Magnitude of picoxystrobin residues in strawberry under Egyptian conditions: dissipation pattern and consumer risk assessment.

Picoxystrobin is a synthetic strobilurin fungicide widely used in Egypt to control downy and powdery mildews, a risk that is significant also in cultivating strawberries. In the ccurrent work, the safety to consumers from the use of picoxystrobin in strawberries along with its residue behaviour was studied. Supervised field trials were conducted to investigate the residue dynamics and terminal residues of picoxystrobin in strawberries under Egyptian conditions for several agricultural practices including worst-case scenarios. For the measurement of residues in fruit, a QuEChERS-based protocol coupled with LC-MS/MS was employed and successfully validated at 0.001 mg kg-1. A decline of picoxystrobin residues in fruit fitted a first-order decay process with a calculated t1/2 of 5.4 days with a significant degradation (79%) after 14 days. A consumer risk assessment was performed employing both FAO/WHO and EFSA approaches, in which no significant health risks after consumption of strawberries were identified.

Utility of some pi-acceptors for spectrophotometric determination of gatifloxacin in pure form and in pharmaceutical preparations.

Four simple, quick and sensitive methods are described for the spectrophotometric determination of gatifloxacin. The methods are based on the reaction of gatifloxacin as n-electron donor with 7,7,8,8-tetracyanoquinodimethane (TCNQ); 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); chloranilic acid (CLA) and p-chloranil (CL) as pi-acceptors to give highly colored complex species. The colored products are quantitated spectrophotometrically at 460, 841, 530 and 545 nm for DDQ, TCNQ, CLA and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5-60, 1.5-18, 30-360 and 20-240 microg ml(-1) of gatifloxacin, but for more accurate analysis, Ringbom optimum concentration range was found to be 7.5-55, 3-16, 35-350 and 25-230 microg ml(-1) of gatifloxacin for DDQ, TCNQ, CLA and CL, respectively. The limits of detection and quantification were calculated and the relative standard deviations for different concentrations of gatifloxacin using various acceptors were <1.28%. The association constants of 1 : 1 complexes and standard free energy changes using Benesi-Hildebrand plots were studied. The proposed methods were successfully applied to the determination of gatifloxacin in pharmaceutical dosage forms without interference from common additives encountered.