Super continuum generation in water doped with Homeopathic medicines

We have carried out systematic studies to investigate the effect on supercontinuumgeneration in water using 40 fs laser pulses when doped with Homeopathic medicines. We perform these studies using five series of medications with different levels of dilution (10-30 to 10-100000). We measure supercontinuum spectra that span from 400-1050nm. We monitor the area under the curve in the range 450-750 nm for each sample at a fixed incident laser energy. Our observations indicate that the yield of supercontinuum generation, in water containing Homeopathic medicine is significantly different from that obtained in water containing plain ethanol. The measurement for different dilutions shows up to 7 times standard deviation variation in the yield of supercontinuum generationEven though linear absorption in the UV-visible region does not show any significant difference for different Homeopathic medicines, the supercontinuum yield which depends on the effective nonlinear refractive index changes with different samples. (AU)

Comparison of different linear calibration approaches for LC-MS bioanalysis.

Many different calibration approaches are used for linear calibration in LC-MS bioanalysis, such as different numbers of concentration levels and replicates. However, direct comparison of these approaches is rare, particularly using experimental results. The purpose of this research is to compare different linear calibration approaches (existing and new ones) through simulations and experiments. Both simulation and experimental results demonstrate that linear calibration using two concentrations (two true concentrations, not forced through zero) is as good as or even better than that using multiple concentrations (e.g. 8 or 10) in terms of accuracy. Additionally, two-concentration calibration not only significantly saves time and cost, but is also more robust. Furthermore, it has been demonstrated that the extrapolation of a linear curve at the high concentration end to a linearity-known region is acceptable. When multi-concentration calibration is used, the difference between the two commonly used approaches, i.e. singlet (one curve) or duplicate (two curves) standards per concentration level is small when a method is very precise. Otherwise, one curve approach can result in larger variation at the low concentration end and higher batch failure rate. To reduce the variation and unnecessary reassays due to batch failure or possible rejection of the lowest and/or highest calibration standards, a partially duplicate-standard approach is proposed, which has duplicate-standard-like performance but still saves time and cost as singlet-standard approach does. Finally, the maximum allowable degrees of quadratic (non-linear) response in linear calibration are determined for different scenarios. Because of its multiple advantages and potential application in regulated bioanalysis, recommendations as how to implement two-concentration linear calibration in practice are given and some typical "concerns" regarding linear calibration using only two concentrations are addressed, e.g. how does one know if the response is truly linear over a given range when only two concentrations are used?.

Determination of mycophenolic acid in human plasma by high-performance liquid chromatography.

The development, validation and evaluation of high-performance liquid chromatography (HPLC) method for quantifying mycophenolic acid in human plasma is described. The method involved protein precipitation using acetonitrile, after addition of terazosin as an internal standard. Separation was achieved with a reversed-phase C18 column (250 mm x 4.6 mm) employing UV detection at 215 nm. The mobile phase consisted of 0.02 M potassium dihydrogenphosphate solution adjusted to pH 6.9 with 2 M potassium hydroxide solution-acetonitrile (80:20 (v/v)) at a flow rate of 1.5 ml/min. The total run time was 21.0 min. The assay was linear from 0.2 to 25 microg/ml with goodness of fit (r2) greater than 0.99 observed with three precision and accuracy batches during validation. The observed mean recoveries were 89.3 and 98.0% for drug and internal standard, respectively. The applicability of this method to pharmacokinetic studies was established after successful application during a 34-subject bioavailability study. The method was found to be precise, accurate and specific during the study.