Mariana C. Marra

Fast batch injection analysis system for on-site determination of ethanol in gasohol and fuel ethanol

A simple, accurate and fast (180 injections h(-1)) batch injection analysis (BIA) system with multiple-pulse amperometric detection has been developed for selective determination of ethanol in gasohol and fuel ethanol. A sample aliquot (100 μL) was directly injected onto a gold electrode immersed in 0.5 mol L(-1) NaOH solution (unique reagent). The proposed BIA method requires minimal sample manipulation and can be easily used for on-site analysis. The results obtained with the BIA method were compared to those obtained by gas-chromatography and similar results were obtained (at 95% of confidence level).

Ultra-fast determination of caffeine, dipyrone, and acetylsalicylic acid by capillary electrophoresis with capacitively coupled contactless conductivity detection and identification of degradation products.

Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D) was used for fast, simultaneous determination of dipyrone (DIP), caffeine (CAF), and acetylsalicylic acid (ASA). In the same run and in less than 1min, the degradation products from DIP and ASA were also detected. In addition, the usage of the CE-C(4)D system allowed, for the first time, the detection of methylamine as a degradation product of DIP. Capillary electrophoresis with electrospray mass spectrometry experiments were carried out in order to confirm the formation of methylamine. The limits of detection by CE-C(4)D were 5, 5, and 6μmolL(-1) for CAF, DIP, and ASA, respectively. The proposed method was applied to the analysis of these compounds in pharmaceutical formulations with similar results to those achieved by HPLC (p<0.05).

Determination of propranolol and hydrochlorothiazide by batch injection analysis with amperometric detection and capillary electrophoresis with capacitively coupled contactless conductivity detection

We report two new electrochemical methods for the simultaneous determination of propranolol (PROP) and hydrochlorothiazide (HCT). One method is based on batch injection analysis with multiple pulse amperometric detection (BIA-MPA) and the other on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). The BIA-MPA procedure is highly precise (RSD < 2.1%, n = 10, for both PROP and HCT), fast (130 injections per h) and has low detection limits (0.17 and 1.9 μmol L−1 for PROP and HCT, respectively). The proposed CE-C4D method allows the determination of PROP and HCT in less than 1 minute with high precision (RSD < 2.8%, n = 10, for both PROP and HCT) and low detection limits (30 and 10 μmol L−1 for PROP and HCT, respectively). Both of the proposed methods were applied to the determination of PROP and HCT in pharmaceutical samples.

Ultra-fast determination of scopolamine, orphenadrine, mepyramine, caffeine, dipyrone, and ascorbic acid by capillary electrophoresis with capacitively coupled contactless conductivity detection

In this paper, we present a simple and low-cost capillary electrophoresis method for ultra-fast determination of active ingredients present in three different pharmaceutical formulations: (i) scopolamine (SCO) and dipyrone (DIP); (ii) orphenadrine (ORP), caffeine (CAF) and DIP; (iii) mepyramine (MEP), CAF, DIP, and ascorbic acid (AA). The proposed method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). The samples can be analyzed in a single run ( 0.993) was obtained from 0.10 to 0.50 mmol L-1 for SCO, from 0.25 to 1.25 mmol L-1 for ORP and MEP, from 0.50 to 2.50 mmol L-1 for DIP and CAF, and from 1.00 to 3.00 mmol L-1 for AA. The limits of detection were 0.02, 0.05, 0.03, 0.04, 0.02, and 0.06 mmol L-1 for SCO, DIP, ORP, CAF, MEP, and AA, respectively. In addition, the proposed method also provided adequate intra (< 4%) and inter-day (< 14%) precision values, as well as satisfactory recovery values for spiked pharmaceutical samples (from 92% to 103%).

