC matrix of the MDs. We compared the overall performances of the analytical methods using standardized and validated criteria in order to provide the scientific community with the guidance and the technical specifications of each method for the intended application. We have shown that routine rapid screening could be performed directly on the MDs using the FTIR technique, with cost-effective analyses. LC techniques may also be used, but with limits and only with individual quantification of the main plasticizers expected in the PVC matrix. GC techniques, especially GC-MS, are both more specific and more sensitive than other techniques. NMR is a robust and specific technique to precisely discriminate all plasticizers in a MD but is limited by its cost and its low ability to detect and quantify plasticizer contamination, e.g. by DEHP. All these results have been confirmed by a real test, called the " blind test " carried out on 10 MD samples.

Towards more realistic in vitro release measurement techniques for biodegradable microparticles.

PURPOSE: To better understand the importance of the environmental conditions for drug release from biodegradable microparticles allowing for the development of more appropriate in vitro release measurement techniques. METHODS: Propranolol HCl diffusion in various agarose gels was characterized by NMR and UV analysis. Fick's law was used to theoretically predict the mass transport kinetics. Drug release from PLGA-based microparticles in such agarose gels was compared to that measured in agitated bulk fluids ("standard" method). RESULTS: NMR analysis revealed that the drug diffusivity was almost independent of the hydrogel concentration, despite of the significant differences in the systems' mechanical properties. This is due to the small size of the drug molecules/ions with respect to the hydrogel mesh size. Interestingly, the theoretically predicted drug concentration-distance-profiles could be confirmed by independent experiments. Most important from a practical point of view, significant differences in the release rates from the same batch of PLGA-based microparticles into a well agitated bulk fluid versus a semi-solid agarose gel were observed. CONCLUSION: Great care must be taken when defining the in vitro conditions for drug release measurements from biodegradable microparticles. The obtained new insight can help facilitating the development of more appropriate in vitro release testing procedures.

Determination of glyphosate in biological fluids by 1H and 31P NMR spectroscopy.

Identification of glyphosate in four cases of poisoning, using nuclear magnetic resonance spectroscopy of biological fluids is reported. It has been performed by using a combination of 1H and 31P NMR analyses. Characterization of the N-(phosphonomethyl) glycine herbicide was achieved by chemical shift considerations and coupling constant patterns: CH2-(P) presents specific resonance at 3.12 ppm and appears as a doublet with a H-P characteristic coupling constant of 12.3 Hz. Moreover, resonances due to isopropylamine were present, confirming the ingestion of the considered trade formulation. After a calibration step, quantitation was performed by 1H and 31P NMR spectroscopy. The benefit and reliability of NMR investigations of biological fluids are discussed, particularly when the clinical picture is quite confusing.

Identification and quantitation of xenobiotics by 1H NMR spectroscopy in poisoning cases.

In order to analyse a wide range of xenobiotics and their metabolites present in biological fluids, NMR spectroscopy can be used. A large variety of xenobiotics (therapeutic agents, pesticides, solvents, alcohols) can be characterized and quantitated directly, without sample preparation. NMR investigations were applied to acute poisoning cases, involving drugs such as salicylates and valproic acid (VPA). In a salicylate poisoning case, the three major metabolites of acetylsalicylic acid have been detected in crude urine, and rapid identification of lysine revealed the origin of the intoxication, namely lysine acetylsalicylate (Aspegic). Valproic acid as its glucuronide was identified in urine samples from two poisoned patients. 1H NMR was also used to identify and quantitate paraquat (Gramoxone) in urine owing to its two aromatic signals at 8.49 and 9.02 ppm, in two acutely poisoned patients (183 and 93 mg/l). An intentional poisoning case with tetrahydrofuran (THF) was also investigated. Serum and urine samples were collected. THF was characterized by its resonances at 1.90 and 3.76 ppm, and quantified at 813 and 850 mg/l in the two biological fluids, respectively. Moreover, two other compounds were detected: lactate and gamma-hydroxybutyric acid (GHB). 1H NMR spectroscopic analysis of serum samples from three poisoned patients revealed methanol in one case and ethylene glycol in the two others. Moreover, in the same spectrum, the corresponding metabolites formate and glycolate were found. Compared with the reference chromatographic or spectrophotometric methods, requiring time-consuming extraction and/or derivatization steps, NMR spectroscopy allows the determination of many exogenous and endogenous compounds, without any pre-selection of the analytes.

