Micro-gas column assisted laser induced breakdown spectroscopy (MGC-LIBS): A metal elements detection method for bulk water in-situ analysis

This manuscript introduces a newly developed method for in situ analysis of bulk water samples, called micro-gas column assisted LIBS (MGC-LIBS). A specially designed MGC assistance system was employed to generate a 1.28 mm diameter stable micro-gas column in situ underwater and laser pulses were focused on the gas-liquid interface of the column to improve LIBS spectral signal of metal elements in water sample. The detection experiments on metal elements in the solution showed that the intensity of ion line in the signal was enhanced by up to 14 times, and the signal RSD value was less than 1%. The detection limits (LOD) of Mg, Ca, Sr, Na, K and Li were all less than 1 mg/L. Compared with the results obtained by direct breakdown experiments in bulk water, the LODs of MGC-LIBS were significantly improved, in which the LOD of Mg element could be reduced by nearly 7.6 times. The concentration calibration curves of the above 6 elements were obtained in the possible concentration ranges of seawater samples, and quantitative inversion experiments were carried out. The results show that the estimated value using MGC-LIBS was basically consistent with the actual value, and the minimum error was 0.12%. This method is expected to be developed into an in situ, online, real-time and highly sensitive detection method for marine investigation or natural water environment monitoring. LIBS signal can be improved in the field of underwater in situ analysis by using a self-developed micro-gas column device to assist LIBS (MGC-LIBS). The experimental results showed that the stability and sensitivity of LIBS signal could be significantly improved by using MGC-LIBS. The quantitative analysis ability of MGC-LIBS was discussed by detecting the solution samples of known concentration in the seawater concentration range. The results showed that the method can accurately estimate the concentration of elements in seawater samples. [Display omitted] •A newly developed method named micro-gas column assisted LIBS (MGC-LIBS) which can improve LIBS signal in situ under water is introduced.•The special designed MCG auxiliary device which is simple and portable can stably generate a millimeter scale gas column in bulk water.•Compared with the breakdown in bulk water, the ionic line intensities of LIBS with MGC assistance is enhanced by 14 times, and the limit of detection of Mg, Ca, Sr, Na, K, Li are all less than 1 mg/L.•Within the range of possible seawater concentration, the estimated c