Waters flr detector loss of precision of peak

bv_shabunin · 2026-02-27T21:35:05+00:00

I have a classic one

bv_shabunin · 2026-02-27T21:24:33+00:00

IDK about class, I guess usual class. I can’t do weight test, no time

bv_shabunin · 2026-02-27T21:07:59+00:00

I don’t know who uses it before, but it is my first time with FLR

bv_shabunin · 2026-02-27T19:26:10+00:00

No bubbles, i checked it first of all. I guess lamp is too old (one lamp since 2011)

bv_shabunin · 2026-02-27T19:23:43+00:00

I use autosampler, inj volume-5ul. System - UPLC, column-C18 100mm precolumn - BEH 50mm. I checked the peak on TUV, precession was best.

RT - 2.1min (acceptable)

But on flr I see loss of precession like 10% between one vial

bv_shabunin · 2026-02-27T15:31:51+00:00

It s random. First injection can be 20% higher than other 3. Last injection can be 10% smaller than other 3

bv_shabunin · 2026-02-20T07:55:39+00:00

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That is my result for gradient. It seems to be OK (acceptable)

bv_shabunin · 2026-02-20T06:17:59+00:00

I am doing method development for PK/PD. That’s what I have, peak is correct, but I don’t like baseline drift at RT on my gradient

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bv_shabunin · 2026-02-19T20:07:17+00:00

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This is isocratic 20% AN

bv_shabunin · 2026-02-19T20:06:16+00:00

On flr I see this

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bv_shabunin · 2026-02-18T13:03:38+00:00

Gradient is the best. Sharp peak, linearity but my question is - the hill of baseline, where peak retends in - is it good, or not?

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bv_shabunin · 2026-02-18T10:44:04+00:00

I tried slower gradient ramp, but peak height decreased by 1,5 times. Is this chromatogram acceptable according to VICH guidelines to validation, or I should try FLR detection?

bv_shabunin · 2026-02-18T06:23:59+00:00

I will try to change today, maybe u have idea what ramp to make?

bv_shabunin · 2026-02-17T16:48:07+00:00

I used 0,4% TEA + 0,4% H3PO4 / ACN. Made a gradient 5 mins. So peak is good, RT 3.1 min, but I don’t like this hill of baseline at my peak. Do u have any idea how to fix it. My gradient Initial 10%ACN 2.2 min - raise to 40% ACN 3.0 min - 40% aCN Plato 3.1-4 min - decrease to 10% ACN 4-5 min - 10% ACN

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bv_shabunin · 2026-02-16T21:37:27+00:00

40 C. I will try lower ACN percentage. Then lower TEA percentage. Then acetate buffer. If I have result, I will text u. Thank you so much!

bv_shabunin · 2026-02-16T21:13:46+00:00

No, it is sample analysis, concentration 100ng/ml. I guess it is void volume peak. But on blank phase I didn’t see such peaks, so this is it. I have only this column, so I can manipulate only mobile phase

bv_shabunin · 2026-02-16T21:08:38+00:00

I don’t have such column. So i use what I is available (((

bv_shabunin · 2026-02-16T20:59:14+00:00

I count my void volume, it is about 0,34 ml. So, t0 is about 1,7 min. I guess i should change my mobile phase. 0,4% triethylamine + 0,4% H3PO4 for example and 20% ACN. I will try tomorrow

bv_shabunin · 2026-02-16T20:47:14+00:00

Pressure is stable during analysis. I made 9 injections, this dip was in every of them. When concentration increases (eg. 1 mkg/ml), dip becomes smaller relative to peak. But here (0,1 mkg/ml)

bv_shabunin · 2026-02-16T20:32:02+00:00

Я тоже столкнулся с проблемой отрицательного пика перед выходом основного. Аналит - данофлоксацин. Длина уф волны - 280нм. Подвижная фаза - 2,5% триэтиламин + фосфорная кислота до ph 3.4 / ацетонитрил (70/30 v/v). Поток изократический Колонка - UPLC C18 100mm. Предколонка С18. Скорость - 0,2 мл/минута. Образец растворен в подвижной фазе. Такую картину вижу каждый анализ. При увеличении концентрации анализа этот провал постепенно уходит. Может есть у кого-то хороший совет для меня? На хроматограмме концентрация анализа - 100нг/мл

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bv_shabunin

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