1H NMR spectroscopic investigation of serum and urine in a case of acute tetrahydrofuran poisoning.

This article reports the investigation by 1H nuclear magnetic resonance (1H NMR) spectroscopy of biological fluids in a case of intentional poisoning with tetrahydrofuran (THF). Occupational exposures to this solvent are well documented, but acute poisoning cases are extremely rare, and the one presented here is the second known case of this kind. Urine and serum samples were collected. Without any pretreatment, the presence of THF was confirmed by characteristic resonances at 1.90 and 3.76 ppm; high lactate levels were also observed. The presence of gamma-hydroxybutyric acid (GHB) was noted. Quantitative analysis was performed by relative integration of peak areas. THF concentrations were 813 and 850 mg/L (11.3 and 11.8 mmol/L), and GHB concentrations 239 and 2,977 mg/L (2.3 and 28.6 mmol/L) in serum and urine, respectively. A gas chromatographic-mass spectrometric method confirmed 1H NMR observations. The origin of GHB detected in serum and urine is also discussed.

Valproic acid intoxication identified by 1H and 1H-(13)C correlated NMR spectroscopy of urine samples.

Analysis of biological fluids by proton and carbon nuclear magnetic resonance spectroscopy (1H and 13C NMR) is a promising tool in clinical biology. We used this method for rapid toxicological screening in the case of two suicide attempts. For each case, a urine sample was analysed at 300 MHz by 1D and 2D sequences (TOCSY and HMBC) in a short experimental time. Quantification was performed by peak integration on the 1D 1H NMR spectrum. For the two patients, results showed the same resonances of the major metabolite, valproyl-O-glucuronide at concentrations of 121 and 44 mmol/l.

Use of 15N reverse gradient two-dimensional nuclear magnetic resonance spectroscopy to follow metabolic activity in Nicotiana plumbaginifolia cell-suspension cultures.

Nitrogen metabolism was monitored in suspension cultured cells of Nicotiana plumbaginifolia Viv. using nuclear magnetic resonance (NMR) spectroscopy following the feeding of (15NH4)2SO4 and K15NO3. By using two-dimensional 15N-1H NMR with heteronuclear single-quantum-coherence spectroscopy and heteronuclear multiple-bond-coherence spectroscopy sequences, an enhanced resolution of the incorporation of 15N label into a range of compounds could be detected. Thus, in addition to the amino acids normally observed in one-dimensional 15N NMR (glutamine, aspartate, alanine), several other amino acids could be resolved, notably serine, glycine and proline. Furthermore, it was found that the peak normally assigned to the non-protein amino-acid gamma-aminobutyric acid in the one-dimensional 15N NMR spectrum was resolved into a several components. A peak of N-acetylated compounds was resolved, probably composed of the intermediates in arginine biosynthesis, N-acetylglutamate and N-acetylornithine and, possibly, the intermediate of putrescine degradation into gamma-aminobutyric acid, N-acetylputrescine. The occurrence of 15N-label in agmatine and the low detection of labelled putrescine indicate that crucial intermediates of the pathway from glutamate to polyamines and/or the tobacco alkaloids could be monitored. For the first time, labelling of the peptide glutathione and of the nucleotide uridine could be seen.

Determination by 1H NMR spectroscopy of paraquat in urine from acutely poisoned patients. Comparison with second-derivative spectroscopy method.

