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This paper describes the development of a sequential injection chromatography (SIC) procedure for separation and quantification of the herbicides simazine, atrazine, and propazine exploring the low backpressure of a 2.5 cm long monolithic C(18) column. The separation of the three compounds was achieved in less than 90 s with resolution >1.5 using a mobile phase composed by ACN/1.25 mmol/L acetate buffer (pH 4.5) at the volumetric ratio of 35:65 and flow rate of 40 microL/s. Detection was made at 223 nm using a flow cell with 40 mm of optical path length. The LOD was 10 microg/L for the three triazines and the quantification limits were of 30 microg/L for simazine and propazine and 40 microg/L for atrazine. The sampling frequency is 27 samples per hour, consuming 1.1 mL of ACN per analysis. The proposed methodology was applied to spiked water samples and no statistically significant differences were observed in comparison to a conventional HPLC-UV method. The major metabolites of atrazine and other herbicides did not interfere in the analysis, being eluted from the column either together with the unretained peak, or at retention times well-resolved from the studied compounds.

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IntroductionSleep bruxism (SB) is a frequent condition in children. Its pathophysiology involves certain neurotransmitters (serotonin, dopamine, noradrenalin, histamine), but the environment seems to influence its occurrence.ObjectiveThe objective of this study was to investigate the prevalence of SB in children and their biological mothers, relating it to stress through a case control study.Methods and MaterialThe group of cases (SG) was composed of 48 subjects, including 24 children with SB and their mothers, and the control group (CG), formed by 36 children without SB and their mothers. The chi-Square test was used and the probability was computed with 95% confidence intervals (p<0.05). Results: The prevalence of probable awareness of SB in children was 22.6%, while it was 30.8% among caregivers. There were no significant associations between the socio-demographic variables and SB. There was an increase in the occurrence of SB in children (p=0.02) when their caregiver also had this condition.ConclusionsPsychological stress did not establish a significant relationship with SB in either the child or their mothers.

This work describes the development and optimization of a sequential injection method to automate the determination of paraquat by square-wave voltammetry employing a hanging mercury drop electrode. Automation by sequential injection enhanced the sampling throughput, improving the sensitivity and precision of the measurements as a consequence of the highly reproducible and efficient conditions of mass transport of the analyte toward the electrode surface. For instance, 212 analyses can be made per hour if the sample/standard solution is prepared off-line and the sequential injection system is used just to inject the solution towards the flow cell. In-line sample conditioning reduces the sampling frequency to 44 h(-1). Experiments were performed in 0.10 M NaCl, which was the carrier solution, using a frequency of 200 Hz, a pulse height of 25 mV, a potential step of 2 mV, and a flow rate of 100 µL s(-1). For a concentration range between 0.010 and 0.25 mg L(-1), the current (i(p), µA) read at the potential corresponding to the peak maximum fitted the following linear equation with the paraquat concentration (mg L(-1)): i(p) = (-20.5 ± 0.3)C (paraquat) - (0.02 ± 0.03). The limits of detection and quantification were 2.0 and 7.0 µg L(-1), respectively. The accuracy of the method was evaluated by recovery studies using spiked water samples that were also analyzed by molecular absorption spectrophotometry after reduction of paraquat with sodium dithionite in an alkaline medium. No evidence of statistically significant differences between the two methods was observed at the 95% confidence level.