Single-run capillary electrophoresis method for the fast simultaneous determination of amoxicillin, clavulanate, and potassium.

We report a new fast method for the simultaneous determination of amoxicillin, clavulanate, and potassium by capillary electrophoresis with capacitively coupled contactless conductivity detection. Samples containing potassium as the cation, and both amoxicillin and clavulanate as anions were determined simultaneously in a single run (in less than 45 s) using 10 mmol/L of both 2-amino-2-hydroxymethyl-propane-1,3-diol and 3-{[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]amino}-1-propanesulfonic acid (pH 8.4) as the background electrolyte. Limits of detection were 25.0, 5.0, and 4.0 µmol/L for amoxicillin, clavulanate, and potassium, respectively. The proposed method is inexpensive, simple, fast (75 injections h-1 ), environment friendly (minimal waste generation), and accurate (recovery values between 98 and 103%). The results obtained with the proposed method were statistically similar (95% confidence level) to those obtained by using high-performance liquid chromatography (amoxicillin and clavulanate) and flame photometry (potassium).

Fast determination of codeine, orphenadrine, promethazine, scopolamine, tramadol, and paracetamol in pharmaceutical formulations by capillary electrophoresis.

Paracetamol is an active ingredient commonly found in pharmaceutical formulations in combination with one of the following compounds: codeine, orphenadrine, promethazine, scopolamine, and tramadol. In this work, we propose a unique analytical method for determination of these active ingredients in pharmaceutical samples. The method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation was achieved on a fused silica capillary (50 cm total length, 40 cm effective length, and 50 µm id) using an optimized background electrolyte composed of 20 mmol/L ß-alanine/4 mmol/L sodium chloride/4 µmol/L sodium hydroxide (pH 9.6). Each sample can be analyzed in a single run (≤2 min) and the limits of detection were 2.5, 0.62, 0.63, 2.5, 15, and 1.6 µmol/L for scopolamine, tramadol, orphenadrine, promethazine, codeine, and paracetamol, respectively. Recovery values for spiked samples were between 94 and 104%.

Simultaneous determination of caffeine, paracetamol, and ibuprofen in pharmaceutical formulations by high-performance liquid chromatography with UV detection and by capillary electrophoresis with conductivity detection.

Paracetamol, caffeine and ibuprofen are found in over-the-counter pharmaceutical formulations. In this work, we propose two new methods for simultaneous determination of paracetamol, caffeine and ibuprofen in pharmaceutical formulations. One method is based on high-performance liquid chromatography with diode-array detection and the other on capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation by high-performance liquid chromatography with diode-array detection was achieved on a C18 column (250×4.6 mm(2), 5 µm) with a gradient mobile phase comprising 20-100% acetonitrile in 40 mmol L(-1) phosphate buffer pH 7.0. The separation by capillary electrophoresis with capacitively coupled contactless conductivity detection was achieved on a fused-silica capillary (40 cm length, 50 µm i.d.) using 10 mmol L(-1) 3,4-dimethoxycinnamate and 10 mmol L(-1) ß-alanine with pH adjustment to 10.4 with lithium hydroxide as background electrolyte. The determination of all three pharmaceuticals was carried out in 9.6 min by liquid chromatography and in 2.2 min by capillary electrophoresis. Detection limits for caffeine, paracetamol and ibuprofen were 4.4, 0.7, and 3.4 µmol L(-1) by liquid chromatography and 39, 32, and 49 µmol L(-1) by capillary electrophoresis, respectively. Recovery values for spiked samples were between 92-107% for both proposed methods.

Simultaneous determination of diclofenac and its common counter-ions in less than 1 minute using capillary electrophoresis with contactless conductivity detection.

This paper presents a method for fast and simultaneous determination of diclofenac (DCF) and its common counter-ions (potassium, sodium, and diethylammonium) using CE with capacitively coupled contactless conductivity detection (CE-C(4) D). On the basis of a single electropherogram (about 50 s), the proposed method allows the determination of the stoichiometry, absolute quantification and evaluation of the degradation degree of the active pharmaceutical ingredient (DCF). A linear working range from 100 to 500 µmol/L was obtained for all analytes in an equimolar TRIS/TAPS (10 mmol/L) solution as the background electrolyte as well as adequate LOD (7, 6, 7, and 10 µmol/L for K(+) , Na(+) , diethylammonium, and DCF, respectively). The proposed method was applied to the analysis of pharmaceutical formulations (tablets and spray form) with similar results to those achieved by HPLC (DCF) or flame photometry (K and Na) at a 95% confidence level.

Fast simultaneous determination of BHA and TBHQ antioxidants in biodiesel by batch injection analysis using pulsed-amperometric detection.

We report the first amperometric method for the simultaneous determination of butylated hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ) in biodiesel using batch-injection analysis (BIA) coupled to pulsed-amperometry. A sequence of potential pulses was selected in order to detect TBHQ and BHA separately in a single injection step at a glassy-carbon electrode. Samples were diluted in 50% v/v hydroethanolic solution with 0.1 mol L(-1) HClO(4) (supporting electrolyte) before injection using an electronic pipette. The method is highly precise (RSD<1%, n=10), fast (170 injections h(-1)), accurate (recovery between 100 and 110%), presents low detection limits (73 and 75 nmol L(-1) BHA and TBHQ, respectively), and can be easily adapted for on-site determinations.

