Dear chromatographers.

We want to buy a photodiode array detector for trace analysis (pesticides in fruit and vegetables)
Our choice must be the more objective but our experience with this detector is poor so
1°) Can someone tell me what are the most important parameters to test for comparison with different models ?
2°) Can someone give me positive or negative experience with 4 models of recent PAD (software and detector) ? :
BIO-TEK Instruments DAD 540 with Kromasystem 2000/3000 software
VARIAN PAD Prostar 330
THERMOQUEST UV 6000LP PAD with PC 1000 software
WATERS 996 PAD with Millenium software

Thanks.

Are you familiar with the work in the Netherlands? Contact Dr. Andre De Kok or Maurice Hiemstra at

andre.de.kok@inspectwv.nl tele 072 561 84 44

They gave a paper at the 1998 International Congress of Pesticide Chemistry dealing with the issues of pesticides and LC, and might be of great help to you.

We have both Beckman (168) and Hitachi (L-7455A)diode array detectors. Both are excellent, software and hardware. The Beckman lamps don't last as long as the Hitachi lamps and it seems that more often than not, I am removing air from the Beckman flow cell. I would choose a L-7455A based on sensitivity and reliability.

We have a Waters 996 (with Millenium 32). It runs quit well (I don't know about the other PDAs in your list). Using it with the Millenium software takes some getting used to.

Have you considered evaluating the Shimadzu SPD-M10Avp.....I know of at least 30 units in my area and all of the users seem quite happy with the detector's performance.

Define what's really important to your assay! Sensitivity or resolution? I would think that sensitivity would be of greater interest in the pesticide lab. I've used many different PDA's and the best one for sensitivity was by a German company called Gynkotek. They have since been purchased by Dionex. The PDA (UVD 340)is still the best thing going.

If you want sensitivity, then you should consider demanding proof. Try to run one of your samples on their detector, if there is one in your area. I was sold a pda that would be more sensitive than my 8 year older UV/VIS; it was about 100 times less sensitive. I run so many low level samples that it is worthless.

I have heard that the Dionex/ Gynkotek is very good for small peaks; the Shimadzu is said to be very good as well.

I use Waters 996 PDA+Millenium32 but sugest TSP UV6000LP
Http://www.thermoseperation.com
TSP UV6000 is a good choice

TSP UV 6000 is a best choise. We have already 2 without any problems for more than 1.5 year. The 5 cm optical pathway is something amazing and the baseline noise is like for usual UV detector.
Dr.A.Weisman
Chemagis Ltd.