# A Compact Instrument for Temperature-Programming-Assisted Capillary-Nanoliquid Chromatography
## 4 Conclusions  
Developing and validating a temperature-programmable capillary-nanoLC system comprising a high-pressure syringe pump, time-based nanoliter injection system, programmable oven, and custom detection cell demonstrated considerable potential for mini  
Figure 11: Separating alkylbenzene compounds using a PLOT column (5 m length, 50 \(\upmu\)m i.d.): (**a**) without temperature programming and (**b**) with temperature programming. Peaks: uracil (1), toluene (2), ethylbenzene (3), butylbenzene (4), pentylbenzene (5), and heptylbenzene (6).  
turized liquid chromatography applications. The results show that the syringe pump achieved precise flow rates from 50 nL/min to 250 nL/min, with flow accuracy surpassing 99.9%, ensuring reliable performance across a broad operational range. The nanoliter injection system exhibited predictable, linear injection behavior up to 50% of the valve loop capacity, while the calibration of the system further improved its accuracy.  
The programmable capillary oven achieved consistent and precise temperature control, even under temperature gradients, with deviations below 0.01 \({}^{\circ}\)C. Temperature programming proved to be an effective means of modulating eluotropic strength, offering an efficient alternative to solvent gradients by achieving high reproducibility and consistent heating.  
Testing the complete system on packed and open tubular capillary columns confirmed that temperature programming considerably enhanced separation efficiency, reducing analysis time by up to 50% while maintaining robust chromatographic resolution. In packed columns, it led to a 3-fold increase in theoretical plates; in open tubular columns, a 2.5-fold efficiency improvement was achieved, demonstrating the suitability of this approach for high-efficiency separations in miniaturized LC.  
In conclusion, this work highlights the feasibility and advantages of temperature programming in capillary and nanoLC, offering a simplified, high-performance solution for miniaturized chromatography without the complexity of solvent gradient systems. This instrument holds promise for diverse analytical applications.  
Conceptualization, L.C.M., A.M.M., F.M.L. and V.L.L.; investigation, L.C.M., A.M.M. and V.L.L.; visualization, D.A.V.M., E.M.C. and F.M.L.; writing--original draft preparation, D.A.V.M., E.M.C. and F.M.L.; writing--review and editing, D.A.V.M., E.M.C. and F.M.L.; funding acquisition, F.M.L. All authors have read and agreed to the published version of the manuscript.  
The authors are grateful for the financial support from (i) the Coordination for the Improvement of Higher Education Personnel (CAPES--Brazil, Finance Code 001), (ii) the Sao Paulo Research Foundation (FAPESP--Brazil, Grants 2019/22724-7, 2017/02147-0, 2015/15462-5, 2014/07347-9, and 2019/26263-4), (iii) the National Council for Scientific and Technological Development (CNPq--Brazil, 307293/2014-9; 308843/2019-3) and (iv) the Ministry of Science, Technology, and Innovation (MINCIENCIAS--Colombia, No. 679).  
The corresponding author's data supporting this study's findings are available upon reasonable request.  
The authors declare no conflicts of interest related to this work.