Automated On-Line GPC-GC-FPD Involving Co-Solvent Trapping and the On-Column Interface for the Determination of Organophosphorus Pesticides in Olive Oils

Injectors for capillary gas chromatography and their application to environmental analysis

“…One common problem in GC analysis is the potential for the analytes to degrade in the injection chamber. Problematic compounds due to thermal or chemical instability that are prone to degradation in the GC injector include pesticides such as N-trihalogenmethylthio compounds (captan, captafol, dichlorfluanid), 4,5 organochlorines (OCs) such as toxaphene, DDT, endrin, aldrin, chlorothalonil, [6][7][8][9][10][11][12][13][14][15][16] organophosphorus pesticides (OPPs) such as dimethoate, acepthate, ethion, methamidophos, 8,9,12,13,15,[17][18][19][20][21] pyrethroids, 9,13,16 and phenyureas. 22 For other compounds such as PCBs, 46 polybrominated diphenyl ethers (BDE), 23,24 PAHs 25 or hydrocarbons 26 the selection of the injector type is often based on the ability to minimize discrimination of either high or low boiling point compounds or congeners.…”

“…Some improvements can also be made in GC analysis by modifying the polarity of the stationary phase, or reducing column diameter and thickness of stationary phase 42 to allow for lower temperatures in the temperature program for separation and faster analysis times. COC injections have been used successfully for thermally unstable compounds or mixtures such as toxaphene, 7 organophosphorus pesticides, 13,17,19 organochlorines, 13,14 pyrethroids, 13 nitroaromatic explosive vapours 43 and for compounds that exhibit discrimination with the split/splitless injector for higher boiling points compounds such as BDE congeners, 23,24 PAHs, 25 chloroanilines 44 and alkanes. 26 COC injections can be used with small volume injections of 1-2 mL without requirements of a retention gap.…”

“…7,17 Both COC and programmable temperature vaporizer (PTV) inlets have also been used with large volume injections (410 mL-250 mL) to allow lower detection limits. 14,17,19,26,43,45 For COC this requires modification of the chromatographic system to include a large diameter retention gap (10-15 m  0.53 mm), connected to a retaining pre-column (3-5 m  0.32 mm) and solvent vapor exit valve prior to the analytical column. 19,26 The sample injection speed is slowed down in LVI-COC to prevent flooding of the system during large volume injections with injection speeds in LVI-COC of 20-300 mL min À1 14,26,45 as compared to LVI-PTV at 50-1500 mL min À1 .…”

“…14,17,19,26,43,45 For COC this requires modification of the chromatographic system to include a large diameter retention gap (10-15 m  0.53 mm), connected to a retaining pre-column (3-5 m  0.32 mm) and solvent vapor exit valve prior to the analytical column. 19,26 The sample injection speed is slowed down in LVI-COC to prevent flooding of the system during large volume injections with injection speeds in LVI-COC of 20-300 mL min À1 14,26,45 as compared to LVI-PTV at 50-1500 mL min À1 . 20,21,46 The solvent vapor exit must be closed prior to the end of solvent vaporization to allow solvent trapping of volatile components, 45 but closing the valve too early can result in overloading the column with solvent.…”

Μελέτη Της Αποδόμησης Υπολειμμάτων Γεωργικών Φαρμάκων Σε Φρούτα Και Λαχανικά Κατά Την Συντήρηση Σε Διαφορετικές Συνθήκες

“…Με αυτό το τρόπο θα έχουμε λιγότερες αποκλίσεις από τις μετρήσιμες τιμές των υπολειμμάτων (Wylie & Uchiyama, 1996). Στον αυτόματο δειγματολήπτη αυτές τις λεπτομέρειες τις εκτελεί επαναλήψιμα και σταθερά το ίδιο το όργανο ύστερα από ένα σωστό προγραμματισμό εισαγωγής δείγματος και ταχύτητας εκτέλεσης του ενέσιμου δείγματος (Jongenotter et al, 1999). Έχει σημασία σε πολλές περιπτώσεις η ταχύτητα εισαγωγής του δείγματος στον ενχυτή του οργάνου αν έχουμε υπόψη μας την υψηλή θερμοκρασία του εισαγωγέα (220 °C -250 °C) κατά τη διάρκεια ανάλυσης.…”