The application of 1H nuclear magnetic resonance (NMR) spectroscopy to characterize and quantitate paraquat in urine is described. Characterization was performed taking advantage of two NMR spectroscopy parameters: chemical shifts and coupling patterns. Without any pretreatment of the biological samples, herbicide was detected by its aromatic doublets at 8.49 and 9.02 ppm. Quantitation of the xenobiotic was realized by relative integration of the dipyridyl protons to an internal standard. After a validation step using control urine samples, quantitation was performed in urine obtained from two poisoned patients. On admission, mean paraquat concentrations were 985 (patient 1) and 500 (patient 2) micromol/L. Results are compared and found to be in good agreement, using a second-derivative spectroscopy method.

[Analysis of two cases of valproic acid intoxication by 1H NMR spectroscopy and gas chromatography/mass spectrometry]. / Analyse de deux cas d'intoxication par l'acide valproïque par spectroscopie RMN 1H et CPG/SM.

Analysis of urine samples from two poisoned patients was performed using proton nuclear magnetic resonance (1H NMR) spectroscopy and a classical GC/MS protocol. Valproic acid as its glucuronide was identified and quantified in the 1H NMR spectra recorded directly from 0.5 mL of the collected samples. Moreover, a significant lactic aciduria could be observed. Comparison with the GC/MS findings suggests that 1H NMR spectroscopy can be clinically useful.

Poisoning with methanol and ethylene glycol:1H NMR spectroscopy as an effective clinical tool for diagnosis and quantification.

Analysis of serum and urine samples from three patients in a metabolic acidotic state was performed using biochemical methods and proton nuclear magnetic resonance (1H NMR). Methanol and ethylene glycol were identified by their singlet peaks in the 1H NMR spectra recorded directly from 0.5 ml of the collected samples. Quantification of these compounds was obtained simultaneously with that of their metabolites, formate and glycolate respectively and of lactate and ethanol, the latter being used as an antidote. The NMR results were found to be very similar to the biochemical findings. The results presented here suggest that 1H NMR can be clinically useful since it quickly provides information on the onset of metabolic acidosis and on the biotransformation of xenobiotics.

1H-NMR analysis of trimethylamine in urine for the diagnosis of fish-odour syndrome.

This paper reports the use of proton NMR spectroscopy for the analysis of trimethylamine in the urine of a patient with trimethylaminuria. Analysis of this compound was also performed for other members of his family. Qualitative and quantitative determination of trimethylamine and trimethylamine-N-oxide was simultaneously performed on untreated urine within a few minutes. The application of the method is discussed.

Diagnosis of a case of acute chloroquine poisoning using 1H NMR spectroscopy: characterisation of drug metabolites in urine.

Analysis of biological fluids by proton nuclear magnetic resonance spectroscopy (1H NMR) is a promising tool in clinical biology. We have used this method for a rapid toxicological screening in the case of a suicide attempt. A urine sample was analysed at 300 and 600 MHz by 1D and 2D sequences (J-resolved and TOCSY) in a short experimental time. Quantification was realized by peak integration of the 1D spectrum. The results showed the presence of chloroquine and its major metabolite monodesethylchloroquine at concentrations of 462 and 140 mg/L, respectively. Ethanol was also detected in the spectrum. It can be concluded that 1H NMR provides many advantages as a tool for clinical diagnosis in a case of acute intoxication.

Salicylate poisoning: two-dimensional J-resolved NMR urinalysis.

Identification of a case of acute salicylate intoxication using 300 MHz 1H NMR spectroscopy of a urine sample is reported. It has been achieved by using a combination of a one-dimensional experiment with water presaturation and a two-dimensional homonuclear J-resolved experiment. By these means, lysine and the three major metabolites of acetylsalicylic acid have been assigned in the crude urine. The results are compared with those obtained at 600 MHz and with classical biochemical methods. The use of this method for routine diagnosis in biological analysis is discussed.