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, C18 Gravity-SB, C8 Gravity, C18 Isis, C18 Pyramid, PolarTec, Phenyl-Hexyl, 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.
Comparison of back pressures
Eluent: 100 % methanol
Flow rate: 1.5 mL/min
Temperature: 22 °C
Column dimensions: 50 x 4.6 mm
  NUCLEODUR® C18 Gravity Competitor
3 µm 70 bar
1.8 µm 130 bar 170 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:

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