Numerical solutions of Green's integral equation for the diffraction of femtosecond laser pulses through a subwavelength aperture

In this letter, we propose a method for the numerical calculations of the femtosecond laser pulse passed through a subwavelength aperture. The time-dependent laser pulse is decomposed into a series of monochromatic simple harmonic waves. For the light field of the harmonic wave with a single frequency, the numerical calculation is made based on the solution of the Green's integral equation set of the electromagnetic waves. Such numerical solution is iterated for all the waves with different frequencies, and all the numerical solutions are transformed into the light fields in the time domain by inverse Fourier transform. The light intensity distributions transmitted the subwavelength aperture are calculated and the results show the propagation of the light field is along the direction of the medium interface.

Determination of zidovudine using anion exchange chromatography with integrated pulsed amperometric detection

A rapid and practical method for direct detection of zidovudine in high performance anion exchange chromatography （HPAEC） has been developed with integrated pulsed amperometric detection （IPAD）. Dionex AS18 （250mm × 2mm） and AG18 （50 mm× 2 mm） columns and 11 mmol/L NaOH solution were used for separation. Multi-step potential waveform parameters were optimized to maximize the signal-to-noise ratio （S/N）. Utilizing an optimized waveform, the repeatability （intra-day） precision and intermediate （inter-day） precision are obtained with relative standard deviation （RSD） of 1.88, 2.27, respectively. The limit of quantification （LOQ） and limit of detection （LOD） were found to be 9.70, 3.0 ng/mL, respectively, with correlation coefficients of 0.9992 over concentration range 0.01-10 μg/mL. The present method was successfully applied to the determination of zidovudine in human plasma. The recoveries of plasma sample spiked by 0.7 μg/mL, 2.7 μg/mL obtained were 95.3-101.5%, with relative standard deviation （RSD） of 2.54%, 2.21%, respectively.

Determination of lisinopril using anion exchange chromatography with integrated pulsed amperometric detection

A rapid and practical method for direct detection of lisinopril in anion exchange chromatography（AEC） has been developed with integrated pulsed amperometric detection（IPAD）.Dionex AS 18（250 mm×2 mm） and AG 18（50 mm×2 mm） columns and 40 mmol/L NaOH solution were used for separation.Multi-step potential waveform parameters were optimized to maximize the signal-to-noise ratio（S/N）.Utilizing the optimized waveform,the repeatability（intra-day） precision and intermediate（inter-day） precision were obtained with relative standard deviation（RSD） of 0.74,0.93,respectively.The limit of quantification（LOQ） and limit of detection（LOD） were found to be 0.37,0.12ng/mL,respectively,with the correlation coefficient of 0.9998 over concentration range 0.01-1μg/mL.The present method was successfully applied to the determination of lisinopril in human plasma.The recoveries of plasma sample spiked by 0.2μg/mL,0.8μg/mL lisinopril were 98.31-103.23%with RSD of 1.41%, 0.61%,respectively.