下圖是在相同分析條件下，1.8 um顆粒的色譜柱顯著提高了樣品的分離度。
色譜柱顆粒對分離度的影響

色譜柱：NUCLEODUR C18 Gravity 50×4mm   A)3 um   B)1.8 um
流動相：乙腈：水=80:20
流  速：2.0毫升/分鐘
進(jìn)樣量：5 ul
柱  壓：A)80bar  B)160bar
檢測器:UV 254nm
樣  品：1.萘  2.乙苯

高流速，縮短分析時(shí)間
    根據(jù)色譜分析原理“Van-Deemter-Plot”，小顆粒的分析柱能夠使用更高的流動相流速，5 um的*流速是1毫升/分鐘，而1.8 um的色譜柱經(jīng)常使用2-3毫升/分鐘的流速。這樣就能夠在保持相同分離度的條件下，大大縮短分析時(shí)間。

色譜柱：NUCLEODUR C18 Isis 50×4.0mm
流動相：*甲醇
檢測器：UV 254nm

訂貨指南

50×2mm

50×3mm

50×4.6mm

C18 Gravity

760079.20

760079.30

760079.46

C8 Gravity

760755.20

760755.30

760755.46

C18 Isis

760405.20

760405.30

760405.46

C18 Pyramid

760272.20

760272.30

760272.46

C18 Sphinx RP

760822.20

760822.30

760822.46

1.8 µm particles for increased separation efficiency

Decrease of analysis time (ultra fast HPLC)
Shorter columns with high separation efficiency
Significant improvement of resolution
Increased detection sensitivity
Suitable for LC/MS due to low bleeding characteristics

All NUCLEODUR® premium phases are available in 1.8 μm:
C18 Gravity, C8 Gravity, C18 Isis, C18 Pyramid, PolarTec, PFP, Sphinx RP, C18 HTec,HILIC

NUCLEODUR® 1.8 μm particles are fractionated to limit the increase in back pressure.

NUCLEODUR® silica with 1.8 µm particle size
Miniaturization in HPLC has a long history. It started in the early stage of HPLC development with the reduction of particle size from 10 µm via 7 μm to standard 5 µm – which is still the most widely used particle diameter in analytical HPLC – to 3 µm spherical particles which so far was the smallest particle size available for gaining higher theoretical plates and efficiencies.
With the introduction of the 1.8 µm NUCLEODUR®particles researchers have turned over an exciting leaf in HPLC column technology.

Features of 1.8 µm NUCLEODUR^® particles

Increase of separation efficiency by higher number of theoretical plates (N):
50 x 4.6 mm NUCLEODUR® C18 Gravity

3 µm:

N ≥ 100 000 plates/m (h value ≤ 10)

1.8 µm:

N ≥ 166 667 plates/m (h value ≤ 6)

Increase of the plate number by ~ 67 % offers the possibility of using shorter columns with equal plate numbers resulting in a decrease of analysis time.

Significant improvement in resolution
Use of 1.8 μm instead of 3 µm particles leads to an increase of resolution by a factor 1.29 (29 %)

Higher flow rates and shorter run times
Optimal flow rate for 1.8 µm particles is higher than for 3 and 5 µm particles – the flow rate should be at the van-Deemter minimum.

Van-Deemter plot

Column back pressure
Due to the smaller particle size the back pressure will increase.
Because of the high sphericity of the NUCLEODUR® particles and the very narrow particle size distribution we are able to keep the back pressure on a moderate level. 
Thus NUCLEODUR® columns can be used on modernen ultra fast HPLC instruments as well as in combination with conventional HPLC systems with pumps up to 400 bar.
 

Technical  requirements
To gain the best result in ultra fast HPLC based on 1.8 μm particles certain technical demands on the instrument are made.

Pumps for pressures of 250–1000 bar

Flow rates of 2–3 mL/min

Minimized dead volumes of the LC system

Fast data recording

Versatile selectivities
All NUCLEODUR® premium phases are available with 1.8 µm particles:

C18 Gravity

C8 Gravity

C18 Isis

C18 Pyramid

PolarTec

PFP

Sphinx RP

C18 HTec

HILIC