Udit Batra
Analyst · TD Cowen
Thank you, Caspar, and good morning, everyone. We had a strong start to the year with sales coming in at the high end of our expectations backed again by excellent operational performance. I want to begin today's call by thanking my colleagues for their continued focus on innovation and supporting our customers. These results reflect our drive to accelerate the benefits of pioneering science with our innovative portfolio.
In the first quarter, market conditions were as expected, with cautious customer spending and later than typical budget releases. But as budgets opened up, we executed well with sales landing at the high end of our guide. We also continued to deliver outstanding operational results. Earnings were above our guidance and margins expanded even with volume and FX headwinds. This is a testament to our team, our resilient business model and our operational initiatives. Waters is well positioned for future growth in our attractive secular end markets. In the first quarter, we added to our revitalized portfolio with new products that serve high-growth areas.
Turning now to our results. In the first quarter, sales landed at the high end of our guidance, declining 7% as reported and 9% in organic constant currency. Our non-GAAP earnings per share exceeded our guidance at $2.21. On a GAAP basis, EPS was $1.72. Outside of China, sales declined mid-single digits as expected. In China, sales declined just under 30%, which was better than expected. Growth remained weak as our prior year baseline does not reflect last year's deterioration in market conditions, which became more pronounced in the second half.
While instruments declined 25% overall, LC sales were slightly better than expected, instrument weakness was led by mass spec, particularly for A&G-related applications, which had a tough prior year comparison from global funding and the China stimulus. Wyatt delivered a 3% M&A contribution to sales. We continue to see strong synergy performance and traction for our recently launched products such as ZetaStar.
Now I will talk more about our operational performance. We believe the best reflection of good operational execution is effective margin management, particularly when things slow down. While facing significant headwinds from volume, FX and inflation, we delivered yet another strong margin result. Our gross margin expanded 40 basis points to 58.9%, and our operating margin expanded 20 basis points for the quarter to 27%. This was achieved through a combination of our operational management initiatives across pricing, productivity and proactive cost alignment. These initiatives position us well for resilience during lower volume periods and give longer-term opportunity when market conditions normalize. You can see further evidence of our operational performance and our free cash flow. We had an exceptional start to the year, generating free cash flow of USD 234 million in the first quarter, which was 37% of sales.
With our excellent free cash flow profile, we made rapid progress in delevering from the Wyatt acquisition, as we approach its 1-year anniversary. We serve attractive secular end markets where testing volume plays a pivotal role in our business. This volume, which is correlated with global prescription consumption is expected to accelerate in the future, supporting our strong long-term growth outlook. Our distinct advantage in downstream applications lines with our full ecosystem of products that complement our innovative instrument portfolio.
In addition, we have strategically aligned with high-growth opportunities that further enhance our core position. We had a busy quarter launching several new products that support a number of exciting, high-growth areas. At Analytica, last month, we launched the Alliance iS Bio, a version of our groundbreaking next-generation liquid chromatography platform suited for biologics applications. In the -- the new HPLC system combines advanced bioseparation technology, bioinert surfaces and built-in intelligence features. This helps Biopharma QC analysts boost efficiency and eliminate up to 40% of common lab errors. We believe that the Alliance iS is the most significant innovation to hit pharma QA/QC labs in over a decade.
We're excited to bring this technology to routine testing applications for biologics. Supporting BioSeparations, we launched a new set of size exclusion chromatography columns called GTxResolve Premier. These columns enable scientists to quickly assess aggregate content, integrity and purity of larger biologic particles. It covers modalities such as lipid nanoparticles, nucleic acids, and viral vectors and give scientists a significant improvement in sensitivity and sample consumption while accelerating run times. This launch supports the development of these modalities into downstream high-volume settings, where Waters has critical instrument technology like LC, mass spec and light scattering as well as highly innovative industry-leading software chemistry and service.
To simplify the detection of PFAS, we launched waters, Oasis, dual-phase analysis cartridges. This consumable streamline sample prep for PFAS workflows when detecting concentrations in water, soils, biosolids and tissues. It joins our comprehensive portfolio of solutions that support the surging demand for PFAS testing, which is a USD 300 million to USD 350 million global market, growing 20% annually. In an environment of increased scrutiny, the ability to accurately test for PFAS at very low levels is becoming a critical compliance need for a broad spectrum of industries.
Our Xevo TQ absolute mass spec has leading sensitivity for detecting these anionic compounds. It can detect PFAS levels at as low as 1 part per quadrillion. Last month, in the United States, the EPA finalized and enforceable 4 parts per trillion limit of PFOA and PFOS in drinking water, which marks a significant regulatory milestone. Later this year, further regulations governing PFAS are expected across the globe. This includes the European Union, where REACH proposed chemicals, regulation contemplates a PFAS ban on products manufactured as well as once imported.
In our TA business, we launched the Rheo-IS, which serves battery testing applications when used with our hybrid rheometers. This Rheo-Impedance Spectroscopy accessory supports characterization of electrode studies, which can lead to more efficient battery production.
I will now cover our 2024 full year guidance. With our first quarter results, we remain on track to achieve our full year revenue outlook, which is unchanged from our previous guidance at negative 0.5% to positive 1.5% growth in organic constant currency.
We expect growth rates to improve over the remainder of the year and as our prior year comparisons, especially in China get easier. We expect improving funnel activity to translate to orders as the year progresses. With our strong operational performance, we expect to build leverage in our P&L despite the flattish revenue guide and delivered 20 to 30 basis points of adjusted operating margin expansion while still reinvesting for growth. As a result, our adjusted EPS guidance is also unchanged at 0% to 3% growth in the range of $11.75 to $12.05.
Now I will pass the call over to Amol to continue covering our financial results in more detail and provide the rest of our guidance. Amol?