Long-term time series of the atmospheric composition are essential for environmental research and thus require compatible, multi-decadal monitoring activities. However,the current data quality objectives of the World Meteorological Organization (WMO) for5 carbon monoxide (CO) in the atmosphere are very challenging to meet with the measurement techniques that have been used until recently. During the past few years, newspectroscopic techniques came on the market with promising properties for trace gasanalytics. The current study compares three instruments that are recently commerciallyavailable (since 2011) with the up to now best available technique (vacuum UV fluo-10 rescence) and provides a link to previous comparison studies. The instruments wereinvestigated for their performance regarding repeatability, reproducibility, drift, temperature dependence, water vapour interference and linearity. Finally, all instruments wereexamined during a short measurement campaign to assess their applicability for longterm field measurements. It could be shown that the new techniques provide a con-15 siderably better performance compared to previous techniques, although some issuessuch as temperature influence and cross sensitivities need further attention.