Effects of different methods of antagonist muscles pre-activation on knee extensors neuromuscular responses / Efeitos da ordem de pré-ativação dos músculos antagonistas nas respostas neuromusculares dos extensores do joelho

BACKGROUND: Pre-activation of antagonistic muscles is used in different modalities of exercise and neuromuscular rehabilitation protocols, but its effectiveness is still controversial. OBJECTIVE: To verify the impact of two different methods of pre-activation of knee antagonist muscles in the neuromuscular performance and electromyographic activity of knee extensors. METHODS: Fifteen healthy men (23.9±4.2 years of age, 1.78±0.08 meters and 81.4±10.7 kg) performed, on different days, two protocols of isokinetic muscle contraction with 4 sets of 10 repetitions at 60°.s-1 and 1 minute between sets: (1) Reciprocal Contraction (RC): reciprocal concentric exercise of agonist/antagonist muscles (knee flexion [KF] immediately followed by knee extension [KE]) and (2) Superset (SS): alternated concentric exercise of agonist/antagonist muscles (KF set followed by a set of KE). A repeated measures ANOVA with least-significant difference post-hoc test was used to detect differences between protocols. RESULTS: There were no significant differences between protocols (p>0.05) for peak torque (PT) and total work (Tw). On the SS protocol there was a significant decrease in Tw on the last two sets (p<0.05) while for RC the decrease occurred only in the last set. There were no significant differences of root mean square (RMS) between protocols, but the activation pattern was more uniform during the RC protocol. CONCLUSION: The results indicated that the peak torque was not influenced by the different pre-activation methods. However, the RC protocol appears to better maintain the total work training volume.

CONTEXTUALIZAÇÃO: A pré-ativação de músculos antagonistas é utilizada em diferentes modalidades de exercício e em diferentes protocolos de reabilitação neuromuscular, porém suas respostas ainda são controversas. OBJETIVO: Verificar o impacto de duas diferentes estratégias de pré-ativação de músculos antagonistas no desempenho neuromuscular e na atividade eletromiográfica dos extensores do joelho. MÉTODOS: Quinze homens sadios (23,9±4,2 anos; 1,78±0,08 m e 81,4±10,7 kg) realizaram, em dias distintos, dois protocolos de ações musculares isocinéticas com quatro séries de dez repetições a 60°.s-1 e intervalo de 1 minuto entre séries: 1) contração recíproca (CR): exercício concêntrico recíproco de antagonistas/agonistas (uma repetição de flexão do joelho [FJ] imediatamente seguida por uma de extensão do joelho [EJ]) e 2) supersérie (SS): exercício concêntrico alternado dos antagonistas/agonistas (dez repetições de FJ seguidas por dez de EJ). Utilizou-se a ANOVA para medidas repetidas com teste post-hoc LSD (Least-significant diference) para verificar a diferença entre protocolos. RESULTADOS: Não houve diferença significante (p>0,05) entre protocolos para o pico de torque (PT) e trabalho total (Tt). Em relação ao Tt, o protocolo SS apresentou quedas significantes nas duas últimas séries (p<0,05) enquanto, no CR, a queda ocorreu apenas na última série de exercício. Não houve diferenças no Root Mean Square (RMS) entre protocolos, mas o padrão de ativação foi mais uniforme durante o CR. CONCLUSÃO: Os resultados indicaram que a queda na força muscular não é influenciada pelas diferentes formas de pré-ativação da musculatura antagonista, no entanto parece que a utilização de CR permite uma melhor manutenção do volume de treinamento.

Effects of different methods of antagonist muscles pre-activation on knee extensors neuromuscular responses.

BACKGROUND: Pre-activation of antagonistic muscles is used in different modalities of exercise and neuromuscular rehabilitation protocols, but its effectiveness is still controversial. OBJECTIVE: To verify the impact of two different methods of pre-activation of knee antagonist muscles in the neuromuscular performance and electromyographic activity of knee extensors. METHODS: Fifteen healthy men (23.9±4.2 years of age, 1.78±0.08 meters and 81.4±10.7 kg) performed, on different days, two protocols of isokinetic muscle contraction with 4 sets of 10 repetitions at 60°.s-1 and 1 minute between sets: (1) Reciprocal Contraction (RC): reciprocal concentric exercise of agonist/antagonist muscles (knee flexion [KF] immediately followed by knee extension [KE]) and (2) Superset (SS): alternated concentric exercise of agonist/antagonist muscles (KF set followed by a set of KE). A repeated measures ANOVA with least-significant difference post-hoc test was used to detect differences between protocols. RESULTS: There were no significant differences between protocols (p>0.05) for peak torque (PT) and total work (Tw). On the SS protocol there was a significant decrease in Tw on the last two sets (p<0.05) while for RC the decrease occurred only in the last set. There were no significant differences of root mean square (RMS) between protocols, but the activation pattern was more uniform during the RC protocol. CONCLUSION: The results indicated that the peak torque was not influenced by the different pre-activation methods. However, the RC protocol appears to better maintain the total work training volume.