A high-throughput BIA-MPA method for the simultaneous determination of amiloride and furosemide

In this work, a simple and fast batch injection analysis system with multiple pulse amperometric detection (BIA-MPA) was developed for the simultaneous determination of amiloride (AMD) and furosemide (FMD). A sample plug (150 μL) was directly injected into the unmodified boron-doped diamond (BDD) electrode immersed in 0.1 mol L−1 borate buffer (pH = 10). Simple and fast sample pre-treatment steps were required (dissolution and dilution). The analytical characteristics of the proposed method include good stability (RSD < 1.1%; n = 20), low detection limits (0.13 and 0.94 mg L−1 for AMD and FMD, respectively), high throughput (72 injections per h) and minimal waste production (∼150 μL by analysis). The results obtained with the BIA-MPA method were compared to those obtained by HPLC; similar results were obtained (at a 95% confidence level).

Fast determination of cocaine and some common adulterants in seized cocaine samples by capillary electrophoresis with capacitively coupled contactless conductivity detection

The determination of cocaine and common adulterants in seized cocaine samples can be used to identify their possible production area and traffic routes. In this paper, capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) was used for fast simultaneous determination of cocaine (COC), procaine (PRO), levamisole (LEV) and lidocaine (LID) (38 injections per hour). The separation was achieved using a fused silica capillary (50 cm total length − 40 cm effective length, 50 μm i.d.) and a background electrolyte composed of boric acid/3,4-dimethoxycinnamic acid (20/10 mmol L−1) with pH adjusted to 8.4 with sodium hydroxide. Linear working ranges (r ≥ 0.996) were obtained from 100 to 900 μmol L−1 for COC and from 50 to 450 μmol L−1 for PRO, LEV, and LID. The limits of detection were 10, 4, 6, and 7 μmol L−1 for PRO, COC, LEV and LID, respectively. In addition, the proposed method also provided adequate intra (≤2.3%) and inter-day (≤4%) precisions, as well as satisfactory recovery values for spiked seized cocaine samples (from 96% to 103%).

Sub-Minute Method for Determination of Naphazoline in the Presence of Diphenhydramine, Pheniramine or Chlorpheniramine by Capillary Electrophoresis

This paper presents a simple and low-cost capillary electrophoresis method for ultra-fast simultaneous determination of naphazoline (NPZ) and one of the following active ingredients: diphenhydramine (DIP), pheniramine (PHEN) or chlorpheniramine (CPHEN). The proposed method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-CD) equipped with a short length capillary column (10 cm). One sample can be analyzed every 35 s (ca. 100 injections per hour) with resolutions between peaks greater than 1.4. The optimized background electrolyte (BGE) was composed by 20 mmol L histidine and 10 mmol L 3,4-dimethoxycinnamic acid (pH = 9.5, adjusted with NaOH). Limits of detection were 25 μmol L for NPZ, DIP, and PHEN and 13 μmol L for CPHEN. The results obtained with the developed procedure were compared to those obtained by high-performance liquid chromatography (HPLC) and no statistically significant differences were observed (95% confidence level).

Screening of seized cocaine samples using electrophoresis microchips with integrated contactless conductivity detection

This study describes the development of a new analytical method for the separation and detection of cocaine (COC) and its adulterants, or cutting agents, using microchip electrophoresis (ME) devices coupled with capacitively coupled contactless conductivity detection (C4D). All the experiments were carried out using a glass commercial ME device containing two pairs of integrated sensing electrodes. The running buffer composed of 20 mmol/L amino‐2‐(hydroxymethyl) propane‐1,3‐diol and 10 mmol/L 3,4‐dimethoxycinnamic acid provided the best separation conditions for COC and its adulterants with baseline resolution (R > 1.6), separation efficiencies ranging from (2.9 ± 0.1) to (3.2 ± 0.2) × 105 plates/m, and estimated LOD values between 40 and 150 μmol/L. The quantification of COC was successfully performed in four samples seized by the Brazilian Federal Police Department and all predicted values agree with values estimated by the reference method. Some other interfering species were detected in the seized samples during the screening procedure on ME–C4D devices. While lidocaine was detected in sample 3, the presence of levamisole was observed in samples 2 and 4. However, their concentrations were estimated to be below the LOQ. ME–C4D devices have proved to be quite efficient for the identification and quantification of COC with errors lower than 10% when compared to the data obtained by a reference method. The approach herein reported offers great potential to be used for on‐site COC screening in seized samples.