Silver-modified nitrogen-doped graphene quantum dots as a sensor for formaldehyde in milk using headspace micro-extraction on a single-drop of aqueous nanoparticles dispersion.

BACKGROUND: Fraudulent practices used to distort the quality of milk and derivatives include the addition of formaldehyde. RESULTS: A formaldehyde sensor was developed based on the luminescence of newly proposed N-doped graphene quantum dots modified with silver (N-GQDs-Ag) that were prepared using a simple method. A microdroplet of the nanoparticle dispersion was used to collect formaldehyde vapor by headspace single-drop micro-extraction (HS-SDME). After, the microdroplet was diluted in water, the nanoparticle photoluminescence quenching, caused by the analyte, was measured. The strong luminescent quenching allowed a detection limit at 1.7 × 10-4% w/v. Response was selective towards formaldehyde. SIGNIFICANCE: The method was effective and a cost-effective method for screening analysis of milk samples with matrix interferences minimized due to the nature of nanoparticle (prepared using Tollen's reagent) and due to the probing at the headspace of the sample cell. Results were statistically similar to those obtained using liquid chromatography.

Biomarkers to assess the efficiency of treatment with platinum-based drugs: what can metallomics add?

Since the approval of cisplatin as an antineoplastic drug, the medical and the scientific communities have been concerned about the side effects of platinum-based drugs, and this has been the dose-limiting factor that leads to reduced treatment efficiency. Another important issue is the intrinsic or acquired resistance of some patients to treatment. Identifying proper biomarkers is crucial in evaluating the efficiency of a treatment, assisting physicians in determining, at early stages, whether or not the patient presents resistance to the drug, minimizing severe side effects, and allowing them to redirect the established course of chemotherapy. A great effort is being made to identify biomarkers that can be used to predict the outcome of the treatment of cancer patients with platinum-based drugs. In this context, the metallomic approach has not yet been used to its full potential. Since the basis of these drugs is platinum, the monitoring of biomarkers containing this metal should be the natural approach to evaluate treatment progress. This review intends to show where the research in this field stands and points out some gaps that can be filled by metallomics.

Determination of the antiretroviral drug nevirapine in diluted alkaline electrolyte by adsorptive stripping voltammetry at the mercury film electrode.

This paper describes a stripping method for the determination of nevirapine at the submicromolar concentration levels. The method is based on controlled adsorptive accumulation of nevirapine at thin-film mercury electrode, followed by a linear cyclic scan voltammetry measurement of the surface species. Optimal experimental conditions include a 2.0 x 10(-3) mol L(-1) NaOH solution (supporting electrolyte), an accumulation potential of -0.20 V, and a scan rate of 100 mV s(-1). The response of nevirapine is linear over the concentration range 0.01-0.14 ppm. For an accumulation time of 6 minutes, the detection limit was found to be 0.87 ppb (3.0 x 10(-9) mol L(-1)). More convenient methods to measure the nevirapine in presence of the efavirenz, acyclovir, didanosine, indinavir, nelfinavir, saquinavir, lamivudine, zidovudine and metals ions were also investigated. The utility of this method is demonstrated by the presence of nevirapine together with ATP or DNA.

Determination of basic azaarenes in aviation kerosene by solid-phase extraction and HPLC-fluorescence detection.

SPE in combination with HPLC and fluorescence detection has been used for sensitive determination of six basic azaarenes (7,8-benzoquinoline, 7,9-dimethylbenz[c]acridine, 9-amino-1,2,3,4-tetrahydroacridine, 9-methylacridine, acridine, and dibenz[a,j]acridine) in aviation kerosene (jet fuel). SPE was performed in a single step using a strong cation exchange sorbent. The HPLC system consisted of C18 column with a selected detection program of optimal lambda(exc) and lambda(em). A gradient elution with ACN and phosphate buffer (pH 6.5) at a flow rate of 1 mL/min allowed efficient and fast separation of azaarenes within 15 min. The LOD and LOQ values (S/N ratio 3:1 and 10:1, respectively) were between 0.0013 and 0.021 and from 0.0044 to 0.072 ng per injection. The calibration curves showed linear behavior from the LOQ to 250 microg/L (r2 >0.99). For the spiked concentration of 6.0 microg/L, recoveries were from 92 to 107% for jet fuel samples, except for 9-amino-1,2,3,4-tetrahydroacridine, which presented 68% recovery. The proposed method was applied to the quantification of those six basic azaarenes in one commercial kerosene and in three aviation kerosene samples. The presence of 7,8-benzoquinoline (up to 3.2 microg/L) and dibenzo[a,j]acridine (up to 6.3 microg/L) was confirmed in aviation kerosene.

Determination of refractory elements in used lubricating oil by ICPOES employing emulsified sample introduction and calibration with inorganic standards.

The quantification of trace elements in used lubricating oil is useful for evaluating the wearing of specific components of engines. In the present work, inductively coupled plasma optical emission spectrometry (ICPOES) was used for determining five refractory elements (Ni, Mo, Cr, V and Ti) in lubricating-oil samples. The methodology was developed while aiming at the introduction of such organic samples into the ICP as emulsions. Several nebulization systems were tested with clear advantage for Meinhard K3 coupled with a cyclonic spray chamber. The carbon deposition on the injector tip as well as the plasma background was minimized through careful optimization of the Ar and O2 gas mixture flows into the plasma. The optimization of instrumental and experimental parameters allowed quantification using calibration curves prepared with analyte inorganic standards. An internal standard (Sc) was used to correct the matrix effects and signal fluctuations. The limits of detection (3Sb/m), in the ng g(-1) range were obtained for all five elements. The methodology was validated through an analysis of standard reference materials (SRM 1084a, 1085a and 1085b). Good analyte recoveries (from 92.6 to 104.7%) were achieved. Comparison studies against established ICPOES methodologies (sample acid decomposition or sample direct dilution in an organic solvent) have shown that the proposed methodology present clear advantages in terms of simplicity of sample preparation, overall analysis time, and the use of inorganic standards for calibration instead of expensive metallorganic standards.